Inter-study reproducibility of left ventricular torsion and torsion rate quantification using MR myocardial feature tracking

Cardiac MRI feature-tracking-derived torsion mechanics in systolic and diastolic dysfunction in systemic light-chain cardiac amyloidosis

AIM

To describe the myocardial torsion mechanics in cardiac amyloidosis (CA), and evaluate the correlations between left ventricle (LV) torsion mechanics and conventional parameters using cardiac magnetic resonance imaging feature tracking (CMR-FT).

MATERIALS AND METHODS

One hundred and thirty-nine patients with light-chain CA (AL-CA) were divided into three groups: group 1 with preserved systolic function (LV ejection fraction [LVEF] ≥50%, n=55), group 2 with mildly reduced systolic function (40% ≤ LVEF <50%, n=51), and group 3 with reduced systolic function (LVEF <40%, n=33), and compared with age- and gender-matched healthy controls (n=26). All patients underwent cine imaging and late gadolinium-enhancement (LGE). Cine images were analysed offline using CMR-FT to estimate torsion parameters.

RESULTS

Global torsion, base-mid torsion, and peak diastolic torsion rate (diasTR) were significantly impaired in patients with preserved systolic function (p<0.05 for all), whereas mid-apex torsion and peak systolic torsion rate (sysTR) were preserved (p>0.05 for both) compared with healthy controls. In patients with mildly reduced systolic function, global torsion and base-mid torsion were lower compared to those with preserved systolic function (p<0.05 for both), while mid-apex torsion, sysTR, and diasTR were preserved (p>0.05 for all). In patients with reduced systolic function, only sysTR was significantly worse compared with mildly reduced systolic function (p<0.05). At multivariable analysis, right ventricle (RV) end-systolic volume RVESV index and NYHA class were independently related to global torsion, whereas LVEF was independently related to sysTR. RV ejection fraction (RVEF) was independently related to diasTR. LV global torsion performed well (AUC 0.71; 95% confidence interval [CI]: 0.61, 0.77) in discriminating transmural from non-transmural LGE in AL-CA patients.

CONCLUSION

LV torsion mechanics derived by CMR-FT could help to monitor LV systolic and diastolic function in AL-CA patients and function as a new imaging marker for LV dysfunction and LGE transmurality.

Evaluation the relationship between myocardial fibrosis and left ventricular torsion measured by cardiac magnetic resonance feature-tracking in hypertrophic cardiomyopathy patients with preserved ejection fraction

The relationship between left ventricular (LV) torsion and myocardial fibrosis (MF) in hypertrophic cardiomyopathy (HCM) patients with preserved ejection fraction was still not well understood. New developments in cardiac magnetic resonance (CMR) enable a much fuller assessment of cardiac characteristics. This study sought to assess the impact of HCM on myocardial function as assessed by LV torsion and its relationship with MF. HCM (n = 79) and healthy controls (n = 40) underwent CMR. According to whether there was late gadolinium enhancement (LGE), patients were divided into LGE+ group and LGE- group. LV torsion and torsion rate were measured by CMR feature-tracking (CMR-FT). MF was quantitatively evaluated through LGE imaging. LGE was present in 44 patients (56%). Compared with healthy controls, torsion increased in the LGE- group (P < 0.001). Compared with LGE+ group, torsion was higher in the LGE- group (P < 0.001). There was no significant difference in torsion between LGE+ group and healthy controls. Correlation analysis showed that torsion was correlated with LGE% (r = - 0.443) and LGE mass (r = - 0.435) respectively. On multivariable logistic regression analysis, LV torsion was the only feature that was independently associated with the presence of LGE (OR 0.130; 95% CI 0.040 to 0.420, P = 0.01). The best torsion value associated with MF was 1.91 (sensitivity 60.0%, specificity 77.3%, AUC = 0.733). In HCM patients with preserved ejection fraction, CMR-FT derived LV torsion analysis holds promise for myocardial fibrosis detection.

Inter-study reproducibility of cardiovascular magnetic resonance-derived hemodynamic force assessments

Cardiovascular magnetic resonance (CMR)-derived hemodynamic force (HDF) analyses have been introduced recently enabling more in-depth cardiac function evaluation. Inter-study reproducibility is important for a widespread clinical use but has not been quantified for this novel CMR post-processing tool yet. Serial CMR imaging was performed in 11 healthy participants in a median interval of 63 days (range 49-87). HDF assessment included left ventricular (LV) longitudinal, systolic peak and impulse, systolic/diastolic transition, diastolic deceleration as well as atrial thrust acceleration forces. Inter-study reproducibility and study sample sizes required to demonstrate 10%, 15% or 20% relative changes of HDF measurements were calculated. In addition, intra- and inter-observer analyses were performed. Intra- and inter-observer reproducibility was excellent for all HDF parameters according to intraclass correlation coefficient (ICC) values (> 0.80 for all). Inter-study reproducibility of all HDF parameters was excellent (ICC ≥ 0.80 for all) with systolic parameters showing lower coeffients of variation (CoV) than diastolic measurements (CoV 15.2% for systolic impulse vs. CoV 30.9% for atrial thrust). Calculated sample sizes to detect relative changes ranged from n = 12 for the detection of a 20% relative change in systolic impulse to n = 200 for the detection of 10% relative change in atrial thrust. Overall inter-study reproducibility of CMR-derived HDF assessments was sufficient with systolic HDF measurements showing lower inter-study variation than diastolic HDF analyses.

Healthy Adult Left and Right Ventricular Torsion and Torsion Rates With MR-Feature Tracking

BACKGROUND

The clinical value of myocardial torsion quantification in prognostic assessment and risk stratification of various cardiovascular diseases is gradually being recognized. However, normal values of left and right ventricular (LV and RV) torsion and torsion rates (TRs) have not been fully determined, and their correlation with age and gender has not been well studied.

PURPOSE

To establish normal ranges of biventricular torsion, peak systolic and diastolic TRs using magnetic resonance feature tracking (MR-FT) technique based on a large sample of healthy adults, and further investigate their relationship with age and gender.

STUDY TYPE

Retrospective.

POPULATION

566 Healthy adults (312 males, aged 43 ± 10 years; 254 females, aged 43 ± 11 years).

FIELD STRENGTH/SEQUENCE

1.5T/gradient echo.

ASSESSMENT

Biventricular torsion, peak systolic, and diastolic TRs.

STATISTICAL TESTS

Shapiro-Wilk test, Student's t-test, Mann-Whitney-U test, linear regression, intraclass correlation coefficient, Bland-Altman analysis. Differences were regarded as statistically significant at P < 0.05.

RESULTS

Women demonstrated greater magnitudes of left ventricle (LV) torsion (1.23 ± 0.44 vs. 1.00 ± 0.42°/cm), peak systolic TR (9.69 ± 3.70 vs. 8.27 ± 3.73°/cm*sec), peak diastolic TR (-7.78 ± 2.82 vs. -6.06 ± 2.44°/cm*sec), and RV torsion (2.20 ± 1.23 vs. 1.65 ± 1.11°/cm*sec), peak systolic TR (16.07 ± 8.18 vs. 12.62 ± 7.08°/cm*sec), peak diastolic TR (-15.39 ± 6.53 vs. -11.70 ± 6.03°/cm*sec). For both genders, the magnitudes of LV and RV torsion, peak systolic, and diastolic TRs increased linearly with age. All the measurements of biventricular torsion, peak systolic and diastolic TRs achieved good to excellent intraobserver and interobserver reproducibility, with all intraclass correlation coefficients >0.70.

DATA CONCLUSION

The present study systematically provided age- and sex-stratified reference values for LV and RV torsion and TRs using MR-FT technique. Women and aging are associated with greater magnitudes of biventricular torsion, peak systolic, and diastolic TRs.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

Reduced left ventricular dynamics modeling based on a cylindrical assumption

Biomechanical modeling and simulation is expected to play a significant role in the development of the next generation tools in many fields of medicine. However, full-order finite element models of complex organs such as the heart can be computationally very expensive, thus limiting their practical usability. Therefore, reduced models are much valuable to be used, for example, for pre-calibration of full-order models, fast predictions, real-time applications, and so forth. In this work, focused on the left ventricle, we develop a reduced model by defining reduced geometry & kinematics while keeping general motion and behavior laws, allowing to derive a reduced model where all variables & parameters have a strong physical meaning. More specifically, we propose a reduced ventricular model based on cylindrical geometry & kinematics, which allows to describe the myofiber orientation through the ventricular wall and to represent contraction patterns such as ventricular twist, two important features of ventricular mechanics. Our model is based on the original cylindrical model of Guccione, McCulloch, & Waldman (1991); Guccione, Waldman, & McCulloch (1993), albeit with multiple differences: we propose a fully dynamical formulation, integrated into an open-loop lumped circulation model, and based on a material behavior that incorporates a fine description of contraction mechanisms; moreover, the issue of the cylinder closure has been completely reformulated; our numerical approach is novel aswell, with consistent spatial (finite element) and time discretizations. Finally, we analyze the sensitivity of the model response to various numerical and physical parameters, and study its physiological response.

Consistency of left ventricular ejection fraction measurements in the early time course of STEMI

BACKGROUND

Early after ST-segment elevation myocardial infarction (STEMI), initial LV reshaping and hypokinesia may affect analysis of LV function. Concomitant microvascular dysfunction may affect LV function.

OBJECTIVE

To perform a comparative evaluation of left ventricular ejection fraction (LVEF) and stroke volume (SV) by different imaging modalities to assess LV function early after STEMI.

METHODS

LVEF and SV were assessed using serial imaging within 24 h and 5 days after STEMI using cineventriculography (CVG), 2-dimensional echocardiography (2DE), 2D/3D cardiovascular magnetic resonance (CMR) (2D/3D) in 82 patients.

RESULTS

2D analyses of LVEF using CVG, 2DE and 2D CMR yielded uniform results within 24 h and 5 days of STEMI. SV assessment between CVG and 2DE was comparable, whereas values for SV were higher using 2D CMR (p <  0.01 all). This was due to higher LVEDV measurements. LVEF by 2D versus 3D CMR was comparable, 3D CMR yielded higher volumetric values. This was not influenced by infarct location or infarct size.

CONCLUSIONS

2D analysis of LVEF yielded robust results across all imaging techniques implying that CVG, 2DE, and 2D CMR can be used interchangeably early after STEMI. SV measurements differed substantially between imaging techniques due to higher intermodality-differences of absolute volumetric measurements.

Left ventricular strain in patients with Takayasu arteritis with preserved ejection fraction: an analysis using cardiac magnetic resonance imaging feature tracking

Background

The alteration of myocardial strain in patients with Takayasu arteritis (TAK) remains unclear. This study aimed to evaluate left ventricular (LV) stain in patients with TAK and preserved left ventricular ejection fraction (pLVEF) using cardiac magnetic resonance imaging feature tracking (CMR-FT) to analyze risk factors for impaired LV strain and to compare the baseline difference of LV strain between patients with reduced and nonreduced LVEF at 6-month follow-up.

Methods

In all, 51 patients with TAK and 30 healthy controls were prospectively enrolled. All participants underwent multiple short- and long-axis cine scans with true fast imaging with steady-state precession sequence. In this observational study, LV global and regional longitudinal, circumferential, and radial strain and their strain rates were analyzed with FT on cine images. The relationship between LV strain and clinical data was explored. The baseline LV strain between patients with TAK and reduced and nonreduced LVEF was compared using transthoracic echocardiography (TTE) at the 6-month follow-up.

Results

Patients with TAK with pLVEF showed a decline in baseline global longitudinal peak strain (GLS) [TAK (-13.35%±3.11%) vs. controls (-14.77%±1.74%), P=0.021] and circumferential peak strain (GCS) [TAK (-21.46%±2.66%) vs. controls (-22.75%±2.57%), P=0.027] in comparison with normal controls. The longitudinal peak strain (LPS) in the apical (P=0.003) and midventricular regions (P=0.027) and the circumferential peak strain (CPS) in the basal (P=0.021) and midventricular regions (P=0.008) also decreased in patients with TAK. Patients with pulmonary hypertension (PH) or myocardial late gadolinium enhancement (LGE) showed a greater reduction in strain compared with those without PH or LGE. GLS showed a negative association with erythrocyte sedimentation rate (ESR), while GCS showed a positive association with disease duration. In the 30 patients who were followed up, the baseline global and apical circumferential diastolic peak strain rates (DPSR) in patients with reduced LVEF were higher than those in patients without reduced LVEF.

Conclusions

In patients with TAK and pLVEF, CMR-FT indicated that both global and segmental myocardial strain decreased. PH, male gender, long disease duration, elevated ESR, and myocardial LGE were associated with declined LV strain. Baseline increased circumferential DPSR may be associated with the decline in LVEF during follow-up.

Prognostic implications of left ventricular torsion measured by feature-tracking cardiac magnetic resonance in patients with ST-elevation myocardial infarction

AIMS

The prognostic implication of left ventricular (LV) torsion on ST-elevation myocardial infarction (STEMI) is unclear.

METHODS AND RESULTS

We analysed cardiovascular magnetic resonance (CMR) findings of 420 patients from a registry study (NCT03768453). These patients received CMR examination within 1 week after timely primary percutaneous coronary intervention. LV torsion and other CMR indexes were measured. Compared with healthy control subjects, STEMI significantly decreased patients' LV torsion (1.04 vs. 1.63°/cm, P < 0.001). During follow-up (median, 52 months), the reduction of LV torsion was greater in patients with than without composite major adverse cardiac and cerebrovascular events (MACCEs, 0.79 vs. 1.08°/cm, P < 0.001). The risk of MACCEs would increase to 1.125- or 1.092-fold, and the risk of 1-year LV remodelling would increase to 1.110- or 1.082-fold for every 0.1°/cm reduction in LV torsion after adjustment for clinical or CMR parameters respectively. When divided dichotomously, patients with LV torsion≤ 0.802°/cm had significantly higher risk of MACCEs (40.2 vs. 12.3%, P < 0.001) and more remarkable LV remodelling (46.1 vs. 11.9%, P < 0.001) than patients with better LV torsion. The addition of LV torsion to conventional prognostic factors such as the LV ejection fraction and infarction size led to a better risk classification model of patients for both MACCEs and LV remodelling. Finally, tobacco use, worse post-PCI flow, and greater microvascular obstruction size were presumptive risk factors for reduced LV torsion.

CONCLUSION

LV torsion measured by CMR is closely associated with the prognosis of STEMI and would be a promising indicator to improve patients' risk stratification.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov, NCT03768453.

Artificial intelligence fully automated myocardial strain quantification for risk stratification following acute myocardial infarction

Feasibility of automated volume-derived cardiac functional evaluation has successfully been demonstrated using cardiovascular magnetic resonance (CMR) imaging. Notwithstanding, strain assessment has proven incremental value for cardiovascular risk stratification. Since introduction of deformation imaging to clinical practice has been complicated by time-consuming post-processing, we sought to investigate automation respectively. CMR data (n = 1095 patients) from two prospectively recruited acute myocardial infarction (AMI) populations with ST-elevation (STEMI) (AIDA STEMI n = 759) and non-STEMI (TATORT-NSTEMI n = 336) were analysed fully automated and manually on conventional cine sequences. LV function assessment included global longitudinal, circumferential, and radial strains (GLS/GCS/GRS). Agreements were assessed between automated and manual strain assessments. The former were assessed for major adverse cardiac event (MACE) prediction within 12 months following AMI. Manually and automated derived GLS showed the best and excellent agreement with an intraclass correlation coefficient (ICC) of 0.81. Agreement was good for GCS and poor for GRS. Amongst automated analyses, GLS (HR 1.12, 95% CI 1.08-1.16, p < 0.001) and GCS (HR 1.07, 95% CI 1.05-1.10, p < 0.001) best predicted MACE with similar diagnostic accuracy compared to manual analyses; area under the curve (AUC) for GLS (auto 0.691 vs. manual 0.693, p = 0.801) and GCS (auto 0.668 vs. manual 0.686, p = 0.425). Amongst automated functional analyses, GLS was the only independent predictor of MACE in multivariate analyses (HR 1.10, 95% CI 1.04-1.15, p < 0.001). Considering high agreement of automated GLS and equally high accuracy for risk prediction compared to the reference standard of manual analyses, automation may improve efficiency and aid in clinical routine implementation.Trial registration: ClinicalTrials.gov, NCT00712101 and NCT01612312.

Quantification of strain analysis and late gadolinium enhancement in coronary chronic total occlusion: a cardiovascular magnetic resonance imaging follow-up study

Background

The present study aimed to investigate the benefits of percutaneous coronary intervention (PCI) in patients with chronic total occlusions (CTOs) by using cardiac magnetic resonance imaging (CMR) feature tracking.

Methods

Fifty-five CTOs with successful CTO-PCI underwent CMR at baseline and 12 months. Feature tracking was applied to measure left ventricle strain index in CTOs with decreased and preserved left ventricular ejection fraction (LVEF). CTOs were also divided into two groups according to the infarct size of 10% or combined with multi-vessel disease. We also measured these parameters in 40 healthy subjects.

Results

Three quarters of CTOs showed preserved ejection fraction and no enlargement of left ventricle at baseline, but the global strains were lower than the controls (all P<0.01). In the entire CTO population, left ventricular ejection fraction did not show significant improvement in the 1-year follow-up (59.8%±11.3% vs. 62.0%±8.6%, P=0.08). However, global strains improved over time, and peak global radial strain and circumferential strain showed significant treatment effect of CTO-PCI in the entire CTO population (31.1%±9.9% vs. 34.3%±8.7%, P<0.01; -17.9±3.6 vs. -19.2±3.1, P<0.01), and the subgroup with decreased LVEF, infarct size less than 10%, or multi-vessel disease, but not with the 1-vessel disease. In the LAD and LCX CTO territory, radial and circumferential strain showed treatment effect of CTO-PCI on the recovery of strain parameters (P<0.01 for both). In the RCA CTO territory, circumferential and longitudinal strain showed treatment effect of CTO-PCI on the recovery of strain parameters (P<0.05 for both).

Conclusions

In this single center study, global radial strain and circumferential strain showed treatment effect of successful CTO-PCI at 1-year follow-up in CTOs with the decreased LVEF, infarct size less than 10%, or multi-vessel disease, and the regional strain also showed a similar trend. However, the benefit of CTO-PCI on the strain recovery was not shown in patients with 1-vessel disease. Therefore, whether patients with CTO benefit from PCI still needs further verification.

Myocardial mechanics in dilated cardiomyopathy: prognostic value of left ventricular torsion and strain

BACKGROUND

Data on the prognostic value of left ventricular (LV) morphological and functional parameters including LV rotation in patients with dilated cardiomyopathy (DCM) using cardiovascular magnetic resonance (CMR) are currently scarce. In this study, we assessed the prognostic value of global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS) and LV torsion using CMR feature tracking (FT).

METHODS

CMR was performed in 350 DCM patients and 70 healthy subjects across 5 different European CMR Centers. Myocardial strain parameters were retrospectively assessed from conventional balanced steady-state free precession cine images applying FT. A combined primary endpoint (cardiac death, heart transplantation, aborted sudden cardiac death) was defined for the assessment of clinical outcome.

RESULTS

GLS, GCS, GRS and LV torsion were significantly lower in DCM patients than in healthy subjects (all p < 0.001). The primary endpoint occurred in 59 (18.7%) patients [median follow-up 4.2 (2.0-5.6) years]. In the univariate analyses all strain parameters showed a significant prognostic value (p < 0.05). In the multivariate model, LV strain parameters, particularly GLS provided an incremental prognostic value compared to established CMR parameters like LV ejection fraction and late gadolinium enhancement. A scoring model including six categorical variables of standard CMR and strain parameters differentiated further risk subgroups.

CONCLUSION

LV strain assessed with CMR FT has a high prognostic value in patients with DCM, surpassing routine and dedicated functional parameters. Thus, CMR strain imaging may contribute to the improvement of risk stratification in DCM.

Morphological and functional cardiac consequences of rapid hypertension treatment: a cohort study

BACKGROUND

Left ventricular (LV) hypertrophy (LVH) in uncontrolled hypertension is an independent predictor of mortality, though its regression with treatment improves outcomes. Retrospective data suggest that early control of hypertension provides a prognostic advantage and this strategy is included in the 2018 European guidelines, which recommend treating grade II/III hypertension to target blood pressure (BP) within 3 months. The earliest LVH regression to date was demonstrated by echocardiography at 24 weeks. The effect of a rapid guideline-based treatment protocol on LV remodelling, with very early BP control by 18 weeks remains controversial and previously unreported. We aimed to determine whether such rapid hypertension treatment is associated with improvements in LV structure and function through paired cardiovascular magnetic resonance (CMR) scanning at baseline and 18 weeks, utilising CMR mass and feature tracking analysis.

METHODS

We recruited participants with never-treated grade II/III hypertension, initiating a guideline-based treatment protocol which aimed to achieve BP control within 18 weeks. CMR and feature tracking were used to assess myocardial morphology and function immediately before and after treatment.

RESULTS

We acquired complete pre- and 18-week post-treatment data for 41 participants. During the interval, LV mass index reduced significantly (43.5 ± 9.8 to 37.6 ± 8.3 g/m2, p < 0.001) following treatment, accompanied by reductions in LV ejection fraction (65.6 ± 6.8 to 63.4 ± 7.1%, p = 0.03), global radial strain (46.1 ± 9.7 to 39.1 ± 10.9, p < 0.001), mid-circumferential strain (- 20.8 ± 4.9 to - 19.1 ± 3.7, p = 0.02), apical circumferential strain (- 26.0 ± 5.3 to - 23.4 ± 4.2, p = 0.003) and apical rotation (9.8 ± 5.0 to 7.5 ± 4.5, p = 0.003).

CONCLUSIONS

LVH regresses following just 18 weeks of intensive antihypertensive treatment in subjects with newly-diagnosed grade II/III hypertension. This is accompanied by potentially advantageous functional changes within the myocardium and supports the hypothesis that rapid treatment of hypertension could improve clinical outcomes.

TRIAL REGISTRATION

ISRCTN registry number: 57475376 (assigned 25/06/2015).

Takotsubo Syndrome-Is There a Need for CMR?

PURPOSE OF REVIEW

Takotsubo syndrome (TTS) is a transient but severe myocardial dysfunction that has been known for decades and is still to be fully understood regarding its clinical presentations and pathophysiological mechanisms. Cardiac magnetic resonance (CMR) imaging plays a key role in the comprehensive analysis of patients with TTS in acute and follow-up examinations. In this review, we focus on the major advantages and latest evolutions of CMR in diagnosis and prognostication of TTS and discuss future perspectives and needs in the field of research and cardiovascular imaging in TTS.

RECENT FINDINGS

Specific CMR criteria for TTS diagnosis at the time of acute presentation are established. In addition to identifying the typical regional wall motion abnormalities, CMR allows for precise quantification of right ventricular and left ventricular (LV) function, the assessment of additional abnormalities/complications (e.g. pericardial and/or pleural effusion, LV thrombi), and most importantly myocardial tissue characterization (myocardial oedema, inflammation, necrosis/fibrosis). CMR enables a comprehensive assessment of the entire spectrum of functional and structural changes that occur in patients with TTS and may have also a prognostic impact. CMR can distinguish between TTS and other important differential diagnoses (myocarditis, myocardial infarction) with direct consequences on medical therapy.

Defining the optimal temporal and spatial resolution for cardiovascular magnetic resonance imaging feature tracking

BACKGROUND

Myocardial deformation analyses using cardiovascular magnetic resonance (CMR) feature tracking (CMR-FT) have incremental value in the assessment of cardiac function beyond volumetric analyses. Since guidelines do not recommend specific imaging parameters, we aimed to define optimal spatial and temporal resolutions for CMR cine images to enable reliable post-processing.

METHODS

Intra- and inter-observer reproducibility was assessed in 12 healthy subjects and 9 heart failure (HF) patients. Cine images were acquired with different temporal (20, 30, 40 and 50 frames/cardiac cycle) and spatial resolutions (high in-plane 1.5 × 1.5 mm through-plane 5 mm, standard 1.8 × 1.8 x 8mm and low 3.0 × 3.0 x 10mm). CMR-FT comprised left ventricular (LV) global and segmental longitudinal/circumferential strain (GLS/GCS) and associated systolic strain rates (SR), and right ventricular (RV) GLS.

RESULTS

Temporal but not spatial resolution did impact absolute strain and SR. Maximum absolute changes between lowest and highest temporal resolution were as follows: 1.8% and 0.3%/s for LV GLS and SR, 2.5% and 0.6%/s for GCS and SR as well as 1.4% for RV GLS. Changes of strain values occurred comparing 20 and 30 frames/cardiac cycle including LV and RV GLS and GCS (p < 0.001-0.046). In contrast, SR values (LV GLS/GCS SR) changed significantly comparing all successive temporal resolutions (p < 0.001-0.013). LV strain and SR reproducibility was not affected by either temporal or spatial resolution, whilst RV strain variability decreased with augmentation of temporal resolution.

CONCLUSION

Temporal but not spatial resolution significantly affects strain and SR in CMR-FT deformation analyses. Strain analyses require lower temporal resolution and 30 frames/cardiac cycle offer consistent strain assessments, whilst SR measurements gain from further increases in temporal resolution.

Clinical validation of three cardiovascular magnetic resonance techniques to measure strain and torsion in patients with suspected coronary artery disease

BACKGROUND

Several cardiovascular magnetic resonance (CMR) techniques can measure myocardial strain and torsion with high accuracy. The purpose of this study was to compare displacement encoding with stimulated echoes (DENSE), tagging and feature tracking (FT) for measuring circumferential and radial myocardial strain and myocardial torsion in order to assess myocardial function and infarct scar burden both at a global and at a segmental level.

METHOD

116 patients with a high likelihood of coronary artery disease (European SCORE > 15%) underwent CMR examination including cine images, tagging, DENSE and late gadolinium enhancement (LGE) in the short axis direction. In total, 97 patients had signs of myocardial disease and 19 had no abnormalities in terms of left ventricular (LV) wall mass index, LV ejection fraction, wall motion, LGE or a history of myocardial infarction. Thirty-four patients had myocardial infarct scar with a transmural LGE extent (transmurality) that exceeded 50% of the wall thickness in at least one segment. Global circumferential strain (GCS) and global radial strain (GRS) was analyzed using FT of cine loops, deformation of tag lines or DENSE displacement.

RESULTS

DENSE and tagging both showed high sensitivity (82% and 71%) at a specificity of 80% for the detection of segments with > 50% LGE transmurality, and receiver operating characteristics (ROC) analysis showed significantly higher area under the curve-values (AUC) for DENSE (0.87) than for tagging (0.83, p < 0.001) and FT (0.66, p = 0.003). GCS correlated with global LGE when determined with DENSE (r = 0.41), tagging (r = 0.37) and FT (r = 0.15). GRS had a low but significant negative correlation with LGE; DENSE r = - 0.10, FT r = - 0.07 and tagging r = - 0.16. Torsion from DENSE and tagging had a weak correlation (- 0.20 and - 0.22 respectively) with global LGE.

CONCLUSION

Circumferential strain from DENSE detected segments with > 50% scar with a higher AUC than strain determined from tagging and FT at a segmental level. GCS and torsion computed from DENSE and tagging showed similar correlation with global scar size, while when computed from FT, the correlation was lower.

CardIAc: an open-source application for myocardial strain analysis

PURPOSE

This paper presents CardIAc, an open-source application designed as an alternative to commercial software for left ventricle myocardial strain quantification in short-axis cardiac magnetic resonance images. The aim is to provide a useful extension for myocardial strain analysis that can be easily adapted to incorporate different strategies of motion tracking to improve the strain accuracy. In this way, users with programming skills can easily modify the code and adjust the program's performance according to their own scientific or clinical requirements. The software is intended for research and clinical use is not advised.

METHODS

CardIAc was developed as a 3D Slicer extension for an easy installation and usability. The main contribution of this article is to provide a general workflow, going from data and segmentation loading, 3D heart modeling, analysis and several options for visualization of the myocardial strain.

RESULTS

CardIAc strain feature was evaluated on a public dataset (Cardiac Motion Analysis Challenge-STACOM 2011) of 15 volunteers, and a synthetic one generated from this real dataset. Results on the real dataset show that cardIAc achieves suitable accuracy for myocardial motion estimation with a median error of 3.66 mm. In particular, global strain curves show strong correlation with the bibliography for healthy patients and similar approaches. On the other hand, results on the synthetic dataset show a mean global error of 4.07%, 7.76% and 8.18% for circumferential, radial and longitudinal strain.

CONCLUSION

This paper introduces a new open-source application for strain analysis distributed under a BSD-style open-source license. Results demonstrate the capability and merits of the proposed application for strain analysis.

Cardiac magnetic resonance T2 mapping and feature tracking in athlete's heart and HCM

Objectives

Distinguishing hypertrophic cardiomyopathy (HCM) from left ventricular hypertrophy (LVH) due to systematic training (athlete’s heart, AH) from morphologic assessment remains challenging. The purpose of this study was to examine the role of T2 mapping and deformation imaging obtained by cardiovascular magnetic resonance (CMR) to discriminate AH from HCM with (HOCM) or without outflow tract obstruction (HNCM).

Methods

Thirty-three patients with HOCM, 9 with HNCM, 13 strength-trained athletes as well as individual age- and gender-matched controls received CMR. For T2 mapping, GRASE-derived multi-echo images were obtained and analyzed using dedicated software. Besides T2 mapping analyses, left ventricular (LV) dimensional and functional parameters were obtained including LV mass per body surface area (LVMi), interventricular septum thickness (IVS), and global longitudinal strain (GLS).

Results

While LVMi was not significantly different, IVS was thickened in HOCM patients compared to athlete’s. Absolute values of GLS were significantly increased in patients with HOCM/HNCM compared to AH. Median T2 values were elevated compared to controls except in athlete’s heart. ROC analysis revealed T2 values (AUC 0.78) and GLS (AUC 0.91) as good parameters to discriminate AH from overall HNCM/HOCM.

Conclusion

Discrimination of pathologic from non-pathologic LVH has implications for risk assessment of competitive sports in athletes. Multiparametric CMR with parametric T2 mapping and deformation imaging may add information to distinguish AH from LVH due to HCM.

Key Points

• Structural analyses using T2 mapping cardiovascular magnetic resonance imaging (CMR) may help to further distinguish myocardial diseases.

• To differentiate pathologic from non-pathologic left ventricular hypertrophy, CMR including T2 mapping was obtained in patients with hypertrophic obstructive/non-obstructive cardiomyopathy (HOCM/HNCM) as well as in strength-trained athletes.

• Elevated median T2 values in HOCM/HNCM compared with athlete’s may add information to distinguish athlete’s heart from pathologic left ventricular hypertrophy.

Association Between Left Ventricular Mechanical Deformation and Myocardial Fibrosis in Nonischemic Cardiomyopathy

Background

In patients with nonischemic cardiomyopathy, nonischemic fibrosis detected by late gadolinium enhancement (LGE) cardiovascular magnetic resonance is related to adverse cardiovascular outcomes. However, its relationship with left ventricular (LV) mechanical deformation parameters remains unclear. We sought to investigate the association between LV mechanics and the presence, location, and extent of fibrosis in patients with nonischemic cardiomyopathy.

Methods and Results

We retrospectively identified 239 patients with nonischemic cardiomyopathy (67% male; 55±14 years) referred for a clinical cardiovascular magnetic resonance. LGE was present in 109 patients (46%), most commonly (n=52; 22%) in the septum. LV deformation parameters did not differentiate between LGE‐positive and LGE‐negative groups. Global longitudinal, radial, and circumferential strains, twist and torsion showed no association with extent of fibrosis. Patients with septal fibrosis had a more depressed LV ejection fraction (30±12% versus 35±14%; P=0.032) and more impaired global circumferential strain (−7.9±3.5% versus −9.7±4.4%; P=0.045) and global radial strain (10.7±5.2% versus 13.3±7.7%; P=0.023) than patients without septal LGE. Global longitudinal strain was similar in both groups. While patients with septal‐only LGE (n=28) and free wall–only LGE (n=32) had similar fibrosis burden, the septal‐only LGE group had more impaired LV ejection fraction and global circumferential, longitudinal, and radial strains (all P<0.05).

Conclusions

There is no association between LV mechanical deformation parameters and presence or extent of fibrosis in patients with nonischemic cardiomyopathy. Septal LGE was associated with poor global LV function, more impaired global circumferential and radial strains, and more impaired global strain rates.

Fully Automated Cardiac Assessment for Diagnostic and Prognostic Stratification Following Myocardial Infarction

Background

Cardiovascular magnetic resonance imaging is considered the reference methodology for cardiac morphology and function but requires manual postprocessing. Whether novel artificial intelligence–based automated analyses deliver similar information for risk stratification is unknown. Therefore, this study aimed to investigate feasibility and prognostic implications of artificial intelligence–based, commercially available software analyses.

Methods and Results

Cardiovascular magnetic resonance data (n=1017 patients) from 2 myocardial infarction multicenter trials were included. Analyses of biventricular parameters including ejection fraction (EF) were manually and automatically assessed using conventional and artificial intelligence–based software. Obtained parameters entered regression analyses for prediction of major adverse cardiac events, defined as death, reinfarction, or congestive heart failure, within 1 year after the acute event. Both manual and uncorrected automated volumetric assessments showed similar impact on outcome in univariate analyses (left ventricular EF, manual: hazard ratio [HR], 0.93 [95% CI 0.91–0.95]; P<0.001; automated: HR, 0.94 [95% CI, 0.92–0.96]; P<0.001) and multivariable analyses (left ventricular EF, manual: HR, 0.95 [95% CI, 0.92–0.98]; P=0.001; automated: HR, 0.95 [95% CI, 0.92–0.98]; P=0.001). Manual correction of the automated contours did not lead to improved risk prediction (left ventricular EF, area under the curve: 0.67 automated versus 0.68 automated corrected; P=0.49). There was acceptable agreement (left ventricular EF: bias, 2.6%; 95% limits of agreement, −9.1% to 14.2%; intraclass correlation coefficient, 0.88 [95% CI, 0.77–0.93]) of manual and automated volumetric assessments.

Conclusions

User‐independent volumetric analyses performed by fully automated software are feasible, and results are equally predictive of major adverse cardiac events compared with conventional analyses in patients following myocardial infarction.

Registration

URL: https://www.clinicaltrials.gov; Unique identifiers: NCT00712101 and NCT01612312.

Head-to-head comparison of cardiovascular MR feature tracking cine versus acquisition-based deformation strain imaging using myocardial tagging and strain encoding

PURPOSE

Myocardial feature-tracking (FT) deformation imaging is superior for risk stratification compared with volumetric approaches. Because there is no clear recommendation regarding FT postprocessing, we compared different FT-strain analyses with reference standard techniques, including tagging and strain-encoded (SENC) MRI.

METHODS

Feature-tracking software from four different vendors (TomTec, Medis, Circle [CVI], and Neosoft), tagging (Segment), and fastSENC (MyoStrain) were used to determine left ventricular global circumferential strains (GCS) and longitudinal strains (GLS) in 12 healthy volunteers and 12 patients with heart failure. Variability and agreements were assessed using intraclass correlation coefficients for absolute agreement (ICCa) and consistency (ICCc) as well as Pearson correlation coefficients.

RESULTS

For FT-GCS, consistency was excellent comparing different FT vendors (ICCc = 0.84-0.97, r = 0.86-0.95) and in comparison to fast SENC (ICCc = 0.78-0.89, r = 0.73-0.81). FT-GCS consistency was excellent compared with tagging (ICCc = 0.79-0.85, r = 0.74-0.77) except for TomTec (ICCc = 0.68, r = 0.72). Absolute FT-GCS agreements among FT vendors were highest for CVI and Medis (ICCa = 0.96) and lowest for TomTec and Neosoft (ICCa = 0.32). Similarly, absolute FT-GCS agreements were excellent for CVI and Medis compared with both tagging and fast SENC (ICCa = 0.84-0.88), good to excellent for Neosoft (ICCa = 0.77 and 0.64), and lowest for TomTec (ICCa = 0.41 and 0.47). For FT-GLS, consistency was excellent (ICCc ≥ 0.86, r ≥ 0.76). Absolute agreements among FT vendors were excellent (ICCa = 0.91-0.93) or good to excellent for TomTec (ICCa = 0.69-0.85). Absolute agreements (ICCa) were good (CVI 0.70, Medis 0.60) and fair (TomTec 0.41, Neosoft 0.59) compared with tagging, but excellent compared with fast SENC (ICCa = 0.77-0.90).

CONCLUSION

Although absolute agreements differ depending on deformation assessment approaches, consistency and correlation are consistently high regardless of the method chosen, thus indicating reliable strain assessment. Further standardisation and introduction of uniform references is warranted for routine clinical implementation.

Left ventricular global myocardial strain assessment: Are CMR feature-tracking algorithms useful in the clinical setting?

OBJECTIVES

Myocardial strains can be calculated using cardiovascular magnetic resonance (CMR) feature-tracking (FT) algorithms. They show excellent intra- and inter-observer agreement but rather disappointing inter-vendor agreement. Currently, it is unknown how well CMR-FT-based strain values agree with manually obtained strain values.

METHODS

In 45 subjects (15 controls, 15 acute myocardial infarction, 15 non-ischemic dilated cardiomyopathy), end-systolic manually derived strains were compared to four CMR-FT software packages. Global radial strain (GRS), global circumferential strain (GCS) and global longitudinal strain (GLS) were determined. Intra- and inter-observer agreement and agreement between manual and CMR-FT analysis were calculated. Statistical analysis included Bland-Altman plots, intra-class correlation coefficient (ICC) and coefficient of variation (CV).

RESULTS

Manual contouring yielded excellent intra-observer (ICC 0.903 (GRS) to 0.995 (GCS)) and inter-observer agreement (ICC 0.915 (GRS) to 0.966 (GCS)) with CV ranging 4.7% (GCS) to 20.7% (GRS) and 12.7% (GCS) to 20.0% (GRS), for intra-observer and inter-observer agreement, respectively. Agreement between manual and CMR-FT strain values ranged from poor to excellent, with best agreement for GCS (ICC 0.857-0.935) and intermediate for GLS (ICC 0.591-0.914), while ICC values for GRS ranged widely (ICC 0.271-0.851). In particular, two software packages showed a strong trend toward systematic underestimation of myocardial strain in radial and longitudinal direction, correlating poorly to moderately with manual contouring, i.e., GRS (ICC 0.271, CV 25.2%) and GLS (ICC 0.591, CV 17.6%).

CONCLUSION

Some CMR-FT values agree poorly with manually derived strains, emphasizing to be cautious to use these software packages in the clinical setting. In particular, radial and longitudinal strain tends to be underestimated when using manually derived strains as reference.

Impact of Right Atrial Physiology on Heart Failure and Adverse Events after Myocardial Infarction

Background: Right ventricular (RV) function is a known predictor of adverse events in heart failure and following acute myocardial infarction (AMI). While right atrial (RA) involvement is well characterized in pulmonary arterial hypertension, its relative contributions to adverse events following AMI especially in patients with heart failure and congestion need further evaluation. Methods: In this cardiovascular magnetic resonance (CMR)-substudy of AIDA STEMI and TATORT NSTEMI, 1235 AMI patients underwent CMR after primary percutaneous coronary intervention (PCI) in 15 centers across Germany (n = 795 with ST-elevation myocardial infarction and 440 with non-ST-elevation MI). Right atrial (RA) performance was evaluated using CMR myocardial feature tracking (CMR-FT) for the assessment of RA reservoir (total strain ε_s), conduit (passive strain ε_e), booster pump function (active strain ε_a), and associated strain rates (SR) in a blinded core-laboratory. The primary endpoint was the occurrence of major adverse cardiac events (MACE) 12 months post AMI. Results: RA reservoir (ε_sp = 0.061, SRs p = 0.049) and conduit functions (ε_ep = 0.006, SRe p = 0.030) were impaired in patients with MACE as opposed to RA booster pump (ε_ap = 0.579, SRa p = 0.118) and RA volume index (p = 0.866). RA conduit function was associated with the clinical onset of heart failure and MACE independently of RV systolic function and atrial fibrillation (AF) (multivariable analysis hazard ratio 0.95, 95% confidence interval 0.92 to 0.99, p = 0.009), while RV systolic function and AF were not independent prognosticators. Furthermore, RA conduit strain identified low- and high-risk groups within patients with reduced RV systolic function (p = 0.019 on log rank testing). Conclusions: RA impairment is a distinct feature and independent risk factor in patients following AMI and can be easily assessed using CMR-FT-derived quantification of RA strain.

Range Variability in CMR Feature Tracking Multilayer Strain across Different Stages of Heart Failure

Heart failure (HF) is associated with progressive ventricular remodeling and impaired contraction that affects distinctly various regions of the myocardium. Our study applied cardiac magnetic resonance (CMR) feature tracking (FT) to assess comparatively myocardial strain at 3 distinct levels: subendocardial (Endo-), mid (Myo-) and subepicardial (Epi-) myocardium across an extended spectrum of patients with HF. 59 patients with HF, divided into 3 subgroups as follows: preserved ejection fraction (HFpEF, N = 18), HF with mid-range ejection fraction (HFmrEF, N = 21), HF with reduced ejection fraction (HFrEF, N = 20) and a group of age- gender- matched volunteers (N = 17) were included. Using CMR FT we assessed systolic longitudinal and circumferential strain and strain-rate at Endo-, Myo- and Epi- levels. Strain values were the highest in the Endo- layer and progressively lower in the Myo- and Epi- layers respectively, this gradient was present in all the patients groups analyzed but decreased progressively in HFmrEF and further on in HFrEF groups. GLS decreased with the severity of the disease in all 3 layers: Normal > HFpEF > HFmrEF > HFrEF (Endo-: −23.0 ± 3.5 > −20.0 ± 3.3 > −16.4 ± 2.2 > −11.0 ± 3.2, p < 0.001, Myo-: −20.7 ± 2.4 > −17.5.0 ± 2.6 > −14.5 ± 2.1 > −9.6 ± 2.7, p < 0.001; Epi-: −15.7 ± 1.9 > −12.2 ± 2.1 > −10.6 ± 2.3 > −7.7 ± 2.3, p < 0.001). In contrast, GCS was not different between the Normal and HFpEF (Endo-: −34.5 ± 6.2 vs −33.9 ± 5.7, p = 0.51; Myo-: −21.9 ± 3.8 vs −21.3 ± 2.2, p = 0.39, Epi-: −11.4 ± 2.0 vs −10.9 ± 2.3, p = 0.54) but was, as well, markedly lower in the systolic heart failure groups: Normal > HFmrEF > HFrEF (Endo-: −34.5 ± 6.2 > −20.0 ± 4.2 > 12.3 ± 4.2, p < 0.001; Myo-: −21.9 ± 3.8 > −13.0 ± 3.4 > −8.0 ± 2.7. p < 0.001; Epi-: −11.4 ± 2.0 > −7.9 ± 2.3 > −4.5 ± 1.9. p < 0.001). CMR feature tracking multilayer strain assessment identifies large range differences between distinct myocardial regions. Our data emphasizes the importance of sub-endocardial myocardium for cardiac contraction and thus, its predilect role in imaging detection of functional impairment. CMR feature tracking offers a convenient, readily available, platform to evaluate myocardial contraction with excellent spatial resolution, rendering further details about discrete areas of the myocardium. Using this technique across distinct groups of patients with heart failure (HF), we demonstrate that subendocardial regions of the myocardium exhibit much higher strain values than mid-myocardium or subepicardial and are more sensitive to detect contractile impairment. We also show comparatively higher values of circumferential strain compared with longitudinal and a higher sensitivity to detect contractile impairment. A newly characterized group of patients, HF with mid-range ejection fraction (EF), shows similar traits of decompensation but has relatively higher strain values as patients with HF with reduced EF.

Determinants of myocardial function characterized by CMR-derived strain parameters in left ventricular non-compaction cardiomyopathy

Clinical presentation of left ventricular non-compaction cardiomyopathy (LVNC) can be heterogeneous from asymptomatic expression to congestive heart failure. Deformation indices assessed by cardiovascular magnetic resonance (CMR) can determine subclinical alterations of myocardial function and have been reported to be more sensitive to functional changes than ejection fraction. The objective of the present study was to investigate the determinants of myocardial deformation indices in patients with LVNC. Twenty patients with LVNC (44.7 ± 14.0 years) and twenty age- and gender-matched controls (49.1 ± 12.4 years) underwent functional CMR imaging using an ECG-triggered steady state-free-precession sequence (SSFP). Deformation indices derived with a feature tracking algorithm were calculated including end-systolic global longitudinal strain (GLS), circumferential strain (GCS), longitudinal and circumferential strain rate (SR_ll and SR_cc). Twist and rotation were determined using an in-house developed post-processing pipeline. Global deformation indices (GLS, GCS, SR_ll and SR_cc) were significantly lower in patients with LVNC compared to healthy controls (all, p < 0.01), especially for midventricular and apical regions. Apical rotation and twist were impaired for LVNC (p = 0.007 and p = 0.012), but basal rotation was preserved. Deformation indices of strain, strain rate and twist correlated well with parameters of the non-compacted myocardium, but not with the total myocardial mass or the thinning of the compacted myocardium, e.g. r = 0.595 between GLS and the non-compacted mass (p < 0.001). In conclusion, CMR deformation indices are reduced in patients with LVNC especially in affected midventricular and apical slices. The impairment of all strain and twist parameters correlates well with the extent of non-compacted myocardium.

Left Atrial Function with MRI Enables Prediction of Cardiovascular Events after Myocardial Infarction: Insights from the AIDA STEMI and TATORT NSTEMI Trials

Background The role of left atrial (LA) performance in acute myocardial infarction (AMI) remains controversial. Cardiac MRI myocardial feature tracking (hereafter, MRI-FT) is a method used to quantify myocardial function that enables reliable assessment of atrial function. Purpose To assess the relationship between LA function assessed with MRI-FT and major adverse cardiovascular events (MACE) after AMI. Materials and Methods This secondary analysis of two prospective multicenter cardiac MRI studies (AIDA STEMI [NCT00712101] and TATORT NSTEMI [NCT01612312]) included 1235 study participants with ST-elevation myocardial infarction (n = 795) or non-ST-elevation myocardial infarction (n = 440) between July 2008 and June 2013. All study participants underwent primary percutaneous coronary intervention. MRI-FT analyses were performed in a core laboratory by researchers blinded to clinical status to determine LA performance using LA reservoir function peak systolic strain (εs), LA conduit strain (εe), and LA booster pump function active strain (εa). The relationship of LA performance to a MACE within 12 months after AMI was evaluated by using Cox proportional hazards models and area under the receiver operating characteristic curve (AUC). Results Study participants with MACE had worse LA performance parameters compared with study participants without MACE (εs = 21.2% vs 16.2%, εe = 8.8% vs 6.9%, εa = 11.8% vs 10%; P < .001 for all). All atrial parameters were strongly associated with MACE (hazard ratio [HR], εs = 0.9, εe = 0.88, εa = 0.89; P < .001 for all). For εs, a cutoff of 18.8% was identified as the only independent atrial parameter with which to predict MACE after accounting for confounders and established prognostic markers in adjusted analysis (HR, 0.95; P = .02). The εs yielded incremental prognostic value above left ventricular ejection fraction, global longitudinal strain, microvascular obstruction, and infarct size (AUC comparisons, P < .04 for all). Conclusion Feature tracking of cardiac MRI to derive left atrial peak reservoir strain provided incremental prognostic value for major adverse cardiovascular events prediction versus established cardiac risk factors after acute myocardial infarction. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Almeida in this issue.

Atrial mechanics and their prognostic impact in Takotsubo syndrome: a cardiovascular magnetic resonance imaging study

Aims

The exact pathophysiology of Takotsubo syndrome (TTS) remains not fully understood with most studies focussing on ventricular pathology. Since atrial involvement may have a significant role, we assessed the diagnostic and prognostic potential of atrial cardiovascular magnetic resonance feature tracking (CMR-FT) in TTS.

Methods and results

This multicentre study recruited 152 TTS patients who underwent CMR on average within 3 days after hospitalization. Reservoir [total strain εs and peak positive strain rate (SR) SRs], conduit (passive strain εe and peak early negative SRe), and booster pump function (active strain εa and peak late negative SRa) were assessed in a core laboratory. Results were compared with 21 control patients with normal biventricular function. A total of 20 patients underwent follow-up CMR (median 3.5 months, interquartile range 3–5). All patients were approached for general follow-up. Left atrial (LA) but not right atrial (RA) reservoir and conduit function were impaired during the acute phase (εs: P = 0.043, εe: P < 0.001, SRe: P = 0.047 vs. controls) and recovered until follow-up (εs: P < 0.001, SRs: P = 0.04, εe: P = 0.001, SRe: P = 0.04). LA and RA booster pump function were increased in the acute setting (LA-εa: P = 0.045, SRa: P = 0.002 and RA-εa: P = 0.004, SRa: P = 0.002 vs. controls). LA-εs predicted mortality [hazard ratio 1.10, 95% confidence interval (CI) 1.01–1.20; P = 0.037] irrespectively of established cardiovascular risk factors (P = 0.019, multivariate analysis) including left ventricular ejection fraction (LVEF) (area under the curve 0.71, 95% CI 0.55–0.86, P = 0.048).

Conclusion

TTS pathophysiology comprises transient impairments in LA reservoir and conduit functions and enhanced bi-atrial active booster pump functions. Atrial CMR-FT may evolve as a superior marker of adverse events over and above established parameters such as LVEF and atrial volume.

Fully automated quantification of biventricular volumes and function in cardiovascular magnetic resonance: applicability to clinical routine settings

BACKGROUND

Cardiovascular magnetic resonance (CMR) represents the clinical gold standard for the assessment of biventricular morphology and function. Since manual post-processing is time-consuming and prone to observer variability, efforts have been directed towards automated volumetric quantification. In this study, we sought to validate the accuracy of a novel approach providing fully automated quantification of biventricular volumes and function in a "real-world" clinical setting.

METHODS

Three-hundred CMR examinations were randomly selected from the local data base. Fully automated quantification of left ventricular (LV) mass, LV and right ventricular (RV) end-diastolic and end-systolic volumes (EDV/ESV), stroke volume (SV) and ejection fraction (EF) were performed overnight using commercially available software (suiteHEART®, Neosoft, Pewaukee, Wisconsin, USA). Parameters were compared to manual assessments (QMass®, Medis Medical Imaging Systems, Leiden, Netherlands). Sub-group analyses were further performed according to image quality, scanner field strength, the presence of implanted aortic valves and repaired Tetralogy of Fallot (ToF).

RESULTS

Biventricular automated segmentation was feasible in all 300 cases. Overall agreement between fully automated and manually derived LV parameters was good (LV-EF: intra-class correlation coefficient [ICC] 0.95; bias - 2.5% [SD 5.9%]), whilst RV agreement was lower (RV-EF: ICC 0.72; bias 5.8% [SD 9.6%]). Lowest agreement was observed in case of severely altered anatomy, e.g. marked RV dilation but normal LV dimensions in repaired ToF (LV parameters ICC 0.73-0.91; RV parameters ICC 0.41-0.94) and/or reduced image quality (LV parameters ICC 0.86-0.95; RV parameters ICC 0.56-0.91), which was more common on 3.0 T than on 1.5 T.

CONCLUSIONS

Fully automated assessments of biventricular morphology and function is robust and accurate in a clinical routine setting with good image quality and can be performed without any user interaction. However, in case of demanding anatomy (e.g. repaired ToF, severe LV hypertrophy) or reduced image quality, quality check and manual re-contouring are still required.

Cardiovascular magnetic resonance imaging feature tracking: Impact of training on observer performance and reproducibility

BACKGROUND

Cardiovascular magnetic resonance feature tracking (CMR-FT) is increasingly used for myocardial deformation assessment including ventricular strain, showing prognostic value beyond established risk markers if used in experienced centres. Little is known about the impact of appropriate training on CMR-FT performance. Consequently, this study aimed to evaluate the impact of training on observer variance using different commercially available CMR-FT software.

METHODS

Intra- and inter-observer reproducibility was assessed prior to and after dedicated one-hour observer training. Employed FT software included 3 different commercially available platforms (TomTec, Medis, Circle). Left (LV) and right (RV) ventricular global longitudinal as well as LV circumferential and radial strains (GLS, GCS and GRS) were studied in 12 heart failure patients and 12 healthy volunteers.

RESULTS

Training improved intra- and inter-observer reproducibility. GCS and LV GLS showed the highest reproducibility before (ICC >0.86 and >0.81) and after training (ICC >0.91 and >0.92). RV GLS and GRS were more susceptible to tracking inaccuracies and reproducibility was lower. Inter-observer reproducibility was lower than intra-observer reproducibility prior to training with more pronounced improvements after training. Before training, LV strain reproducibility was lower in healthy volunteers as compared to patients with no differences after training. Whilst LV strain reproducibility was sufficient within individual software solutions inter-software comparisons revealed considerable software related variance.

CONCLUSION

Observer experience is an important source of variance in CMR-FT derived strain assessment. Dedicated observer training significantly improves reproducibility with most profound benefits in states of high myocardial contractility and potential to facilitate widespread clinical implementation due to optimized robustness and diagnostic performance.

Temporal changes within mechanical dyssynchrony and rotational mechanics in Takotsubo syndrome: A cardiovascular magnetic resonance imaging study

BACKGROUND

The pathophysiological significance of dyssynchrony and rotation in Takotsubo syndrome (TTS) is unknown. We aimed to define the influence of cardiovascular magnetic resonance feature tracking (CMR-FT) dyssynchrony and rotational mechanics in acute and during clinical course of TTS.

METHODS

This multicenter study included 152 TTS patients undergoing CMR (mean 3 days after symptom onset). Apical, midventricular and basal short axis views were analysed in a core-laboratory. Systolic torsion, diastolic recoil and dyssynchrony expressed as circumferential and radial uniformity ratio estimates (CURE and RURE: 0 to 1; 1 = perfect synchrony) were compared to a matched control group (n = 21). Follow-up CMR (n = 20 patients; mean 62 days, SD 7.2) and general follow-up (n = 136; mean 3.3 years, SD 2.4) were performed.

RESULTS

CURE was initially reduced compared to controls (p = 0.001) and recovered at follow-up (p < 0.001) as opposed to RURE (p = 0.116 and p = 0.179). CURE and RURE discriminated between ballooning patterns (p = 0.001 and p = 0.045). Recoil was generally impaired during the acute phase (p = 0.015), torsion only in highly dyssynchronous patients (p = 0.024). Diabetes (p = 0.007), physical triggers (p = 0.013) and malignancies (p = 0.001) predicted mortality. The latter showed a distinct association with impaired torsion (p = 0.042) and dyssynchrony (p = 0.047). Physical triggers and malignancies were related to biventricular impairment (p = 0.004 and p = 0.026), showing higher dyssynchrony (p < 0.01), greater reduction of left ventricular function (p < 0.001) and a strong trend towards increased mortality (p = 0.074).

CONCLUSION

Transient circumferential dyssynchrony and impaired rotational mechanics are distinct features of TTS with different severities according to the pattern of ballooning. Patients with malignancies and precipitating physical triggers frequently show biventricular affection, greater dyssynchrony and high mortality risk.

Clinical applications of feature-tracking cardiac magnetic resonance imaging

Cardiovascular diseases represent the leading cause of mortality and morbidity in the western world. Assessment of cardiac function is pivotal for early diagnosis of primitive myocardial disorders, identification of cardiac involvement in systemic diseases, detection of drug-related cardiac toxicity as well as risk stratification and monitor of treatment effects in patients with heart failure of various etiology. Determination of ejection fraction with different imaging modalities currently represents the gold standard for evaluation of cardiac function. However, in the last few years, cardiovascular magnetic resonance feature tracking techniques has emerged as a more accurate tool for quantitative evaluation of cardiovascular function with several parameters including strain, strain-rate, torsion and mechanical dispersion. This imaging modality allows precise quantification of ventricular and atrial mechanics by directly evaluating myocardial fiber deformation. The purpose of this article is to review the basic principles, current clinical applications and future perspectives of cardiovascular magnetic resonance myocardial feature tracking, highlighting its prognostic implications.

Comparison of left ventricular strains and torsion derived from feature tracking and DENSE CMR

BACKGROUND

Cardiovascular magnetic resonance (CMR) feature tracking is increasingly used to quantify cardiac mechanics from cine CMR imaging, although validation against reference standard techniques has been limited. Furthermore, studies have suggested that commonly-derived metrics, such as peak global strain (reported in 63% of feature tracking studies), can be quantified using contours from just two frames - end-diastole (ED) and end-systole (ES) - without requiring tracking software. We hypothesized that mechanics derived from feature tracking would not agree with those derived from a reference standard (displacement-encoding with stimulated echoes (DENSE) imaging), and that peak strain from feature tracking would agree with that derived using simple processing of only ED and ES contours.

METHODS

We retrospectively identified 88 participants with 186 pairs of DENSE and balanced steady state free precession (bSSFP) image slices acquired at the same locations across two institutions. Left ventricular (LV) strains, torsion, and dyssynchrony were quantified from both feature tracking (TomTec Imaging Systems, Circle Cardiovascular Imaging) and DENSE. Contour-based strains from bSSFP images were derived from ED and ES contours. Agreement was assessed with Bland-Altman analyses and coefficients of variation (CoV). All biases are reported in absolute percentage.

RESULTS

Comparison results were similar for both vendor packages (TomTec and Circle), and thus only TomTec Imaging System data are reported in the abstract for simplicity. Compared to DENSE, mid-ventricular circumferential strain (Ecc) from feature tracking had acceptable agreement (bias: - 0.4%, p = 0.36, CoV: 11%). However, feature tracking significantly overestimated the magnitude of Ecc at the base (bias: - 4.0% absolute, p < 0.001, CoV: 18%) and apex (bias: - 2.4% absolute, p = 0.01, CoV: 15%), underestimated torsion (bias: - 1.4 deg/cm, p < 0.001, CoV: 41%), and overestimated dyssynchrony (bias: 26 ms, p < 0.001, CoV: 76%). Longitudinal strain (Ell) had borderline-acceptable agreement (bias: - 0.2%, p = 0.77, CoV: 19%). Contour-based strains had excellent agreement with feature tracking (biases: - 1.3-0.2%, CoVs: 3-7%).

CONCLUSION

Compared to DENSE as a reference standard, feature tracking was inaccurate for quantification of apical and basal LV circumferential strains, longitudinal strain, torsion, and dyssynchrony. Feature tracking was only accurate for quantification of mid LV circumferential strain. Moreover, feature tracking is unnecessary for quantification of whole-slice strains (e.g. base, apex), since simplified processing of only ED and ES contours yields very similar results to those derived from feature tracking. Current feature tracking technology therefore has limited utility for quantification of cardiac mechanics.

Normal Values of Myocardial Deformation Assessed by Cardiovascular Magnetic Resonance Feature Tracking in a Healthy Chinese Population: A Multicenter Study

Reference values on atrial and ventricular strain from cardiovascular magnetic resonance (CMR) are essential in identifying patients with impaired atrial and ventricular function. However, reference values have not been established for Chinese subjects. One hundred and fifty healthy volunteers (75 Males/75 Females; 18–82 years) were recruited. All underwent CMR scans with images acceptable for further strain analysis. Subjects were stratified by age: Group 1, 18–44 years; Group 2, 45–59 years; Group 3, ≥60 years. Feature tracking of CMR cine imaging was used to obtain left atrial global longitudinal (LA E_ll) and circumferential strains (LA E_cc) and respective systolic strain rates, left ventricular longitudinal (LV E_ll), circumferential (LV E_cc) and radial strains (LV E_rr) and their respective strain rates, and right ventricular longitudinal strain (RV E_ll) and strain rate. LA E_ll and LA E_cc were 32.8 ± 9.2% and 40.3 ± 13.4%, respectively, and RV E_ll was −29.3 ± 6.0%. LV E_ll, LV E_cc and LV E_rr were −22.4 ± 2.9%, −24.3 ± 3.1%, and 79.0 ± 19.4%, respectively. LV E_ll and LV E_cc were higher in females than males (P < 0.05). LA E_ll, LA E_cc, and LV E_cc decreased, while LV E_rr increased with age (P < 0.05). LV E_ll and RV E_ll were not shown to be associated with age. Normal ranges for atrial and ventricular strain and strain rates are provided using CMR feature tracking in Chinese subjects.

Left ventricular myocardial deformation in Takotsubo syndrome: a cardiovascular magnetic resonance myocardial feature tracking study

OBJECTIVES

This study assessed the applicability and prognostic value of cardiovascular magnetic resonance (CMR) left ventricular deformation analysis in Takotsubo syndrome (TTS).

METHODS

CMR-feature tracking was performed blinded in a core laboratory to determine circumferential (CS), radial (RS) and longitudinal strain (LS) in 141 TTS patients participating in this cohort study. A subgroup of consecutive TTS patients (n = 20) was compared with age- and sex-matched controls with anterior ST-segment elevation myocardial infarction (STEMI) and non-STEMI as well as healthy subjects.

RESULTS

Median global CS, RS and LS were -19%, 19% and -12%, respectively. Apical ballooning was associated with significantly lower global CS (p < 0.01) and LS (p < 0.01) compared with midventricular and basal ballooning. Global RS was lowest in patients with basal ballooning (p < 0.01). Segmental analysis resulted in a reliable discrimination of different ballooning patterns using CS and LS. Strain values were significantly lower in TTS compared with non-STEMI patients and healthy subjects, whereas STEMI patients showed similar values. While global CS and RS were not associated with long-term mortality, global LS (cutoff -14.75%) was identified as a potential parameter for long-term risk stratification (mortality rate 17.9% versus 2.5%; p = 0.02).

CONCLUSIONS

The transient contraction abnormalities in TTS can be quantitatively assessed with CMR-feature tracking. GLS is a potential determinant of outcome in TTS, which, however, requires further validation.

KEY POINTS

• Cardiovascular magnetic resonance myocardial feature tracking enables accurate assessment of regional and global left ventricular dysfunction in Takotsubo syndrome (TTS). • Global strain in TTS is similar to patients with anterior STEMI and lower compared with non-STEMI and healthy subjects. • Global longitudinal strain is a potential tool for risk prediction in TTS patients.

Feasibility and reproducibility of feature-tracking-based strain and strain rate measures of the left ventricle in different diseases and genders

BACKGROUND

The measurement of myocardial deformation by strain analysis is an evolving tool to quantify regional and global myocardial function.

PURPOSE

To assess the feasibility and reproducibility of myocardial strain/strain rate measurements with magnetic resonance feature tracking (MR-FT) in healthy subjects and in patient groups.

STUDY TYPE

Prospective study.

POPULATION

Sixty patients (20 hypertensives with left ventricular (LV) hypertrophy (H); 20 nonischemic dilated cardiomyopathy (D); 20 ischemic heart disease (I); as well as 20 controls (C) were included, 10 men and 10 women in each group.

FIELD STRENGTH/SEQUENCE

A 1.5T MR protocol including steady-state free precession (SSFP) cine sequences in the standard views and late enhancement sequences.

ASSESSMENT

LV volumes, mass, global and regional radial, circumferential, and longitudinal strain/strain rate were measured using CVI42 software. The analysis time was recorded.

STATISTICAL TESTS

Intraobserver and interobserver agreement and intraclass correlation coefficients (ICC) were obtained for reproducibility assessment as well as differences according to gender and group of pertinence.

RESULTS

Strain/strain rate analysis could be achieved in all subjects. The average analysis time was 14 ± 3 minutes. The average intraobserver ICC was excellent (ICC >0.90) for strain and good (ICC >0.75) for strain rate. Reproducibility of strain measurements was good to excellent (ICC >0.75) for all groups of subjects and both genders. Reproducibility of strain measurements was good for basal segments (ICC >0.75) and excellent for middle and apical segments (ICC >0.90). Reproducibility of strain rate measurements was moderate for basal segments (ICC >0.50) and good for middle and apical segments.

DATA CONCLUSION

MR-FT for strain/strain rate analysis is a feasible and highly reproducible technique. CVI42 FT analysis was equally feasible and reproducible in various pathologies and between genders. Better reproducibility was seen globally for middle and apical segments, which needs further clarification.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage 2 J. Magn. Reson. Imaging 2018;47:1415-1425.

Cardiovascular magnetic resonance feature tracking in small animals - a preliminary study on reproducibility and sample size calculation

Background

Cardiovascular magnetic resonance feature tracking (CMR-FT) is a novel tissue tracking technique developed for noninvasive assessment of myocardial motion and deformation. This preliminary study aimed to evaluate the observer’s reproducibility of CMR-FT in a small animal (mouse) model and define sample size calculation for future trials.

Methods

Six C57BL/6 J mice were selected from the ongoing experimental mouse model onsite and underwent CMR with a 3 Tesla small animal MRI scanner. Myocardial deformation was analyzed using dedicated software (TomTec, Germany) by two observers. Left ventricular (LV) longitudinal, circumferential and radial strain (Ell_LAX, Ecc_SAX and Err_SAX) were calculated. To assess intra-observer agreement data analysis was repeated after 4 weeks. The sample size required to detect a relative change in strain was calculated.

Results

In general, Ecc_SAX and Ell_LAX demonstrated highest inter-observer reproducibility (ICC 0.79 (0.46–0.91) and 0.73 (0.56–0.83) Ecc_SAX and Ell_LAX respectively). In contrast, at the intra-observer level Ell_LAX was more reproducible than Ecc_SAX (ICC 0.83 (0.73–0.90) and 0.74 (0.49–0.87) Ell_LAX and Ecc_SAX respectively). The reproducibility of Err_SAX was weak at both observer levels. Preliminary sample size calculation showed that a small study sample (e.g. ten animals to detect a relative 10% change in Ecc_SAX) could be sufficient to detect changes if parameter variability is low.

Conclusions

This pilot study demonstrates good to excellent inter- and intra-observer reproducibility of CMR-FT technique in small animal model. The most reproducible measures are global circumferential and global longitudinal strain, whereas reproducibility of radial strain is weak. Furthermore, sample size calculation demonstrates that a small number of animals could be sufficient for future trials.

Quantifying left atrial structure and function using single-plane tissue-tracking cardiac magnetic resonance

PURPOSE

Left atrial (LA) structure and function are important markers of adverse cardiovascular outcomes. Tissue-tracking cardiovascular magnetic resonance (CMR) accurately quantifies LA volume, strain, and strain rate based on biplane long-axis imaging. We aimed to assess the accuracy of the LA indices quantification from single-plane tissue-tracking CMR.

METHODS

We included 388 subjects (mean age 57±13, male 70%) whose cine CMR images in sinus rhythm were available in both four-chamber and two-chamber views: 162 patients from the Prospective Observational Study of Implantable Cardioverter-Defibrillators (PROSE-ICD) Study, 208 patients from atrial fibrillation cohort, and 18 healthy volunteers. The group was divided into the training set (n=291) and the test set (n=97). In the training set, we compared the LA indices derived from biplane imaging and single-plane imaging (a four-chamber view), and developed regression equations. In the test set, we used the regression equations to estimate the LA indices from the single-plane imaging, and quantified the accuracy of the estimation against the LA indices from the biplane.

RESULTS

In the training set, all the LA indices from the single-plane imaging tended to be systematically underestimated compared with those from the biplane imaging, however, the correlation coefficient was high (r²=0.73-0.90, p<0.001). In the test set, LA volumetric indices showed excellent reproducibility (intra-class correlation coefficient (ICC): 0.91-0.92) with relatively low variability (16.3-22.3%); For LA strain and strain rate indices, reproducibility was excellent (ICC: 0.81-0.93), however, the variability was slightly higher than that of volumetric indices (21.7-25.4%).

CONCLUSIONS

LA volumetric indices measured from single-plane tissue-tracking CMR are highly accurate and reproducible with reference to those derived from the standard biplane imaging. The reproducibility of LA strain and strain rate indices from single-plane tissue-tracking CMR is excellent but the variability is higher than that of the volumetric indices.

Fatty metaplasia quantification and impact on regional myocardial function as assessed by advanced cardiac MR imaging

Objective

This study aimed to investigate the advantages of recently developed cardiac imaging techniques of fat–water separation and feature tracking to characterize better individuals with chronic myocardial infarction (MI).

Materials and methods

Twenty patients who had a previous MI underwent CMR imaging. The study protocol included routine cine and late gadolinium enhancement (LGE) technique. In addition, mDixon LGE imaging was performed in every patient. Left ventricular (LV) circumferential (Ecc_LV) and radial (Err_LV) strain were calculated using dedicated software (CMR⁴², Circle, Calgary, Canada). The extent of global scar was measured in LGE and fat–water separated images to compare conventional and recent CMR imaging techniques.

Results

The infarct size derived from conventional LGE and fat–water separated images was similar. However, detection of lipomatous metaplasia was only possible with mDixon imaging. Subjects with fat deposition demonstrated a significantly smaller percentage of fibrosis than those without fat (10.68 ± 5.07% vs. 13.83 ± 6.30%; p = 0.005). There was no significant difference in Ecc_LV or Err_LV between myocardial segments containing fibrosis only and fibrosis with fat. However, Ecc_LV and Err_LV values were significantly higher in myocardial segments adjacent to fibrosis with fat deposition than in those adjacent to LGE only.

Conclusions

Advanced CMR imaging ensures more detailed tissue characterization in patients with chronic MI without a relevant increase in imaging and post-processing time. Fatty metaplasia may influence regional myocardial deformation especially in the myocardial segments adjacent to scar tissue. A simplified and shortened myocardial viability CMR protocol might be useful to better characterize and stratify patients with chronic MI.

Automated Description of Regional Left Ventricular Motion in Patients With Cardiac Amyloidosis: A Quantitative Study Using Heart Deformation Analysis

OBJECTIVE

The purpose of this article is to test the hypothesis that heart deformation analysis can automatically quantify regional myocardial motion patterns in patients with cardiac amyloidosis.

SUBJECTS AND METHODS

Eleven patients with cardiac amyloidosis and 11 healthy control subjects were recruited to undergo cardiac MRI. Cine images were analyzed using heart deformation analysis and feature tracking. Heart deformation analysis-derived myocardial motion indexes in radial and circumferential directions, including radial and circumferential displacement, radial and circumferential velocity, radial and circumferential strain, and radial and circumferential strain rate, were compared between the two groups.

RESULTS

) than did healthy control subjects. Heart deformation analysis-derived indexes correlated with feature tracking-derived indexes (r = 0.411 and 0.552).

CONCLUSION

Heart deformation analysis is able to automatically quantify regional myocardial motion in patients with cardiac amyloidosis without the need for operator interaction.

Quantitative assessment of left ventricular mechanical dyssynchrony using cine cardiovascular magnetic resonance imaging: Inter-study reproducibility

OBJECTIVES

To determine the inter-study reproducibility of left ventricular (LV) mechanical dyssynchrony measures based on standard cardiovascular magnetic resonance (CMR) cine images.

DESIGN

Steady-state free precession (SSFP) LV short-axis stacks and three long-axes were acquired on the same day at three time points. Circumferential strain systolic dyssynchrony indexes (SDI), area-SDI as well as circumferential and radial uniformity ratio estimates (CURE and RURE, respectively) were derived from CMR myocardial feature-tracking (CMR-FT) based on the tracking of three SSFP short-axis planes. Furthermore, 4D-LV-analysis based on SSFP short-axis stacks and longitudinal planes was performed to quantify 4D-volume-SDI.

SETTING

A single-centre London teaching hospital.

PARTICIPANTS

16 healthy volunteers.

MAIN OUTCOME MEASURES

Inter-study reproducibility between the repeated exams.

RESULTS

CURE and RURE as well as 4D-volume-SDI showed good inter-study reproducibility (coefficient of variation [CoV] 6.4%-12.9%). Circumferential strain and area-SDI showed higher variability between the repeated measurements (CoV 24.9%-37.5%). Uniformity ratio estimates showed the lowest inter-study variability (CoV 6.4%-8.5%).

CONCLUSIONS

Derivation of LV mechanical dyssynchrony measures from standard cine images is feasible using CMR-FT and 4D-LV-analysis tools. Uniformity ratio estimates and 4D-volume-SDI showed good inter-study reproducibility. Their clinical value should next be explored in patients who potentially benefit from cardiac resynchronization therapy.

Using a respiratory navigator significantly reduces variability when quantifying left ventricular torsion with cardiovascular magnetic resonance

BACKGROUND

Left ventricular (LV) torsion is an important indicator of cardiac function that is limited by high inter-test variability (50% of the mean value). We hypothesized that this high inter-test variability is partly due to inconsistent breath-hold positions during serial image acquisitions, which could be significantly improved by using a respiratory navigator for cardiovascular magnetic resonance (CMR) based quantification of LV torsion.

METHODS

We assessed respiratory-related variability in measured LV torsion with two distinct experimental protocols. First, 17 volunteers were recruited for CMR with cine displacement encoding with stimulated echoes (DENSE) in which a respiratory navigator was used to measure and then enforce variability in end-expiratory position between all LV basal and apical acquisitions. From these data, we quantified the inter-test variability of torsion in the absence and presence of enforced end-expiratory position variability, which established an upper bound for the expected torsion variability. For the second experiment (in 20 new, healthy volunteers), 10 pairs of cine DENSE basal and apical images were each acquired from consecutive breath-holds and consecutive navigator-gated scans (with a single acceptance position). Inter-test variability of torsion was compared between the breath-hold and navigator-gated scans to quantify the variability due to natural breath-hold variation. To demonstrate the importance of these variability reductions, we quantified the reduction in sample size required to detect a clinically meaningful change in LV torsion with the use of a respiratory navigator.

RESULTS

The mean torsion was 3.4 ± 0.2°/cm. From the first experiment, enforced variability in end-expiratory position translated to considerable variability in measured torsion (0.56 ± 0.34°/cm), whereas inter-test variability with consistent end-expiratory position was 57% lower (0.24 ± 0.16°/cm, p < 0.001). From the second experiment, natural respiratory variability from consecutive breath-holds translated to a variability in torsion of 0.24 ± 0.10°/cm, which was significantly higher than the variability from navigator-gated scans (0.18 ± 0.06°/cm, p = 0.02). By using a respiratory navigator with DENSE, theoretical sample sizes were reduced from 66 to 16 and 26 to 15 as calculated from the two experiments.

CONCLUSIONS

A substantial portion (22-57%) of the inter-test variability of LV torsion can be reduced by using a respiratory navigator to ensure a consistent breath-hold position between image acquisitions.

Cardiovascular magnetic resonance myocardial feature tracking using a non-rigid, elastic image registration algorithm: assessment of variability in a real-life clinical setting

BACKGROUND

Cardiovascular magnetic resonance myocardial feature tracking (CMR-FT) is a promising technique for quantification of myocardial strain from steady-state free precession (SSFP) cine images. We sought to determine the variability of CMR-FT using a non-rigid elastic registration algorithm recently available in a commercial software package (Segment, Medviso) in a real-life clinical setting.

METHODS

Firstly, we studied the variability in a healthy volunteer who underwent 10 CMR studies over five consecutive days. Secondly, 10 patients were selected from our CMR database yielding normal findings (normal group). Finally, we prospectively studied 10 patients with known or suspected myocardial pathology referred for further investigation to CMR (patient group). In the patient group a second study was performed respecting an interval of 30 min between studies. All studies were manually segmented at the end-diastolic phase by three observers. In all subjects left ventricular (LV) circumferential and radial strain were calculated in the short-axis direction (EccSAX and ErrSAX, respectively) and longitudinal strain in the long-axis direction (EllLAX). The level of CMR experience of the observers was 2 weeks, 6 months and >20 years.

RESULTS

Mean contouring time was 7 ± 1 min, mean FT calculation time 13 ± 2 min. Intra- and inter-observer variability was good to excellent with an coefficient of reproducibility (CR) ranging 1.6% to 11.5%, and 1.7% to 16.0%, respectively and an intraclass correlation coefficient (ICC) ranging 0.89 to 1.00 and 0.74 to 0.99, respectively. Variability considerably increased in the test-retest setting with a CR ranging 4.2% to 29.1% and an ICC ranging 0.66 to 0.95 in the patient group. Variability was not influenced by level of expertise of the observers. Neither did the presence of myocardial pathology at CMR negatively impact variability. However, compared to global myocardial strain, segmental myocardial strain variability increased with a factor 2-3, in particular for the basal and apical short-axis slices.

CONCLUSIONS

CMR-FT using non-rigid, elastic registration is a reproducible approach for strain analysis in patients routinely scheduled for CMR, and is not influenced by the level of training. However, further improvement is needed to reliably depict small variations in segmental myocardial strain.

Principles of cardiovascular magnetic resonance feature tracking and echocardiographic speckle tracking for informed clinical use

Tissue tracking technology of routinely acquired cardiovascular magnetic resonance (CMR) cine acquisitions has increased the apparent ease and availability of non-invasive assessments of myocardial deformation in clinical research and practice. Its widespread availability thanks to the fact that this technology can in principle be applied on images that are part of every CMR or echocardiographic protocol. However, the two modalities are based on very different methods of image acquisition and reconstruction, each with their respective strengths and limitations. The image tracking methods applied are not necessarily directly comparable between the modalities, or with those based on dedicated CMR acquisitions for strain measurement such as tagging or displacement encoding. Here we describe the principles underlying the image tracking methods for CMR and echocardiography, and the translation of the resulting tracking estimates into parameters suited to describe myocardial mechanics. Technical limitations are presented with the objective of suggesting potential solutions that may allow informed and appropriate use in clinical applications.

Optimal configuration of respiratory navigator gating for the quantification of left ventricular strain using spiral cine displacement encoding with stimulated echoes (DENSE) MRI

PURPOSE

To determine the optimal respiratory navigator gating configuration for the quantification of left ventricular strain using spiral cine displacement encoding with stimulated echoes (DENSE) MRI.

MATERIALS AND METHODS

Two-dimensional spiral cine DENSE was performed on a 3 Tesla MRI using two single-navigator configurations (retrospective, prospective) and a combined "dual-navigator" configuration in 10 healthy adults and 20 healthy children. The adults also underwent breathhold DENSE as a reference standard for comparisons. Peak left ventricular strains, signal-to-noise ratio (SNR), and navigator efficiency were compared. Subjects also underwent dual-navigator gating with and without visual feedback to determine the effect on navigator efficiency.

RESULTS

There were no differences in circumferential, radial, and longitudinal strains between navigator-gated and breathhold DENSE (P = 0.09-0.95) (as confidence intervals, retrospective: [-1.0%-1.1%], [-7.4%-2.0%], [-1.0%-1.2%]; prospective: [-0.6%-2.7%], [-2.8%-8.3%], [-0.3%-2.9%]; dual: [-1.6%-0.5%], [-8.3%-3.2%], [-0.8%-1.9%], respectively). The dual configuration maintained SNR compared with breathhold acquisitions (16 versus 18, P = 0.06). SNR for the prospective configuration was lower than for the dual navigator in adults (P = 0.004) and children (P < 0.001). Navigator efficiency was higher (P < 0.001) for both retrospective (54%) and prospective (56%) configurations compared with the dual configuration (35%). Visual feedback improved the dual configuration navigator efficiency to 55% (P < 0.001).

CONCLUSION

When quantifying left ventricular strains using spiral cine DENSE MRI, a dual navigator configuration results in the highest SNR in adults and children. In adults, a retrospective configuration has good navigator efficiency without a substantial drop in SNR. Prospective gating should be avoided because it has the lowest SNR. Visual feedback represents an effective option to maintain navigator efficiency while using a dual navigator configuration.

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:786-794.

Cardiovascular Magnetic Resonance Myocardial Feature Tracking: Concepts and Clinical Applications

Heart failure-induced cardiovascular morbidity and mortality constitute a major health problem worldwide and result from diverse pathogeneses, including coronary artery disease, nonischemic cardiomyopathies, and arrhythmias. Assessment of cardiovascular performance is important for early diagnosis and accurate management of patients at risk of heart failure. During the past decade, cardiovascular magnetic resonance myocardial feature tracking has emerged as a useful tool for the quantitative evaluation of cardiovascular function. The method allows quantification of biatrial and biventricular mechanics from measures of deformation: strain, torsion, and dyssynchrony. The purpose of this article is to review the basic principles, clinical applications, accuracy, and reproducibility of cardiovascular magnetic resonance myocardial feature tracking, highlighting the prognostic implications. It will also provide an outlook on how this field might evolve in the future.