press information / news

01.08.2022

Heart attack on hot days - which role do cardiovascular drugs play?

On days with high temperatures, people taking certain medications have an increased risk of heart attack: this was found by a team of researchers led by Alexandra Schneider, PhD, research group leader 'Environmental Risks' at the Helmholtz Munich Institute of Epidemiology and Kai Chen, PhD from Yale Institute for Global Health.

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For people with coronary artery disease, beta-blockers may improve quality of life and antiplatelet drugs may reduce the risk of heart attack. However, the results of the new study suggest that these protective measures may also have an opposite effect on particularly hot days.

It is well known that environmental factors, such as air pollution and low outdoor temperatures, can trigger heart attacks. In addition, there is growing evidence that acute myocardial infarction can also be triggered by heat. However, it was previously unclear whether patients who take certain cardiovascular medications have a higher risk of suffering a heart attack on hot days than patients who do not take these regular medications. The researchers investigated this question and used data from the Augsburg Myocardial Infarction Registry from 2001 to 2014 for their analyses. A total of 2,494 cases were examined during the months of May to September.

Increasing risk of heart attack by more than 60%

The researchers found a significantly increased risk of nonfatal myocardial infarction on hot days compared with cooler control days in patients taking antiplatelet medications or beta-blockers compared with patients not taking these drugs. Antiplatelet use was associated with a 63% increase in risk, and beta-blockers use was associated with a 65% increase in risk. Patients who took both medications had a 75% higher risk. Non-users of these medications were not more likely to have a heart attack on hot days. It is also interesting to note that the effect of medication use was stronger in the younger age group (25-59 years) than for older patients (60-74 years), although the latter were more likely to have underlying coronary heart disease.

Possible reasons

The research findings do not prove that these drugs caused the heart attacks in the heat. However, based on these data, the scientists speculate that taking the medications makes it more difficult for the body to thermoregulate, i.e., adapt to high temperatures. Thus, the medication could actually make these patients more sensitive to heat exposure. However, it is also conceivable that the underlying severe heart disease explains both the prescription of the drugs mentioned and the higher sensitivity of these patients to heat. The latter hypothesis is contradicted by the fact that the observed increase in risk due to the use of the drugs was particularly pronounced in the younger and generally healthier group of patients. Furthermore, no other medication frequently taken by cardiac patients was found to increase the risk of myocardial infarction in the heat (with the exception of statins).

Patients should take special care during hot days

"The results suggest that heart attacks may become a greater risk for patients with existing cardiovascular diseases as climate change progresses and hot and very hot days become more frequent”, explains Dr. Alexandra Schneider. Especially during heat waves, she says, it is therefore advisable for patients to be cautious and stay in cool areas. "However, which subgroups of the population are most susceptible to these environmental extremes, and thus would benefit most from health heat protection tailored to them, is still unclear and requires further research," she says. In particular, the scientist explained, more research is needed on the effect of medications on thermoregulation, the altered effectiveness of medications during heat, and the interaction of medications with health-related heat effects such as dehydration. "Only then general practitioners can react to announced hot days and heat waves and adjust the medication of their patients accordingly at short notice," Dr. Alexandra Schneider states.

Funding

The study was funded by the German Foundation of Heart Research, the University of Augsburg, and the University Hospital of Augsburg, Germany.

Original publication
Kai Chen et al.: Triggering of myocardial infarction by heat exposure is modified by medication intake, Nature Cardiovascular Research. DOI: 10.1038/s44161-022-00102-z