Left atrioventricular coupling index in patients undergoing cardiac resynchronization therapy.

The left atrioventricular coupling index (LACI), defined as the ratio of left atrial (LA) to left ventricular (LV) end-diastolic volumes, serves as a surrogate for atrioventricular coupling. Cardiac resynchronization therapy (CRT) promotes reverse remodeling of both chambers and may enhance atrioventricular coupling, yet the clinical utility of LACI in CRT patients remains unclear. This study evaluated the effect of CRT on LACI and assessed its prognostic value for CRT response. In 123 patients enrolled in the ADVISE-CRT III trial (mean age 66 ± 10 years; 63% male; and 81% with a Class I CRT indication), LACI was measured by echocardiography before and six months after CRT implantation. Multivariable linear and logistic regression analyses were performed to assess the association between LACI and CRT response (≥ 15% LV end-systolic volume reduction), adjusting for potential confounders. Low baseline LACI was independently associated with an 11.2% greater LV end-systolic volume reduction (Quartile 1–2 vs. Quartile 3–4; p = 0.009) and 3.6-fold higher odds of CRT response (p = 0.041). At six months, LACI increased significantly in responders (16.5% to 20.7%; p < 0.001), driven by greater LV versus LA end-diastolic volume reduction. In non-responders, LACI remained stable (20.9% to 20.3%; p = 0.077). LACI was independently associated with CRT response and provided incremental value over individual LA and LV volumetric parameters. While LACI may reflect favorable structural substrate and atrioventricular coupling at baseline, it is not suitable for post-CRT assessment of atrioventricular coupling, as disproportionate LV versus LA remodeling may conceal coupling improvements.