Do Your Genes Put You at Risk for Sudden Cardiac Arrest?
It’s an unimaginably tragic scene: a seemingly healthy child or adult unexpectedly collapses and never regains consciousness.
Sudden cardiac arrest (SCA) strikes more than 356,000 adults and 7,000 children and teens in the U.S. every year. An episode can cause disabling brain damage for survivors who aren’t promptly resuscitated — or can cause immediate death. While SCA accounts for half of all cardiovascular deaths, and is often unpredictable, being aware of your cardiac health and genetic risk factors can save lives.
What causes SCA?
SCA is an electrical malfunctioning of the heart that causes it to stop beating without warning, preventing blood from reaching the brain, lungs, and other organs. Victims lose consciousness within seconds and may die within minutes (which is called sudden cardiac death, or SCD) if medical treatment isn’t immediately available.
SCA is typically the result of an existing heart condition that may have no recognized symptoms before the first episode. Coronary artery disease or a prior heart attack is the most common underlying causes for SCA in middle-aged and older adults. When there’s a family history of SCA due to coronary artery disease, there’s an increased risk of SCA as the first cardiac event in close relatives.
In children, adolescents and young adults, rare inherited disorders can cause irregular heartbeats (arrhythmia), which can trigger SCA. Such conditions include hypertrophic cardiomyopathy, right ventricular dysplasia, long QT syndrome, and Brugada syndrome. Life-threatening arrhythmia can also be prompted by very low levels of potassium or magnesium, major blood loss or lack of oxygen. When SCA occurs during intense physical activity, an inborn blood vessel abnormality of a coronary artery is often the culprit.
While children who experience SCA are often engaged in intense physical activity at the time, middle-aged adults are more likely to experience the onset during normal daily activities. For older adults with underlying heart disease, extreme exercise can create a risk for SCA, but the level of exercise associated with a healthy lifestyle does not. “We don’t want to discourage asymptomatic (without symptoms) middle-aged and older adults from exercising regularly out of fear of suddenly collapsing,” says Dr. Robert J. Myerburg, a cardiologist with the University of Miami Health System. “The heart health benefits of regular exercise outweigh their risk of sudden cardiac death.”
“While there’s a genetic basis for the risk of SCA, we don’t yet know the specific genes predisposing to SCA in the older population,” says Dr. Myerburg. “We know that a family history of SCA warrants careful attention to risk factor identification and control to reduce the probability of developing coronary artery plaques in the middle-aged and older population. Current research is seeking to identify specific genetic factors that might help identify such a risk.”
Can sudden cardiac arrest be prevented?
Unfortunately, most adults and parents of children at risk aren’t even aware that they have a related heart condition, because they often don’t have significant warning symptoms.
Older children may experience symptoms including heart palpitations, a fluttering feeling in the chest or episodes of dizziness or fainting. Others may include impaired exercise capacity, chest pain or discomfort, or shortness of breath. If a heart murmur is detected in an infant, adolescent or young adult, a cardiac evaluation may lead to a diagnosis that reveals the child is at higher risk for life-threatening arrhythmia.
Because some heart conditions are passed down through genes, the diagnosis of a heart condition in a family member may be a good reason to have infants, children, and other relatives screened by a cardiologist and have genetic testing when appropriate.
“At UHealth, our cardiology researchers are actively looking for new approaches to screen children and adults for unsuspected cardiac conditions, and particularly the genetic disorders associated with the risk of heart rhythm disturbances,” says Dr. Myerburg. If a heart condition is detected, a cardiologist can advise patients about safe levels of physical activity and how to take precautions to avoid triggering dangerous arrhythmia, including medications or implantable defibrillator devices. Children may be required to meet certain cardiovascular standards to qualify for competitive athletics or extracurricular activities.
What should you do if someone collapses?
“The ability to respond quickly and appropriately — with the right tools and skills — can help save a life or avoid brain damage for someone experiencing sudden cardiac arrest,” says Dr. Myerburg.
As with any medical emergency, a bystander should immediately call 911 when someone collapses. During cardiac emergencies such as SCA, a trained bystander should promptly administer CPR. “When a child or adult has been diagnosed with a heart condition that can cause life-threatening irregular heartbeats, it’s particularly important for family members and childcare providers to learn how to effectively administer CPR and should consider carrying a portable heart defibrillator,” says Dr. Myerburg.
If an automated external defibrillator (AED) is available at the scene, it should be used as soon as possible to help jumpstart the victim’s heart to restore a normal rhythm. These life-saving devices are designed for use by laypersons and provide visual, and voice prompts. AEDs are available in most schools, community centers, amusement parks, movie theaters, and other popular public areas.
If the victim immediately receives CPR and an AED is promptly used, the chance of survival increases significantly.
“While the diagnosis of a potentially life-threatening heart condition can be frightening,” Dr. Myerburg advises that “being prepared to respond appropriately in an emergency can make all the difference.”
Dana Kantrowitz is a contributing writer for UMiami Health News.