Left atrioventricular coupling index in cardiac resynchronization therapy responders and non-responders

Abstract Background The left atrioventricular coupling index (LACI) is a novel imaging metric, providing insight into the relationship between the left atrium (LA) and left ventricle (LV). LACI has been shown to be an independent predictor of atrial fibrillation, heart failure, cardiovascular-related hospitalization, and mortality in different patient populations. It is also strongly correlated with diastolic function. Cardiac resynchronization therapy (CRT) promotes remodeling of both the LA and LV, along with the restoration of atrioventricular coupling, thereby improving diastolic function. However, no research has yet been conducted on comparing LACI in CRT responders and non-responders. Aim To assess LACI in CRT patients, with stratification for responders and non-responders. Methods A total of 127 heart failure patients scheduled for CRT implantation were included. LA and LV volumes were assessed by transthoracic echocardiography at baseline and six months post-implantation. LACI was calculated as the ratio of LA to LV end-diastolic volumes. Changes in LACI after six months of follow-up, in addition to between-group differences in responders and non-responders were tested for significance. CRT response was defined as ≥ 15% reduction in LV end-systolic volume six months post-implantation. Results LACI at baseline was 16.96% [12.94 to 23.52] for responders and 21.87% [17.86 to 42.93] for non-responders, with a significant difference between the groups (p=0.009). After six months, LACI remained consistent in non-responders (21.85% [10.83 to 29.57]), whereas it showed an increase in responders, resulting in comparable values between both groups (21.28% [16.12 to 28.19]; p=0.70). This increase in LACI was driven by a substantial decrease in LV end-diastolic volume (99.78 [80.65 to 125.98] to 65.15 [50.49 to 77.18] mL/m2; p<0.001) in responders, outweighing the reduction in LA end-diastolic volume (18.62 [11.11 to 25.04] to 14.45 [9.92 to 19.52] mL/ m2; p<0.001). In contrast, no significant differences in end-diastolic LA or LV volume were observed in non-responders after six months (p>0.05). Responders also demonstrated a more pronounced percentage change in end-diastolic LV volume compared with non-responders (-36.27% [-46.29 to -25.50] vs +2.90% [-2.66 to 11.33]; p<0.001), while the percentage change in LA end-diastolic volume did not differ between the groups (p>0.05). Conclusion CRT responders show a worsening in LACI six months after CRT implantation, whereas non-responders remain stable. The increase in LACI among responders is driven by a substantial decrease in LV end-diastolic volume, outweighing the reduction in LA end-diastolic volume. This increase contradicts the expected improvement in atrioventricular coupling as a result of CRT response. Therefore, LACI may not be a reliable parameter for assessing atrioventricular coupling in CRT responders.Responders  Non-responders