Hot weather and your heart

Hot weather and your heart

How do heatwaves and hot weather affect my heart?

Hot weather means your body has to work harder to keep its core temperature at a normal level. This can put extra strain on your heart, lungs and kidneys.

For people with a heart condition, this can mean that you can be at greater risk of becoming unwell. So, it's particularly important to stay cool and hydrated.

How does hot weather affect my blood pressure and heart rate?

When it’s hot your body gives off heat to try and cool itself down on the inside.

It does this by opening your blood vessels wider than normal (called vasodilation). Your heart will also beat quicker to help pump blood around your body.

This can cause your heart rate to increase and your blood pressure to drop. Some people may feel dizzy or lightheaded.

Drinking plenty of fluids will help you stay hydrated and stop your blood pressure from dropping too much.

Who is most at risk in hot weather?

Some people are more at risk during the hot weather and heatwaves, such as:

• Older people, over 75, and very young children find it harder to regulate their temperature and so can be more at risk from extreme temperatures.
• Older people can also be at a higher risk because they're more likely to live on their own and have less social contact.
• People with long-term health conditions, including heart or circulatory conditions, lung conditions, kidney problems, diabetes and Parkinson's disease.
• People who find it harder to avoid the heat or to adapt their behaviour, such as people who are bedbound, have a disability, dementia, or work outdoors.

It’s important to check on your friends and family regularly in hot weather to make sure they are cool and comfortable.

Heart conditions, medicine and hot weather

Angina and hot weather

If you use a GTN spray to control your angina you should take extra care in hot weather.

GTN spray can dilate (expand) your blood vessels quickly, which causes your blood pressure to suddenly drop, and you may feel dizzy and faint.   

Heart failure and hot weather

It’s particularly important to stay cool if you have heart failure.

If you’ve been told to restrict your fluid intake, speak to your GP about other ways to keep cool during summer. If you take water tablets (diuretics) and feel dizzy or lightheaded let your doctor know.

Staying cool in hot weather

How can I stay cool in hot weather?

There are some simple things you can do to keep cool in hot weather:

• Keep hydrated. Drink plenty of water or other drinks. While water is best, low-fat milk, sugar-free drinks, tea and coffee all count. Try and stick to no more than 3 to 5 cups of tea or coffee a day or switch to decaffeinated versions.
• Avoid too much alcohol. Drinking too much alcohol can make you more dehydrated.
• Eat cold foods. Colder foods like salads and fruit have a higher water content and are good sources of vitamins and minerals. You could also try freezing some healthy snacks, like blending banana and milk then freezing it. Or making ice cream by blending frozen fruit. 
• Keep your home cool. Keep your windows shut when the outside temperature is hotter than inside your home and shut curtains or blinds to keep out the sun. When the weather cools down in the evenings, open your windows for a fresh breeze. Turn off any lights or electrical equipment you do not need, as they can make your home hotter.
• Sleep in the coolest room. It can help to temporarily sleep in another room if it's cooler, you could get friends or family to help you move bedding to keep you comfortable. You could also swap your duvet for a lightweight sheet.
• Wear clothes that keep you cool. Wearing light, loose-fitting clothes can help keep you cool. Try to avoid synthetic materials (like polyester) if you can as they can make you sweat more.
• Avoid the hottest part of the day. To stay safe while enjoying the warmer weather, it's important to try and stay out of the sun during the hottest part of the day, between 11am and 3pm. 
• Sunscreen, hat and water. Always go out with sunscreen, a hat and water to make sure you're safe in the heat. 
• Avoid some types of exercise. Some types of exercise, like running, football and other sports, can make you very hot and dehydrated. They will also put extra pressure on your heart during hot weather. 
• Use cold water to cool down. Cold showers, baths or soaking your feet in cold water can help cool you down. You can also wet a hand towel with cold water to put on your head. 

When to get help in hot weather

What should I do if the heat makes me feel ill?

These are 4 quick ways to feel better if you are feeling ill in the heat: 

1. move to a cool place
2. lie down and raise your feet slightly
3. drink plenty of water
4. cool down your skin by having a cold shower, using a fan or ice packs.

If you do not start to feel better, contact NHS 111 or your doctor. 

What are the symptoms of heat stroke?

Symptoms of heat stroke include:

• sweating
• cold clammy skin
• dizziness
• fainting
• muscle cramps
• heat rash
• swelling (oedema) in your ankles
• shallow or fast breathing
• feeling sick (nausea) and being sick (vomiting).  

Losing too much body fluid can increase your internal body temperature, which could be life-threatening if left untreated. 

If you think that you or someone else has heat stroke, get medical attention immediately by calling 999 or going to your nearest A&E department.

Get support

• Speak to our cardiac nurses by phone, callback, email or online chat on Heart Helpline (Monday to Friday, 9am to 5pm).
• Join our HealthUnlocked online community to connect with others with a heart or circulatory condition.
• Sign up to our Heart Matters magazine for online information packed with health and lifestyle information.