Comparison between the positive inotropic effects of enoximone, a cardiac phosphodiesterase III inhibitor, and dobutamine in patients with moderate to severe congestive heart failure. A study using the end-systolic pressure-volume relationship method.

This study was designed to compare the positive inotropic properties of enoximone, a cardiac phosphodiesterase III inhibitor, with those of dobutamine in a population of moderate to severe congestive heart failure patients. The end-systolic pressure-volume relationship method was used. In addition, the haemodynamic effects of both drugs were compared. In seven of the 11 patients studied, enoximone induced a significant shift upwards and to the left of the end-ejection pressure/end-systolic volume (EEP/ESV) relation, giving evidence of a true positive inotropic effect. In the remaining patients, improvement in cardiac pump function was observed together with a shift of the EEP/ESV relation along the line of iso-inotropism and appeared to be the result of the vasodilatory effect of the drug alone. Data from nine patients were available for comparison with dobutamine which induced a shift upward and to the left of the EEP/ESV relation in seven patients. At the therapeutic doses chosen, the difference between the inotropic effects of the two drugs was not significant (P = 0.07). Of the three patients available for comparison who did not manifest inotropic response with enoximone, two were also dobutamine 'non-responders': they differed from the 'responder' patients in two respects: they had undergone surgery for correction of valvular disease and had significantly higher pulmonary artery pressures. The haemodynamic measurements confirmed the vasodilatory properties of enoximone; in particular, the fall in ventricular filling pressures was much greater with enoximone than with dobutamine.(ABSTRACT TRUNCATED AT 250 WORDS)