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Severity of MI dependent on time of day
Reiter R. Circ Res. 2011;doi:10.1161/CIRCRESAHA.111.254284.
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Researchers recently discovered that the time-of-day onset of ischemia may significantly affect the size of an MI and subsequent left ventricular function.
Previous research revealed that the infarct size in rodents after ischemia and reperfusion exhibited a circadian dependence on the time of coronary occlusion. However, it was unknown whether a similar circadian dependence of infarct size occurs in humans.
Researchers for this study conducted a retrospective analysis of 1,031 patients with STEMI who were referred for primary percutaneous coronary intervention. All patients had known ischemic times between 1 and 6 hours. Analysis identified 165 patients with occluded arteries on presentation without evidence of preinfarction angina or collateral blood flow. All of the patients had well-defined ischemic times, and the data were supported by a subgroup with cardiac MRI measurements of infarct size and area at risk.
The greatest myocardial injury occurred at 1 a.m. onset of ischemia and 5 a.m. onset of reperfusion, with the peak injury 82% higher than that recorded at the lowest time of injury. LV ejection fraction measured within 2 days of infarction was 7% higher during these times, according to the results.
“It is important to understand that the heart’s ability to protect itself against more severe damage varies over a 24-hour cycle,” study researcher Jay H. Traverse, MD, a cardiologist at the Minneapolis Heart Institute Foundation, said in a press release. “Identifying those protective changes may be particularly relevant for pharmaceutical manufactures that are seeking to develop cardioprotective drugs.”
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