The effects on left ventricular function of postextrasystolic potentiation and the dihydropyridinic calcium antagonist diperdipine, alone or in combination, were studied in 14 patients with coronary heart disease by means of two consecutive left ventricular angiographies. To ensure the reproducibility of coupling intervals of the extrasystolic and postextrasystolic beats, the heart was paced during both angiographies. Results showed that postextrasystolic potentiation and diperdipine improved left ventricular ejection fraction to the same degree, but the mechanisms of such an improvement were different and consisted, respectively, of a positive inotropic effect associated with an increase in preload and a slight increase in preload coupled with a marked decrease in afterload. Diperdipine did not abolish the inotropic component of postextrasystolic potentiation, and a combination of the two interventions had additive effects on the improvements in left ventricular ejection fraction and regional wall motion analyzed by the centerline method. Ventricular segments that were normokinetic or hypokinetic during the control basal cycle responded equally to postextrasystolic potentiation and to diperdipine, whereas the former intervention alone had no significant effect on akinetic segments. Diperdipine restored the responsiveness of akinetic segments to postextrasystolic potentiation, a finding that, although it remains to be confirmed by independent techniques, may be interpreted as a possible consequence of improved calcium metabolism or coronary flow in ischemic but still viable myocardium. However, it is concluded that the calcium antagonist revealed a contractile reserve in most of the severely asynergic areas, which would have otherwise been judged to be irreversibly damaged on the basis of the unresponsiveness to postextrasystolic potentiation alone.