Table of Contents
- 1 First, how does the heart work?
- 2 What’s a heart attack?
- 3 How do you know you’re having a heart attack?
- 4 What causes a heart attack? Why does the blood flow get blocked?
- 5 Can you tell if you’re on the edge of a heart attack?
- 6 Who’s at risk of heart attack?
- 7 What should you do if you have a heart attack?
- 8 To what extent can heart attacks be prevented?
It’s a symbol of love and courage. It flutters with excitement and panic. It knows when to rest and when to quicken. But, most importantly, the heart is an extraordinary machine. “These doors inside your heart [the valves] have to flap open and closed 100,000 times a day,” says cardiologist James Wong. “If you did that to your front door it would be gone in the afternoon.”
Yet, as with all complex machinery, over time the heart can develop issues. One of the more insidious problems lies in its plumbing – the coronary arteries – which, when blocked, cause a heart attack.
One in every 25 deaths in Australia in 2020 was due to a heart attack. That’s the equivalent of 18 deaths a day, or one every 80 minutes. Sometimes, heart attacks are sudden and brutal. Other times, people don’t realise they are having one. And they are often different for women and men.
So, how do you know if you are having a heart attack? What does a “massive” heart attack mean? Can you test for signs? And to what extent can you prevent them?
First, how does the heart work?
The heart is a pump made of muscle with its own electrical circuits and plumbing. Its job is to bring oxygen and nutrients to all our organs in just the right amount. It normally beats up to 100 times a minute – more when you exercise. With each beat, it squeezes to circulate blood from the lungs to the rest of body then back again. Valves keep blood flowing in the right direction, pieces of thin, strong tissue like parachute material. “It’s amazing how resilient they are to withstand pressure without tearing,” says Wong, an associate professor of medicine, who is director of the Royal Melbourne Hospital’s echocardiography laboratory.
It’s the best pump that Professor Garry Jennings knows of – and the most hardy. “Not many pumps work for 90 years, 100,000 times a day,” says Jennings, the Heart Foundation’s chief medical adviser.
It’s a lot of responsibility for an organ the size of a fist, but it has its own electrical system to help.
Tiny electrical impulses trigger each heartbeat, beginning in the sinus node at the top of the heart before travelling, like a Mexican wave, through the heart’s four chambers – two atria and two ventricles – with the atria contracting a fraction of a second before the ventricles to push the blood. Wong likens the sinus node to “the guy that beats the drum, which the rest of the heart follows, thereby controlling the heart rate”.
Researchers have found that every time the heart beats, the brain pulses in sync ever so slightly.
An electrocardiogram, or ECG, produces the pulsing graph you see on screens at hospitals (and much beloved by makers of TV dramas). It detects the heart’s contractions by reading its electrical activity via electrodes on the skin.
The heart contracts automatically, but the brain’s autonomic nervous system regulates the strength and pace of the contractions. The brain and heart depend on each other: the brain supports the heart’s pumping, and the heart keeps the brain oxygenated. In fact, researchers have found that every time the heart beats, the brain pulses in sync ever so slightly.
But to do its job, the heart relies on having a rich blood supply, which is where its plumbing comes in: the coronary arteries are the blood vessels that wrap around the heart to nourish it with oxygenated blood. A heart attack occurs when that supply is impeded, cutting off nourishment and preventing the heart from keeping up with the demands of the body. “The heart has to work pretty hard, and if you cut off the blood supply to a part of the muscle then it runs into trouble,” says Jennings.
What’s a heart attack?
A heart attack is a medical event where blood flow in the coronary arteries becomes restricted, resulting in irreversible damage to the heart muscle. “Because there’s no blood flow being delivered to that part of the heart muscle, that part dies,” Wong says.
The extent of the damage will vary but the consequences can be devastating, leading to a life sentence of chronic heart failure, or death.
What tends to determine a heart attack’s severity is the location of the artery blockage and the time taken to clear it, as these two factors will dictate how much irreversible scarring is left behind.
You might hear that someone died of a “massive” heart attack. Picture the coronary arteries as being made up of three major freeways then side streets, avenues and laneways. Wong explains: “If the blockage happened very much downstream and one of the side streets is blocked off, we’re not talking about a big volume of heart [that’s low on supply]. Compare that to the start of the freeway being blocked – then everything downstream is going to get wiped out because the narrowing happened to be at the wrong spot.”
Blocked at the start of the “freeway”, the heart simply can’t pump the blood out to the brain and other organs, and that can result in life-threatening cardiac shock. Wong says there is a particularly “bad zone” for a blockage, which is the left main stem where blood vessels lead into the heart. “If it blocks off, probably two-thirds of the heart will go. That is not sustainable at all.”
It’s estimated that more than half of people killed by a heart attack die suddenly. In other cases, a blockage can harm the heart’s electrical system causing cardiac arrhythmia, which can be fatal too: the heart’s rhythm goes berserk and can’t pump. “The heart doesn’t have time to fill then it can’t empty properly. So it’s just fluttering instead of a regular beat in and out,” Jennings says.
This can then lead to cardiac arrest, which is not the same as a heart attack, although heart attack is a common cause of cardiac arrest. You might think of a heart attack as more of a plumbing-related issue caused by a blockage while cardiac arrest is due to a malfunctioning of the heart’s electrical system, prompting the heart to beat erratically – that’s where defibrillators come in, as an arrest is treated with electric shock.
A heart attack is usually a result of coronary heart disease (also called ischaemic heart disease or coronary artery disease), an umbrella term for a range of conditions that can affect the heart when blood flow in the coronary arteries is compromised.
For some people, a heart attack is the first time a person realises they have the disease. It’s Australia’s biggest killer overall; the leading cause of death in men, and, in women, it is the second-leading cause after dementia. Heart attacks are responsible for two-fifths of all coronary heart disease deaths.
Another important distinction: coronary heart disease is just one form of heart disease. Heart disease and cardiovascular disease are the same thing and are broad terms that include any disease of the heart or blood vessels, such as stroke and congenital heart conditions.
Angina, meanwhile, is a short-lived chest pain caused by blood flow issues – it’s a sign of coronary heart disease but less intense than heart attack pain.
How do you know you’re having a heart attack?
Most of us probably have an image in our heads of someone clutching their chest and collapsing. Wong says the textbooks don’t always reflect real life but they’re the best place to start. “People often get chest pains across the front of the chest, which radiate to their jaw or down their left arm. It’s also associated with some breathlessness, sweatiness or nausea,” he says.
It’s not always like that, though. Women, for example, are less likely to have chest pains, more likely to have breathlessness, excessive sweating, dizziness or neck and back pain. One day in 2020, disability support worker Kath Moorby felt discomfort in her right shoulder and hand followed by tingling in her arms and fingers. Then she felt hot, clammy and sweaty. There was no chest pain, just a heaviness.
“It was a surreal moment. Really? I’m 44 and I’m having a heart attack?”
Paramedics eventually determined she was having a heart attack. “It was a surreal moment,” she recalls. “Really? I’m 44 and I’m having a heart attack?”
Moorby had two stents implanted. She says the effect was instant: the pressure in her upper-body reduced and her blood could flow freely again. “They said I had a 20 per cent chance of surviving had I not made it to hospital when I did,” she recalls.
Other people experience tightness rather than crushing pain.
“People usually become cold, white and clammy,” Jennings says. “But symptoms can be variable.”
Andrew van Vloten, a 53-year-old Victorian park ranger, had his first heart attack in 2014. With a family history of heart disease, he says, looking back, there had been signs for months that something was off: he felt occasional chest and jaw pain, especially when exercising, as well as shortness of breath. One day at work, the chest pains returned and wouldn’t subside. “It was getting quite intense, the pressure right on the centre of my chest … I then started to get pins and needles in my fingers and toes. It was full-on,” van Vloten says.
He had a stent put in that day.
To avoid a repeat, he set about exercising more and ate less saturated fat, red meat and processed food. “Six months down the track, I felt as fit as I’d been in 10 years.”
It’s why he was so shocked when he had a second heart attack in 2020. This time he had no symptoms in the lead-up other than feeling a bit unwell. Then, as he was loading up timber into a ute, he was hit by nausea, breathlessness and chest pains. “It just came on really quickly and intensely,” he says. “Everything started coming back to me.”
It can be easy to mix up heart attack symptoms with heartburn, oesophageal spasms or angina. If the pain lasts more than 10 minutes, it’s worth seeking urgent medical attention. “It’s a heart attack when an artery blocks off and nothing a patient does makes it better,” Jennings says.
Sometimes a heart attack can happen when the heart is under more pressure, such as during exercise or even following a big fright. Other times, there’s no particular exertion. To complicate matters, one-sixth of people experience silent heart attacks – no symptoms. This is more likely in people who have diabetes because their nerve endings can be blunted.
“Sometimes we do ECGs on people for insurance purposes, and we find that they’ve had an old heart attack somewhere along the way,” Wong says. “It’s like if you damaged any part of you, you would scar, with scar tissue replacing the damaged tissue. The same thing happens in the heart.”
What causes a heart attack? Why does the blood flow get blocked?
They might seem to come out of the blue but a heart attack often reflects a process that has been going on throughout a person’s life. Atherosclerosis is the narrowing and hardening of arteries. It starts in adolescence, if not before, brought on by a build-up of plaque (made of cholesterol and other substances) on the inner wall of the arteries. “Once it gets underneath that inner lining of the vessel wall, it’s really hard to get out again,” Wong says, “so it’s almost like a one-way street.”
“By the time the guy who’s been doing absolutely nothing, sitting all day, comes to you with chest pain, that’s really late.”
You won’t be aware of much of the gradual narrowing because the body manages fine – until it reaches a particular point. It’s only once a coronary artery narrows by between 60 and 70 per cent that blood flow falls off noticeably and someone might begin to tire more easily or feel bursts of chest discomfort. “That partly explains why some people feel great one week and don’t feel good the next,” Wong says.
This is also when coronary heart disease is in full swing. The artery wall becomes more unstable, so a blob of plaque can crack off and lead to clotting. This is the most common way a blockage happens before a heart attack – but there are others. Sometimes, heart attacks occur in people without significantly clogged arteries, Wong says. There might be a spasm of the muscle lining in the artery that causes it to clamp down or, in rare cases (about 2 per cent of heart attacks) mainly in women, there can be a tear in the inner artery wall that peels off and blocks circulation (this is called spontaneous coronary artery dissection, or SCAD). Or plaque might simply be unstable, slough off and clog an artery – more common in smokers.
Can you tell if you’re on the edge of a heart attack?
If someone’s exercise capacity is consistently worsening, it can be a sign their arteries are narrowing dangerously. “It means when the heart is being asked to do more work, it’s not getting enough blood flow to it,” Wong says. Maybe you used to be fine walking five kilometres, three the next month, then two; or walking room to room becomes too much. “It will be unrelenting, it’s not something that would come and go away,” Wong says. “People need to be honest with themselves – by the time the guy who’s been doing absolutely nothing, sitting all day, comes to you with chest pain, that’s really late. The artery is likely to be quite narrowed.”
There are various tests you can do. As a first step, Wong advises his patients to try an online calculator such as cvdcalculator.com, where you punch in your data (for example, age, smoking status, cholesterol levels) to get an understanding of your risk and how making small lifestyle changes can make a big difference.
You don’t have to have symptoms of heart disease to get a heart health check. Any patient over 30 is eligible.
A basic heart health check, usually done by a GP, can determine risk levels and help work out whether you are harbouring artery disease. You don’t have to have symptoms of heart disease to get a heart health check. Any patient over 30 is eligible. It’s covered by Medicare once in a 12-month period and is recommended for adults aged 45 and over, or Aboriginal and Torres Strait Islander people aged 30 and over.
A patient might have further tests if it’s appropriate, such as a calcium-score CT scan (more calcium deposits in the coronary arteries means there’s a higher chance they’re narrowed) or an ECG or a cardiac stress test, which examines how the heart responds to exercise. These tests can cost a few hundred dollars, which Medicare generally covers only if someone has heart disease symptoms.
To check to what extent someone’s arteries have narrowed, a coronary angiogram involves injecting dye into the heart’s blood vessels, which is picked up using an X-ray machine.
Depending on the patient, they might be prescribed medication to treat cholesterol, blood pressure or clotting. Or a doctor might recommend inserting a stent or doing coronary artery bypass surgery to redirect blood flow by grafting a healthy blood vessel.
Who’s at risk of heart attack?
It’s difficult not to be alarmed by the stories of fit, healthy people who collapse suddenly with a heart attack. Wong says these are rare events often caused by inherited, underlying heart disease. But anyone who has concerns can talk to their doctor about tests that will help them ascertain their heart’s health, and what level of physical activity is safe for them.
Twice as many men are admitted to hospital with a heart attack compared to women, although the disparity in deaths is slimmer: in 2020, 2800 women and 3700 Australian men. This is, in large part, because of differences between how these events present in the two sexes – studies having long shown that many women have their symptoms dismissed or misdiagnosed.
The average age of a first heart attack is 72 for women – about 10 years older than men.
The average age of a first heart attack is 72 for women – about 10 years older than men – and they’re more likely to have a spontaneous artery tear, a blockage in a small coronary blood vessel or a mini heart attack where a smaller artery doesn’t open up properly, despite no significant narrowing. “The biology that causes heart attacks can be a bit more varied in women than men,” Jennings says.
Women with a history of pre-eclampsia or gestational diabetes during pregnancy or endometriosis also have a higher risk of coronary heart disease.
There are some inequalities in who suffers most from heart attacks. The rate of hospitalisations and deaths is about 1.5 times higher for people in remote or lower socioeconomic areas, the Australian Institute of Health and Welfare reports. For Indigenous Australians, the rate is double that of non-Indigenous Australians.
People with diabetes are roughly four times more likely to have a heart attack. And mental health is important for the heart: depression can increase your risk of developing coronary heart disease just as much as smoking and high blood pressure.
What should you do if you have a heart attack?
Phone triple zero. While you wait for an ambulance, it helps to focus on breathing steadily to try to calm yourself. With any heart attack, Wong says the key is to have as short a “door-to-needle” time as possible. Normally, paramedics alert a hospital of a heart attack patient before arrival.
Sometimes they’ll be given clot-dissolving medication, or a catheter tube is threaded up the arm or leg and a tiny balloon widens the narrowed coronary artery to leave behind a wire mesh, called a stent, to prop it open. “Every minute counts in doing that,” Jennings says, “because the longer you wait, the more the heart muscle cells will be dying.”
The part of the heart not affected by the blockage will keep working to contract, but it will be strained and the damage can spread. There is a risk of chronic heart failure, where the heart’s pump mechanism is weakened long-term. “They could be fine sitting or lying down but when they start walking up a hill, they can’t do it. They have a limit and their lifestyle has to be adjusted to what the heart allows them to do,” Wong explains. In severe heart failure cases, an artificial pacemaker or organ transplant may be needed.
“We’ve seen some horrendous things that could have been dealt with a lot sooner.”
Treatment involves looking after the other arteries because you can’t afford to lose any more heart muscle with another heart attack.“If we get them from their home to hospital within two to three hours then we have a very high chance of salvaging their heart muscle and keeping them alive. If it’s five to six hours after the onset of the heart attack, even if you unblock the artery, the amount that’s salvaged is much less,” says Wong.
There have been too many preventable heart attack deaths from patients who stayed away from hospital during the pandemic, Wong says. “We’ve seen some horrendous things that could have been dealt with a lot sooner,” he says. Having ambulances ramped outside emergency rooms is a particular concern in heart attack cases.
When treatment is swift, you can go on to lead a normal life, with medication and lifestyle adjustments to help keep your arteries open. Still, it’s estimated that about 20 per cent of heart attack patients will be hospitalised with a second one within five years, a reality that Wong says can make people feel very anxious.
It’s why cardiac rehabilitation is so important as it involves structured physical activity and education on lifestyle and medicines, Jennings says, urging people to speak to their doctor about enrolling in a program or use the Heart Foundation’s directory to find one.
To what extent can heart attacks be prevented?
“The heart does age and wear out eventually,” Wong says. “Sometimes I have to say to patients, ‘It’s more a case of you’ve had too many birthdays.’” That said, a heart attack is eminently preventable, Jennings says, particularly under the age of 80. The goal is to slow the rate at which the coronary arteries are narrowing and stiffening.
First, it’s good to understand what we can control. We can’t change our age nor our genetics, both of which are unavoidable factors in our risk of heart disease. “Some people can do all the wrong things [for their health] and never have a heart problem. Other people barely infringe and suffer from heart disease,” says Jennings.
Some people have a family history of heart disease. Wong starts to treat such patients about five years before their close relative who had heart trouble started having issues. Some people might have naturally high cholesterol (called familial hypercholesterolemia). Here, heart complications tend to occur in someone’s 20s.
Health issues such as high cholesterol or blood pressure have effective medications. “But whatever your genetic background, you’ll still be better off with a better lifestyle, so never give up,” Jennings says. Poor nutrition, low physical activity, drinking alcohol, smoking and being overweight: these are all major risk factors that can be improved. A 2019 study of more than 26,000 people aged over 18 found that a healthy lifestyle was linked to a 44 per cent lower risk of coronary heart disease.
This might sound a bit airy-fairy, but I say ‘thank you’ to my heart every day. I am in absolute awe of my heart.”
Sometimes people become scared of putting pressure on their heart with exercise but Jennings urges people to ditch the fear. “There’s nothing better you can do for your heart than being physically active,” he says. “Sensible exercise, where people build up a program and get fit, is one of the healthiest things.”
The Mediterranean diet remains the gold standard for a healthy heart, he says, and instead of focusing on food components, such as fat and cholesterol, there is increasing emphasis on healthy food combinations – so, lots of fruit and vegetables, olive oil, fish and chicken “because people eat food, not ‘polyunsaturated fat’” .
Kath Moorby had many risk factors, from family history to years of weight struggles. Before her heart attack she had lost 100 kilograms but her diet remained unhealthy, and she was smoking 50 cigarettes a day. “What you do in your younger years comes back to bite you on the bum,” Moorby says. Today, she eats better, walks, doesn’t drink and no longer smokes.
While coronary heart disease kills more Australians than any cancer (lung cancer is the fourth-leading cause of death in men and women), Jennings observes that cancer tends to be more feared in society, not least “because people fade away in front of us, whereas with a heart attack [often] they’re just gone [suddenly]“.
He says there is a degree of unfair blame that is heaped on heart disease patients too. “It’s not necessarily their fault if they’re overweight or have undetected risk factors. We just need to help them a bit more,” he says.
Andrew van Vloten, who had two heart attacks, urges people to learn about their bodies and their limits and take any heart disease risk factors seriously by visiting a doctor. Today, he’s a proud 10-kilometre race finisher, and he connects with his heart through meditation. “This might sound a bit airy-fairy, but I say ‘thank you’ to my heart every day,” van Vloten says. “I am in absolute awe of my heart, the function it does and what it’s capable of doing.”
Sign up here for the Explainer newsletter for interviews with explainer writers and more – straight to your inbox Sundays at 8pm.