[Effects of diltiazem on cardiac and coronary circulation, at rest and during rapid auricular electric stimulation].

The effects on cardiac performance and systemic and coronary blood flow of rapid atrial pacing alone and associated with an intravenous infusion of a slow calcium channel inhibitor, diltiazem, at a dose of 20 mg/kg were studied in 20 patients with chronic coronary artery disease. Atrial pacing increased coronary flow and myocardial oxygen consumption: it decreased coronary arterial resistance and the coronary arteriovenous difference in lactates. Left ventricular end diastolic pressure rose significantly compared to the basal state in the period following pacing. The administration of diltiazem was associated with a significant fall of femoral arterial pressure, of coronary arteriovenous difference and myocardial consumption of oxygen, and an increase in the coronary arteriovenous difference in lactate. Left ventricular end diastolic pressure did not differ significantly from the basal values recorded after terminating atrial pacing. Left ventricular end diastolic volume decreased. Diltiazem opposed or cancelled the undesirable effects of rapid atrial pacing with respect to coronary arteriovenous difference in lactate content. The beneficial action of diltiazem does not seem to be closely related to its hemodynamic effects. It could be related to a reduction in myocardial oxygen demands due to a decrease in systolic ventricular strain and the specific metabolic effects of the drug, and also to an increase in myocardial oxygen supply due to the reduction in left ventricular end diastolic stress and the coronary vasodilation caused by the drug.