Mechanistic Evaluation of Echocardiographic Dyssynchrony Indices

The mechanistic interaction between mechanical dyssynchrony and filling pressure in cardiac resynchronisation therapy candidates

AIMS

Both left ventricular (LV) mechanical dyssynchrony and filling pressure have been shown to be associated with outcome in heart failure patient treated with cardiac resynchronisation therapy (CRT). To investigate the mechanistic link between mechanical dyssynchrony and filling pressure and to assess their combined prognostic value in CRT candidates.

METHODS AND RESULTS

Left atrial pressure (LAP) estimation and quantification of mechanical dyssynchrony were retrospectively performed in 219 CRT patients using echocardiography. LAP was elevated (eLAP) in 49% of the population, normal (nLAP) in 40%, and indeterminate in 11%. CRT response was defined as per cent-decrease in LV end-systolic volume after 12 ± 6 months CRT. Clinical endpoint was all-cause mortality during 4.8 years (interquartile range: 2.7-6.0 years). To investigate the mechanistic link between mechanical dyssynchrony and filling pressure, the CircAdapt computer model was used to simulate cardiac mechanics and haemodynamics in virtual hearts with left bundle branch block (LBBB) and various causes of increased filling pressure. Patients with nLAP had more significant mechanical dyssynchrony than those with eLAP. The combined assessment of both parameters before CRT was significantly associated with reverse LV remodelling and post-CRT survival. Simulations revealed that mechanical dyssynchrony is attenuated by increased LV operational chamber stiffness, regardless of whether it is caused by passive or active factors, explaining the link between mechanical dyssynchrony and filling pressure.

CONCLUSION

Our combined clinical-computational data demonstrate that in patients with LBBB, the presence of mechanical dyssynchrony indicates relatively normal LV compliance and low filling pressure, which may explain their strong association with positive outcomes after CRT.

Myocardial Strain Imaging: Theory, Current Practice, and the Future

Myocardial strain imaging by echocardiography or cardiac magnetic resonance (CMR) is a powerful method to diagnose cardiac disease. Strain imaging provides measures of myocardial shortening, thickening, and lengthening and can be applied to any cardiac chamber. Left ventricular (LV) global longitudinal strain by speckle-tracking echocardiography is the most widely used clinical strain parameter. Several CMR-based modalities are available and are ready to be implemented clinically. Clinical applications of strain include global longitudinal strain as a more sensitive method than ejection fraction for diagnosing mild systolic dysfunction. This applies to patients suspected of having heart failure with normal LV ejection fraction, to early systolic dysfunction in valvular disease, and when monitoring myocardial function during cancer chemotherapy. Segmental LV strain maps provide diagnostic clues in specific cardiomyopathies, when evaluating LV dyssynchrony and ischemic dysfunction. Strain imaging is a promising modality to quantify right ventricular function. Left atrial strain may be used to evaluate LV diastolic function and filling pressure.

Electrical and mechanical interventricular dyssynchrony coupling in patients with bradycardia: A UHF-ECG validation trial

BACKGROUND

Ultra-high-frequency electrocardiography (UHF-ECG) is a noninvasive tool visualizing the ventricular activation sequence. It was never compared with other methods of dyssynchrony assessment in patients with bradycardia.

OBJECTIVE

We aimed to compare UHF-ECG interventricular electrical dyssynchrony (e-DYS) with interventricular mechanical delay (IVMD) measured by echocardiography in patients receiving right ventricular pacing (RVP) or conduction system pacing (CSP).

METHODS

Fifty-three patients with advanced atrioventricular conduction disease and preserved ventricular systolic function were prospectively assigned to RVP (n=32 [60 %]) or CSP (n=21 [40 %]). IVMD was measured as the time difference between left ventricular and right ventricular preejection periods. Interventricular e-DYS was calculated by software as the time difference between activation in V1 and V7 chest electrodes using UHF-ECG.

RESULTS

The median age of patients was 75 (interquartile range 72-80) years, and both groups had similar clinical characteristics. Baseline IVMD and interventricular e-DYS were similar in the entire population (-2 [-8 to 5] ms vs-1 [-6 to 5] ms, respectively; P=.52). Both methods showed the same dyssynchrony trends after pacemaker implantation; that is, while both IVMD and interventricular e-DYS increased in the RVP group (IVMD 28 [23-33] ms vs interventricular e-DYS 26 [19-33] ms; P=.99), they remained low in the CSP group (IVMD -7 [-16 to 2] ms vs interventricular e-DYS -5 [-12 to 2] ms; P=.91). There was a moderate overall correlation between IVMD and interventricular e-DYS for all studied ventricular rhythms (R=0.74).

CONCLUSION

UHF-ECG noninvasively expresses interventricular dyssynchrony from V7-V1 chest leads with similar results to echocardiography. RVP increases interventricular dyssynchrony, while CSP preserves synchronous ventricular activation.

Clinical significance of regional constructive and wasted work in patients receiving cardiac resynchronization therapy

Background

Previous studies have shown that global constructive work (CW) and wasted work (WW) predict response to cardiac resynchronization therapy (CRT). This study evaluated the predictive value of regional CW and WW for reverse remodeling and clinical outcomes after CRT.

Methods

We performed a prospective study involving 134 CRT candidates with left bundle branch block and left ventricular ejection fraction ≤35%. Global and regional CW and WW were calculated using pressure-strain loop analysis. CRT response was defined by reverse remodeling as a reduction of ≥15% in left ventricular end-systolic volume after six months.

Results

At six-month follow-up, 92 (69%) patients responded to CRT. Of the regional CW and WW measures, lateral wall (LW) CW and septal WW were most strongly and significantly correlated with reverse remodeling. At multivariate analysis, LW CW and septal WW were both independent determinants of reverse remodeling. When LW CW and septal WW were included in the model, global CW and WW were not independently associated with reverse remodeling. LW CW and septal WW predicted reverse remodeling with an area under the curve (AUC) of 0.783 (95% CI: 0.700-0.866) and 0.737 (95% CI: 0.644-0.831), respectively. Using both variables increased the AUC to 0.832 (95% CI: 0.755-0.908). Both LW CW ≤878 mmHg% (HR 2.01; 95% CI: 1.07-3.79) and septal WW ≤181 mmHg% (HR 2.60; 95% CI: 1.38-4.90) were significant predictors of combined death and HF hospitalization at two-year follow-up.

Conclusion

LW CW and septal WW before CRT are important determinants of reverse remodeling and clinical outcomes.

Imaging in patients with cardiovascular implantable electronic devices: part 1-imaging before and during device implantation. A clinical consensus statement of the European Association of Cardiovascular Imaging (EACVI) and the European Heart Rhythm Association (EHRA) of the ESC

More than 500 000 cardiovascular implantable electronic devices (CIEDs) are implanted in the European Society of Cardiology countries each year. The role of cardiovascular imaging in patients being considered for CIED is distinctly different from imaging in CIED recipients. In the former group, imaging can help identify specific or potentially reversible causes of heart block, the underlying tissue characteristics associated with malignant arrhythmias, and the mechanical consequences of conduction delays and can also aid challenging lead placements. On the other hand, cardiovascular imaging is required in CIED recipients for standard indications and to assess the response to device implantation, to diagnose immediate and delayed complications after implantation, and to guide device optimization. The present clinical consensus statement (Part 1) from the European Association of Cardiovascular Imaging, in collaboration with the European Heart Rhythm Association, provides comprehensive, up-to-date, and evidence-based guidance to cardiologists, cardiac imagers, and pacing specialists regarding the use of imaging in patients undergoing implantation of conventional pacemakers, cardioverter defibrillators, and resynchronization therapy devices. The document summarizes the existing evidence regarding the use of imaging in patient selection and during the implantation procedure and also underlines gaps in evidence in the field. The role of imaging after CIED implantation is discussed in the second document (Part 2).

Cardiac Magnetic Resonance Identifies Responders to Cardiac Resynchronization Therapy with an Assessment of Septal Scar and Left Ventricular Dyssynchrony

Background: The response to cardiac resynchronization therapy (CRT) depends on septal viability and correction of abnormal septal motion. This study investigates if cardiac magnetic resonance (CMR) as a single modality can identify CRT responders with combined imaging of pathological septal motion (septal flash) and septal scar. Methods: In a prospective, multicenter, observational study of 136 CRT recipients, septal scar was assessed using late gadolinium enhancement (LGE) (n = 127) and septal flash visually from cine CMR sequences. The primary endpoint was CRT response, defined as ≥15% reduction in LV end-systolic volume with echocardiography after 6 months. The secondary endpoint was heart transplantation or death of any cause assessed after 39 ± 13 months. Results: Septal scar and septal flash were independent predictors of CRT response in multivariable analysis (both p < 0.001), while QRS duration and morphology were not. The combined approach of septal scar and septal flash predicted CRT response with an area under the curve of 0.86 (95% confidence interval (CI): 0.78-0.94) and was a strong predictor of long-term survival without heart transplantation (hazard ratio 0.27, 95% CI: 0.10-0.79). The accuracy of the approach was similar in the subgroup with intermediate (130-150 ms) QRS duration. The combined approach was superior to septal scar and septal flash alone (p < 0.01). Conclusions: The combined assessment of septal scar and septal flash using CMR as a single-image modality identifies CRT responders with high accuracy and predicts long-term survival.

The saga of dyssynchrony imaging: Are we getting to the point

Cardiac resynchronisation therapy (CRT) has an established role in the management of patients with heart failure, reduced left ventricular ejection fraction (LVEF &lt; 35%) and widened QRS (&gt;130 msec). Despite the complex pathophysiology of left ventricular (LV) dyssynchrony and the increasing evidence supporting the identification of specific electromechanical substrates that are associated with a higher probability of CRT response, the assessment of LVEF is the only imaging-derived parameter used for the selection of CRT candidates.

This review aims to (1) provide an overview of the evolution of cardiac imaging for the assessment of LV dyssynchrony and its role in the selection of patients undergoing CRT; (2) highlight the main pitfalls and advantages of the application of cardiac imaging for the assessment of LV dyssynchrony; (3) provide some perspectives for clinical application and future research in this field.

Conclusion

the road for a more individualized approach to resynchronization therapy delivery is open and imaging might provide important input beyond the assessment of LVEF.

Evaluation of Cardiac Mechanical Dyssynchrony in Heart Failure Patients Using Current Echo-Doppler Modalities

BACKGROUND

Current guidelines indicate electrical dyssynchrony as the major criteria for selecting patients for cardiac resynchronization therapy, and 25-35% of patients exhibit unfavorable responses to cardiac resynchronization therapy (CRT). We aimed to evaluate different cardiac mechanical dyssynchrony parameters in heart failure patients using current echo-Doppler modalities and we analyzed their association with electrical dyssynchrony.

METHODS

The study included 120 heart failure with reduced ejection fraction (HFrEF) who underwent assessments for left ventricular mechanical dyssynchrony (LVMD) and interventricular mechanical dyssynchrony (IVMD).

RESULTS

Patients were classified according to QRS duration: group I with QRS < 120 ms, group II with QRS 120-149 ms, and group III with QRS ≥ 150 ms. Group III had significantly higher IVMD, LVMD indices, TS-SD speckle-tracking echocardiography (STE) 12 segments (standard deviation of time to peak longitudinal strain speckle tracking echocardiography in 12 LV-segments), and LVMD score compared with group I and group II. Group II and group III were classified according to QRS morphology into left bundle branch block (LBBB) and non-LBBB subgroups. LVMD score, TS-SD 12 TDI, and TS-SD 12 STE had good correlations with QRS duration.

CONCLUSIONS

HFrEF patients with wide QRS duration (> 150 ms) had more evident LVMD compared with patients with narrow or intermediate QRS. Those patients with intermediate QRS duration (120-150 ms) had substantial LVMD assessed by both TDI and 2D STE, regardless of QRS morphology. Subsequently, we suggest that LVMD indices might be employed as additive criteria to predict CRT response in that patient subgroup. Electrical and mechanical dyssynchrony were strongly correlated in HFrEF patients.

Electromechanical factors associated with favourable outcome in cardiac resynchronization therapy

AIMS

Electromechanical coupling in patients receiving cardiac resynchronization therapy (CRT) is not fully understood. Our aim was to determine the best combination of electrical and mechanical substrates associated with effective CRT.

METHODS AND RESULTS

Sixty-two patients were prospectively enrolled from two centres. Patients underwent 12-lead electrocardiogram (ECG), cardiovascular magnetic resonance (CMR), echocardiography, and anatomo-electromechanical mapping (AEMM). Remodelling was measured as the end-systolic volume (ΔESV) decrease at 6 months. CRT was defined effective with ΔESV ≤ -15%. QRS duration (QRSd) was measured from ECG. Area strain was obtained from AEMM and used to derive systolic stretch index (SSI) and total left-ventricular mechanical time. Total left-ventricular activation time (TLVAT) and transeptal time (TST) were derived from AEMM and ECG. Scar was measured from CMR. Significant correlations were observed between ΔESV and TST [rho = 0.42; responder: 50 (20-58) vs. non-responder: 33 (8-44) ms], TLVAT [-0.68; 81 (73-97) vs. 112 (96-127) ms], scar [-0.27; 0.0 (0.0-1.2) vs. 8.7 (0.0-19.1)%], and SSI [0.41; 10.7 (7.1-16.8) vs. 4.2 (2.9-5.5)], but not QRSd [-0.13; 155 (140-176) vs. 167 (155-177) ms]. TLVAT and SSI were highly accurate in identifying CRT response [area under the curve (AUC) > 0.80], followed by scar (AUC > 0.70). Total left-ventricular activation time (odds ratio = 0.91), scar (0.94), and SSI (1.29) were independent factors associated with effective CRT. Subjects with SSI >7.9% and TLVAT <91 ms all responded to CRT with a median ΔESV ≈ -50%, while low SSI and prolonged TLVAT were more common in non-responders (ΔESV ≈ -5%).

CONCLUSION

Electromechanical measurements are better associated with CRT response than conventional ECG variables. The absence of scar combined with high SSI and low TLVAT ensures effectiveness of CRT.

CARDIOSIM©: The First Italian Software Platform for Simulation of the Cardiovascular System and Mechanical Circulatory and Ventilatory Support

This review is devoted to presenting the history of the CARDIOSIM^© software simulator platform, which was developed in Italy to simulate the human cardiovascular and respiratory systems. The first version of CARDIOSIM^© was developed at the Institute of Biomedical Technologies of the National Research Council in Rome. The first platform version published in 1991 ran on a PC with a disk operating system (MS-DOS) and was developed using the Turbo Basic language. The latest version runs on PC with Microsoft Windows 10 operating system; it is implemented in Visual Basic and C++ languages. The platform has a modular structure consisting of seven different general sections, which can be assembled to reproduce the most important pathophysiological conditions. One or more zero-dimensional (0-D) modules have been implemented in the platform for each section. The different modules can be assembled to reproduce part or the whole circulation according to Starling’s law of the heart. Different mechanical ventilatory and circulatory devices have been implemented in the platform, including thoracic artificial lungs, ECMO, IABPs, pulsatile and continuous right and left ventricular assist devices, biventricular pacemakers and biventricular assist devices. CARDIOSIM^© is used in clinical and educational environments.

Four-dimensional computed tomography of the left ventricle, Part II: Estimation of mechanical activation times

PURPOSE

We demonstrate the viability of a four-dimensional X-ray computed tomography (4DCT) imaging system to accurately and precisely estimate mechanical activation times of left ventricular (LV) wall motion. Accurate and reproducible timing estimates of LV wall motion may be beneficial in the successful planning and management of cardiac resynchronization therapy (CRT).

METHODS

We developed an anthropomorphically accurate in silico LV phantom based on human CT images with programmed septal-lateral wall dyssynchrony. Twenty-six temporal phases of the in silico phantom were used to sample the cardiac cycle of 1 s. For each of the 26 phases, 1 cm thick axial slabs emulating axial CT image volumes were extracted, 3D printed, and imaged using a commercially available CT scanner. A continuous dynamic sinogram was synthesized by blending sinograms from these static phases; the synthesized sinogram emulated the sinogram that would be acquired under true continuous phantom motion. Using the synthesized dynamic sinogram, images were reconstructed at 70 ms intervals spanning the full cardiac cycle; these images exhibited expected motion artifact characteristics seen in images reconstructed from real dynamic data. The motion corrupted images were then processed with a novel motion correction algorithm (ResyncCT) to yield motion corrected images. Five pairs of motion uncorrected and motion corrected images were generated, each corresponding to a different starting gantry angle (0 to 180 degrees in 45 degree increments). Two line profiles perpendicular to the endocardial surface were used to sample local myocardial motion trajectories at the septum and the lateral wall. The mechanical activation time of wall motion was defined as the time at which the endocardial boundary crossed a fixed position defined on either of the two line profiles while moving toward the center of the LV during systolic contraction. The mechanical activation times of these myocardial trajectories estimated from the motion uncorrected and the motion corrected images were then compared with those derived from the static images of the 3D printed phantoms (ground truth). The precision of the timing estimates was obtained from the five different starting gantry angle simulations.

RESULTS

The range of estimated mechanical activation times observed across all starting gantry angles was significantly larger for the motion uncorrected images than for the motion corrected images (lateral wall: 58 ± 15 ms vs 12 ± 4 ms, p < 0.005; septal wall: 61 ± 13 ms vs 13 ± 9 ms, p < 0.005).

CONCLUSIONS

4DCT images processed with the ResyncCT motion correction algorithm yield estimates of mechanical activation times of LV wall motion with significantly improved accuracy and precision. The promising results reported in this study highlight the potential utility of 4DCT in estimating the timing of mechanical events of interest for CRT guidance.

Desynchronization Strain Patterns and Contractility in Left Bundle Branch Block through Computer Model Simulation

Left bundle branch block (LBBB) is associated with specific septal-to-lateral wall activation patterns which are strongly influenced by the intrinsic left ventricular (LV) contractility and myocardial scar localization. The objective of this study was to propose a computational-model-based interpretation of the different patterns of LV contraction observed in the case of LBBB and preserved contractility or myocardial scarring. Two-dimensional transthoracic echocardiography was used to obtain LV volumes and deformation patterns in three patients with LBBB: (1) a patient with non-ischemic dilated cardiomyopathy, (2) a patient with antero-septal myocardial scar, and (3) a patient with lateral myocardial scar. Scar was confirmed by the distribution of late gadolinium enhancement with cardiac magnetic resonance imaging (cMRI). Model parameters were evaluated manually to reproduce patient-derived data such as strain curves obtained from echocardiographic apical views. The model was able to reproduce the specific strain patterns observed in patients. A typical septal flash with pre-ejection shortening, rebound stretch, and delayed lateral wall activation was observed in the case of non-ischemic cardiomyopathy. In the case of lateral scar, the contractility of the lateral wall was significantly impaired and septal flash was absent. In the case of septal scar, septal flash and rebound stretch were also present as previously described in the literature. Interestingly, the model was also able to simulate the specific contractile properties of the myocardium, providing an excellent localization of LV scar in ischemic patients. The model was able to simulate the electromechanical delay and specific contractility patterns observed in patients with LBBB of ischemic and non-ischemic etiology. With further improvement and validation, this technique might be a useful tool for the diagnosis and treatment planning of heart failure patients needing CRT.

Acute redistribution of regional left ventricular work by cardiac resynchronization therapy determines long-term remodelling

Aims 

Investigating the acute impact of cardiac resynchronization therapy (CRT) on regional myocardial work distribution in the left ventricle (LV) and to which extent it is related to long-term reverse remodelling.

Methods and results 

One hundred and thirty heart failure patients, referred for CRT implantation, were recruited in our prospective multicentre study. Regional myocardial work was calculated from non-invasive segmental stress–strain loop area before and immediately after CRT. The magnitude of volumetric reverse remodelling was determined from the change in LV end-systolic volume, 11 ± 2 months after implantation. CRT caused acute redistribution of myocardial work across the LV, with an increase in septal work, and decrease in LV lateral wall work (all P &lt; 0.05). Amongst all LV walls, the acute change in work in the septum and lateral wall of the four-chamber view correlated best and significantly with volumetric reverse remodelling (r = 0.62, P &lt; 0.0001), with largest change seen in patients with most volumetric reverse remodelling. In multivariate linear regression analysis, including conventional parameters, such as pre-implant QRS morphology and duration, LV ejection fraction, ischaemic origin of cardiomyopathy, and the redistribution of work across the septal and lateral walls, the latter appeared as the strongest determinant of volumetric reverse remodelling after CRT (model R2 = 0.414, P &lt; 0.0001).

Conclusion 

The acute redistribution of regional myocardial work between the septal and lateral wall of the LV is an important determinant of reverse remodelling after CRT implantation. Our data suggest that the treatment of the loading imbalance should, therefore, be the main aim of CRT.

Contractility surrogates derived from three-dimensional lead motion analysis and prediction of acute haemodynamic response to CRT

Background

Patient-specific left ventricular (LV) lead optimisation strategies with immediate feedback on cardiac resynchronisation therapy (CRT) effectiveness are needed. The purpose of this study was to compare contractility surrogates derived from biventricular lead motion analysis to the peak positive time derivative of LV pressure (dP/dt_max) in patients undergoing CRT implantation.

Methods

Twenty-seven patients underwent CRT implantation with continuous haemodynamic monitoring. The right ventricular (RV) lead was placed in apex and a quadripolar LV lead was placed laterally. Biplane fluoroscopy cine films facilitated construction of three-dimensional RV–LV interlead distance waveforms at baseline and under biventricular pacing (BIVP) from which the following contractility surrogates were derived; fractional shortening (FS), time to peak systolic contraction and peak shortening of the interlead distance (negative slope). Acute haemodynamic CRT response was defined as LV ∆dP/dt_max ≥ 10 %.

Results

We observed a mean increase in dP/dt_max under BIVP (899±205 mm Hg/s vs 777±180 mm Hg/s, p<0.001). Based on ΔdP/dt_max, 18 patients were classified as acute CRT responders and nine as non-responders (23.3%±10.6% vs 1.9±5.3%, p<0.001). The baseline RV–LV interlead distance was associated with echocardiographic LV dimensions (end diastole: R=0.61, p=0.001 and end systole: R=0.54, p=0.004). However, none of the contractility surrogates could discriminate between the acute CRT responders and non-responders (ΔFS: −2.5±2.6% vs − 2.0±3.1%, p=0.50; Δtime to peak systolic contraction: −9.7±18.1% vs −10.8±15.1%, p=0.43 and Δpeak negative slope: −8.7±45.9% vs 12.5±54.8 %, p=0.09).

Conclusion

The baseline RV–LV interlead distance was associated with echocardiographic LV dimensions. In CRT recipients, contractility surrogates derived from the RV–LV interlead distance waveform could not discriminate between acute haemodynamic responders and non-responders.

Systolic Stretch Characterizes the Electromechanical Substrate Responsive to Cardiac Resynchronization Therapy

OBJECTIVES

In this study, the authors tested the hypotheses that the systolic stretch index (SSI) developed by computer modeling and applied using echocardiographic strain imaging may characterize the electromechanical substrate predictive of outcome following cardiac resynchronization therapy (CRT). They included patients with QRS width 120 to 149 ms or non-left bundle branch block (LBBB), where clinical uncertainty for CRT exists. They further tested the hypothesis that global longitudinal strain (GLS) has additional prognostic value.

BACKGROUND

Response to CRT is variable. Guidelines favor patient selection by electrocardiographic LBBB with QRS width ≥150 ms.

METHODS

The authors studied 442 patients enrolled in the Adaptive CRT 94-site randomized trial with New York Heart Association functional class III-IV heart failure, ejection fraction ≤35%, and QRS ≥120 ms. A novel computer program semiautomatically calculated the SSI from strain curves as the sum of posterolateral prestretch percent before aortic valve opening and the septal rebound stretch percent during ejection. The primary endpoint was hospitalization for heart failure (HF) or death, and the secondary endpoint was death over 2 years after CRT.

RESULTS

In all patients, high longitudinal SSI (≥ group median of 3.1%) was significantly associated with freedom from the primary endpoint of HF hospitalization or death (hazard ratio [HR] for low SSI: 2.17; 95% confidence interval [CI]: 1.45 to 3.24, p < 0.001) and secondary endpoint of death (HR for low SSI: 4.06; 95% CI: 1.95 to 8.45, p < 0.001). Among the 203 patients with QRS 120 to 149 ms or non-LBBB, those with high longitudinal SSI (≥ group median of 2.6%) had significantly fewer HF hospitalizations or deaths (HR for low SSI: 2.08; 95% CI: 1.27 to 3.41, p = 0.004) and longer survival (HR for low SSI: 5.08; 95% CI: 1.94 to 13.31, p < 0.001), similar to patients with LBBB ≥150 ms. SSI by circumferential strain had similar associations with clinical outcomes, and GLS was additive to SSI in predicting clinical events (p = 0.001).

CONCLUSIONS

Systolic stretch by strain imaging characterized the myocardial substrate associated with favorable CRT response, including in the important patient subgroup with QRS width 120 to 149 ms or non-LBBB. GLS had additive prognostic value.

Cardiac resynchronization therapy: mechanisms of action and scope for further improvement in cardiac function

Aims

Cardiac resynchronization therapy (CRT) may exert its beneficial haemodynamic effect by improving ventricular synchrony and improving atrioventricular (AV) timing. The aim of this study was to establish the relative importance of the mechanisms through which CRT improves cardiac function and explore the potential for additional improvements with improved ventricular resynchronization.

Methods and Results

We performed simulations using the CircAdapt haemodynamic model and performed haemodynamic measurements while adjusting AV delay, at low and high heart rates, in 87 patients with CRT devices. We assessed QRS duration, presence of fusion, and haemodynamic response. The simulations suggest that intrinsic PR interval and the magnitude of reduction in ventricular activation determine the relative importance of the mechanisms of benefit. For example, if PR interval is 201 ms and LV activation time is reduced by 25 ms (typical for current CRT methods), then AV delay optimization is responsible for 69% of overall improvement. Reducing LV activation time by an additional 25 ms produced an additional 2.6 mmHg increase in blood pressure (30% of effect size observed with current CRT). In the clinical population, ventricular fusion significantly shortened QRS duration (Δ-27 ± 23 ms, P < 0.001) and improved systolic blood pressure (mean 2.5 mmHg increase). Ventricular fusion was present in 69% of patients, yet in 40% of patients with fusion, shortening AV delay (to a delay where fusion was not present) produced the optimal haemodynamic response.

Conclusions

Improving LV preloading by shortening AV delay is an important mechanism through which cardiac function is improved with CRT. There is substantial scope for further improvement if methods for delivering more efficient ventricular resynchronization can be developed.

Clinical Trial Registration

Our clinical data were obtained from a subpopulation of the British Randomised Controlled Trial of AV and VV Optimisation (BRAVO), which is a registered clinical trial with unique identifier: NCT01258829, https://clinicaltrials.gov

Simulation as a preoperative planning approach in advanced heart failure patients. A retrospective clinical analysis

BACKGROUND

Modelling and simulation may become clinically applicable tools for detailed evaluation of the cardiovascular system and clinical decision-making to guide therapeutic intervention. Models based on pressure-volume relationship and zero-dimensional representation of the cardiovascular system may be a suitable choice given their simplicity and versatility. This approach has great potential for application in heart failure where the impact of left ventricular assist devices has played a significant role as a bridge to transplant and more recently as a long-term solution for non eligible candidates.

RESULTS

We sought to investigate the value of simulation in the context of three heart failure patients with a view to predict or guide further management. CARDIOSIM^© was the software used for this purpose. The study was based on retrospective analysis of haemodynamic data previously discussed at a multidisciplinary meeting. The outcome of the simulations addressed the value of a more quantitative approach in the clinical decision process.

CONCLUSIONS

Although previous experience, co-morbidities and the risk of potentially fatal complications play a role in clinical decision-making, patient-specific modelling may become a daily approach for selection and optimisation of device-based treatment for heart failure patients. Willingness to adopt this integrated approach may be the key to further progress.

Simulation as a preoperative planning approach in advanced heart failure patients. A retrospective clinical analysis

BACKGROUND

Modelling and simulation may become clinically applicable tools for detailed evaluation of the cardiovascular system and clinical decision-making to guide therapeutic intervention. Models based on pressure-volume relationship and zero-dimensional representation of the cardiovascular system may be a suitable choice given their simplicity and versatility. This approach has great potential for application in heart failure where the impact of left ventricular assist devices has played a significant role as a bridge to transplant and more recently as a long-term solution for non eligible candidates.

RESULTS

We sought to investigate the value of simulation in the context of three heart failure patients with a view to predict or guide further management. CARDIOSIM© was the software used for this purpose. The study was based on retrospective analysis of haemodynamic data previously discussed at a multidisciplinary meeting. The outcome of the simulations addressed the value of a more quantitative approach in the clinical decision process.

CONCLUSIONS

Although previous experience, co-morbidities and the risk of potentially fatal complications play a role in clinical decision-making, patient-specific modelling may become a daily approach for selection and optimisation of device-based treatment for heart failure patients. Willingness to adopt this integrated approach may be the key to further progress.

Characterizing left ventricular mechanical and electrical activation in patients with normal and impaired systolic function using a non-fluoroscopic cardiovascular navigation system

PURPOSE

Cardiac disease frequently has a degenerative effect on cardiac pump function and regional myocardial contraction. Therefore, an accurate assessment of regional wall motion is a measure of the extent and severity of the disease. We sought to further validate an intra-operative, sensor-based technology for measuring wall motion and strain by characterizing left ventricular (LV) mechanical and electrical activation patterns in patients with normal (NSF) and impaired systolic function (ISF).

METHODS

NSF (n = 10; ejection fraction = 62.9 ± 6.1%) and ISF (n = 18; ejection fraction = 35.1 ± 13.6%) patients underwent simultaneous electrical and motion mapping of the LV endocardium using electroanatomical mapping and navigational systems (EnSite™ NavX™ and MediGuide™, Abbott). Motion trajectories, strain profiles, and activation times were calculated over the six standard LV walls.

RESULTS

NSF patients had significantly greater motion and systolic strains across all LV walls than ISF patients. LV walls with low-voltage areas showed less motion and systolic strain than walls with normal voltage. LV electrical dyssynchrony was significantly smaller in NSF and ISF patients with narrow-QRS complexes than ISF patients with wide-QRS complexes, but mechanical dyssynchrony was larger in all ISF patients than NSF patients. The latest mechanical activation was most often the lateral/posterior walls in NSF and wide-QRS ISF patients but varied in narrow-QRS ISF patients.

CONCLUSIONS

This intra-operative technique can be used to characterize LV wall motion and strain in patients with impaired systolic function. This technique may be utilized clinically to provide individually tailored LV lead positioning at the region of latest mechanical activation for patients undergoing cardiac resynchronization therapy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01629160.

Left ventricular diastolic and systolic dyssynchrony and dysfunction in heart failure with preserved ejection fraction and a narrow QRS complex

Aims: Mechanical dyssynchrony has been reported in heart failure with preserved ejection fraction (HFpEF), with a majority of patients having a narrow QRS complex; however, whether any benefit is observed with restoration of dyssynchrony remains unclear. We sought to assess left ventricular (LV) dyssynchrony and function in HFpEF and elucidate the underlying mechanisms that may account for HFpEF. Methods: Seventy-eighty patients with a narrow QRS complex including 47 with HFpEF, 31 with heart failure with reduced ejection fraction (HFrEF) patients, and 29 with asymptomatic left ventricular diastolic dysfunction (LVDD) were recruited. Forty-five normal subjects acted as controls. Systolic LV longitudinal strain (LS), systolic longitudinal strain rate (LSrS), early diastolic longitudinal strain rate (LSrE), and late diastolic longitudinal strain rate (LSrA) were measured using speckle tracking echocardiography. LV diastolic and systolic dyssynchrony (Te-SD and Ts-SD) were calculated. Results: Te-SD and Ts-SD were prolonged in HFpEF and HFrEF patients than in the control group (p<0.05). However, Ts-SD was shorter in HFpEF patients compared to HFrEF patients despite a narrow QRS complex (p<0.05). LV global LS, LSrS, and LSrE were decreased in patients with HFpEF and HFrEF compared to other groups, with HFrEF being even more reduced than HFpEF (p<0.05). Reduced LS, LSrS, and LSrE could effectively differentiate HF from asymptomatic LVDD patients (p<0.05). Conclusion: HFrEF exhibited increased systolic dyssynchrony compared to HFpEF despite a narrow QRS complex in addition to the more reduced diastolic and systolic function. Therefore, targeting to improve diastolic and systolic function instead of managing systolic dyssynchrony might be of great importance in the treatment of HFpEF.

Ventricular dyssynchrony assessment using ultra-high frequency ECG technique

Purpose

The aim of this proof-of-concept study is to introduce new high-dynamic ECG technique with potential to detect temporal-spatial distribution of ventricular electrical depolarization and to assess the level of ventricular dyssynchrony.

Methods

5-kHz 12-lead ECG data was collected. The amplitude envelopes of the QRS were computed in an ultra-high frequency band of 500–1000 Hz and were averaged (UHFQRS). UHFQRS V lead maps were compiled, and numerical descriptor identifying ventricular dyssynchrony (UHFDYS) was detected.

Results

An electrical UHFQRS maps describe the ventricular dyssynchrony distribution in resolution of milliseconds and correlate with strain rate results obtained by speckle tracking echocardiography. The effect of biventricular stimulation is demonstrated by the UHFQRS morphology and by the UHFDYS descriptor in selected examples.

Conclusions

UHFQRS offers a new and simple technique for assessing electrical activation patterns in ventricular dyssynchrony with a temporal-spatial resolution that cannot be obtained by processing standard surface ECG. The main clinical potential of UHFQRS lies in the identification of differences in electrical activation among CRT candidates and detection of improvements in electrical synchrony in patients with biventricular pacing.

Electronic supplementary material

The online version of this article (doi:10.1007/s10840-017-0268-0) contains supplementary material, which is available to authorized users.

Identification of Typical Left Bundle Branch Block Contraction by Strain Echocardiography Is Additive to Electrocardiography in Prediction of Long-Term Outcome After Cardiac Resynchronization Therapy

BACKGROUND

Current guidelines suggest that patients with left bundle branch block (LBBB) be treated with cardiac resynchronization therapy (CRT); however, one-third do not have a significant activation delay, which can result in nonresponse. By identifying characteristic opposing wall contraction, 2-dimensional strain echocardiography (2DSE) may detect true LBBB activation.

OBJECTIVES

This study sought to investigate whether the absence of a typical LBBB mechanical activation pattern by 2DSE was associated with unfavorable long-term outcome and if this is additive to electrocardiographic (ECG) morphology and duration.

METHODS

From 2 centers, 208 CRT candidates (New York Heart Association classes II to IV, ejection fraction ≤35%, QRS duration ≥120 ms) with LBBB by ECG were prospectively included. Before CRT implantation, longitudinal strain in the apical 4-chamber view determined whether typical LBBB contraction was present. The pre-defined outcome was freedom from death, left ventricular assist device, or heart transplantation over 4 years.

RESULTS

Two-thirds of patients (63%) had a typical LBBB contraction pattern. During 4 years, 48 patients (23%) reached the primary endpoint. Absence of a typical LBBB contraction was independently associated with increased risk of adverse outcome after adjustment for ischemic heart disease and QRS width (hazard ratio [HR]: 3.1; 95% CI: 1.64 to 5.88; p < 0.005). Adding pattern assessment to a risk prediction model including QRS duration and ischemic heart disease significantly improved the net reclassification index to 0.14 (p = 0.04) and improved the C-statistics (0.63 [95% CI: 0.54 to 0.72] vs. 0.71 [95% CI: 0.63 to 0.80]; p = 0.02). Use of strict LBBB ECG criteria was not independently associated with outcome in the multivariate model (HR: 1.72; 95% CI: 0.89 to 3.33; p = 0.11. Assessment of LBBB contraction pattern was superior to time-to-peak indexes of dyssynchrony (p < 0.01 for all).

CONCLUSIONS

Contraction pattern assessment to identify true LBBB activation provided important prognostic information in CRT candidates.

Newer Echocardiographic Techniques in Cardiac Resynchronization Therapy

Echocardiographic imaging plays a major role in patient selection for cardiac resynchronization therapy (CRT). One-third of patients do not respond; there is interest in advanced echocardiographic imaging to improve response. Current guidelines favor CRT for patients with electrocardiographic (ECG) QRS width of 150 milliseconds or greater and left bundle branch block. ECG criteria are imperfect; there is interest in advanced echocardiographic imaging to improve patient selection. This discussion focuses on newer echocardiographic methods to improve patient selection, improve delivery, and identify patients at risk for poor outcomes and serious ventricular arrhythmias.

Clinical utility of speckle-tracking echocardiography in cardiac resynchronisation therapy

Cardiac resynchronisation therapy (CRT) can profoundly improve outcome in selected patients with heart failure; however, response is difficult to predict and can be absent in up to one in three patients. There has been a substantial amount of interest in the echocardiographic assessment of left ventricular dyssynchrony, with the ultimate aim of reliably identifying patients who will respond to CRT. The measurement of myocardial deformation (strain) has conventionally been assessed using tissue Doppler imaging (TDI), which is limited by its angle dependence and ability to measure in a single plane. Two-dimensional speckle-tracking echocardiography is a technique that provides measurements of strain in three planes, by tracking patterns of ultrasound interference ('speckles') in the myocardial wall throughout the cardiac cycle. Since its initial use over 15 years ago, it has emerged as a tool that provides more robust, reproducible and sensitive markers of dyssynchrony than TDI. This article reviews the use of two-dimensional and three-dimensional speckle-tracking echocardiography in the assessment of dyssynchrony, including the identification of echocardiographic parameters that may hold predictive potential for the response to CRT. It also reviews the application of these techniques in guiding optimal LV lead placement pre-implant, with promising results in clinical improvement post-CRT.

Cardiac Resynchronization Therapy in Non-Ischemic Cardiomyopathy

Cardiac resynchronization therapy (CRT) is an established therapy for heart failure patients who remain symptomatic despite optimal medical therapy, have reduced left ventricular ejection fraction (<35%) and wide QRS duration (>120 ms), preferably with left bundle branch block morphology. The response to CRT depends on the cardiac substrate: presence of correctable left ventricular mechanical dyssynchrony, presence of myocardial fibrosis (scar) and position of the left ventricular pacing lead. Patients with non-ischemic cardiomyopathy have shown higher response rates to CRT compared with patients with ischemic cardiomyopathy. Differences in myocardial substrate may partly explain this disparity. Multimodality imaging plays an important role to assess the cardiac substrate and the pathophysiological determinants of response to CRT.

Septal flash and septal rebound stretch have different underlying mechanisms

Abnormal left-right motion of the interventricular septum in early systole, known as septal flash (SF), is frequently observed in patients with left bundle branch block (LBBB). Transseptal pressure gradient and early active septal contraction have been proposed as explanations for SF. Similarities in timing (early systole) and location (septum) suggest that SF may be related to septal systolic rebound stretch (SRSsept). We aimed to clarify the mechanisms generating SF and SRSsept. The CircAdapt computer model was used to isolate the effects of timing of activation of the left ventricular free wall (LVFW), right ventricular free wall (RVFW), and septum on SF and SRSsept. LVFW and septal activation times were varied by ±80 ms relative to RVFW activation time. M-mode-derived wall motions and septal strains were computed and used to quantify SF and SRSsept, respectively. SF depended on early activation of the RVFW relative to the LVFW. SF and SRSsept occurred in LBBB-like simulations and against a rising transseptal pressure gradient. When the septum was activated before both LVFW and RVFW, no SF occurred despite the presence of SRSsept. Computer simulations therefore indicate that SF and SRSsept have different underlying mechanisms, even though both can occur in LBBB. The mechanism of leftward motion during SF is early RVFW contraction pulling on and straightening the septum when unopposed by the LVFW. SRSsept is caused by late LVFW contraction following early contraction of the septum. Changes in transseptal pressure gradient are not the main cause of SF in LBBB.

Can we hear ventricle dyssynchrony? Yes, we can

This study introduces a method for detection of ventricular depolarization activity and the transfer of this activity into an audible stereo audio signal. Heart potentials are measured by an ultra-high-frequency high-dynamic-range electrocardiograph (UHF-ECG) with a 25-kHz sampling rate. Averaged and prolonged UHF amplitude envelopes of V1-3 and V4-6 leads at a frequency range of 500-1000 Hz are used as a modulating function for two carrier audio frequencies. The right speaker makes it possible to listen to the depolarization of the septum and right ventricle (V1-3) and the left speaker the left ventricle lateral wall (V4-6). In the healthy heart, both speakers can be heard simultaneously. A delayed L or R speaker represents the dyssynchronous electrical activation of the ventricles. Examples of the normal heart, right bundle branch block and left bundle branch block can be heard at www.medisig.com/uhfecg.

Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging

The rapid technological developments of the past decade and the changes in echocardiographic practice brought about by these developments have resulted in the need for updated recommendations to the previously published guidelines for cardiac chamber quantification, which was the goal of the joint writing group assembled by the American Society of Echocardiography and the European Association of Cardiovascular Imaging. This document provides updated normal values for all four cardiac chambers, including three-dimensional echocardiography and myocardial deformation, when possible, on the basis of considerably larger numbers of normal subjects, compiled from multiple databases. In addition, this document attempts to eliminate several minor discrepancies that existed between previously published guidelines.

Newer Echocardiographic Techniques in Cardiac Resynchronization Therapy

Echocardiographic imaging plays a major role in patient selection for cardiac resynchronization therapy (CRT). One-third of patients do not respond; there is interest in advanced echocardiographic imaging to improve response. Current guidelines favor CRT for patients with electrocardiographic (ECG) QRS width of 150 milliseconds or greater and left bundle branch block. ECG criteria are imperfect; there is interest in advanced echocardiographic imaging to improve patient selection. This discussion focuses on newer echocardiographic methods to improve patient selection, improve delivery, and identify patients at risk for poor outcomes and serious ventricular arrhythmias.

Differentiating Electromechanical From Non-Electrical Substrates of Mechanical Discoordination to Identify Responders to Cardiac Resynchronization Therapy

BACKGROUND

Left ventricular (LV) mechanical discoordination, often referred to as dyssynchrony, is often observed in patients with heart failure regardless of QRS duration. We hypothesized that different myocardial substrates for LV mechanical discoordination exist from (1) electromechanical activation delay, (2) regional differences in contractility, or (3) regional scar and that we could differentiate electromechanical substrates responsive to cardiac resynchronization therapy (CRT) from unresponsive non-electrical substrates.

METHODS AND RESULTS

First, we used computer simulations to characterize mechanical discoordination patterns arising from electromechanical and non-electrical substrates and accordingly devise the novel systolic stretch index (SSI), as the sum of posterolateral systolic prestretch and septal systolic rebound stretch. Second, 191 patients with heart failure (QRS duration ≥120 ms; LV ejection fraction ≤35%) had baseline SSI quantified by automated echocardiographic radial strain analysis. Patients with SSI≥9.7% had significantly less heart failure hospitalizations or deaths 2 years after CRT (hazard ratio, 0.32; 95% confidence interval, 0.19-0.53; P<0.001) and less deaths, transplants, or LV assist devices (hazard ratio, 0.28; 95% confidence interval, 0.15-0.55; P<0.001). Furthermore, in a subgroup of 113 patients with intermediate electrocardiographic criteria (QRS duration of 120-149 ms or non-left bundle branch block), SSI≥9.7% was independently associated with significantly less heart failure hospitalizations or deaths (hazard ratio, 0.41; 95% confidence interval, 0.23-0.79; P=0.004) and less deaths, transplants, or LV assist devices (hazard ratio, 0.27; 95% confidence interval, 0.12-0.60; P=0.001).

CONCLUSIONS

Computer simulations differentiated patterns of LV mechanical discoordination caused by electromechanical substrates responsive to CRT from those related to regional hypocontractility or scar unresponsive to CRT. The novel SSI identified patients who benefited more favorably from CRT, including those with intermediate electrocardiographic criteria, where CRT response is less certain by ECG alone.

Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging

The rapid technological developments of the past decade and the changes in echocardiographic practice brought about by these developments have resulted in the need for updated recommendations to the previously published guidelines for cardiac chamber quantification, which was the goal of the joint writing group assembled by the American Society of Echocardiography and the European Association of Cardiovascular Imaging. This document provides updated normal values for all four cardiac chambers, including three-dimensional echocardiography and myocardial deformation, when possible, on the basis of considerably larger numbers of normal subjects, compiled from multiple databases. In addition, this document attempts to eliminate several minor discrepancies that existed between previously published guidelines.

Fast Simulation of Mechanical Heterogeneity in the Electrically Asynchronous Heart Using the MultiPatch Module

Cardiac electrical asynchrony occurs as a result of cardiac pacing or conduction disorders such as left bundle-branch block (LBBB). Electrically asynchronous activation causes myocardial contraction heterogeneity that can be detrimental for cardiac function. Computational models provide a tool for understanding pathological consequences of dyssynchronous contraction. Simulations of mechanical dyssynchrony within the heart are typically performed using the finite element method, whose computational intensity may present an obstacle to clinical deployment of patient-specific models. We present an alternative based on the CircAdapt lumped-parameter model of the heart and circulatory system, called the MultiPatch module. Cardiac walls are subdivided into an arbitrary number of patches of homogeneous tissue. Tissue properties and activation time can differ between patches. All patches within a wall share a common wall tension and curvature. Consequently, spatial location within the wall is not required to calculate deformation in a patch. We test the hypothesis that activation time is more important than tissue location for determining mechanical deformation in asynchronous hearts. We perform simulations representing an experimental study of myocardial deformation induced by ventricular pacing, and a patient with LBBB and heart failure using endocardial recordings of electrical activation, wall volumes, and end-diastolic volumes. Direct comparison between simulated and experimental strain patterns shows both qualitative and quantitative agreement between model fibre strain and experimental circumferential strain in terms of shortening and rebound stretch during ejection. Local myofibre strain in the patient simulation shows qualitative agreement with circumferential strain patterns observed in the patient using tagged MRI. We conclude that the MultiPatch module produces realistic regional deformation patterns in the asynchronous heart and that activation time is more important than tissue location within a wall for determining myocardial deformation. The CircAdapt model is therefore capable of fast and realistic simulations of dyssynchronous myocardial deformation embedded within the closed-loop cardiovascular system.

Under normal conditions, the electrical activation of the heart is almost synchronous, leading to uniform contraction. Due to either pathology or electrical pacing, the heart can be activated asynchronously. The result is discoordinated contraction and a reduction in the ability to pump blood. There is considerable interest in using computer simulations to understand how asynchronous electrical activation affects cardiac deformation, and how pathologies of the cardiac conduction system can be treated by pacing the heart. We present the MultiPatch module for simulating the effects of asynchronous electrical activation on cardiac contraction in the relatively simple CircAdapt model of the heart and circulation. We quantitatively compare model simulations to deformation patterns recorded during an experimental study of pacing-induced electrical asynchrony. We then demonstrate a ‘patient-specific’ simulation of deformation in a patient with a conduction disorder called left bundle-branch block. We use timings from endocardial mapping of electrical activation in a patient as an input for the model, and compare the resulting simulated deformation patterns to tagged magnetic resonance imaging recordings from the same patient. The model qualitatively reproduces deformation as observed in the patient. We conclude that the MultiPatch module makes CircAdapt appropriate for simulation of dyssynchronous heart failure in patients.

Computer Modelling for Better Diagnosis and Therapy of Patients by Cardiac Resynchronisation Therapy

Mathematical or computer models have become increasingly popular in biomedical science. Although they are a simplification of reality, computer models are able to link a multitude of processes to each other. In the fields of cardiac physiology and cardiology, models can be used to describe the combined activity of all ion channels (electrical models) or contraction-related processes (mechanical models) in potentially millions of cardiac cells. Electromechanical models go one step further by coupling electrical and mechanical processes and incorporating mechano-electrical feedback. The field of cardiac computer modelling is making rapid progress due to advances in research and the ever-increasing calculation power of computers. Computer models have helped to provide better understanding of disease mechanisms and treatment. The ultimate goal will be to create patient-specific models using diagnostic measurements from the individual patient. This paper gives a brief overview of computer models in the field of cardiology and mentions some scientific achievements and clinical applications, especially in relation to cardiac resynchronisation therapy (CRT).

Volumetric Response beyond Six Months of Cardiac Resynchronization Therapy and Clinical Outcome

Aims

Response to cardiac resynchronization therapy (CRT) is often assessed six months after implantation. Our objective was to assess the number of patients changing from responder to non-responder between six and 14 months, so-called late non-responders, and compare them to patients who were responder both at six and 14 months, so-called stable responders. Furthermore, we assessed predictive values of six and 14-month response concerning clinical outcome.

Methods

105 patients eligible for CRT were enrolled. Clinical, laboratory, ECG, and echocardiographic parameters and patient-reported health status (Kansas City Cardiomyopathy Questionnaire [KCCQ]) were assessed before, and six and 14 months after implantation. Response was defined as ≥15% LVESV decrease as compared to baseline. Major adverse cardiac events (MACE) were registered until 24 months after implantation. Predictive values of six and 14-month response for MACE were examined.

Results

In total, 75 (71%) patients were six-month responders of which 12 (16%) patients became late non-responder. At baseline, late non-responders more often had ischemic cardiomyopathy and atrial fibrillation, higher BNP and less dyssynchrony compared to stable responders. At six months, late non-responders showed significantly less LVESV decrease, and higher creatinine levels. Mean KCCQ scores of late non-responders were lower than those of stable responders at every time point, with the difference being significant at 14 months. The 14 months response was a better predictor of MACE than six months response.

Conclusions

The assessment of treatment outcomes after six months of CRT could be premature and response rates beyond might better correlate to long-term clinical outcome.