Contractile asymmetry and survival in patients with left bundle branch abnormality treated with cardiac
Nareen Kader1, Liv Therese Holm-Nielsen1, Bhupendar Tayal1
1Department of Cardiology, Aalborg University Hospital, Hobrovej 18-22, 9100 Aalborg, Denmark.
Insights
A new measure of heart wall movement, the index of contractile asymmetry (ICA), can predict survival in heart failure patients receiving cardiac resynchronization therapy (CRT). Higher ICA values indicate better long-term outcomes and survival post-CRT.
Area of Science:
- Cardiology
- Biomedical Engineering
- Echocardiography
Background:
- Current cardiac resynchronization therapy (CRT) patient selection relies on electrical, not mechanical, parameters.
- Approximately one-third of heart failure (HF) patients do not benefit from CRT despite guideline adherence.
- Delayed left ventricular (LV) activation is a key criterion, but its predictive power for CRT response is limited.
Purpose of the Study:
- To evaluate the prognostic survival significance of the index of contractile asymmetry (ICA) in HF patients with left bundle branch block (LBBB) undergoing CRT.
- To determine if ICA can improve patient selection for CRT compared to current electrical criteria.
- To investigate ICA as a novel mechanical parameter for predicting long-term outcomes after CRT.
Main Methods:
- Analysis of 367 HF patients with LBBB undergoing CRT.
- Calculation of ICA using LV strain rate values from apical 2D echocardiography.
- Assessment of ICA's predictive value using Kaplan-Meier analysis and Cox proportional hazards models.
- Evaluation of ICA in predicting survival across clinical subgroups and its impact on risk models.
Main Results:
- Higher baseline ICA values, especially ICA-2ch, were associated with increased event-free survival.
- Unadjusted hazard ratio for ICA was 0.28 (95% CI 0.18-0.46), indicating reduced risk of adverse events.
- Higher ICA-2ch (>0.319 s⁻¹) consistently predicted survival after covariate adjustment.
- Low ICA-2ch values were linked to a sharp increase in adverse event rates.
- Incorporating ICA-2ch improved the predictive accuracy of multivariate risk models for LBBB patients.
Conclusions:
- Pre-implantation ICA provides a quantitative prognostic threshold for long-term survival and adverse outcomes in CRT recipients.
- ICA represents a promising mechanical biomarker for optimizing CRT patient selection.
- This study highlights the importance of mechanical dyssynchrony assessment in predicting CRT response.
Aims:
Currently, electrical rather than mechanical parameters of delayed left ventricular (LV) activation are used for patient selection for cardiac resynchronization therapy (CRT). However, despite adhering to current guideline-based criteria, about one-third of heart failure (HF) patients fail to derive benefit from CRT. This study sought to investigate the prognostic survival significance of a recently introduced index of contractile asymmetry (ICA) based on the deformation of entire opposing LV walls in the context of selecting patients with HF and left bundle branch abnormality (LBBB) for CRT.
Methods And Results:
We analysed 367 patients with HF and LBBB undergoing CRT (31.6% females, 69 ± 9 years, ischaemic aetiology in 50.7%, LV ejection fraction 27 ± 6%). ICA was calculated using LV strain rate values from curved anatomical M-mode plots of apical 2D echocardiography images. The predictive value of ICA was assessed using Kaplan-Meier analysis and Cox proportional hazards models. During a median follow-up time of 5.54 years, death or cardiac transplantation occurred in 105 (28.6%) cases. Higher baseline ICA values in all apical views, particularly in the two-chamber view (ICA-2ch), were associated with increased event-free survival, and the unadjusted hazard ratio was 0.28 (95% confidence interval 0.18-0.46). Higher ICA-2ch (>0.319 s-1) consistently predicted survival across clinical subgroups and remained significant after covariate adjustment, while the event rate sharply increased in low ICA-2ch cases. Additionally, including ICA-2ch improved the predictive value of the multivariate risk model containing the typical LBBB pattern.
Conclusion:
Pre-implant ICA suggests a quantitative prognostic threshold for both long-term survival and adverse outcomes following CRT implantation.
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