DETERMINANTS OF FUNCTIONAL-CAPACITY IN CHRONIC MITRAL REGURGITATION UNASSOCIATED WITH CORONARY-ARTERY DISEASE OR LEFT-VENTRICULAR DYSFUNCTION

Impaired functional capacity is common in patients with mitral regurgi tation (MR), but the determinants of functional capacity in patients w ith normal left ventricular (LV) function are unclear. Forty patients with chronic, isolated, nonrheumatic MR with no coronary artery diseas e underwent exercise echocardiography with continuous expired gas anal ysis, Cardiac output and regurgitant stroke volume were measured at re st and immediately after exercise by pulsed-wave Doppler echocardiogra phy. For controls, 17 healthy volunteers without MR were also studied. patients achieved a significantly lower VO(2)max compared with contro ls (25.6 +/- 7.7 vs 31.7 +/- 7.7 ml/kg/min, p = 0.008). VO(2)max showe d better correlations with exercise cardiac output than with cardiac o utput at rest in both patients and controls. Multiple linear regressio n identified exercise cardiac output (partial r = 0.65), patient age ( partial r = -0.56), and gender as independent determinants of VO(2)max (multiple R = 0.85, p <0.001). Cardiac output at rest, LV ejection fr action, regurgitant stroke volume, and fraction were not significant d eterminants, With exercise, the regurgitant stroke volume increased in 13 patients and decreased in 27 patients, The former 13 patients had a significantly lower exercise cardiac output (7.4 +/- 2.5 vs 9.4 +/- 2.6 L/min, p = 0.026). Patients who stopped exercise due to dyspnea (n = 7) had a significantly lower exercise cardiac output and VO(2)max c ompared with those who stopped due to fatigue (n = 33), with no differ ences in resting or exercise regurgitant volume. Patients with an incr ease in LV end-systolic volume with exercise (n = 8) also had a signif icantly lower exercise cardiac output (6.9 +/- 1.9 vs 9.2 +/- 2.7 L/mi n, p = 0.037) and showed a trend toward a lower VO(2)max (21 +/- 7.5 v s 26 +/- 6.4 ml/kg/min, p = 0.07), In patients with chronic MR, exerci se cardiac output is the major determinant of VO(2)max. Regurgitant vo lume and fraction are not related to functional capacity. Limitations in functional capacity in these patients may be more related to a dimi nished cardiac reserve than to a large regurgitant volume. (C) 1997 by Excerpta Medica, Inc.