[Emergency/resuscitation systems and problems].

The proportion of cardiac etiology is more than 50% of the patients of out-of-hospital cardiac arrest and the cause of cardiac etiology is acute coronary syndromes (ACS) in about 70%. Although the mortality rate of acute myocardial infarction with ST elevation was about 7% in the cardiac reperfusion era, there is a high mortality rate in the patients with ACS who developed out-of-hospital cardiac arrest. We summarized the emergency medical service system in Japan and its problems. Achieving the optimal survival rate for out-of-hospital cardiac arrest due to ACS is the challenge now and in the future.