Management of less-than-severe mitral regurgitation: should guidelines recommend earlier surgical intervention?

It is well accepted that patients with severe mitral regurgitation (MR) benefit from mitral valve repair; however, the management of those with less than severe leakage is controversial. Watchful waiting is often advocated and considered safe, but the risk of developing left ventricular (LV) dysfunction under medical management is unknown.

Using a population-based County-wide study database, we analyzed echocardiograms during clinical follow-up and medical management of 204 patients with mitral valve prolapse and less-than-severe MR. LV dysfunction was defined per American Heart Association guidelines as an ejection fraction (EF) <60% or LV end-systolic dimension > 40 mm.

At index examination, mean age was 57 years and 121 (59%) were women. The mean EF was 62%, and 62 (30%) had evidence of LV dysfunction. MR severity was mild in 121 (59%), mild-moderate in 23 (11%), moderate in 36 (18%) and moderate-severe in 24 (12%). During follow-up (mean 8.6 years), 79 patients (39%) demonstrated progression of MR by at least one grade. Greater degrees of regurgitation at index echocardiogram were associated with greater progression during follow-up (P=0.0001). After adjusting for age, sex, body surface area (BSA), and baseline regurgitation grade, multivariable modeling revealed that larger LV end-diastolic dimension (odds ratio (OR)=1.14; P=0.0018) and greater diastolic septal thickness (OR=1.40; P=0.0211) predicted greater progression of MR with time. From initial diagnosis to follow-up echocardiography, EF declined, while left-heart dimensions and pulmonary arterial pressure increased. Of the 142 patients with normal baseline LV function, 52% developed either worsening MR or de novo LV dysfunction. Importantly, even in the 87 patients with stable regurgitation, 18 (21%) developed new LV dysfunction during follow-up. Fifty-two patients (25%) eventually underwent mitral valve repair. Following surgery, there were significant decreases in EF, LV end-diastolic dimensions and LV mass; while 11 developed de novo LV dysfunction.

Over half of patients with chronic persistent, but sub-severe MR due to mitral leaflet prolapse develop LV dysfunction or worsening regurgitation despite optimal medical management. LV deterioration can occur even in the absence of MR progression. These data advocate for the development of detailed guidelines supporting frequent echocardiographic monitoring and the identification of earlier triggers for surgical consideration prior to the development of LV dysfunction in this patient population.