Do you know the difference between a heart attack and cardiac arrest?

As questions swirl about how heart-related emergencies occur and who is most at risk, Mayo Clinic cardiologist Brian Shapiro, M.D., is drawing a clear distinction between two often-confused medical crises: sudden cardiac arrest and heart attack. 

Though the terms are frequently used interchangeably, they represent fundamentally different — and sometimes interconnected — conditions.

Sudden cardiac arrest strikes without warning. A person may be walking, exercising, or socializing when the heart abruptly falls into a lethal rhythm. 

“When the heart beats abnormally and can’t pump blood efficiently, blood flow to the brain stops, and that’s what causes the collapse,” Shapiro explained.

A heart attack, by contrast, results from a blockage in a coronary artery. With oxygen-rich blood unable to reach the heart muscle, patients often feel chest pain, pressure, or shortness of breath. While heart attacks don’t always result in sudden cardiac arrest, the lack of oxygen can irritate the heart’s electrical system and provoke life-threatening arrhythmias such as ventricular fibrillation or ventricular tachycardia.

When every second counts

Shapiro emphasizes that bystanders play a crucial role in survival.

“If someone collapses and is unresponsive, call 911 immediately,” he said. Ask for an automated external defibrillator (AED) and begin CPR if it’s safe to do so. Modern AEDs guide users step-by-step and will only deliver a shock if a dangerous rhythm is detected.

The overall likelihood of sudden cardiac arrest remains low, but the causes shift dramatically across a person’s lifespan.

• Under age 35, the biggest concern is cardiomyopathy, particularly hypertrophic cardiomyopathy, which thickens parts of the heart muscle and increases the risk of arrhythmia. It affects roughly 1 in 500 people and is a leading cause of collapse in young athletes.
• Over age 35, risk centers around coronary artery disease, driven by factors such as high blood pressure, diabetes, tobacco use, cholesterol buildup, and family history. A ruptured plaque in a heart artery can trigger dangerous rhythms or a full heart attack.

Activity level: Both ends of the spectrum carry risks

Sedentary lifestyles contribute to cardiovascular problems — but elite athleticism isn’t risk-free either.

“Triathletes and marathon runners place significant stress on their hearts,” Shapiro noted. That doesn’t mean they must stop; it simply means they may need more careful screening and tailored exercise plans, especially if they have underlying heart disease.

For example, a 65-year-old lifelong runner with a history of coronary bypass surgery can often continue the sport safely by exercising at lower intensities under medical guidance.

During physical exams, physicians may listen for murmurs, check for electrical abnormalities with an ECG, or order chest X-rays and cardiopulmonary stress tests. These evaluations can reveal subtle signs of cardiomyopathy or other heart or lung issues before they become dangerous.

Know your symptoms — and don’t ignore them

Shapiro urges anyone experiencing symptoms such as:

• shortness of breath during minimal activity,
• chest tightness,
• dizziness, or
• unexplained fainting

to seek further testing. Early evaluation could prevent a life-threatening event.

Whether a patient wants to return to 5K races or weekend softball, Shapiro’s message is consistent: exercise is vital for longevity and mental health — but it should be done safely and with awareness of personal risk.

“People can absolutely get back to the activities they love,” he said. “The key is understanding your heart, knowing the warning signs, and taking the right precautions.”