Therapeutic hypothermia in ST elevation myocardial infarction: a systematic review and meta-analysis of randomised control trials

Objective Our objective is to gain a better understanding of the efficacy and safety of therapeutic hypothermia (TH) in patients with acute ST elevation myocardial infarction (STEMI) through an analysis of randomised controlled trials (RCTs). Background Several RCTs have suggested a positive outcome with the use of TH in the prevention of myocardial injury in the setting of an acute STEMI. However, there are currently no clinical trials that have conclusively shown any significant benefit. Methods Electronic databases were used to identify RCTs of TH in the patient population with STEMI. The primary efficacy end point was major adverse cardiovascular event (MACE). Secondary efficacy end points included all-cause mortality, infarct size, new myocardial infarction and heart failure/pulmonary oedema (HF/PO). All-bleeding, ventricular arrhythmias and bradycardias were recorded as the safety end points. Results Six RCTs were included in this meta-analysis, enrolling a total of 819 patients. There was no significant benefit from TH in preventing MACE (OR, 01.04; 95% CI 0.37 to 2.89), all-cause mortality (OR, 1.48; 95% CI 0.68 to 3.19), new myocardial infarction (OR, 0.99; 95% CI 0.20 to 4.94), HF/PO (OR, 0.52; 95% CI 0.15 to 1.77) or infarct size (standard difference of the mean (SDM), -0.1; 95% CI -0.23 to 0.04). However, a significant reduction of infarct size was observed with TH utilisation in anterior wall myocardial infarction (SDM, -0.23; 95% CI -0.45 to -0.02). There was no significant difference seen for the safety end points all-bleeding (OR 1.32; 95% CI 0.77 to 2.24), ventricular arrhythmias (OR, 0.85; 95% CI 0.54 to 1.36) or bradycardias (OR, 1.16; 95% CI 0.74 to 1.83). Conclusions Although TH appears to be safe in patients with STEMI, meta-analysis of published RCTs indicates that benefit is limited to reduction of infarct size in patients with anterior wall involvement with no demonstrable effect on all-cause mortality, recurrent myocardial infarction or HF/PO.