When the heart struggles to pump blood through widening vessels and the body desperately sheds water to cool itself, a single heat wave can become a medical crisis—a truth that cardiologists at Weill Cornell Medicine and other leading institutions are now amplifying with urgent clarity. The American Heart Association has released a groundbreaking scientific statement published in Circulation, warning that extreme temperatures are emerging as formidable cardiovascular risks, capable of triggering heart attacks, strokes, heart failure, and sudden cardiac death.
This matters now more than ever. Historically, cold weather has been the primary temperature-related killer—simply because cold days are more frequent. Yet the report delivers a sobering pivot: extreme heat events are increasing in frequency, intensity, and duration. With 2024 already holding the record as the hottest year since the National Oceanic and Atmospheric Administration began record-keeping in 1880, the calculus is shifting. Heat-related deaths may soon outweigh cold-related mortality, even as scientists are still learning how to prevent them.
The physiology is merciless. When temperatures soar, the body attempts cooling by dilating blood vessels and increasing perspiration—a process that simultaneously lowers blood pressure and drains body fluids. To compensate, the heart must work harder and faster, a dangerous demand for anyone with existing cardiovascular disease. The situation intensifies for millions taking heart medications like diuretics, which cause additional water loss. The cumulative stress can trigger a fatal event.
Certain populations face disproportionate risk. Older adults are especially vulnerable because aging diminishes the body's ability to self-regulate temperature. Pregnant individuals, infants, outdoor workers, and people with low incomes—who often lack access to air conditioning and live in neighborhoods with minimal shade—also occupy the frontlines of heat exposure.
Dr. Arnab Ghosh, associate professor of medicine at Weill Cornell and an internist at NewYork-Presbyterian/Weill Cornell Medical Center who led the statement's policy section, frames the challenge with unflinching honesty. Critical gaps remain in the science. Researchers still do not know the precise temperature threshold at which a person with cardiovascular risk becomes endangered. They cannot yet predict how repeated, long-term heat exposure compounds danger. And perhaps most troublingly for clinicians, the interaction between heart medications and heat stress remains largely unmapped—especially when patients take multiple drugs simultaneously. "When it's a hundred degrees outside, should I be adjusting my patients' medications? Right now, we just don't know," Dr. Ghosh said.
The authors call for multi-level action spanning research, clinical practice, and policy. Mitigating greenhouse gas emissions would remain the most effective long-term solution, yet Dr. Ghosh emphasizes that learning to live safely in a hotter world today cannot wait. Healthcare systems themselves must reimagine operations—expanding telehealth to reduce travel emissions, reconsidering unnecessary procedures, and eliminating wasteful disposables. Yet policy leaders hold equal power: keeping energy costs affordable so people can afford air conditioning, establishing cooling centers in vulnerable neighborhoods, and planting trees to lower urban temperatures.
The work ahead is vast. But the cardiologists speaking through this statement have made one thing clear: protecting hearts in an age of temperature extremes is not optional. It is urgent.