Verapamil in a new model of severe local myocardial ischaemia due to combined coronary occlusion and stenosis.

The effect of verapamil was studied in a new canine model of local myocardial ischaemia. In this model in addition to the critical construction of the left circumflex coronary artery, the left anterior descending branch was suddenly occluded. Experiments were performed in the anaesthetized, thoracotomized and artificially respired dog. The model represents a severe form of myocardial ischaemia and mimics the clinical situation in which usually more than one coronary artery is involved in the stenotic process. Verapamil (0.15 mg kg -1 i.v.) moderated the extent of the ischaemic changes (indicated by the ST segment elevation in the epicardial and endocardial ECG) as well as their consequences e.g. the incidence and severity of early postocclusion and reperfusion arrhythmias. This beneficial effect was probably due to the drug-induced favourable haemodynamic action (reduction of left ventricular end-diastolic pressure and slight increase in left ventricular dP/dtmax) and to the electrophysiological effects (e.g. decreased inhomogeneity of electrical activation, diminution of extrasystolic activity) and blood flow changes (enhanced blood supply to the ischaemic subepicardium).