Prognostic Implications of Left Atrial Enlargement in Degenerative Mitral Regurgitation

Background: Left atrial enlargement is frequent in degenerative mitral regurgitation (DMR), but its link to outcomes remains unproven in routine clinical practice.

Objectives: The purpose of this study was to assess whether left atrial volume index (LAVI) measured in routine clinical practice of multiple sonographers/cardiologists is associated independently with DMR survival.

Methods: A cohort of 5,769 (63 ± 16 years, 47% women) consecutive patients with degenerative mitral valve disease, in whom LAVI was prospectively measured, was enrolled and the long-term survival was analyzed.

Results: LAVI (43 ± 24 ml/m²) was widely distributed (<40 ml/m² in 3,154 patients, 40 to 59 ml/m² in 1,606, and ≥60 ml/m² in 1,009). Overall survival throughout follow-up (10-year 66 ± 1%) was strongly associated with LAVI (79 ± 1% vs. 65 ± 2% and 54 ± 2% for LAVI <40, 40 to 59, and ≥60 ml/m², respectively; p < 0.0001) even after comprehensive adjustment, including for DMR severity (adjusted hazard ratio [HR]: 1.05 [95% confidence interval (CI): 1.03 to 1.08] per 10 ml/m²; p < 0.0001). Mortality under medical management was profoundly affected by LAVI (adjusted HR: 1.07 [95% CI: 1.04 to 1.10] per 10 ml/mm² and 1.55 [95% CI: 1.31 to 1.84] for LAVI ≥60 ml/m² vs. <40 ml/m²; both p < 0.0001) incrementally to adjusting variables (p < 0.0001) and in all subgroups, particularly sinus rhythm (adjusted HR: 1.25 [95% CI: 1.21 to 1.28]) or atrial fibrillation (adjusted HR: 1.10 [95% CI: 1.06 to 1.13] per 10 ml/m²; both p < 0.0001). Thresholds of excess mortality in spline curve analysis were approximated at 40 ml/m² in all subgroups. Survival markedly improved after mitral surgery (time-dependent adjusted HR: 0.43 [95% CI: 0.36 to 0.53]; p < 0.0001) but remained modestly linked to LAVI (10-year survival 85 ± 3% vs. 86 ± 2% and 75 ± 3% for LAVI <40, 40 to 59, and ≥60 ml/m², respectively; p < 0.0001).

Conclusions: The frequent left atrial enlargement of DMR as measured by LAVI in routine practice displays, overall and in all subsets, a powerful, incremental, and independent link to excess mortality, which is partially alleviated by mitral surgery. Hence, LAVI measurement should be part of routine DMR evaluation and the clinical decision-making process.