Heat-related nonfatal myocardial infarction (MI) risk was elevated by 63% among patients taking antiplatelet medications and by 65% in those prescribed ß-blockers, according to a new study from investigators at the Yale School of Public Health, with higher risk seen among younger patients taking drugs in either class despite a lower prevalence in this group of pre-existing coronary heart disease (CHD).
The findings, arriving as record-breaking extreme temperatures are being recorded globally, were published August 1, 2022, in Nature Cardiovascular Research.
While acute exposure to elevated temperatures has been associated with increased risk of MI, very few epidemiologic studies have assessed the potential role that CV medication use might play in heat-related MI risk, the authors write. In the team’s previous research of the impact of temperature on MI they found that both heat and cold exposure could trigger MI onset and that the burden of heat-related MI “will likely increase at a 2 °C and 3 °C rise in global warming.” Thus, they stress “Identifying vulnerable subpopulations based on medication intake is critically needed to reduce the burden of heat-related MI in a warming climate.”
Their study examined whether medication use before hospitalization modifies the association between extreme heat exposure on the day of nonfatal MI onset and risk of MI occurrence.
The double-blind crossover study used data from the MONICA/KORA MI registry in Augsburg, Germany collected during warm seasons (May to September) from 2001–2014. The registry, ongoing since 1984, has recorded all cases of MI occurring among area residents aged 25 to 74 years. The study was restricted to non-fatal cases of MI, ie, patients who survived to at least the 28th day after hospital admission.
There were a total of 2494 nonfatal MI occurrences recorded during the study period. Of those, 76.4% were men, 60.9% were aged 60–74 years, 31.3% had diabetes, 77.7% had hypertension, and 27.7% had CHD. Medication intake before the event is below.
The researchers found a significant heat-related risk for nonfatal MI among patients taking antiplatelet medications (odds ratio [OR] 1.63; 95% CI 1.07-2.46) but not among nonusers (OR=0.94; 95% CI, 0.68-1.29). They observed a similar risk among those taking ß-blockers (OR=1.65; 95% CI, 1.11-2.45) vs nonusers (OR=0.90; 95% CI, 0.64-1.26). The OR among patients taking antiplatelet drugs was significantly higher than among nonusers (P=.04) as was the OR among those taking ß-blockers vs those not taking them (P=.02)
For patients taking both classes of medication, risk of heat-related MI was significant (OR=1.75; 95% CI, 1.12-2.73) but did not meet significance among nonusers of both (OR=0.84; 95% CI, 0.59-1.19). Further analysis found the OR among users significantly higher than among non-users (P=.01)
When investigators looked at the cohort by age group, younger patients (aged 25-59 years), were generally healthier than older patients (aged 60-74 years), as evidenced by prevalence of diabetes (23.7% vs 26.2%), hypertension (67.6% vs 84.1%) and pre-existing CHD (18.9% vs 33.3%).
The effect modification by the 2 types of medication observed in all patients became stronger in the younger patients (P<.01) but weaker in the older patients (P>.05). The team also observed that among younger patients there was a significant heat-related risk for non-fatal MI among those taking statins but not among statin non-users, with the OR among users significantly higher vs among non-users (P<.01).
Although their findings are not evidence of a cause-and-effect relationship between elevated heat and MI, the researchers speculate that the medications may hamper human thermoregulation, potentially making patients more heat sensitive. Further research is needed, however, “to disentangle effect modification by medication use from effect modification by pre-existing CHD.”
Also, we are still a long way, the authors suggest, from the day general practitioners can adjust patient medications in response to a morning news alert of a heat wave or a blistering day ahead. However, the findings do suggest that the risk of MI may become greater for patients with existing cardiovascular diseases as climate change progresses and extreme heat becomes more frequent. For now, they add, urge patients to be cautious and to stay cool.
Reference: Chen K, Dubrow R, Breitner S, et al. Triggering of myocardial infarction by heat exposure is modified by medication intake. Nat Cardiovasc Res. 2022. doi.org/10.1038/s44161-022-00102-z