It is easy to think that acute cardiovascular diseases such as myocardial infarction cluster in winter, when temperatures drop and blood vessels constrict. However, experts advise that there are actually more patients in summer, so those with underlying conditions such as hypertension or diabetes need year-round vigilance.

Acute myocardial infarction is a severe emergency in which heart muscle dies because a coronary artery that supplies it with blood is suddenly blocked by a thrombus (blood clot) or other causes. High cholesterol and inflammation can lead to atherosclerotic plaques forming on vessel walls, and when these detach they can block a coronary artery. According to Health Insurance Review and Assessment Service statistics, from December 2020 to August 2025, the cumulative number of patients who visited hospitals for acute myocardial infarction totaled 502,086 in summer (June to August), higher than 488,506 in winter (December to February). About 80% of all patients were men, with the proportion highest among men in their sixties.

Representative factors that raise summer myocardial infarction risk include dehydration and excessive air conditioning. When you sweat heavily and body water rapidly declines, blood viscosity rises and a milieu that favors clot formation develops. Excessive cooling can also be problematic, as moving from hot outdoor conditions into an indoor space with strong air conditioning can cause blood vessels that had dilated to shed heat to constrict abruptly. During this process, pressure on the heart can spike and an atherosclerotic plaque inside a vessel may rupture, so caution is needed.

A prodromal sign of myocardial infarction is a tearing chest pain unlike anything previously experienced. It may feel like a heavy, crushing pain as if an elephant is stepping on you. If such symptoms do not subside for more than 30 minutes even at rest, or are accompanied by radiating pain that spreads to the inner side of the left arm or to the tip of the jaw, you should head to the emergency department promptly. Some older adults or people with diabetes experience silent myocardial infarction without chest pain, and even without chest pain there may be sudden shortness of breath, overwhelming fatigue, cold sweat, nausea, or a sense of pressure in the pit of the stomach. In such cases, accurate diagnosis with electrocardiogram and blood tests is required.

The most important thing is to arrive at the hospital within two hours, the golden time after symptom onset. Thrombolytic drug therapy to dissolve the clot in a coronary artery can be used, but when possible a procedure that mechanically opens the blocked vessel is more effective. The representative approach is percutaneous coronary intervention, which expands the vessel with a balloon or metallic stent, and the golden time is two hours because opening the blocked artery by then minimizes myocardial damage.

Experts advise that although the heat has arrived early this year, those at risk of myocardial infarction can help prevent it by keeping the indoor-outdoor temperature difference around 5 degrees and carrying a light outer layer to prevent abrupt body temperature changes. Im Sang-yeop, a professor in the Division of Cardiology at Korea University Ansan Hospital, said, “Acute myocardial infarction differs greatly in survival and prognosis depending on how quickly the blocked artery is reopened after onset, so you should be diagnosed rapidly in the emergency department as soon as symptoms appear and, if necessary, undergo percutaneous coronary intervention without delay” and “Middle-aged adults who have underlying conditions such as hypertension, diabetes, or hyperlipidemia, or who smoke, should avoid strenuous outdoor activity during heat waves.”