Morning heart attacks are more dangerous than evening ones

Apparently, the time of day when a heart attack occurs may determine how deadly it is.

Myocardial infarctions that strike between 6 AM and noon tend to leave a much larger area of dead tissue than those occurring at other times of the day, according to the results of a retrospective, single-center study from Spain. Infarcts occurring between noon and 6 PM apparently are the least harmful.

Researchers included 811 patients who suffered an ST segment elevation myocardial infarction (STEMI) between 2003 and 2009. Most of the patients had their heart attacks between 6 AM and noon (n=269); 240 had them between noon and 6 PM; 161 occurred between 6 PM and midnight; and 141 happened between midnight and 6 AM.

They also found that those who had an anterior wall STEMI had significantly more damage that those with STEMI in other locations.

The authors of the study believe the findings could affect significantly the interpretation of clinical trials involving cardioprotective strategies for STEMI.

Suárez-Barrientos A, López-Romero P, Vivas D, et al. Circadian variations of infarct size in acute myocardial infarction. Heart. April 27, 2011. [Epub ahead of print.]