Genetic testing helps family uncover inherited heart condition

by NCN Health And Science Team Posted on April 1st, 2019

Kristen Criss’ father died of complications from a stroke, her mother died from a heart condition at age 40 and her sister passed away at 33. Still, it would be many years—and health struggles of her own—before she realized the full meaning of having a family history of heart disease.

Criss discovered in 2017 that her mother died of the same heart disease that killed her sister: hypertrophic cardiomyopathy, or HCM. The disease occurs when heart muscle cells enlarge, causing the walls of the ventricles to thicken and possibly block blood flow. Although rare, it also is associated with sudden cardiac death.

A recent genetic test revealed that the 38-year-old from Riverside, California, also has HCM.

Starting in her 20s, however, Criss had developed a series of arrhythmias, or irregular heartbeats caused by electrical malfunctions in the heart that can lead to serious health problems. Later, she found out that arrhythmias can be a symptom of HCM.

After her heart was shocked back into a normal rhythm eight times while pregnant with her third child in 2016, Criss wanted to know the exact cause of her own mother’s death.

“After I had my daughter, my mind frame totally changed,” she said. “I thought I should know to benefit or share with others.”

So, in November 2017, Criss requested her mother’s death certificate from 1995, learning that her mother died of HCM. The condition is usually inherited and caused by a genetic mutation, but it also can mimic heart muscle changes associated with other conditions, such as high blood pressure.

“I was shocked and hysterical,” Criss said. “I fell to the floor. Now, I had to do something.”

The next month, genetic testing showed Criss also has HCM.

In February 2018, Criss received an implantable cardioverter defibrillator because of a high risk of cardiac arrest due to HCM. The small, battery-operated device placed under the skin to shock the heart back into a normal rhythm if it starts to beat chaotically. By her side were her husband, Dominque, and best friend, Melanie Taylor.

“She’s a fighter,” Taylor said.

Knowledge has helped Criss make sense of the past, but it also sparked fear for her three young children. Did they have HCM? Would they pass it on to their children?

Criss recently arranged genetic tests for son Braxon, 10; son Avery, 6; and daughter Sariah, 2. They were brave, but scared.

The results showed all three children tested negative for the genetic mutation behind HCM.

“It was very emotional,” said Criss, who treated the kids to ice cream to celebrate.

If Criss’ children don’t have the same genetic mutation, they’re unlikely to have HCM or pass it on to their children, said Dr. Maged Nageh, Criss’ cardiac electrophysiologist at Kaiser Permanente’s Regional Arrhythmia Center in Los Angeles. He stresses the importance of genetic testing for HCM patients with unclear family history or symptoms related to HCM.

Guidelines from the American Heart Association and American College of Cardiology recommend genetic testing to identify patients with HCM, including those with atypical presentation or if another genetic condition is suspected as the cause, as well as parents, children and siblings of those patients.

Criss has shared much of her experience on Instagram and Facebook to make others aware of heart disease and genetic testing.

“The disease literally stops with me,” Criss said.

Image: A new genetic test revealed Kristen Criss had the same heart condition that took her mom’s life at 40. (Photo courtesy of Kristen Criss)

Hypertrophic cardiomyopathy (HCM)

Hypertrophic cardiomyopathy (HCM) is very common and can affect people of any age. It affects men and women equally. It is a common cause of sudden cardiac arrest in young people, including young athletes.

Hypertrophic cardiomyopathy occurs if heart muscle cells enlarge and cause the walls of the ventricles (usually the left ventricle) to thicken. The ventricle size often remains normal,but the thickening may block blood flow out of the ventricle. If this happens, the condition is called obstructive hypertrophic cardiomyopathy.

Sometimes the septum, the wall that divides the left and right sides of the heart, thickens and bulges into the left ventricle. This can block blood flow out of the left ventricle. Then the ventricle must work hard to pump blood. Symptoms can include chest pain, dizziness, shortness of breath, or fainting.

Hypertrophic cardiomyopathy also can affect the heart’s mitral valve, causing blood to leak backward through the valve. Sometimes, the thickened heart muscle doesn’t block blood flow out of the left ventricle. This is referred to as non-obstructive hypertrophic cardiomyopathy. The entire ventricle may thicken, or the thickening may happen only at the bottom of the heart. The right ventricle also may be affected.

In both obstructive and non-obstructive HCM, the thickened muscle makes the inside of the left ventricle smaller, so it holds less blood. The walls of the ventricle may stiffen, and as a result, the ventricle is less able to relax and fill with blood.

This can raise blood pressure in the ventricles and the blood vessels of the lungs. Changes also occur to the cells in the damaged heart muscle, which may disrupt the heart’s electrical signals and lead to arrhythmias.

Some people who have HCM have no signs or symptoms, and the disease doesn’t affect their lives. Others have severe symptoms and complications. They may have shortness of breath, serious arrhythmias or an inability to exercise.

It is rare, but some people with hypertrophic cardiomyopathy can have sudden cardiac arrest during very vigorous physical activity. The physical activity can trigger dangerous arrhythmias. Ask your doctor what types and amounts of physical activity are safe for you.

Other Names for Hypertrophic Cardiomyopathy

  • Asymmetric septal hypertrophy
  • Familial hypertrophic cardiomyopathy
  • Hypertrophic nonobstructive cardiomyopathy
  • Hypertrophic obstructive cardiomyopathy
  • Idiopathic hypertrophic subaortic stenosis (IHSS)

What causes hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy usually is inherited. It’s caused by a change in some of the genes in heart muscle proteins. HCM also can develop over time because of high blood pressure or aging. Diseases such as diabetes or thyroid disease can cause hypertrophic cardiomyopathy.

Other Types of Cardiomyopathy:

  • Dilated Cardiomyopathy
  • Restrictive Cardiomyopathy
  • Arrhythmogenic Right Ventricular Dysplasia

Leave a Reply