Mortality due to acute myocardial infarction (AMI) has been declining in past decades [1]. Admission to the intensive care unit (ICU) after developing AMI has been widely accepted as a standard practice and is thought to play a major role in improving outcomes. On the other hand, ICU stays represent a substantial financial burden [2]. In addition, evidence that justifies its use, such as a reduction in mortality, has never been shown in the contemporary revascularization era.No randomized controlled trials have been conducted to investigate the mortality benefit of ICU admission in patients with AMI. There are several observational studies with conflicting results [3][4][5][6][7][8][9][10][11][12]. The clinical guidelines in the USA recommend admission to a coronary care unit under specific conditions for non-ST-elevation acute coronary syndromes, and the use of an ICU is not mentioned for those with ST-elevation myocardial infarction (STEMI) [13,14]. The clinical guidelines of the European Society of Cardiology and the Japanese Circulation Society recommend that patients suffering from AMI be admitted to the ICU [15][16][17][18], although supporting evidence is lacking thus far.Among the major limitations of the previous studies are small sample sizes, a limited number of study sites, or lack of clinically