The value of
nifedipine in reducing the ultimate size of an
infarct associated with a period of
coronary occlusion followed by reperfusion was assessed. Eight baboons were administered a bolus dose of
nifedipine, 5 micrograms/kg intravenously, and then a maintenance dose of 30 micrograms/kg per hour was begun 1 hour before occlusion. This regimen resulted in an 8.5 +/- 1.2 percent (mean +/- standard error) decrease in mean arterial pressure. The left anterior descending coronary artery was occluded for 2 hours and then perfusion restored. At 2 hours after reperfusion the
nifedipine infusion was discontinued. Eight control baboons underwent an identical protocol without
nifedipine therapy. At 24 hours after occlusion, microvascular
dyes were injected into the left anterior descending coronary artery and adjacent arteries to delineate the perfusion bed of the previously occluded artery. The volume of
infarction was determined with planimetry and compared with the volume of the perfusion bed of the occluded artery. The area of
infarction was always contained within the perfusion bed of the occluded artery. The mean percent of the perfusion bed with
infarction was 50.1 +/- 5.8 in the control group and 41.7 +/- 9.5 in the treated group (difference not significant; p greater than 0.05). In both control and treated groups of baboons
hemorrhage occurred only within the region of
infarction. In both groups electron microscopy revealed large electron-dense granules within the mitochondria. In conclusion
nifedipine therapy during a 2 hour period of
coronary occlusion followed by reperfusion did not result in any significant reduction in ultimate
infarct size in the baboon.