Background Abnormalities of diastolic function are an important determinant of exercise intolerance in patients with heart failure. However, the relation between left ventricular filling pattern and cardiopulmonary exercise performance has not been adequately studied. Methods Thirty-one patients with idiopathic (n = 14) or ischemic (n = 17) dilated cardiomyopathy, demonstrated by coronary angiography, and radionuclide ejection fraction 30.5% ± 9% underwent cardiopulmonary exercise testing with a modified Naughton protocol and a complete echocardiographic study. Patients were subdivided into restrictive and nonrestrictive groups according to their Doppler transmitral flow pattern. Gas exchange data were measured during exercise testing. The relation of left ventricular filling pattern to cardiopulmonary parameters was assessed in both groups. Results Exercise duration was similar in the restrictive and nonrestrictive groups but significant differences were found in oxygen consumption (VO₂) at peak exercise (14.3 ± 2.4 vs 20.4 ± 4.7 mL/kg per minute; P <.001) and at the anaerobic threshold (VO_2AT) (13 ± 2.2 vs 17.3 ± 3 mL/kg per minute; P <.001). Simple linear regression analysis revealed that both peak VO₂ and VO_2AT were significantly correlated with the ratio of peak early (E wave) to late (A wave) transmitral filling velocity, early filling deceleration time, atrial filling fraction, and A-wave velocity but not with left ventricular ejection fraction. Multivariate regression analysis gave only the peak A-wave velocity as an independent predictor for both peak VO₂ and VO_2AT. Conclusions In patients with heart failure, abnormalities of diastolic function are the most important determinant of exercise intolerance. A restrictive transmitral flow pattern by Doppler echocardiography is a marker of diminished cardiopulmonary exercise performance in these patients. (Am Heart J 2000;140:338-44.)