Exercise eco-Doppler in hypertrophic cardiomyopathy patients. Determinant factors of exercise intolerance.

INTRODUCTION AND OBJECTIVES At-rest echocardiography is a poor predictor of exercise capacity in patients with hypertrophic cardiomyopathy. We aimed to test the performance of treadmill exercise Doppler echocardiography in the prediction of functional limitations in these patients. METHODS Eighty-seven consecutive patients with hypertrophic cardiomyopathy underwent treadmill exercise echocardiography with direct measurement of oxygen consumption. Both at rest and at peak exercise, the mitral inflow, mitral regurgitation, left ventricular outflow tract obstruction and mitral annulus velocities were assessed. RESULTS Forty-three patients developed left ventricular outflow tract obstruction during exercise, which significantly decreased oxygen consumption (21.3 [5.7] mL/kg/min vs 24.6 [6.1] mL/kg/min; P=.012), and had greater left atrial volume (42.1 [14.5] mL/m(2) vs 31.1 [11.6] mL/m(2); P<.001) and a higher degree of mitral regurgitation and E/E' ratio during exercise. Exercise variables improved the predictive value of functional capacity (adjusted R(2) rose from 0.38 to 0.49). Independent predictors of oxygen consumption were age, left atrial volume, E/E' ratio and the presence of left ventricular outflow tract obstruction. In a subset of patients without left ventricular outflow obstruction, only left ventricular and atrial volume indexes were independent predictors of exercise capacity. CONCLUSIONS In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction and left atrial volume are the main predictors of exercise capacity. Exercise echocardiography is a better predictor of functional performance than at-rest echocardiography, although its predictive power is under 50%. In nonobstructed patients, left atrial and ventricular volumes were the independent factors.