Cardiopulmonary Exercise Testing Determination of Functional Capacity in Mitral Regurgitation

Objectives

This study was designed to evaluate prevalence, determinants, and clinical outcome implications of reduced functional capacity (FC) in patients with organic mitral regurgitation (MR).

Background

Evaluation of FC by exercise testing is rarely performed in MR because little is known about the clinical determinants and outcome implications of FC.

Methods

Cardiopulmonary exercise testing (CPET) was prospectively performed in 134 asymptomatic patients with organic MR to assess FC (peak oxygen consumption [Vo₂]) simultaneously to Doppler-echocardiographic quantitation of MR (effective regurgitant orifice [ERO]) and left ventricular (LV) systolic and diastolic function.

Results

Peak Vo₂was 26 ± 6 ml/kg/min (96 ± 16% of age-predicted), but varied widely (57% to 145% of predicted) and was markedly reduced (≤84% of predicted) in 19% of patients. Although ERO of MR was univariately associated with reduced FC (26 vs. 9% with ERO ≥40 vs. <40 mm²), independent determinants of reduced FC were LV diastolic function (higher E/E′ ratio, p = 0.006), atrial fibrillation (p = 0.01), and lower forward stroke volume (p = 0.03). Clinical events (death, heart failure, new atrial fibrillation) and clinical events or surgery were more frequent with than without reduced FC (3 years, 36 ± 14% vs. 13 ± 4%, p = 0.02; and 66 ± 11% vs. 29 ± 5%, p = 0.001, respectively), even adjusting (risk ratios 1.80 and 1.54 respectively, both p ≤ 0.03) for age and ERO.

Conclusions

In asymptomatic organic MR, FC quantitatively assessed by CPET is unexpectedly markedly reduced in one out of every four to five patients. Reduced FC is independently determined by consequences rather than severity of MR and predicts increased subsequent clinical events. Therefore, CPET frequently reveals functional limitations not detected clinically and is an important tool in managing patients with organic MR.