People with heart conditions are being urged to take extra measures to prevent life-threatening heat illnesses and heart attacks as record-breaking temperatures grip the southern states.

The NSW Bureau of Meteorology forecast a high of 34 degrees in Sydney on Saturday with Olympic Park in the city’s west likely to reach 36 degrees by mid afternoon.

In the west of the state, temperatures, while not as high as Friday’s record-breaking temperatures in the southern Riverina, places like Dubbo will experience extreme heatwave conditions of 43 degrees and 45 degrees in Bourke.

The southern states of Victoria and Tasmania, while breathing a sigh of relief at milder conditions over the Australia Day long weekend, will experience temperatures of 35 degrees again by Wednesday.

Anyone who has had a previous heart event, or is taking medication for blood pressure or excess fluid, such as a diuretic, is at increased risk during the heatwave, the Heart Foundation warned on Friday.

“It’s a battle of the organs. It’s the tension between the heart and the skin,” Ms Rachelle Foreman, Heart Foundation’s Director of Support and Care, told The New Daily.

“People with any heart disease might not realise that this sort of temperature would be putting their heart under increased stress.”

Heat continues. An inland trough draws hot northerly winds, raising temperatures well above average. Some relief along the south coast on Saturday with a weak southerly wind change. A stronger change late Sunday will cool the southern half of NSW. Check: https://t.co/UqlGxUaTcW pic.twitter.com/EEf0tjdrnd

— Bureau of Meteorology, New South Wales (@BOM_NSW) January 26, 2019

This includes individuals with a previous history of heart attack, heart failure or abnormal heart rhythm, Ms Foreman said.

As the temperature rises, the body responds to counteract the effects of the heat by increasing blood flow to the skin and by sweating. This leads to dehydration and reduces the volume of blood.

Once this occurs, the heart has to pump harder to circulate the reduced blood around the body, causing the organ to become overwhelmed, resulting in a heart attack.

Individuals with heart conditions are also at increased risk for heat stress, which can mimic some of the lesser-known heart attack symptoms, Ms Foreman said.

“People often think that with a heart attack it’s going to be that crushing chest pain. Or that tight pressure around your chest. However, that is the case for less than 50 per cent of people,” she said.

Symptoms common to both events include nausea, vomiting, feeling faint, sweaty hands, shortness of breath, or rapid heart rate.

Ms Foreman said everyone should learn to recognise these warning signs, and if in doubt, call an ambulance, as heat stress is also a life-threatening situation.

“They’re the symptoms that we know where people often hesitate to call triple zero. Our message is that the ambulance is there to help in that situation.

“Time is muscle. The longer you wait, the longer your heart muscle is dying. It’s that delay that causes unnecessary death and disability,” Ms Foreman said.

Heart Foundation NSW CEO Kerry Doyle said people should make sure they are adequately prepared and to think about how they will look out for each other as temperatures continue to soar.

“Heatwaves also take a particular toll on the health of our elderly relatives and friends – and I would urge people to be vigilant about looking out for them during these hotter days,” she said.

Heatwave health tips:

• Keep cool and stay indoors
• Drink plenty of water (with caution if your doctor has recommended limiting your fluids with heart medication)
• Wear light clothing
• Recognise the warning signs of heat stress and a heart attack, and call triple zero if you need help
• Look after loved ones who are at increased risk
• Avoid alcohol