NATURAL-HISTORY OF THE ASYMPTOMATIC MINIMALLY SYMPTOMATIC PATIENT WITH SEVERE MITRAL REGURGITATION SECONDARY TO MITRAL-VALVE PROLAPSE AND NORMAL RIGHT AND LEFT-VENTRICULAR PERFORMANCE

The natural history of patients with severe nonischemic mitral regurgi tation (MR) from mitral valve prolapse, who are asymptomatic or minima lly symptomatic and have normal right ventricular (RV) and left ventri cular (LV) performance, has not been evaluated previously. To define n atural history in this population and to deter mine if any objective v ariables could predict disease progression, 31 patients were followed annually with severe MR due to prolapse, who at entry were asymptomati c or minimally symptomatic and had normal RV and LV performance at res t by radionuclide cineangiography. Average follow-up in patients not r eaching surgical end point was 4.7 years. The Kaplan-Meier product lim it estimates were used to determine the rate of progression to either ''operable'' symptoms or to previously defined ''high risk'' ventricul ar performance descriptors, if the latter occurred first. Univariate c omparisons of Kaplan-Meier curves and multivariate Cox proportional ha zards analyses were used to define prognostically Important variables measured at entry. Fourteen patients developed symptoms warranting ref erral for operation; none developed high-risk ventricular performance descriptors. The annual end point risk was 10.3%. Of all covariates, o nly change in RV ejection fraction from rest to exercise was significa ntly associated with disease progression. Annual risk of progession to surgical end point was 4.9% in the subgroup in which this parameter i ncreased with exercise and 14.7% in the subgroup without an increase ( p = 0.04). Patients with severe MR due to mitral valve prolapse, who a re asymptomatic or minimally symptomatic with normal ventricular perfo rmance, can be expected to progress to surgical indications at an annu al rate of 10.3%. The change in RV ejection fraction during exercise i s useful in predicting the likelihood of such progression.