Athletic sudden collapse could be serious heart condition

Hypertrophic cardiomyopathy is common genetic heart condition

A line of cross country runners' legs are shown in this illustration for a story about hypertrophic cardiomyopathy/

Among the top identified causes of sudden death in young athletes is hypertrophic cardiomyopathy.

For no apparent reason, a high school or college athlete collapses on the basketball court. The football field. The track.

Hopefully, someone nearby grabs an AED, or automated external defibrillator, and revives the athlete. But the scenario doesn’t always turn out that well.

Hypertrophic cardiomyopathy (HCM) is a condition where a wall of the heart thickens, usually the left ventricle, which is the chamber that pumps blood out to other parts of the body, explained Sanford Health pediatric cardiologist Justin Horner.

If the wall gets too thick, the chamber may have trouble filling with blood and sending the blood out quickly enough.

“That thickening doesn’t always have to occur in the teenage years,” he said, “but that’s typically when it starts to become an issue.”

Many people may never know they have hypertrophic cardiomyopathy, the most common genetic heart condition. But about 1 in 500 adults does have it, according to the Hypertrophic Cardiomyopathy Assocation.

The two types of hypertrophic cardiomyopathy depend on determining whether the disease involves an obstruction in the ventricle. An obstruction makes HCM more severe and requires more treatment. But HCM without an obstruction can still lead to a cardiac event, Dr. Horner said.

When an athlete exercises, the heart pumps faster than normal. That gives the ventricle, with its thickened wall, less time to fill with blood and a narrower path to pump the blood out again. Then less blood — and less oxygen — flows out to the rest of the body. Muscles, including the heart, get tired. Also, HCM can cause a serious abnormal heart rhythm to occur.

Symptoms to get checked

Dr. Horner emphasizes the need to take symptoms seriously and get them checked by a cardiologist to identify whether hypertrophic cardiomyopathy has caused them and to hopefully prevent sudden cardiac death from occurring.

During exercise, people with hypertrophic cardiomyopathy might feel:

  • Chest pain
  • Shortness of breath
  • Palpitations (heart fluttering as if it skipped a beat)
  • Can’t keep up with their peers or more tired than their peers

A fainting episode during exertion — such as a sports activity — should send you straight to the hospital, Dr. Horner said.

“People faint all the time from: They got a shot, they saw blood, they stood up too quickly and they’re dehydrated. All kinds of things cause people to faint,” he said. “But if you exert yourself and you fainted, that’s not normal until somebody tells you it’s normal. And you need a lot of testing for that to occur.”

Additional reasons to see a cardiologist: If a primary care provider detects a heart murmur. If an electrocardiogram (an ECG or EKG) turns out abnormal. Or if you have a family history of hypertrophic cardiomyopathy or sudden cardiac death.

Sudden cardiac arrest presents the most extreme, and often fatal, symptom. Survivors must see a cardiologist after receiving emergency treatment.

Diagnosing HCM

Certain tests can help diagnose hypertrophic cardiomyopathy. An ECG checks whether the heartbeat’s rhythm is normal. An echocardiogram, or an ultrasound of the heart, measures the wall thickness. Sometimes, Dr. Horner said, the wall is so thick it’s visually obvious. Other times, a mild thickness has to be compared in proportion to a younger person’s body surface area to see that it’s a problem.

If a genetic test finds that a young child has the HCM gene, or someone in the family has it and the child risks having it, too, the cardiologist will want to follow the child regularly and check for wall thickening — more frequently after the child reaches the age of 10 or 12, Dr. Horner said.

If a parent has gene-positive hypertrophic cardiomyopathy, each of his or her children has a 50% chance of having it, too. First-degree family members of a person with hypertrophic cardiomyopathy should get screened, which means parents, siblings and children. If a child also tests positive, any children they have should get checked also. If a child tests negative, they don’t have HCM and couldn’t pass it along to their children.

In addition, a person could test positive and never show signs of wall thickness. But they still could develop an abnormal heart rhythm, and they still could pass the gene along to their children.


Treatment for hypertrophic cardiomyopathy varies, depending on whether the left ventricle has an obstruction, which may be heard as a murmur.

If an obstruction exists and has reached a certain level, and the wall has thickened considerably, the condition can call for surgery. “For children, that would be a heart surgery, and cutting out some of that muscle or that obstruction so the blood can get out of the heart easier,” Dr. Horner said.

Medication can be used to slow the heart rate down in order to allow better filling as well as hopefully control the rhythm and/or prevent an abnormal heart rhythm.

For a very thick wall, or if a child has had an event, then an implantable cardioverter defibrillator would be placed. That way, if the heart began to have an abnormal rhythm, the defibrillator potentially could shock the heart out of the abnormal rhythm and return it to normal.

With no ventricle obstruction, typically the person would simply be monitored. They might receive medication to help slow the heart.

Living with HCM

Under the care of a cardiologist, and taking any medications as prescribed, people who have hypertrophic cardiomyopathy can live a normal life, with some special considerations.

An HCM patient with a heart obstruction would definitely refrain from physical exertion such as sports activities. Even without an obstruction, that’s typically the recommendation.

HCM patients especially must stay well-hydrated to help keep plenty of blood flowing out of the heart to the rest of the body. Dehydration gives the heart less time to fill, Dr. Horner said. “The heart can be underfilled and then collapse on itself, causing obstruction to blood flow out of the heart.”

If they notice any changes in symptoms, or have any kind of fainting episode, they need to see a doctor immediately and not wait for their regularly scheduled follow-up appointment.

“The vast majority of hypertrophic cardiomyopathy patients are somebody a cardiologist will diagnose. They are likely going to live well into adulthood and be a productive member of society with appropriate cardiology care,” Dr. Horner said.

It’s those with unknown, or unmanaged, hypertrophic cardiomyopathy who could potentially collapse on the football field or basketball court.

For those people, recognizing and checking out symptoms could have prevented a cardiac event. But if someone nearby uses an AED — which gives audible instructions — they could get a second chance.

“That’s been shown to be the biggest lifesaver for anybody that collapses,” Dr. Horner said.

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Posted In Children's, Emergency Medicine, Genetics, Heart, Sports Medicine

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