Background
The authors write that "previous studies reported an association of cold weather conditions with an excess incidence of acute coronary syndromes (ACS) according to hospital discharge reports (Eurowinter Group, 1997; Spencer et al., 1998; Danet et al., 1999; Kloner et al., 1999; Dilaveris et al., 2006 )." But they go on to say that "whether these epidemiologic facts also translate into a significantly different rate of acute coronary angiographies between two consecutive winters characterized by a dramatic temperature increase is less clear." So they thus decided to attempt a clarification of the situation.

What was done
Noting that the 2005/2006 winter was very cold, while the 2006/2007 winter was extraordinarily warm, Wanitschek et al. studied the cases of patients who were suffering acute myocardial infarctions and had been referred to the University Clinic of Internal Medicine III (Cardiology) at Innsbruck Medical University, Tyrol, Austria, for coronary angiography (CA), comparing their risk factors and in-hospital mortality rates between these two consecutive winters, the latter of which was 7.5°C warmer than the former.

What was learned
The six Austrian researchers report that in terms of the colder winter vs. the warmer winter, the percentages of an essentially identical total CA in each winter (987 vs. 983) that were acute CA were 12.9 vs. 10.4%, while diagnoses of STEMI (ST Elevation Myocardial Infarction) as an indication of acute CA were74.0 vs. 62.7%.

What it means
In the words of Wanitschek et al., "the average temperature increase of 7.5°C from the cold to the warm winter was associated with a decrease in acute coronary angiographies, in particular due to a lower incidence of STEMI referred for primary percutaneous intervention."

References
Danet, S., Richard, F., Montaye, M., Beauchant, S., Lemaire, B., Graux, C., Cottel, D., Marecaux, N. and Amouvel, P. 1999. Unhealthy effects of atmospheric temperature and pressure on the occurrence of myocardial infarction and coronary deaths. A 10-year survey: the Lille-World Health Organization MONICA project (Monitoring trends and determinants in cardiovascular disease). Circulation 100: E1-7.

Dilaveris, P., Synetos, A., Giannopoulos, G., Gialafos, E., Pantazis, A. and Stefanadis, C. 2006. Climate impacts on myocardial infarction deaths in the Athens territory: the CLIMATE study. Heart 92: 1747-1751.

Eurowinter Group. 1997. Cold exposure and winter mortality from ischaemic heart disease, cerebrovascular disease, respiratory disease, and all causes in warm and cold regions of Europe. Lancet 349: 1341-1346.

Kloner, R.A., Poole, W.K and Perritt, R.L. 1999. When throughout the year is coronary death most likely to occur? A 12-year population-based analysis of more than 220,000 cases. Circulation 100: 1630-1634.

Spencer, F.A., Goldberg, R.J., Becker, R.C. and Gore, J.M. 1998. Seasonal distribution of acute myocardial infarction in the second National Registry of Myocardial Infarction. Journal of the American College of Cardiology 31: 1226-1233.