Cooling as an Adjunctive Therapy to Percutaneous Intervention in Acute Myocardial Infarction: COOL-MI InCor Trial

Endovascular Therapeutic hypothermia (ETH) reduces the damage caused by postischemia reperfusion injury syndrome in cardiopulmonary arrest and has already established its role in patients with sudden death; however, its role in ST-segment elevation myocardial infarction (STEMI) remains controversial. The objectives of this study were to investigate the safety, feasibility, and 30-day efficacy of rapid induction of therapeutic hypothermia as adjunctive therapy to percutaneous coronary intervention (PCI) in patients with anterior and inferior STEMIs. This was a prospective, controlled, randomized, two-arm, prospective, interventional study of patients admitted to the emergency department within 6 hours of angina onset, with anterior or inferior STEMI eligible for PCI. Subjects were randomized to the hypothermia group (primary PCI+ETH) or to the control group (primary PCI) at a 4:1 ratio. The ETH was induced by 1 L cold saline (1-4°C) associated with the Proteus™ System, by cooling for at least 18 minutes before coronary reperfusion with a target temperature of 32°C ± 1°C. Maintenance of ETH was conducted for 1-3 hours, and active reheating was done at a rate of 1°C/h for 4 hours. Primary safety outcomes were the feasibility of ETH in the absence of (1) door-to-balloon (DTB) delay; (2) major adverse cardiac events (MACE) within 30 days after randomization. The primary outcomes of effectiveness were infarct size (IS) and left ventricular ejection fraction (LVEF) at 30 days. An as-treated statistical analysis was performed. Fifty patients were included: 35 (70%) randomized to the hypothermia group and 15 (30%) to the control group. The mean age was 58 ± 12 years; 78% were men; and associated diseases were 60% hypertension, 42% diabetes, and 72% dyslipidemia. The compromised myocardial wall was anterior in 38% and inferior in 62%, and the culprit vessels were left anterior descending artery (LAD) (40%), right coronary artery (38%), and left circumflex (18%). All 35 patients who attempted ETH (100%) had successful cooling, with a mean endovascular coronary reperfusion temperature of 33.1°C ± 0.9°C. The mean ischemic time was 375 ± 89.4 minutes in the hypothermia group and 359.5 ± 99.4 minutes in the control group. The mean DTB was 92.1 ± 20.5 minutes in the hypothermia group and 87 ± 24.4 minutes in the control group. The absolute difference of 5.1 minutes was not statistically significant (p = 0.509). The MACE rates were similar between both groups (21.7% vs. 20% respectively, p = 0.237). In the comparison between the hypothermia and control groups, no statistically significant differences were observed at 30 days between mean IS (13.9% ± 8% vs. 13.8% ± 10.8%, respectively, p = 0.801) and mean final LVEF (43.3% ± 11.2% vs. 48.3 ± 10.9%, respectively; p = 0.194). Hypothermia as an adjunctive therapy to primary PCI in STEMI is feasible and can be implemented without delay in coronary reperfusion. Hypothermia was safe regarding the incidence of MACE at 30 days. However, there was a higher incidence of arrhythmia and in-hospital infection in the hypothermia group, with no increase in mortality. Regarding efficacy, there was no difference in IS or LVEF at 30 days that would suggest additional myocardial protection with ETH. ClinicalTrials.gov: NCT02664194.