Exercise ventilation after balloon dilatation of the mitral valve

Abstract

Background: Exertional dyspnoea is a limiting symptom in many patients with mitral stenosis but its causes remain incompletely understood. Ventilation during exercise is abnormal in chronic heart failure of all causes and there is increased ventilatory cost of carbon dioxide production. Patients: 23 patients with rheumatic mitral stenosis undergoing percutaneous balloon dilatation of the mitral valve were studied to investigate exercise ventilation. Methods: Treadmill exercise tests with respiratory gas analysis were performed before and 1 day, 7 days, and 10 weeks after balloon dilatation of the mitral valve. The relation between ventilation (V̇E) and production (V̇CO2) was analysed by linear regression. Results: The V̇E/V̇CO2 slope was linear in all patients and before balloon dilatation of the mitral valve it correlated inversely with peak minute oxygen consumption (V̇O2) (r(s) = -0.47, P < 0.05), exercise duration (r(s) = -0.66, P < 0.01), and mitral valve area (r(s) = -0.5, P < 0.05). The V̇E/V̇CO2 slope declined acutely after balloon dilatation of the mitral valve (n = 10) (mean (SD) 41 (4) v 36 (2.9), P < 0.05) and did not change again thereafter. At 10 weeks (n = 23) exercise duration (460 (230) v 630 (240) s, P < 0.01) and peak V̇O2 (12.7 (4.3) v 14.9 (4.8) ml/kg/min, P < 0.05) increased significantly. Conclusions: Patients with rheumatic mitral stenosis have a similar increase in the V̇E/V̇CO2 slope to that of patients with heart failure from other causes. Successful balloon dilatation of the mitral valve is associated with an acute reduction in the exercise V̇E/V̇CO2 slope.