5 health issues that can worsen in a heat wave — including how high temps can trigger a heart attack and stroke

This week, millions of Americans — including New Yorkers — are grappling with what forecasters are calling a “very sweaty” heat wave.

It’s miserable — but it’s worth remembering that, without the proper precautions, it’s also extremely dangerous.

Dehydration can cause dizziness, headaches, low blood pressure, blurred vision, kidney problems and, in extreme cases, fatal heatstroke.

And that’s just in healthy people.

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While everyone should try to stay cool and hydrated in these sizzling temperatures, The Post spoke to two doctors who warn that people with these health issues are at especially high risk.

Heart disease

“Those with cardiovascular disease are at high risk since these patients are often asked to limit fluid intake,” Dr. Thomas Gut, associate chair of medicine at Northwell’s Staten Island University Hospital, told The Post.

“Sweating beyond the normal daily expected amount can lead to significant fluid shifts and electrolyte imbalances that can cause significant harm, especially to those already taking diuretics medications.”

Dr. Nima Majlesi, who practices emergency medicine at the same hospital, told The Post that high temperatures can mess with the normal blood flow to the heart, potentially causing acute coronary syndrome, which spikes the risk of heart attack.

When you get really hot, your body needs to work harder to cool you down, which can also place more strain on the heart.

For this reason, people who are at risk for heart failure are also in danger of getting worse in the heat, Majlesi noted.

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Respiratory diseases

It’s normal to experience some difficulty breathing when it’s really hot, because your body’s attempts to cool down require more oxygen.

However, Gut warns that people with respiratory diseases are at greater risk because “hot air, especially if humid, can trigger patients with even well-controlled breathing conditions into rapid and shallow breathing.”

Those who depend on supplied oxygen are of particular concern, since power outages are more common during heat waves due to “the increased demand for homes needing cooling — power outages can leave those vulnerable patients without additional oxygen supplies,” he said.  

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Kidney disease

“Patients with kidney disease are also at high risk for electrolyte imbalances as their hydration status and sweating fluctuates during heat waves,” Gut said.

Psychiatric conditions and drug users

“In younger populations, neuropsychiatric conditions and underlying drug use disorders create a very high risk for issues with heat stroke,” Majlesi said.

“Cocaine-related deaths increase exponentially during heat waves, for example.”

Cocaine is a stimulant that increases your body temperature and puts extra strain on your heart, both of which can cause serious issues during a heat wave.

The same goes for other psychological conditions that put your heart to work — such as anxiety.

Anyone on medication that slows the body’s natural cooling process

“Diuretics, allergy medications and psychiatric medications can all create issues in this patient population,” Majlesi said.

What’s the worst that can happen?

According to Gut, dehydration can lead to headaches, fatigue and nausea — and in worse cases, confusion, muscle spasms, seizures and even coma.

“Heat stroke has dire consequences for a large percentage of patients,” said Majlesi. “Time [it takes] to cool is the No. 1 risk for death and severe injury.

“Gastrointestinal hemorrhage, vomiting and diarrhea occur frequently as blood is shifted away from intestinal perfusion.”

Liver and kidney injury are also possible, though the former won’t happen until the second or third day.

“Cerebral ischemia leading to stroke is common in the setting of excessive heat stress also for similar reasons as blood shunts away from central circulation to cool,” he added.

How can you avoid getting sick?

To stay safe, Gut recommends the following:

• Drink half a glass of water per hour, or as instructed by your doctor
• Consume drinks that contain electrolytes without added sugar
• Avoid coffee, soda and alcohol
• Stay in the shade or, better yet, indoors
• Avoid being in direct sunlight
• If you have to be in the sun, wear sunscreen and cover your head
• Cool off with a misting spray bottle with water