The impact of foreshortening on regional strain--a comparison of regional strain evaluation between speckle tracking and tissue velocity imaging

The relationship between coronary artery calcium and layer-specific global longitudinal strain in patients with suspected coronary artery disease

PURPOSE

Layer-specific global longitudinal strain (GLS) may provide important insights in patients with suspected coronary artery disease (CAD). We aimed to investigate the association between layer-specific GLS and coronary artery calcium score (CACS) in patients suspected of CAD.

METHODS

We performed a retrospective study of patients suspected of CAD who underwent both an echocardiogram and cardiac computed tomography (median 42 days between). Layer-specific (endocardial-, whole-layer-, and epicardial-) GLS was measured using speckle tracking echocardiography. We assessed the continuous association between layer-specific GLS and CACS by negative binomial regression, and the association with high CACS (≥400) using logistic regression.

RESULTS

Of the 496 patients included (mean age 59 years, 56% male), 64 (13%) had a high CACS. Those with high CACS had reduced GLS in all layers compared to those with CACS < 400 (endocardial GLS: -20.5 vs. -22.7%, whole-layer GLS: -17.7 vs. -19.4%, epicardial GLS: -15.3 vs. -16.9%, p < .001 for all). Negative binomial regression revealed a significant continuous association showing increasing CACS with worsening GLS in all layers, which remained significant after multivariable adjustment including SCORE chart risk factors. All layers of GLS were associated with high CACS in univariable analyses, which was consistent after multivariable adjustment (endocardial GLS: OR = 1.11 (1.03-1.20); whole-layer GLS: OR = 1.14 (1.04-1.24); epicardial GLS: OR = 1.16 (1.05-1.29), per 1% absolute decrease).

CONCLUSION

In this study population with patients suspected of CAD and normal systolic function, impaired layer-specific GLS was continuously associated with increasing CACS, and decreasing GLS in all layers were associated with presence of high CACS.

Automated Detection of Apical Foreshortening in Echocardiography Using Statistical Shape Modelling

OBJECTIVE

Automated detection of foreshortening, a common challenge in routine 2-D echocardiography, has the potential to improve quality of acquisitions and reduce the variability of left ventricular measurements. Acquiring and labelling the required training data is challenging due to the time-intensive and highly subjective nature of foreshortened apical views. We aimed to develop an automatic pipeline for the detection of foreshortening. To this end, we propose a method to generate synthetic apical-four-chamber (A4C) views with matching ground truth foreshortening labels.

METHODS

A statistical shape model of the four chambers of the heart was used to synthesise idealised A4C views with varying degrees of foreshortening. Contours of the left ventricular endocardium were segmented in the images, and a partial least squares (PLS) model was trained to learn the morphological traits of foreshortening. The predictive capability of the learned synthetic features was evaluated on an independent set of manually labelled and automatically curated real echocardiographic A4C images.

RESULTS

Acceptable classification accuracy for identification of foreshortened views in the testing set was achieved using logistic regression based on 11 PLS shape modes, with a sensitivity, specificity and area under the receiver operating characteristic curve of 0.84, 0.82 and 0.84, respectively. Both synthetic and real cohorts showed interpretable traits of foreshortening within the first two PLS shape modes, reflected as a shortening in the long-axis length and apical rounding.

CONCLUSION

A contour shape model trained only on synthesized A4C views allowed accurate prediction of foreshortening in real echocardiographic images.

Automated Force-Coupled Ultrasound Method for Calibration-Free Carotid Artery Blood Pressure Estimation

We develop, automate and evaluate a calibration-free technique to estimate human carotid artery blood pressure from force-coupled ultrasound images. After acquiring images and force, we use peak detection to align the raw force signal with an optical flow signal derived from the images. A trained convolutional neural network selects a seed point within the carotid in a single image. We then employ a region-growing algorithm to segment and track the carotid in subsequent images. A finite-element deformation model is fit to the observed segmentation and force via a two-stage iterative non-linear optimization. The first-stage optimization estimates carotid artery wall stiffness parameters along with systolic and diastolic carotid pressures. The second-stage optimization takes the output parameters from the first optimization and estimates the carotid blood pressure waveform. Diastolic and systolic measurements are compared with those of an oscillometric brachial blood pressure cuff. In 20 participants, average absolute diastolic and systolic errors are 6.2 and 5.6 mm Hg, respectively, and correlation coefficients are r = 0.7 and r = 0.8, respectively. Force-coupled ultrasound imaging represents an automated, standalone ultrasound-based technique for carotid blood pressure estimation, which motivates its further development and expansion of its applications.

Layer-specific global longitudinal strain and the risk of heart failure and cardiovascular mortality in the general population: the Copenhagen City Heart Study

AIMS

Layer-specific global longitudinal strain (GLS) has been demonstrated to predict outcome in various patient cohorts. However, little is known regarding the prognostic value of layer-specific GLS in the general population and whether different layers entail differential prognostic information. The aim of the present study was to investigate the prognostic value of whole wall (GLS_WW ), endomyocardial (GLS_Endo ), and epimyocardial (GLS_Epi ) GLS in the general population.

METHODS AND RESULTS

A total of 4013 citizens were included in the present study. All 4013 had two-dimensional speckle tracking echocardiography performed and analysed. Outcome was a composite endpoint of incident heart failure and/or cardiovascular death. Mean age was 56 years and 57% were female. During a median follow-up time of 3.5 years, 133 participants (3.3%) reached the composite outcome. Sex modified the relationship between all GLS parameters and outcome. In sex-stratified analysis, no GLS parameter remained significant predictors of outcome in females. In contrast, GLS_WW [hazard ratio (HR) 1.16, 95% confidence interval (CI) 1.02-1.31, per 1% decrease] and GLS_Epi (HR 1.19, 95% CI 1.04-1.38, per 1% decrease) remained as significant predictors of outcome in males after multivariable adjustment (including demographic, clinical, biochemistry, and echocardiographic parameters). Lastly, only in males did GLS parameters provide incremental prognostic information to general population risk models.

CONCLUSIONS

In the general population, sex modifies the prognostic value of GLS resulting in GLS_Epi being the only layer-specific prognosticator in males, while no GLS parameter provides independent prognostic information in females.

Layer-specific global longitudinal strain obtained by speckle tracking echocardiography for predicting heart failure and cardiovascular death following STEMI treated with primary PCI

The aim of this study was to evaluate layer-specific global longitudinal strain (GLS), obtained by speckle tracking, in predicting outcomes following ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI). Echocardiography, including layer-specific GLS, was performed at median two days after the STEMI in a prospective study of STEMI patients treated with pPCI between September 2006 and December 2008. The outcome was the composite of heart failure hospitalization and/or cardiovascular death (HF/CVD). A total of 349 patients were included. Mean age was 62.2 ± 11.5 years, 76% were male, and mean ejection fraction (LVEF) was 46 ± 9. Seventy-seven (22%) patients developed HF/CVD during median follow-up 5.4 years. Patients with HF/CVD had lower absolute values for all GLS-layers: endocardial (GLS_Endo) 11.4%vs 14.5% (p < 0.001), midmyocardial (GLS_Mid) 9.8% vs 12.5% (p < 0.001) and epicardial (GLS_Epi) 8.5% vs 10.9% (p < 0.001). In unadjusted analysis, all layers were significant predictors of HF/CVD; hazard ratio (HR) per 1% decrease for GLS_Endo: HR 1.18 (95%CI 1.11-1.25), GLS_Mid: HR 1.22 (95%CI 1.14-1.30) and GLS_Epi: HR 1.26 (95%CI 1.16-1.36), p < 0.0001 for all. The risk of HF/CVD increased incrementally with increasing tertiles for all layers, being more than three times higher in 3rd tertile compared to 1st tertile. In multivariable models, including baseline clinical and echocardiographic parameters, only GLS_Mid and GLS_Epi remained independent predictors of HF/CVD. Global longitudinal strain obtained from all myocardial layers were significant predictors of incident HF and CVD following STEMI, however, only GLS_Mid and GLS_Epi remained independent predictors after multivariable adjustment.

Time to shape up - assessment and reporting standards for data quality in clinical research using echocardiographic imaging techniques require improvement

Advanced echocardiography techniques such as speckle tracking imaging are sensitive diagnostic tools frequently used in various clinical and scientific scenarios. Importantly, imperfect reproducibility and dependence of post-processing algorithms on echocardiographic image quality are potential methodological limitations. Therefore, meticulous assessment of data quality and detailed reporting of study methodology, sample specifics, technical peculiarities and measurement conditions are crucial. Unfortunately, despite the recognized importance of this, there is still no broadly accepted standard for assessing the quality of echocardiographic images in clinical research reports. This article quintessentially highlights important shortcomings of data quality assessment and methodological study design, commonly occurring in clinical research reports using advanced echocardiography techniques. Finally, suggestions are made as to how researchers, scientific communities and biomedical journals can contribute to the ever-lasting process of improving the quality of clinical research in cardiovascular imaging.

Impact of apical foreshortening on deformation measurements: a report from the EACVI-ASE Strain Standardization Task Force

Aims

Foreshortening of apical views is a common problem in echocardiography. It results in an abnormally thick false apex and a shortened left ventricular (LV) long axis. We sought to evaluate the impact of foreshortened (FS) on LV ejection fraction (LVEF) and layer-specific 2D speckle tracking based segmental (S) and global (G) longitudinal strain (LS) measurements.

Methods and results

We examined 72 participants using a GE Vivid E9 system. FS apical views were collected from an imaging window one rib-space higher than the optimal images. Ejection fraction as well as layer-specific GLS and SLS measurements were analysed by GE EchoPAC v201 and TomTec Image Arena 4.6 and compared between optimal and FS images. On average, LV long axis was 10% shorter in FS images than in optimal images. FS induced a relative change in LVEF of 3.3% and 6.9% for GE and TomTec, respectively (both, P < 0.001). Endocardial GLS was 9.0% higher with GE and 23.2% with TomTec (P < 0.001). Midwall GLS measurements were less affected (7.8% for GE and 14.1% for TomTec, respectively, both P < 0.001). Segmental strain analysis revealed that the mid-ventricular and apical segments were more affected by foreshortening, and endocardial measurements were more affected than midwall.

Conclusion

Optimal image geometry is crucial for accurate LV function assessment. Foreshorhening of apical views has a substantial impact on longitudinal strain measurements, predominantly in the apex and in the endocardial layer. Our data suggest that measuring midwall strain might therefore be the more robust approach for clinical routine use.

Variability of longitudinal strain measurements: levelling the playing field

Speckle tracking echocardiography offers a unique opportunity to evaluate myocardial function, and global longitudinal strain (GLS) is currently recommended as a measurement of global left ventricular function. To facilitate clinical applicability of the method, collective efforts have been made to standardise strain measurements and to raise awareness of the potential sources of variability. The purpose of this review is to familiarise the reader with the most common sources of variability of longitudinal strain measurements and detail the possible measures to increase the accuracy and reproducibility of strain parameters.