We assessed the ventricular-arterial coupling at peak exercise in 20 patients with dilated cardiomyopathy (ejection fraction, 27±12%) and 7 normal subjects by radionuclide ventriculography during exercise, coupled with respiratory gas analysis. The end-systolic pressure-volume ratio, taken as an index of contractility, and the effective arterial elastance were calculated at rest and at peak exercise. The end-systolic pressure/volume ratio increased from 3.7±2.7 to 6.9±4.0 mm Hg/mL at peak exercise in the normal subjects, but did not change significantly (from 0.9±0.5 to 1.0±0.6 mm Hg/mL) in the patients. Arterial elastance did not change significantly in the patients (+17±32%, not significant [NS] vs rest) or in the normal subjects (+22±28%, NS vs rest). The change in ejection fraction during exercise correlated both with the end-systolic pressure/volume ratio and with effective arterial elastance changes (r=0.60 and 0.68, respectively). We conclude that ventricular arterial coupling is further altered at peak exercise in these patients because of the lack of increase in contractility and not of altered effective arterial elastance response.