A pooled analysis of the effect of endovascular cooling on infarct size in patients with ST-elevation myocardial infarction

Aims: Prior evaluations of endovascular cooling during primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) have suggested variability in treatment effect related to core temperature at the time of reperfusion, to infarct location and time from symptom onset to reperfusion. Recent results from a randomised feasibility study suggest rapid induction of hypothermia in primary PCI results in a significant reduction in infarct size (IS). Methods and results: Outcomes from two randomised trials of hypothermia in primary PCI were pooled to examine IS as a percentage of left ventricular myocardium assessed by SPECT or magnetic resonance imaging. Compared with controls (n=103), hypothermia (n=94) was associated with a significant 24% relative reduction (RR) in IS (10.7+/-1.3% vs. 14.1+/-1.6%, mean+/-SEM, p=0.049). Among hypothermia-treated patients for whom core temperature <35C degrees was achieved before reperfusion, IS was reduced by 37% (8.8+/-1.7% vs. 14.1+/-1.6%, p=0.01), a benefit observed for both anterior (14.9+/-2.9% vs. 22.2+/-2.7%, RR 33%; p=0.03) and inferior infarcts (4.5+/-1.4% vs. 7.7+/-1.3%, RR 42%; p=0.04). Conclusions: In a pooled analysis of randomised trials evaluating adjunctive hypothermia in primary PCI, achievement of core body temperature <35 degrees C before reperfusion may reduce infarct size with a similar efficacy for both anterior and inferior MI.