Extreme heat, why the heart is at risk with scorching temperatures

Heat. Unbearable temperatures, with the mercury column that doesn't even drop at night. So there is also a lack of nocturnal "regeneration" for the heart and brain. If we then add a minimum of physical activity, then an explosive mixture can be created for blood circulation, with an increase in the risk of suffering from heart attacks or strokes. All of this, starting from the same reaction of the organism.

When temperatures rise, the heart rate must increase and the heart must work harder to pump blood to the skin to help sweat and cool the body. Evaporation, therefore, puts a strain on the cardiovascular system. Sweat disperses body heat, but it also causes the loss of sodium, potassium and other minerals needed for muscle contractions, nerve transmission and water balance. To counteract these losses, the body begins to secrete hormones that help the body retain water and reduce the impact of salt loss. In these cases, if the control system is not optimal, the dangers for blood circulation, the heart and the brain increase.

An example is heat stroke or heat exhaustion, caused by the loss of fluids due to excessive sweating, after exposure to heat in conditions of high humidity (greater than 80 percent). Initially it causes fatigue and weakness, then low blood pressure, slowing of the pulse, drop in blood pressure and even fever appear. In terms of pathologies, in particular, those who are obese and/or suffer from chronic diseases affecting the heart and lungs, from heart failure to COPD, can more easily encounter a series of complications, which obviously depend on the duration of the increase in body temperature.

The danger of hypotension

The heat and the humidity spikes can also contribute to excessively lowering the blood pressure, both due to the increase in blood flow to the skin (and to the stomach, during digestion) and due to dehydration. The warning signs of this condition are the appearance of sudden headaches, dizziness that arises especially when standing up, feeling "slowed down" or very tired, dry mouth, contraction of diuresis with very concentrated urine (dark and scanty).

Sometimes, therefore, one loses consciousness almost suddenly, because the brain does not receive enough blood and somehow “switches off”. The excessive drop in blood pressure – especially the elderly and women are at risk – is one of the most frequent causes of fainting in the summer. If, while standing, the maximum blood pressure quickly drops below 70 millimeters of mercury, one can, in fact, lose consciousness: the heart is unable to “overcome” the force of gravity needed to push the blood and oxygen to the brain, which then “fogs” and loses control of the organism.

A risky moment for those who are advanced in years and whose internal blood pressure detection systems are not exactly optimal is the sudden transition from a lying position to a standing one. Experts call this situation orthostatic hypotension: it is better to remain seated for some time before shooting, so as to give the body time to adapt.

Pay attention to the table and to your efforts

“Elderly people are especially at risk these days,” explains Claudio Borghi , Director of Cardiovascular Internal Medicine at the Policlinico S.Orsola in Bologna. The sun, for example, has a strong vasodilatory effect, meaning it causes blood vessels to widen and therefore tends to reduce blood pressure. As if that weren’t enough, the adaptation of blood vessels to stimuli from the outside environment is reduced, especially after lunch. This is a particularly risky time for those who suffer from blood pressure changes.”

“On average, digestion leads to a drop of about 10 millimeters of mercury for the maximum pressure and 5 for the minimum – adds the professor -. But in some people this decrease can be much more significant, even 20-30 millimeters of mercury. And it is obvious that in those who are particularly subject to pressure changes of this type, exposure to heat or physical activity during the digestion period can also give rise to serious problems”.

Watch the Heat Index

“Heat Index” is the parameter that expresses the relationship between humidity and heat. This index says a lot about the risks of suffering from heat stroke and consequent damage to the body, including cerebral stroke. Heat stroke, therefore the most serious form of exposure to the combined effect of high temperature and very high humidity, can favor the onset of cerebral ischemia, especially if intense efforts are made that increase the intensity of the body's thermal rise.

Elderly people more at risk

At risk are especially people with poorly reactive thermoregulation systems, such as the elderly, as well as subjects suffering from chronic diseases. But what happens and how does heat stroke develop that puts the brain at risk? First of all, dehydration, resulting from sweating (in an attempt to lower the temperature), affects the risk, which leads to a reduction in the volume of circulating blood and an increase in the viscosity of the blood itself, with the possibility of occlusion of a cerebral artery. Vasodilation, always in response to heat, can have effects on cerebral hemodynamics, with alterations in blood pressure and cerebral perfusion pressure. If we also add the risk related to physical activity, we risk increasing the dangers.

Ask your doctor about medications

Finally, don't forget that there are also medications that interfere with heat regulation. For example, those taking beta-blockers may have a reduced heart rate that prevents the heart from circulating blood as quickly as possible for effective heat exchange. Diuretics worsen dehydration by increasing urine production.

In short: those with high blood pressure should reassess their therapy with their doctor (no do-it-yourself, mind you). If your doctor recommends it, diuretics should be reduced or, if possible, avoided, as they lead to dehydration, potassium loss, and disturbances in the salts circulating in the blood. Finally, be careful if you also take vasodilator drugs, such as calcium antagonists and nitroderivatives, and ACE inhibitors and angiotensin antagonists.