Index of contractile asymmetry improves patient selection for CRT: a proof-of-concept study
Tomas Zaremba1, Bhupendar Tayal2, Sam Riahi2,3
1Department of Cardiology, Aalborg University Hospital, Hobrovej 18-22, 9100, Aalborg, Denmark. tz@rn.dk.
Insights
A new method, the Index of Contractile Asymmetry (ICA), can predict heart failure (HF) patients with left bundle branch block (LBBB) who will benefit from cardiac resynchronization therapy (CRT). Higher baseline ICA indicates better CRT response.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Imaging
Background:
- Cardiac resynchronization therapy (CRT) is ineffective for nearly one-third of heart failure (HF) patients with left bundle branch block (LBBB).
- Accurate patient selection is crucial for optimizing CRT outcomes.
- Existing methods may not fully capture the complex mechanical dyssynchrony in LBBB.
Purpose of the Study:
- To introduce and validate a novel method for quantifying left ventricular (LV) contractile asymmetry in HF patients with LBBB.
- To assess the predictive value of this novel method for CRT response.
Main Methods:
- Analysis of 89 HF patients with LBBB undergoing CRT.
- Calculation of the Index of Contractile Asymmetry (ICA) using 3D echocardiography and strain rate analysis.
- Correlation of baseline ICA and ICA changes with LV end-systolic volume (ESV) reduction post-CRT.
Main Results:
- 74.2% of patients responded to CRT.
- Higher baseline ICA and greater ICA reduction after CRT were observed in responders compared to non-responders.
- Baseline ICA and its reduction correlated with the degree of ESV reduction, indicating improved LV function.
Conclusions:
- The Index of Contractile Asymmetry (ICA) offers valuable insights into LV contraction patterns in LBBB.
- ICA is a promising tool for improving patient selection for CRT.
- This quantitative method may enhance CRT efficacy by identifying suitable candidates.
Background:
Nearly one-third of heart failure (HF) patients do not respond to cardiac resynchronization therapy (CRT) despite having left bundle branch block (LBBB). The aim of the study was to investigate a novel method of quantifying left ventricular (LV) contractile asymmetry in HF.
Methods:
Patients with HF and LBBB undergoing CRT (n = 89, 37.1% females, 68 ± 9 years, ischemic etiology in 61%, LV ejection fraction 27.1 ± 7.1%) were analyzed. LV longitudinal systolic strain rate values were extracted from curved anatomical M-mode plots of standard long-axis 2D-echocardiography images and cubic spline interpolation was used to generate a 3D-phantom. Index of contractile asymmetry (ICA) was calculated based on standard deviation of differences in strain rate of opposing walls. Average ICA was individually assessed pairwise in 12 opposing 30-degree LV sectors. Reduction in LV end-systolic volume (ESV) ≥15% after 6 months was considered as positive response to CRT.
Results:
CRT response was found in 66 (74.2%) patients. Responders with both ischemic and non-ischemic cardiomyopathy had a higher and more extensive contractile asymmetry at baseline and achieved a greater ICA reduction after CRT than non-responders. Higher baseline ICA predicted higher degree and wider extent of ICA improvement. Also, both ICA at baseline and reduction of ICA correlated with the degree of ESV reduction after CRT.
Conclusions:
Quantification of asymmetrical LV activation in 3D by ICA provides valuable insights into LV contraction in case of LBBB and is a promising tool for improved patient selection for CRT.
