Comparative echocardiographic study of recovery of diastolic versus systolic function after brief periods of coronary occlusion: differential effects of intravenous nifedipine administered before and during occlusion.

The effect of intravenous nifedipine (5 micrograms/kg) on the recovery of myocardial function after occlusion of the left anterior descending coronary artery was studied in 18 closed chest dogs. Using computer-aided analysis of two-dimensional echocardiograms, systolic and diastolic function of ischemic segments in low papillary left ventricular cross sections were characterized, respectively, as holosystolic fractional area change and early diastolic velocity of luminal area change. The time required for systolic function to return to preocclusion values after a 1 minute untreated control occlusion (n = 12) was 5 to 10 minutes, and after a 2 minute occlusion (n = 6) it was 20 to 30 minutes. When nifedipine was administered during the occlusion, recovery after a 2 minute occlusion was accelerated slightly to 10 to 15 minutes. Recovery times of early diastolic function were substantially longer, and nifedipine effects were more pronounced. After a 1 or 2 minute control coronary occlusion, 60 to 75 minutes or 90 to 105 minutes were needed to return early diastolic function to normal levels. Nifedipine administered during a 1 or 2 minute coronary occlusion improved these recovery times to 10 to 15 minutes. When the dogs were treated with intravenous nifedipine before coronary occlusion, recovery after 1 or 2 minutes of acute ischemia was apparent as early as 2 minutes after reperfusion. Thus, intravenous nifedipine accelerates the recovery of myocardial function after brief periods of ischemia, and when administered before coronary occlusion, it assures very prompt recovery of function.