The efficacy of short-term synchronized coronary venous retroperfusion (SRP) before full arterial reperfusion was studied in a canine model. A control group (n = 6) was subjected to 90 minutes of occlusion of the left anterior descending coronary artery, which was followed by 6 hours of reperfusion. In another group (n = 6) the left anterior descending coronary artery was occluded for 2 hours followed by 5.5 hours of reperfusion. In this group SRP was applied for 30 minutes before full reperfusion. Myocardial regional blood flow was measured with the use of colored microspheres. During occlusion of the left anterior descending coronary artery, there was severe myocardial ischemia in both groups. Blood flow in the subendocardial area was, however, significantly better in the SRP group (0.51 +/- 0.17 ml/min/gm after 3.5 hours of reperfusion) than in the control group (0.29 +/- 0.16 ml/min/gm) after 4 hours of reperfusion (p less than 0.05). Left ventricular function was assessed as global ejection fraction from a left ventriculogram. Ejection fraction was reduced during ischemia in both groups (control = 38% +/- 3%, SRP = 32% +/- 8%). This dysfunction remained after 4 hours of reperfusion. Infarct size was assessed by means of triphenyltetrazolium chloride staining. The myocardial area at risk was similar in the two groups (control = 33.1% +/- 5.3%, SRP = 30.6% +/- 6.5%). Infarct size, which was expressed as the percent of the area at risk, was significantly smaller in the SRP group (17.2% +/- 14.6%) than in the control group (36.0% +/- 8.1%; p = 0.0197).(ABSTRACT TRUNCATED AT 250 WORDS).