UAE heat and humidity can put extra strain on the heart - here are the warning signs

Dubai: August is nearing its end, but the UAE heat is still taking a toll, with temperatures reaching 48°C and humidity making even evenings feel hotter. While heat exhaustion and dehydration are well-known summer risks, there is another part of the body that can come under pressure - the heart.

Doctors told Gulf News that extreme heat makes the heart work harder and beat faster, while dehydration reduces blood volume, adding further strain. For some people, this can increase the risk of palpitations, irregular heart rhythms, heart failure complications and, in vulnerable cases, heart attacks.

“High temperatures and high humidity create a particularly demanding environment for the cardiovascular system. When the body becomes hot, blood vessels near the skin widen so that more blood can be directed toward the skin to release heat. To maintain blood pressure and circulation at the same time, the heart has to beat faster and pump more blood,” Dr. Jan Niclas Strickling, Consultant Cardiology at Medcare Hospital Al Safa, explained.

Dehydration adds another layer of stress because losing fluid reduces the amount of blood circulating through the body. With less blood returning to the heart, the amount of blood pumped with each heartbeat, known as stroke volume can fall. The heart then compensates by increasing its rate to help maintain circulation.

Research involving healthy people exercising in the heat has demonstrated that progressively greater dehydration is associated with a progressively higher heart rate and lower stroke volume.

It is not just high temperatures that put pressure on the body. With summer temperatures in much of the UAE rising to 47°C, high humidity can make it harder for the body to cool itself.

“Humidity makes this situation more challenging. Sweating cools us primarily when sweat evaporates from the skin. In high humidity, evaporation becomes less efficient, so the body has greater difficulty releasing heat even though it may continue sweating and losing fluid. This is why temperature alone does not tell the whole story when assessing heat stress,” Strickling said.

In a climate such as the UAE’s, heat, humidity and dehydration can work together. The body is working harder to cool itself while the heart is simultaneously trying to maintain adequate circulation with a reduced fluid volume.

“The cardiovascular demand becomes even greater during outdoor exercise, prolonged sun exposure or physical work,” Strickling said.

Dehydration can increase the risk of abnormal heart rhythms, particularly in people who already have cardiovascular disease. Fluid loss is often accompanied by changes in electrolytes, particularly sodium and potassium, which play an important role in the heart’s electrical activity.

“For patients with coronary artery disease, dehydration can also contribute to reduced blood flow to the heart. The combination of reduced circulating blood volume, increased heart rate and increased cardiovascular demand can potentially provoke myocardial ischemia and, in vulnerable patients, contribute to an acute coronary syndrome or heart attack,” Dr. Ahmed Sharafeldin, Consultant Interventional Cardiologist at RAK Hospital, said.

Common medications used to treat cardiovascular conditions, particularly diuretics, can increase the risk of dehydration during hot weather. Often referred to by patients as “water pills”, diuretics increase fluid loss through the kidneys.

“In particular, diuretics used in combination with other medications such as ACE inhibitors or angiotensin receptor blockers (ARBs) can make individuals more susceptible to low blood pressure, especially when dehydration occurs. Patients taking these medications should be mindful of maintaining adequate hydration,” Dr. Jesse Bracamonte, a family medicine physician at Mayo Clinic, told Gulf News.

People taking these medications should try to stay ahead of dehydration rather than waiting for symptoms to appear.

“Signs of dehydration can include increased thirst, dry mouth, dark urine, dizziness, lightheadedness, fatigue, palpitations, or a rapid heartbeat. Patients should drink fluids regularly throughout the day, avoid prolonged heat exposure when possible, and pay attention to urine color, which can be a simple indicator of hydration status,” Bracamonte explained.

Pale-yellow urine generally suggests adequate hydration, while darker urine may indicate the need for more fluids.

The first signs of dehydration are not always dramatic. Increased thirst, unusual fatigue, weakness, headache and reduced exercise tolerance can be among the earliest indications.

People may also notice a faster-than-usual heart rate or palpitations, dizziness or light-headedness, particularly when standing, muscle cramps, reduced or darker-coloured urine, excessive thirst and sweating initially, or a feeling of faintness after prolonged standing or exertion.

“For people with Coronary Artery disease, heart failure, arrhythmias or other cardiovascular disease, the threshold for concern should be lower. Dehydration and heat can increase cardiovascular demand and may aggravate underlying disease,” Dr. Ahsanul Hoque, Specialist Cardiology, Aster Cedars Hospital & Clinic, Jebel Ali, said.

Hoque said chest pain or pressure, significant shortness of breath, persistent palpitations, fainting, confusion, severe weakness or a marked deterioration in a person’s condition require urgent medical assessment.

“Confusion, loss of consciousness and very high body temperature are particularly concerning for heat stroke, which is a medical emergency.”

Strickling also warned against dismissing serious symptoms as simple dehydration.

“From a cardiology perspective, chest pain, persistent or very rapid palpitations, significant shortness of breath, fainting, confusion or loss of consciousness during heat exposure should not simply be attributed to dehydration and should prompt urgent medical assessment,” Strickling said.

For an otherwise healthy person, mild dehydration is much more likely to cause a faster heartbeat, noticeable palpitations, dizziness or light-headedness than a serious cardiac event. Severe dehydration, particularly when combined with extreme heat or strenuous exercise, can be more serious.

It is important to put the risk into perspective: dehydration alone would be an unusual cause of a heart attack in a genuinely healthy person.

“In an otherwise healthy person, mild dehydration is much more likely to cause a faster heartbeat, noticeable palpitations, dizziness or light-headedness than a serious cardiac event. The heart increases its rate to compensate for the reduction in circulating volume and maintains blood pressure and blood flow,” Strickling noted.

“Dehydration does not simply make you thirsty. It makes your cardiovascular system work harder. In extreme heat and humidity, particularly during exercise, that additional workload can become clinically significant even in someone who considers themselves healthy,” Strickling noted.

There is no single amount of water that is appropriate for everyone. Fluid requirements depend on body size, temperature, humidity, physical activity, sweating and medical conditions.

In the UAE, people who spend prolonged periods outdoors generally need to drink regularly rather than waiting until they feel thirsty.

“For most healthy people doing routine daily activities, water is sufficient. During prolonged or intense exercise, heavy sweating, or several hours of outdoor work in extreme heat, however, water alone may not always replace the sodium and other electrolytes lost through sweat. In these circumstances, an electrolyte-containing drink can be useful, particularly if sweating is substantial,” Sharafeldin said.

“The key message is to avoid both extremes - do not wait until you are very thirsty to drink, but also do not force excessive amounts of plain water in a short period, as this can rarely lead to dangerously low blood sodium levels,” Sharafeldin noted.

“Do not wait until you feel extremely thirsty. In hot conditions, regular fluid intake, limiting prolonged exposure to peak heat, and paying attention to urine concentration and symptoms are sensible preventive measures. People with heart failure or other conditions requiring fluid restriction should follow their clinician’s individualized fluid plan rather than simply increasing fluids.”

People with heart failure, kidney disease or other conditions requiring fluid restriction should follow their physician’s individualised recommendations rather than changing their fluid intake on their own.