title: Hypothermia during reperfusion does not reduce myocardial infarct size in pigs.
abstract: We previously described a method for regional myocardial cooling that reaches the target temperature within 4 min. The present study evaluated whether this method for regional myocardial cooling during reperfusion reduces myocardial infarct size (IS) in 75-kg pigs. Myocardial infarction was induced by inflation of an angioplasty balloon in the left anterior descendent artery for 45 min followed by 3 h reperfusion. First, 15 pigs were randomized to regional myocardial cooling during reperfusion (n = 8) or control (n = 7). As further control experiments, systemic hypothermia was induced prior to ischemia (n = 3) and during reperfusion (n = 3). IS and area at risk (AAR) were evaluated in vivo by single photon emission cardiac tomography (SPECT) and by standard histochemical staining. Regional cooling during reperfusion did not reduce IS/AAR as assessed by histochemistry (cooling: 0.71 +/- 0.8; control: 0.68 +/- 0.10; p = ns) and SPECT (cooling: 0.90 +/- 0.20; control: 0.88 +/- 0.32; p = ns). Systemic hypothermia during ischemia reduced IS/AAR (histochemistry: 0.09 +/- 0.11; SPECT: 0.25 +/- 0.22; p < 0.001 and p = 0.01 vs control, respectively). Induction of systemic hypothermia during reperfusion had no significant effect on IS/AAR (histochemistry: 0.63 +/- 0.07; SPECT: 0.74 +/- 0.09; p = ns vs control for both comparisons). In conclusion, hypothermia during ischemia is strongly myocardioprotective while hypothermia during reperfusion does not reduce myocardial infarct size in human-sized pigs.
authors.affiliation: Department of Cardiology, Skejby Hospital, Aarhus University Hospital, Brendstrupgaardsvej, 8200 Aarhus N, Denmark. michael.maeng@ki.au.dk
authors.forename: Michael
authors.initials: M
authors.lastname: Maeng
authors.forename: Ulrik M
authors.initials: UM
authors.lastname: Mortensen
authors.forename: Jens
authors.initials: J
authors.lastname: Kristensen
authors.forename: Steen B
authors.initials: SB
authors.lastname: Kristiansen
authors.forename: Henning R
authors.initials: HR
authors.lastname: Andersen
mesh_terms: D000818:Animals; D001794:Blood Pressure; D001831:Body Temperature; D006339:Heart Rate; D007036:Hypothermia, Induced; D009203:Myocardial Infarction / Q000473:pathology* / Q000628:therapy; D015425:Myocardial Reperfusion / Q000379:methods*; D009206:Myocardium / Q000473:pathology; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation