PERCUTANEOUS COOLING OF ISCHEMIC MYOCARDIUM BY HYPOTHERMIC RETROPERFUSION OF AUTOLOGOUS ARTERIAL BLOOD - EFFECTS ON REGIONAL MYOCARDIAL TEMPERATURE DISTRIBUTION AND INFARCT SIZE

The effects of synchronized coronary venous retroperfusion of cooled autologous arterial blood on regional myocardial temperature distribution and infarct size were studied in open chest dogs with 3.5 h of left anterior descending coronary artery occlusion. After 30 min of occlusion, the dogs were randomly assigned to one of three groups: 1) untreated control group (n = 5), 2) normothermic retroperfusion group (infusion temperature 32-degrees-C) (n = 7), and 3) hypothermic retroperfusion group (infusion temperature 15-degrees-C) (n = 7). Regional myocardial temperatures were measured by using needle-tipped thermistors stabbed in the 1) anterior wall distal to the occlusion site, 2) anterior wall proximal to the occlusion site, 3) left lateral wall, 4) posterior wall, and 5) right ventricular free wall. Rectal and pulmonary artery temperatures were also measured. In the hypothermic retroperfusion group, the anterior wall temperature decreased rapidly by 5-degrees-C at 15 min of retroperfusion (p < 0.05 vs. normothermic retroperfusion or untreated control groups), whereas the temperature at other sites decreased with a linear trend over time. Myocardial temperatures in the ischemic area (distal anterior wall) were generally lower than those in the other sites during the first 60 min of hypothermic retroperfusion and the largest intramyocardial temperature difference (3.6-degrees-C) was found at 15 min after retroperfusion. Infarct size expressed as a percent of the risk area was significantly smaller in the hypothermic retroperfusion group (6.2 +/- 3.3%) than in the control (64.9 +/- 14%) or normothermic retroperfusion groups (24.1 +/- 6.7%). These results indicate that hypothermic retroperfusion provides rapid regional cooling of acutely ischemic myocardium with small intramyocardial temperature gradients, affording better myocardial protection from ischemic damage compared with normothermic retroperfusion.