[Pharmacologic evaluation of electrical processes in the myocardium]

The pharmacologist is interested both in the therapeutic effect of the drug and in its mode of action. This latter is mainly studied in the isolated heart "in vitro". However, in vitro experiments are not satisfactory to predict antiarrhythmic activity "in vivo", because: 1) they are mostly performed in preparations made from the normal myocardium; 2) "in vitro" the autonomic and hormonal effects are absent; 3) some drugs as nitroglycerin or strophanthin do not produce antiarrhythmic electrophysiological changes in "vitro" but under appropriate conditions they may have a clear-cut antiarrhythmic action "in vivo"; 4) arrhythmias mostly arise from the interaction of changes in several fundamental electrophysiological parameters which could be best studied "in vivo". These facts are demonstrated by the example of the pathomechanism and pharmacotherapy of early postinfarction arrhythmias. In spite of these shortcomings, there is, however, some promising development in this field: 1) progress in the "in vivo" recording of electric events in the heart (multiple KC1-suction electrodes "in vivo" recording of Purkinje activity); 2) prolonged drug treatment can evoke electrophysiological changes "in vitro" characteristic of the action of the drug "in vivo"; 3) in the donor perfused isolated heart-preparation the drug administered to the donor animal will evoke responses in concentrations producing the "in vivo" effect, and the possibility of drug metabolization and binding to plasma proteins is also given.