Recently, young and seemingly healthy athletes like college basketball player Bronny James and NFL player Damar Hamlin have suffered cardiac arrest. In our second Diagnosing the Headlines, Dr. Tony Hsu, an Envision emergency medicine physician at Ann Arbor St. Joseph Mercy Hospital Emergency Center, explains cardiac arrest, who is risk, the symptoms to look for and how bystanders can help in an emergency.

Diagnosing the Headlines is a series that aims to provide expert insight on important healthcare topics that have captured headlines and to unpack the key takeaways that are the most important to patients and clinicians.

Cardiac arrest is when the heart stops contracting enough for a pulse of blood to sustain brain and other critical end-organ functions. There are multiple potential causes that lead to this, and rapid recognition of the lack of a pulse and initiation of chest compressions can improve survival rates with good neurologic outcomes.

The most recognizable symptom is the loss of consciousness and muscle tone. Sometimes chest pain, shortness of breath or confusion can be preceding signs. Occasionally, a collapse with a seizure can be a symptom of cardiac arrest. When cardiac arrest occurs in public settings, a bystander witness can check for a pulse and try to test consciousness with loud yelling into their ears or a painful sternal rub and then quickly start CPR. There is additional new research on warning signs associated with cardiac arrest.

There is significant overlap since, more often than not, cardiac arrest is a result of a heart attack — otherwise known as an acute myocardial infarction — especially in adults older than 40. While few heart attacks result in immediate cardiac arrest, of those that do, treatable but non-beating rhythms, including ventricular fibrillation or ventricular tachycardia, can be shocked successfully with an automated external defibrillator (AED) for the first few minutes. Acute myocardial infarctions occur mostly from clogged arteries but can also result from spontaneous coronary artery dissections or aneurysms.

Very few young athletes suffer a sudden cardiac arrest — approximately less than one in every 300 athletes. However, regular exercise reduces the risk of atherosclerosis, and thus cardiac arrest, as one ages. Close relatives who have had sudden cardiac arrest can be a clue. Athletes with prodromal symptoms, such as fainting or near-fainting, especially with exertion, can provide a good reason to check an EKG, an echocardiogram and other studies to look for correctable anomalies.

Less than 3 percent of all cardiac arrest cases occur in young people (less than 18 years), but heroes are found when resuscitation is attempted and lauded when successful[1]. Young athletes receive significant attention since they appear to be in good health and suffer an immediate decline even though they are a minority of cases (39 percent) in children[2]. Generally, young patients with prior medical conditions, such as congenital heart defects, or those prone to infections and metabolic disorders suffer cardiac arrest more often and with poorer outcomes. A study of athletes who suffered a cardiac arrest[3] showed the following:

  • 26 percent had genetically linked hypertrophic cardiomyopathy (HCM)
  • 20 percent had commotio cordis, a sudden physical strike to the anterior chest wall at a specific time in the electrical rhythm
  • 14 percent had likely congenital coronary artery anomalies found
  • 7 percent had left ventricular hypertrophy, which could be from hypertension or a variant of HCM
  • 15 percent of athletes had an evenly split risk of an aortic aneurysm from genetically linked Marfan’s syndrome, genetically linked arrhythmogenic right ventricular cardiomyopathy, a congenitally acquired tunneled coronary artery, aortic valve stenosis, or atherosclerotic coronary artery disease
  • 13 percent had a variety of other causes

Around 20 percent of cardiac arrests are found to have a shockable rhythm. It is likely that many instances of the less survivable rhythms, such as asystole and pulseless electrical activity, result from delayed application of an AED. AEDs are sturdy battery-powered devices that provide a strong and precise electrical shock to the heart when the pads are placed on the chest wall. If applied within four minutes of someone collapsing, the likelihood of successful defibrillation with an AED is much higher, as the heart cells retain energy to restart circulation. Beyond four minutes, the success rate quickly drops.

The AED should be applied as soon as it is brought to the side of the patient and compressions can be interrupted for pad placement and as the AED checks for electrical activity. AEDs now have directions on when to check for a rhythm and pulse, which is every 2 minutes. It’s important to remember that chest compressions at the target rate of 100-120 beats per minute (bpm) are still needed before and after each defibrillation attempt.

Bystanders willing to provide chest compressions are the key to improved survival rates for people suffering cardiac arrest. Recognizing that someone isn’t breathing normally, such as too slowly with deep, agonal, breaths or not at all, is the first clue. Sometimes seizures are the initial presenting symptom, and if someone is seizing, their pulse should be checked. If the bystander knows how to check a pulse — using a light touch on one side of the neck — and doesn’t feel a regular pulse within 10 seconds, they should dial 9-1-1. They should then place the phone on speaker beside the head of the patient and immediately start compressing the chest 2 to 3 inches deep at a rate of 100-120 bpm while speaking with the emergency dispatcher. Interestingly, the beat of “Stayin’ Alive” by the Bee Gees is 104 bpm, and “Life is a Highway” by Rascal Flatts runs at 103 bpm.

A metronome is frequently a feature of an AED. If other bystanders are available, have them check for the closest AED on a mobile application like PulsePoint AED or look for the closest gym or hotel lobby, as those businesses are mandated to have one. Many schools and churches also have an AED.

You can be a champion of your community in cardiac arrest survival. It strikes seemingly randomly but mostly in a home or residence (~74 percent of the time). Have your family and neighbors learn CPR together and empower children to learn how to save lives by starting with calling 911. The simple act of calling 911 to mobilize emergency medical services can be lifesaving.

The families and neighborhoods most in need of training opportunities are those that are predominantly underserved. All witnessed cases, which are about half of cardiac arrest cases[4], should have someone attempt CPR as soon as possible in a safe area — unless there are legal documents that state otherwise — and continue CPR until trained personnel arrive. Physicians and health professionals can ensure their schools, churches and frequented businesses have AEDs, especially in rural areas where first responder arrival times can be longer than normal.

[1] 2022 CARES Annual Report (

[2] Latest Statistics | Sudden Cardiac Arrest Foundation (

[3] Sudden Death in Young Athletes | NEJM

[4] 2022 CARES Annual Report (