Athletes are often viewed as symbols of cardiovascular health. They train harder, move faster, and frequently demonstrate levels of endurance that most people never reach. That makes sudden cardiac arrest in an athlete difficult to understand.
How can someone who can run miles, play an entire basketball game, or complete intense conditioning have a dangerous heart condition? The answer begins with an important principle: performance capacity and cardiac risk are not the same measurement.
The athlete’s heart is different
Long-term training causes normal cardiovascular adaptation. Depending on the sport and training load, an athlete may develop a slower resting heart rate, larger cardiac chambers, increased ventricular wall thickness, or characteristic electrocardiographic changes. These adaptations are often referred to as the athlete’s heart.
The clinical challenge is that some normal athletic adaptations overlap with findings seen in disease. A heart that looks unusual compared with a sedentary person’s heart may be normal for a highly trained athlete. Conversely, assuming every unusual finding is simply athletic adaptation can miss genuine disease. Athlete-specific interpretation matters.
Cardiomyopathies
Cardiomyopathy refers broadly to disease of heart muscle. Hypertrophic cardiomyopathy can cause abnormal thickening of the heart muscle. Arrhythmogenic cardiomyopathy can create a substrate for dangerous ventricular arrhythmias. Dilated and other inherited cardiomyopathies can also affect athletes.
Some people remain asymptomatic for years. Others may experience exertional chest discomfort, shortness of breath, palpitations, lightheadedness, or fainting. The absence of symptoms therefore does not prove the absence of disease.
Coronary artery abnormalities
Some athletes are born with coronary arteries that follow an unusual anatomical course. Certain coronary anomalies can compromise blood flow during intense exercise or create conditions in which ischemia or malignant arrhythmias can occur. Prospective U.S. surveillance has found coronary anomalies to be especially important among younger athletes.
Electrical disorders can exist in a structurally normal heart
Some dangerous conditions primarily affect electrical function rather than cardiac structure. Long QT syndrome alters electrical recovery. Catecholaminergic polymorphic ventricular tachycardia can produce exercise- or adrenaline-triggered ventricular arrhythmias. Brugada syndrome and other channelopathies involve abnormal ion-channel behavior.
These disorders illustrate why a normal echocardiogram does not automatically equal zero arrhythmic risk. Different tests answer different clinical questions.
Myocarditis
Myocarditis is inflammation of heart muscle. It can occur after viral infections and for other reasons. In some people it can impair ventricular function or increase susceptibility to arrhythmias. Athletes with suspected myocarditis require individualized evaluation rather than automatic assumptions based on fitness or symptom intensity.
Sometimes the cause is not visible at autopsy
One of the most difficult findings in sports cardiology is sudden death in a person whose heart appears structurally normal at autopsy. The 20-year NCAA study reported autopsy-negative sudden unexplained death as the most common postmortem category among cases with sufficient information. Some inherited electrical disorders leave no obvious anatomical signature, which is why family and genetic evaluation can become important in selected cases.
Age changes the risk profile
The causes of SCA change with age. In masters athletes, acquired coronary artery disease becomes much more prominent. That distinction matters because prevention and evaluation should be age- and context-specific rather than built around a single stereotype of the athlete at risk.
The RTH takeaway
Fitness is not immunity. Exercise capacity is useful clinical information, but it is not a comprehensive cardiac screening test. An athlete’s appearance also tells us little about electrical stability, coronary anatomy, or genetic risk.
The goal is not to make athletes afraid of exercise. The goal is to replace false reassurance with informed awareness: take symptoms seriously, know meaningful family history, use qualified sports-cardiology interpretation when needed, and maintain emergency readiness even in apparently healthy populations.
Educational note
This article is educational and does not establish an individual athlete’s diagnosis, cardiovascular risk, or eligibility for participation.
Sources and further reading
- Lampert R, Rubin A. Sudden Cardiac Arrest in Athletes. New England Journal of Medicine. 2026.
- Kim JH, et al. Clinical Considerations for Competitive Sports Participation for Athletes With Cardiovascular Abnormalities. AHA/ACC Scientific Statement. 2025.
- Peterson DF, et al. Aetiology and incidence of sudden cardiac arrest and death in young competitive athletes in the USA. 2021.
Author: Restarting The Heart | Source review: September 25, 2026
Published May 14, 2026 · Last reviewed September 25, 2026