EXERCISE VENTILATION AFTER BALLOON DILATATION OF THE MITRAL-VALVE

Background-Exertional dyspnoea is a limiting symptom in many patients with mitral stenosis but its causes remain incompletely understood. Ve ntilation during exercise is abnormal in chronic heart failure of all causes and there is increased ventilatory cost of carbon dioxide produ ction. Patients-23 patients with rheumatic mitral stenosis undergoing percutaneous balloon dilatation of the mitral valve were studied to in vestigate 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 be tween ventilation (VE) and production (Vco(2)) was analysed by linear regression. Results-The VE/Vco(2) slope was linear in all patients and before balloon dilatation of the mitral valve it correlated inversely with peak minute oxygen consumption (Vo(2)) (r(s) = -0.47, P < 0.05), exercise duration (rs = -0.66, P < 0.01), and mitral valve area (rs - 0.5, P < 0.05). The VE/Vco(2) slope declined acutely after balloon dil atation 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) exerc ise duration (460 (230) v 630 (240) s, P < 0.01) and peak Vo(2) (12.7 (4.3) v 14.9 (4.8) ml/kg/min, P < 0.05) increased significantly. Concl usions-Patients with rheumatic mitral stenosis have a similar increase in the VE/Vco(2) slope to that of patients with heart failure from ot her causes. Successful balloon dilatation of the mitral valve is assoc iated with an acute reduction in the exercise VE/Vco(2) slope.