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 Hypertrophic cardiomyopathy (HCM) is a leading cause of sudden cardiac death people under 30, diagnosed most often among athletes, according to Kathleen Dracup, DNSc, FNP, RN, FAAN, dean and professor at University of California, San Francisco School of Nursing. She also has an extensive cardiac background.
"HCM is a very complicated diagnosis and fairly unusual. Most of us have probably never met anyone with the disease," Dracup said. "Whenever the death of a [well-known] athlete is caused by HCM, there is a little flurry of activity but generally it's a relatively low priority in public media."
The most common inherited heart defect, HCM is characterized by a thickening of the left ventricle, most often along the septum. The normal size of the muscle wall is 0.8-1.2 cm; with HCM, the septal wall can thicken from 1.3 cm to more than 6 cm.1
Occurring in 1 in 500 people, the severity of the disease ranges from patients who remain asymptomatic or experience no major problems to those who experience extensive limitations. If a parent has HCM, there is a 50 percent chance a child will inherit the disease.
"One was a patient with HCM, who was a professional basketball player. He had to give up his sports career when he didn't respond optimally to treatment. It's definitely a familial disease. He had two brothers also diagnosed with the condition," Dracup said.
Genetic Mutations
Specific gene mutations change the elements of cardiac muscle sarcomeres, causing them to grow abnormally, explained Dracup, who has an extensive background as a cardiac nurse practitioner. Essentially, the alignment of these heart muscle fibers is irregular and disorganized.1 Hallmark symptoms are shortness of breath, angina and syncope, Dracup noted.
 Parents, children or siblings of those with HCM might have an enlarged septum but remain asymptomatic. The disease is most common in young adults, according to the American Heart Association. Among older adults, chronic high blood pressure may cause the disease.
In the majority of patients - about 70 percent - the enlarged septum obstructs blood flow out of the heart. In other cases, the septum becomes stiff, limiting the volume of blood the left ventricle can accommodate and pump out.
"Unfortunately, HCM usually presents itself after exertion. The person might pass out and if he or she has a sudden cardiac arrest, resuscitation efforts might not be successful," Dracup noted.
Hallmark symptoms - which typically present on exertion - are shortness of breath, angina and syncope. If the outflow track is blocked, blood isn't pumped to the brain adequately, resulting in fainting.
"There's no relationship between being athletic and having hypertrophic cardiomyopathy," she stressed. "It's more likely it's found post mortem after sudden cardiac death in an athlete or it's picked up in a physical exam."
Diagnosing HCM
Most often, HCM is detected by an echocardiogram. Physicians might order additional tests, like ECG, a Holter monitor, cardiac cath or a cardiac MRI, to help plan the course of treatment.2
"We might see this disease undiagnosed for a long time. There are gradations in severity - from having little problems in the outflow track to severe gradient picked up in young people playing sports."
Treating the Disease
The first line of intervention is beta blockers to help keep the heart rate lower - sboth to maintain optimal filling of the left ventricle and suppress any arrhythmias that might occur, said Patricia Metoyer, MS, APN-C, RN, advanced heart, lung and vascular care, Deborah Heart and Lung Center, Browns Mills, NJ.
Physicians might also prescribe calcium channel blockers - such as verapamil, nifedipine or diltiazem - or in some cases anti-arrhythmic medications like disopyramide or amiodarone.3,4
If medications fail to work, the patient might undergo more invasive procedures, like septal alcohol ablation. Performed via cardiac catheter, involves injecting alcohol into a small branch of one of the heart arteries to kill a portion of the extra heart muscle.
A septal myectomy - "shaving" the ventricle septum on the left side - reduces the thickness of the muscle wall. The technique can help improve blood flow and reduce mitral regurgitation. The majority of patients who undergo the open-heart procedure don't experience additional symptoms.3
About 1 in 4 people with HCM present with an obstruction, and a "small percentage" of those patients will need septal reduction, according to the Hypertrophic Cardiomyopathy Association. Decreasing the size of the septum is not a cure for the disease; it is designed to relieve only obstruction-related symptoms or complications.4
Physicians may recommend a pacemaker for older patients who do not want an invasive procedure; the treatment, however, is less effective than surgical interventions.
ICDs are used in a handful of high-risk patients who, because of abnormal heart rhythms, are at risk of sudden cardiac death. They might include patients who have had priori cardiac arrest or a relative who experienced HCM-related sudden cardiac death; those with an "extremely thick" left ventricle wall detected on an echocardiogram; or unexplained syncope.3
Psychological Impact
Cardiac diseases like HCM can affect patients psychologically as well as physically, Dracup noted.
Many of the patients are young when the diagnosis is made, and they are told that they cannot play sports until the HCM is treated. That admonition sets them apart from their friends in school, Dracup noted, which is always painful for a teenager.
If the diagnosis is made at an older age, the patient may be aware of the heightened risk for sudden cardiac death, a condition that can lead to anxiety and depression in both the patient and their family members.
Healthcare providers can stress the need for genetic testing, family counseling and education about the nature of the disease. For instance, especially in cases of severe HCM, family members should be trained in CPR and know how to contact emergency providers.
Emphasis on Education
Clinicians at Deborah Heart and Lung Center follow patients every 3-6 months, depending on the severity of the disease.
"Most do really well and haven't had too many problems," said Jennifer Mazzoni, DO, a cardiovascular physician with Deborah Heart and Lung Center. "Good patient education is the key. When they have a clear understanding of what's happening, they follow treatment plans.
"Most of the younger people we see are compliant, especially if they've had a single episode. We can show them the monitor strip or EKG and explain what happened with the heart because of this," Metoyer added.
"If [a patient is well optimized on medications], he or she can lead a normal life as far as activities go. They might be able to participate in non-impact sports, like swimming," Mazzoni added. "Most have a fairly normal life expectancy. It's mainly a matter of working with providers, seeing patients frequently and communication."
Karin Lillis is senior regional editor at ADVANCE.
References
1. Hypertrophic Cardiomyopathy Association. (2008, Dec. 10). What is hypertrophic cardiomyopathy (HCM)? Retrieved June 4, 2009 from the World Wide Web: http://www.4hcm.org/hcm/overview/3005.html
2. Mayo Foundation for Medical Education and Research. (2009, March 25). Hypertrophic cardiomyopathy: Tests and diagnoses. Retrieved June 4, 2009 from the World Wide Web: http://www.mayoclinic.com/health/hypertrophic-cardiomyopathy/DS00948/DSECTION=tests-and-diagnosis
3. Mayo Foundation for Medical Education and Research. (2009, March 25). Hypertrophic cardiomyopathy: Treatment and drugs. Retrieved June 4, 2009 from the World Wide Web: http://www.mayoclinic.com/health/hypertrophic-cardiomyopathy/DS00948/DSECTION=treatments-and-drugs
4. Hypertrophic Cardiomyopathy Association. Treatment. Retrieved June 4, 2009 from the World Wide Web: http://www.4hcm.org/hcm/treatment/index.1.html
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