When a fit, active, apparently healthy person collapses during intense exercise, the question that follows is always the same: how does someone in that kind of physical condition have a heart problem no one ever detected?
Dr Piyanart Preeyanont, an interventional cardiologist at MedPark Hospital who performs balloon angioplasty to reopen blocked heart arteries, has a direct answer.
“Heart disease has a very wide, broad spectrum. Some conditions are occult, masked, with no symptoms at all. You may appear healthy, but inside you could have a hidden heart issue.”
What is actually happening inside
The popular image of a heart patient is someone who cannot climb stairs, struggles for breath and is visibly unwell. That describes only a fraction of people with serious cardiac conditions, but two heart conditions in particular are responsible for the vast majority of sudden cardiac arrests in athletes, and both can develop without a single warning sign.
The first is a heart attack caused by acute blockage of a coronary artery. This is not always the result of years of visible disease. A small deposit of plaque, a combination of calcium and cholesterol, can sit inside an artery without causing any narrowing or symptoms.
Then, on a random day during high-intensity exercise, that plaque ruptures. A blood clot forms within minutes. Blood supply to the heart muscle is cut off, the heart goes into ventricular fibrillation, and the person collapses.
“You don’t have any symptoms before,” Dr Piyanart explains. “The plaque ruptures, you have a blood clot inside, you have chest pain, and then ventricular fibrillation, and you collapse.”
The second condition is ventricular fibrillation triggered by a hypertrophic heart, one with abnormally thickened muscle. This can be hereditary, running through a family under the name hypertrophic cardiomyopathy, or it can develop gradually in athletes who train intensively over many years.
In either case, the thickened muscle is far more vulnerable to the kind of abnormal electrical activity that causes the heart to stop pumping effectively.
“When your heart wouldn’t pump, you don’t have enough blood supply to your brain or your organs. You collapse, and you may die if you don’t get proper rescue.”
The red flags to stop for immediately
Being active makes certain symptoms easy to dismiss. A racing heart and shortness of breath are expected during hard training. But Dr Piyanart identifies four specific warning signs that should prompt an immediate stop, not a mental note.
- Racing heart with chest tightness or chest pain. This combination suggests the heart muscle may not be receiving enough blood and should be treated as a potential heart attack.
- Racing heart with dizziness, lightheadedness, or near-fainting. The heart may be in an abnormal rhythm pushing into a dangerous zone.
- Unexplained shortness of breath that comes too early. If breathlessness arrives earlier relative to the effort being made, this is a red flag for the heart muscle.
- A heart rate higher than usual for the same effort. Not normal exertion variance, but a noticeably faster rate than is typical for the same workout.
“If you feel these symptoms, what you have to do is to immediately stop what you are doing,” Dr Piyanart says. None of these signals should be pushed through.
The problem with too much confidence
Physical fitness creates a particular psychological hazard. The stronger and more capable a person feels, the more convincing their internal case for denial becomes.
“Some patients felt something. They felt they might have some symptoms, but they denied. They told themselves they shouldn’t have any problem because they have a very strong heart.”
A strong heart is not the same as a heart without disease. A person who has trained for years without incident may have gradually developing coronary artery disease that has never produced a symptom, right up until the plaque ruptures. Confidence and denial allow these heart conditions to continue developing unchecked until the event arrives.
Who should be screened and what to test
Dr Piyanart’s answer to the question of who should have their heart checked is unambiguous: everyone who exercises regularly, not only competitive athletes or those preparing for high-intensity events.
“Every single one, if they go to the gym regularly, they do cardio, the weight training quite intensively. First, you should have your heart checked as your baseline.”
A standard annual health check, including a chest X-ray or basic ECG, is not sufficient for detecting the two most common causes of sudden cardiac arrest in athletes. The tests Dr Piyanart recommends are:
- Echocardiography to assess heart muscle thickness and detect hypertrophic cardiomyopathy, ideally combined with a treadmill stress test.
- Coronary CT angiography to visualise the heart arteries directly and identify plaque that may not yet be causing symptoms. For anyone preparing for high-intensity competition, Dr Piyanart recommends this over the basic calcium scoring alone.
Family history is also a meaningful risk factor. A parent or sibling who had a heart attack before the age of 45 for men or 55 for women, or a family member who died suddenly at a young age, elevates the risk and makes earlier screening more urgent.
If someone collapses in front of you
The window for effective intervention is measured in minutes. Brain damage from insufficient blood supply can begin within five to ten minutes of cardiac arrest. The steps are straightforward and worth rehearsing before they are ever needed.
Call for help immediately. Check whether the person is responsive. Call for an AED, the automated external defibrillator that should be present in every public venue. Turn it on and follow its audio instructions. Begin chest compressions. “If you can do the chest compression properly, it could save your friend’s life, your family member’s life.”
How to keep training without overstraining the heart
None of this means stopping exercise. It means training with awareness rather than blind confidence. Dr Piyanart recommends three monitoring practices for anyone training regularly.
First, track heart rate variability. A high HRV reading indicates the cardiovascular system has fully recovered from the previous session. Training on a low HRV is training on an unrecovered heart. Second, use heart rate zones deliberately.
Zone 2 cardio, roughly 150 minutes per week, provides the cardiovascular conditioning that keeps the heart healthy. Zone 4 and 5 training is not forbidden, but keeping the heart rate persistently very high for extended periods, as was documented in at least one HYROX participant whose rate held between 140 and 150 beats per minute for two hours, significantly increases the risk of ventricular fibrillation.
“If you keep your heart rate too fast for too long, your heart muscle will be more vulnerable to be triggered to get into an abnormal rhythm.”
Third, allow a gradual cool-down after every session. An abrupt stop can cause blood to pool and increase cardiac stress at exactly the wrong moment.
Fitness is an asset. The cardiovascular system of a well-trained athlete can handle extraordinary demands. But it can also develop heart conditions that no amount of training prevents, conditions that remain invisible right up until the moment they are not.
The check is simple. The alternative is not.
To book a cardiac screening appointment with Dr Piyanart Preeyanont at MedPark Hospital’s Cardiology Center, visit the MedPark appointment page or call the Cardiology Center on the 8th floor, Counter D, at 02-090-3104. The centre is open daily from 8am to 8pm.
This article is based on an interview with Dr Piyanart Preeyanont, Interventional Cardiologist, MedPark Hospital. It is for informational purposes only. Consult a qualified cardiologist before making any decisions about cardiac screening or changes to your training programme.
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