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The time of onset of a heart attack causes the degree of damage to the myocardium
Last reviewed: 16.10.2021
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The size of the infarction and subsequent left ventricular failure is significantly different from the time of onset of ischemia, according to the first such study in humans. The greatest damage to the heart occurs when a heart attack occurs between 1:00 and 5:00 in the morning.
In previous studies, the size of the infarct in rodents after ischemia and reperfusion showed a circadian dependence on the time of coronary occlusion. Previously, it was not known whether there was such a circadian dependence of the size of the infarct in humans.
"We tried to establish whether the time of day of the onset of a heart attack affects the amount of damage in the heart, or this phenomenon is inherent only in rodents," says senior study author JH Travers, a cardiologist at the Minneapolis Heart Institute.
In a retrospective analysis of 1,031 patients with acute myocardial infarction, myocardial infarction with ST elevation (STEMI), the researchers identified 165 patients with the first heart attack, as a result of blockage of the artery without evidence of angina before the infarction.
All 165 patients had clearly defined ischemic periods. The data were confirmed by cardiac MRI with the measurement of the size of the infarction, or the area of increased risk of myocardial infarction.
The researchers noted that the extent of the infarct size was significantly related to the time of onset of the infarction. The greatest damage to the myocardium was observed at 1:00 am from the onset of ischemia and at 5:00 am from the onset of reperfusion.
"It is important to understand that the ability of the heart to protect itself from more serious damage varies within a 24-hour cycle." Identifying these protective changes may be particularly important for pharmaceutical manufacturers who are seeking to develop cardioprotective medicines, "Traverse explained.