Impact of secondary mitral regurgitation on survival in atrial and ventricular dysfunction

Natural history of atrial and ventricular secondary mitral regurgitation (SMR) is poorly understood. We compared the impact of the degree of SMR on survival between atrial and ventricular dysfunction. We conducted a retrospective cohort study of patients who underwent echocardiography in a healthcare network between 2013-2018. We compared the survival of patients with atrial and ventricular dysfunction, using propensity scores developed from differences in patient demographics and comorbidities within SMR severity strata (none, mild, moderate or severe). We fitted Cox proportional hazards models to estimate the risk-adjusted hazards of death across different severities of SMR between patients with atrial and ventricular dysfunction. Of 11,987 patients included (median age 69 years [IQR 58-80]; 46% women), 6,254 (52%) had isolated atrial dysfunction, and 5,733 (48%) had ventricular dysfunction. 3,522 patients were matched from each arm using coarsened exact matching. Hazard of death in atrial dysfunction without SMR was comparable to ventricular dysfunction without SMR (HR 1.1, 95% CI 0.9-1.3). Using ventricular dysfunction without SMR as reference, hazards of death remained higher in ventricular dysfunction than in atrial dysfunction across increasing severities of SMR: mild SMR (HR 2.1, 95% CI 1.8-2.4 in ventricular dysfunction versus HR 1.7, 95%CI 1.5-2.0 in atrial dysfunction) and moderate/severe SMR (HR 2.8, 95%CI 2.4-3.4 versus HR 2.4, 95%CI 2.0-2.9). SMR across all severities were associated with better survival in atrial dysfunction than in ventricular dysfunction, though the magnitude of the diminishing survival were similar between atrial and ventricular dysfunction in increasing severity of SMRs.