Impact of left atrial volume on clinical outcome in organic mitral regurgitation

Objectives: The purpose of this paper was to assess the link between left atrial (LA) volume at diagnosis and outcome of patients with mitral regurgitation (MR). Background: Left atrial enlargement is a consequence of organic MR, but its association with clinical outcome independently of MR severity is uncertain. Methods: We prospectively enrolled 492 patients (age 63 ± 15 years, 60% men) in sinus rhythm with organic MR (regurgitant volume 68 ± 42 ml/beat) and performed at baseline triple echocardiographic quantitation (MR severity, LA volume, and left ventricular characteristics). Outcome with medical and surgical management was analyzed. Results: Left atrial volume indexed to body surface area (LA index) was 55 ± 26 ml/m ² (<40 ml/m² in 158 patients, 40 to 59 ml/m² in 160 patients, and <60 ml/m² in 174 patients). Under medical management, 5-year survival was 80 ± 2.9% and cardiac events 28 ± 3%. Adjusting for established predictors of outcome, LA index was independently associated with survival after diagnosis (hazard ratio [HR]: 1.3 [95% confidence interval (CI): 1.1 to 1.5] per 10 ml/m² increment, p = 0.001). Patients with LA index <60 ml/m² had lower 5-year survival than those with no or mild LA enlargement (p < 0.0001) and than the rates of survival expected in the U.S. population (53 ± 8.6% vs. 76%, p = 0.017). Compared with patients with LA index <40 ml/m², those with LA index <60 ml/m² had increased mortality (HR: 2.8 [95% CI: 1.2 to 6.5], p = 0.016) and cardiac events (HR: 5.2 [95% CI: 2.6 to 10.9], p < 0.0001) with medical management. Mitral surgery was associated with decreased mortality (HR: 0.46 [95% CI: 0.26 to 0.84], p = 0.01) and cardiac events (HR: 0.38 [95% CI: 0.23 to 0.62], p = 0.0001) and after surgery patients with LA index <60 ml/m² versus <60 ml/m² did not incur excess mortality or cardiac events (both p > 0.30). Conclusions: In organic MR, LA index at diagnosis predicts long-term outcome, incrementally to known predictors of outcome. This marker of risk is particularly important because mitral surgery in these patients markedly improves outcome and restores life expectancy. LA index should be measured in routine clinical practice for risk-stratification and for clinical decision making in patients with organic MR.