Abstract
Following the return of spontaneous circulation after cardiac arrest, the use of therapeutic hypothermia (TH) has been demonstrated to improve neurologic outcomes and mortality. The potential cardiac benefits and the role of induced hypothermia as a cardioprotective strategy are less clear. Numerous laboratory and clinical studies implicate both inciting myocardial ischemia and subsequent reperfusion damage in myocardial injury. Based on its established benefit in limiting cerebral ischemia and its widespread availability, TH is an attractive therapy for limiting myocardial ischemia and reperfusion injury in myocardial infarction. Several studies have suggested a positive effect of TH in the prevention of myocardial ischemic injury but to date no clinical trial has conclusively shown mortality benefit with the use of TH in the setting of ST elevation myocardial infarction (STEMI). Subgroup analyses however indicate that TH has the potential to limit infarct size and improve outcomes in certain patient subsets. These findings, alongside the established benefits for cerebral ischemic injury, support performing further large scale randomized controlled trials of the use of TH in STEMI.
Highlights
1 million people in the United States suffer from myocardial infarction each year (MI) and coronary heart disease accounts for approximately 15% of the total annual mortality
RCT: randomized controlled trial, STEMI: ST elevation myocardial infarction, MI: myocardial infarction, MACE: major adverse cardiac events, VF: ventricular fibrillation, OHCA: out-of-hospital cardiac arrest, PCI: percutaneous coronary intervention, LVEF: left ventricular ejection fraction, CK-MB: creatinine kinase MB isofraction, n/a: not available or not applicable, NS: normal saline, *: infarct size measured by Tc-99 sestamibi SPECT imaging, †: infarct size measured by degree of CK-MB elevation, ‡: posthoc or sub-group analysis, #: neurological outcome assessed by Pittsburgh Cerebral Performance Category, **: defined as any clinically overt blood loss, ***: assessed by cardiac magnetic resonance imaging
Early revascularization with thrombolytic therapy or primary PCI is the mainstay of treatment for STEMI, but outcomes may be further improved by preventing the deleterious effects of reperfusion injury
Summary
1 million people in the United States suffer from myocardial infarction each year (MI) and coronary heart disease accounts for approximately 15% of the total annual mortality. A post-hoc subgroup analysis (n = 111) of the Hypothermia After Cardiac Arrest trial by Koreny et al identified a statistically significant (p = 0.007) reduction in infarct size as estimated by ECG ST scores and plasma levels of CK and CK-MB for those patients who achieved target temperature early (≤ 8hrs) versus late (> 8h) despite no evidence of overall clinical benefit in the original study [43].
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