Prognostic Implications of Left Atrial Enlargement in Degenerative Mitral Regurgitation

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

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.

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.

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).

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.