R-wave amplitude changes in lead aVL predict outcomes in cardiac resynchronization therapy: Exploring the role of papillary muscle dyssynchrony and mitral regurgitation

Background: Reduction in R-wave amplitude in lead aVL (RaVL) is often noted after cardiac resynchronization therapy (CRT), together with a shorter QRS duration and reduced mitral regurgitation (MR). Given that lead aVL reflects electrical activity in the anterolateral left ventricular wall, where the anterolateral papillary muscle (PM) resides, opposing the posteromedial one, we hypothesized that these electrocardiographic changes may reflect improved electrical resynchronization of the PMs, contributing to MR reduction. Objective: This study aimed to evaluate the relationship between post-CRT changes in RaVL and MR severity and assess whether RaVL can serve as a surface electrocardiographic marker of PM dyssynchrony and a predictor of clinical response and long-term survival. Methods: We analyzed 231 patients who underwent CRT implantation and were followed for a median of 41 months (interquartile range 29–55); 88 patients died during this period. Results: Baseline RaVL correlated with QRS duration (r = 0.20, P = .0018) and aVL–aVF intrinsicoid deflection difference (r = 0.36, P < .0001), supporting its role as a marker of electrical dyssynchrony. RaVL significantly decreased after CRT (0.66 ± 0.42 mV to 0.41 ± 0.41 mV, P < .0001) and independently predicted MR response in multivariable logistic regression. Patients who experienced a reduction in RaVL or a decrease in QRS duration after CRT had significantly better survival than those whose corresponding parameters remained unchanged or increased. Both variables independently predicted survival in multivariable Cox regression. Conclusion: A decrease in RaVL after CRT predicts MR improvement and survival, likely reflecting improved PM synchronization and mechanical resynchronization.