Index of contractile asymmetry and risk of arrhythmia after cardiac resynchronization therapy
S Toft Sten, C Stephansen, A M Sommer, M B Kronborg, N Risum, J C Nielsen, K H Kragholm, T Zaremba, P SoegaardAbstract
Background
Index of contractile asymmetry (ICA) is a new approach for evaluating the mechanical function of the left ventricle (LV). In patients with heart failure (HF) and left bundle branch block (LBBB), ICA has demonstrated promising potential as a predictor of both functional improvement and long-term survival after cardiac resynchronization therapy (CRT). Notably, higher ICA levels have been associated with greater response to CRT. Despite CRT being a well-established treatment for HF, recipients remain at risk of atrial fibrillation or flutter (AF) and ventricular arrhythmias (VA). The development of AF and VA after CRT is associated with a poorer prognosis.
Purpose
This study sought to investigate the association between pre-implantation systolic ICA, reverse LV remodeling, and the risk of new-onset AF and VA following CRT.
Method
The study analyzed 367 patients with HF and LBBB who received CRT. At baseline, the mean LV ejection fraction was 26.7%, with 186 patients (50.7%) having an ischemic etiology. LV strain rate values obtained from curved anatomical M-mode plots were used to calculate ICA in standard apical views, with the operator unaware of outcome events. ICA represents the standard deviation of the differences in strain rate values between the opposing LV walls. Baseline ICA was dichotomized based on a receiver operating characteristic analysis. The association between ICA and new-onset AF and VA over five years after CRT was evaluated using pseudo-observation, modified Poisson regression with robust standard errors, and cumulative incidence plots. Death and heart transplant were considered as competing risks in the analysis. No patients were lost to follow-up.
Results
Over five years, 48 patients (13.1%) developed AF after CRT, while 26 patients (7.1%) experienced VA. The median follow-up time was 4.35 years (IQR 2.84-6.27). Multivariate analysis showed a significant association between high pre-implantation ICA in standard apical views and a lower risk of any arrhythmia. The relative risk (RR) of developing arrhythmia was 0.44 (95% CI 0.55-0.95) for ICA ≥ 0.71 s-1 in the three-chamber view, and 0.52 (95% CI 0.41-0.65) for ICA ≥ 0.72 s-1 in the four-chamber view. A significant association was found between high ICA ≥ 0.72 s-1 in the four-chamber view and new-onset AF, with a RR of 0.48 (95% CI 0.36-0.65). Furthermore, high baseline ICA ≥ 0.71 s-1 in the three-chamber view was associated with a lower risk of both new-onset AF and VA, with RRs of 0.46 (95% CI 0.33-0.63) and 0.59 (95% CI 0.37-0.95), respectively. Additionally, a reduction in LVESV greater than 15% post-CRT was significantly associated with a lower risk of arrhythmia, with a RR of 0.6 (95% CI 0.46-0.78).
Conclusion
Among patients with HF and LBBB undergoing CRT, a high pre-implantation ICA was associated with reverse LV remodeling and a lower long-term risk of both new-onset AF and VA.Figure - Abstract