Very Mild Hypothermia During Ischemia and Reperfusion Improves Postinfarction Ventricular Remodeling

Background Mild hypothermia ( Methods In the initial phase of the experiment the effect of progressive degrees of hypothermia on infarct size was quantified. Thirty-eight male sheep were subjected to 1 hour of ischemia using a standardized anteroapical infarct followed by 3 hours of reperfusion. Temperature was maintained at either 39.5°C (n = 11), 38.5°C (n = 7), 37.5°C (n = 7), 36.5°C (n = 7), or 35.5°C (n = 6) for the entire period of ischemia and reperfusion. The area at risk (AR) and infarct size as a percentage of AR (I/AR) were determined with a double staining and planimetry technique. In the second phase of the study, chronic post-infarction remodeling was assessed in animals with nonreperfused infarcts (n = 6), 1 hour of ischemia followed by reperfusion at 39.5°C (n = 6) and 1 hour of ischemia followed by reperfusion at 37.5°C (n = 6). Remodeling was determined at 8 weeks after infarction using echocardiography. Results The I/AR in the 39.5°C, 38.5°C, 37.5°C, 36.5°C, and the 35.5°C groups was 71.8 ± 3.0%, 63.1 ± 1.9%, 49.4 ± 1.4%, 38.7 ± 1.4%, and 21.7 ± 2.2%, respectively ( p p Conclusions Subtle degrees of hypothermia can significantly improve immediate myocardial salvage and long-term LV remodeling after infarct reperfusion.