[Effects of the phosphodiesterase III inhibitor in ischemic heart disease]

Positive inotropy requires a rise in myocardial oxygen consumption (MVO2); as far as PDE-III-inhibitors' beneficial hemodynamic effects, increases in contractility are controversial, in part probably because accurate proving is rather tedious. The clinician, however, requires a clear concept of whether or not enoximone (EN), for example, carries the risk of myocardial ischemia when used in patients with coronary artery disease. Using the analysis of pressure-volume relations, we recently established contractility-increasing as a partial effect of EN. There are indications suggesting that the inotropy-induced added increase in MVO2 of the PDE-III-inhibitor drugs could be compensated for by the simultaneous vasodilation and changes in compliance, so that as a net effect an unchanged MVO2 might result. Since, on the other hand, PDE-III-inhibitor drugs have been said to generate antiischemic properties, further clinical investigations with EN clearly seemed indicated and they are the subject of the present report: In five patient groups with stabile angina (AP) studied the following parameters and methods, respectively, were used for the evaluation of EN-induced changes of the anginal threshold: exercise, using pacing and ergometry; PA- and PC-pressure measurements; MVO2, indirectly assessed; hemodynamic profile and regional wall motion as assessed in the immediate post pacing phase; ST- T-segment evaluation; thalium-201 perfusion scintigraphy; myocardial perfusion, indirectly assessed. Lack of EN-induced AP (ischemia) and an increased AP threshold indicated that the drug can be used safety in patients with heart failure, including that due to coronary artery disease.