Heart attacks more severe in morning

Here’s another reason to dread mornings: Heart attacks may be slightly larger early in the day.

Scientists already knew that heart attacks were more common in the morning. But they were unsure about the size of those heart attacks. In rodents, the size of heart attacks roughly follows the body’s natural circadian rhythms, so they suspected the same might be true of people.

Spanish researchers analyzed records of 811 patients brought to the Hospital Clínico San Carlos in Madrid, Spain, between 2003 and 2009 for a STEMI -- ST segment elevation myocardial infarction -- a severe type heart attack. They gauged the size of the heart attack by the peak levels of two heart-attack-related enzymes, creatine kinase and troponin-I. (Here’s more on blood tests for heart-attack diagnosis.)

As expected, more patients were treated between 6 a.m. and noon. But the size of their heart attacks was “significantly larger” too -- the concentration of creatine kinase was 18% higher and troponin-I was almost 25% higher for heart attacks that occurred between 6 a.m. and noon than it was for heart attacks that occurred at other times of day. 

The researchers, who published their findings online Wednesday in the journal Heart, acknowledge that enzyme levels are an indirect way to measure the ultimate effect of the heart attack -- that is, the extent of dead heart tissue.

And if the body’s circadian rhythms -- blamed for the frequency of morning heart attacks -- are also somehow affecting the size of the heart attack, the precise connection is unclear. 

But if follow-up studies confirm their findings, the authors say, doctors and scientists conducting clinical trials that measure heart attacks will need to take the day of time into account. 


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