Extreme heat puts the heart at risk: 70 per cent of deaths are due to cardiovascular causes
Heatwaves should be regarded as a modifiable risk factor, just like high blood pressure, diabetes and smoking: here are the principles of Climate Cardiology
Unfortunately, heatwaves are no longer an occasional emergency, but a situation that the healthcare system must, and will have to, deal with ever more frequently. Climate change, even before being an environmental issue, could now be considered a cardiovascular issue. It is no coincidence that the international scientific community has begun to talk about “Climate Cardiology”: the discipline that studies the effects of climate on the heart and blood vessels, with a view to developing new prevention strategies.
The data
From an epidemiological perspective, the evidence shows that, on days of extreme heat, there is an increase in both A&E visits and hospital admissions, as well as in mortality from cardiovascular causes. In fact, these same epidemiological studies show that over 70 per cent of heatwave-related deaths are attributable to cardiovascular causes, thus making the heart one of the main organs affected by extreme heat.
The explanation is physiological. To dissipate heat, vasodilation occurs alongside increased sweating: the heart has to work harder to ensure adequate perfusion, whilst fluid loss can lead to dehydration, hypotension and electrolyte imbalances.
Natural stress test
In young people, these mechanisms are better compensated for, whereas in patients with chronic cardiovascular disease, or in the elderly, there is instead a fragile balance that is easily disrupted.
The latest evidence suggests that heat is not merely an environmental stressor, but a genuine “natural cardiovascular stress test”. In fact, a rise in temperature simultaneously triggers haemodynamic, neuroendocrine, inflammatory and thrombotic mechanisms which, in vulnerable individuals, can transform a stable chronic condition into an acute event.
