Therapeutic hypothermia and postreperfusion myocardial injury in myocardial infarction

Myocardial infarction is one of the main causes of death worldwide. Since the introduction of primary percutaneous coronary intervention (PPCI), the rate of patients who die of a myocardial infarction or suffer from numerous complications afterwards has significantly decreased. During PPCI, the patient sustains postreperfusion myocardial injury, which entails an extension of the myocardial infarct size related to ischemia. Research on the ways of limiting this phenomenon has been carried out for years. One of the investigated methods is hypothermia. The first animal studies have yielded promising results. The application of hypothermia has been proved to reduce the myocardial injury size provided that the cooling commenced before reperfusion. Moreover, the trial conducted by Götberg M. et al. showed a significant reduction of microvascular obstruction (MVO) in pigs subjected to hypothermia before reperfusion. MVO was assessed via ex vivo magnetic resonance imaging. The conducted randomized clinical trials have shown the possibility of applying mild hypothermia in conscious patients without causing significant complications. In the presented trials, hypothermia was induced and maintained using an intravascular catheter inserted into the inferior vena cava, cold saline solution infusions into peripheral veins or directly into the coronary arteries or via peritoneal hypothermia. The myocardial injury size was assessed via magnetic resonance imaging (MRI) or single photon emission computed tomography (SPECT). Despite the promising results obtained by Young-Sheng Wang et al., who applied selective intracoronary hypothermia and the myocardial infarct size (IS/MaR) was significantly reduced (p=0.022), it has not been unambiguously confirmed yet that hypothermia is effective as an adjunctive therapy for revascularization in myocardial injury size reduction during a myocardial infarction.