Scientific Statement on Nonoptimal Ambient Temperature and Acute Cardiovascular Risk

Article Impact Level: HIGH
Data Quality: STRONG
Summary of  Circulation  https://doi.org/10.1161/CIR.0000000000001419
Dr. Kate Hanneman et al.

Points

Extreme environmental temperatures represent critical drivers of acute cardiovascular morbidity and are clinically shown to trigger sudden cardiac death, myocardial infarction, and ischemic stroke.
Heatwaves force the human body to dilate peripheral blood vessels and increase sweating, which dangerously lowers baseline blood pressure while simultaneously forcing the heart to pump harder.
Common cardiovascular medications such as diuretics can inadvertently increase patient vulnerability during extreme heat events by accelerating dehydration and fluid loss.
The United States healthcare delivery system paradoxically contributes to these environmental health hazards by generating approximately 8.5% of all national greenhouse gas emissions.
Experts recommend establishing dense urban tree canopies near residential zones and expanding digital telehealth infrastructure to actively reduce travel-related carbon emissions.

Summary

This scientific statement evaluated the physiological mechanisms, population-level vulnerabilities, and healthcare systemic impacts associated with exposure to nonoptimal ambient temperatures. Short-term environmental exposures to both extreme heat and extreme cold function as primary drivers of acute cardiovascular morbidity. These thermal stresses are clinically shown to precipitate myocardial infarction, ischemic stroke, heart failure decompensation, cardiac arrhythmias, and sudden cardiac death. While cold weather has historically accounted for a greater absolute volume of seasonal cardiovascular deaths, the escalating frequency, intensity, and duration of extreme heatwaves threaten to rapidly surpass cold-related mortality rates globally.

Physiologically, thermal stress compromises homeostatic equilibrium through distinct autonomic and neurohormonal pathways. High ambient heat triggers significant cutaneous vasodilation and heavy sweating to facilitate evaporative cooling, which reduces central blood pressure and fluid volumes. To maintain cardiac output under hypovolemia, the myocardium increases heart rate and contractility, inducing severe stress that can destabilize vulnerable atheromatous plaques. This strain is further compounded by essential cardiovascular pharmaceuticals, such as diuretics, which aggravate volume depletion. Conversely, cold exposure induces profound peripheral vasoconstriction and hemoconcentration, significantly elevating baseline blood pressure and systemic vascular resistance.

The statement highlights a critical paradox where cardiovascular care heavily fuels the environmental drivers of its own patient volume, with the United States healthcare sector generating approximately 8.5% of total national greenhouse gas emissions. Nonoptimal temperatures alter clinical operations by surging emergency department volumes and threatening the physical infrastructure of regional healthcare facilities. Mitigating these climate-driven cardiovascular events requires a multi-level framework, including proactive microclimatic urban planning, strategic telehealth expansion, and clinical investigation into seasonal drug adjustments. Extensive prospective research is immediately required to determine precise ambient temperature thresholds that jeopardize high-risk cardiac patients and to map long-term relative risk hazard ratios.

Link to the article: https://www.ahajournals.org/doi/10.1161/CIR.0000000000001419

References

Hanneman, K., Alahmad, B., Ghosh, A., Khatana, S. A. M., Huang, M., Liu, J., Abadi, A., Khraishah, H., Beckie, T., Rajagopalan, S., Angell, S., on behalf of the American Heart Association Council on Cardiovascular Radiology and Intervention, Council on Epidemiology and Prevention, Council on Lifestyle and Cardiometabolic Health; Council on Cardiovascular and Stroke Nursing, Council on Clinical Cardiology, & Council on Lifelong Congenital Heart Disease and Heart Health in the Young. (2026). Nonoptimal temperature and cardiovascular health: A scientific statement from the american heart association. Circulation, 153(16). https://doi.org/10.1161/CIR.0000000000001419