The effect of low-dose (15 ml/kg) intracoronary perfluorochemical (Fluosol-DA) on infarct size, regional myocardial blood flow, and ventricular function was studied in 20 anesthetized closed-chest dogs subjected to 11/2 hr of proximal left anterior descending occlusion. In this preparation reperfusion was simulated with fibrinolytic therapy. The animals were randomly assigned one of two treatment groups and given 15 ml/kg of either oxygenated intracoronary perfluorochemical (n = 9) or saline (n = 1 1). Contrast ventriculograms were obtained at baseline, 1 hr after occlusion, and at 24 hr after reperfusion and were analyzed with a radial fractional shortening method. Regional myocardial blood flow was measured with radioactive microspheres. At 24 hr the area at risk was defined in vivo with monastryl blue staining and the area of necrosis was estimated after incubation of left ventricular slices with triphenyltetrazolium chloride. No significant changes were noted in heart rate, blood pressure, pulmonary capillary wedge pressure, or dP/dt during the experimental protocol. Infarct size was significantly reduced (p < .02) in the perfluorochemical-treated group, both when expressed as a percentage of the total left ventricular mass (7.9 + 1.7% vs 14.7 ± 2.5%) and as a percentage of the area at risk (20.1 ± 5.0% vs 46.8 + 8.5%). This was associated with significant improvement in fractional shortening in the jeopardized zone at 24 hr after reperfusion. Although endocardial blood flow was significantly greater in the central ischemic zone and lateral region at risk immediately after reperfusion in the perfluorochemical-treated group, no difference was found 1 hr after reperfusion. Intracoronary perfluorochemical significantly reduces infarct size and improves regional contractile function in a preparation of occlusion-reperfusion without increasing left ventricular filling pressure. Circulation 71, No. 5, 1060-1068, 1985 MEDICAL REPERFUSION with thrombolytic therapy has been shown to reduce infarct size and improve ventricular function in both experimental preparations and in man. -10 However, reperfusion can result in morphologic and metabolic derangements (so-called reperfusion injury) that may reduce the amount of myocardium that can be salvaged.1 I"' Perfluorochemicals are substances that may be useful in treating ischemia because of their high oxygen-carrying capacity. [19][20][21][22] Reduction of infarct size with perfluorochemicals has been shown by others,23 27 but previously the drugs were either used in a preparation of permanent occlusion or were studied only after brief periods of ischemia. Since large intravenous doses of perfluorochemicals were used in these studies, an exchange blood transfusion was required to prevent volume overload. This study was designed to determine whether a low dose of intracoronary perfluorochemical in an occlusion-reperfusion preparation results in greater reduction of infarct size than reperfusion with saline alone. We also determined the effect of perfluorochemical...