[Myocardial response to ischemia produced by repeated coronary occlusions: an experimental study].

The aim of our study was to see whether diltiazem (DZ) infused intravenously at 10 mcg Kg-1 min-1: 1) influenced left ventricular systolic and diastolic function; 2) had a cardioprotective action during acute myocardial ischemia of short duration. We utilized 15 pigs, in 9 of which DZ was infused; 6 animals were utilized as controls. In both groups 2 minutes ischemia was induced by occlusion of the left anterior descending coronary artery (LAD). Heart rate (HR), mean systemic arterial pressure (MAP), left ventricular peak systolic (LVPSP) and end-diastolic pressure (LVEDP), double product (DP), peak positive and negative dP/dt (dP/dt+ and -) were measured: 1) in the basal state and after 30 minutes of DZ infusion in one group; 2) in both groups before LAD occlusion, during occlusion and the ensuing 10 minutes of reperfusion. The results were analyzed in order to assess statistical significance. 1) 30 minutes of DZ infusion induced a significant change of all parameters, except HR and LVEDP: MAP increased 11%, LVPSP 9%, DP 12%, dP/dt+ 11% and DP/dt- 18%. 2) LAD occlusion induced less deterioration of systolic and diastolic ventricular function in the group treated with DZ: in fact MAP decreased 8% vs 13% of the control group, LVPSP 9% vs 12%, dP/dt+ 24% vs 28%, dP/dt- 15% vs 26%, while DP showed the same decrease in both groups; HR and LVEDP did not change. Our results indicate that DZ, at this dose: 1) has a positive inotropic action and has a favorable effect on isovolumetric relaxion; 2) has a cardioprotective action during acute myocardial ischemia of short duration.