Hypertrophic cardiomyopathy (HCM) is a genetic disease in which the walls of the left ventricle are thickened.
It is of concern to all physicians because it is a leading cause of cardiovascular sudden death in high school and college atheltes. The incidence of cardiac sudden death from all causes in this group is estimated to be 1 per 200,000 atheletes per year. And one-third of those deaths are thought to be due to hypertrophic cardiomyopathy. (1) So, there is one sudden death in young athletes due to hypertrophic cardiomyopathy per 600,000 athletes per year.
It has a prevalence in the general population of 1 in 500 persons but “This estimated frequency in the general population appears to exceed the relatively uncommon occurrence of HCM in cardiology
practices, implying that most affected individuals remain unidentified, probably in most cases without symptoms or shortened life expectancy.” (2)
The reason that I reviewed the 2011 guidelines (2) is to see what light they shed on the question “Should we screen asymptomatic young athletes for hypertrophic cardiopathy?”
The guidelines did not address whether or not asymptomatic patients without a positive family history for HCM should be screened.
So let’s go over some highlights of the guidelines to see how they relate to the question of screening asymptomatic athletes for HCM.
HCM is diagnosed by thickening of the wall of the left ventricle without dilatation of the left ventricle (by an echocardiogram—an ultrasound heart scan).
There are other diseases that can cause the same appearance on scan and the guidelines give details on how to distinguish those diseases.
The guidelines observe that “HCM is a heterogeneous cardiac disease with a diverse clinical presentation and course, presenting in all age groups from infancy to the very elderly (9,10,39,45).* Most affected individuals probably achieve a normal life expectancy without disability or the necessity for major therapeutic interventions (46–49). *
In some patients HCM does cause disease that causes disability or sudden death. There are three pathways and a given individual can follow one or more of the pathways.
The first is the most feared—sudden death due to an irregular heart beat.
The second is heart failure manifested by shortness of breath with exercise.
And the third is atrial fibrillation, an irregular heart rhythm that can cause an increased of stroke and blood clots to other parts of the body.
Treatments can include devices (an implantable cardiac defibrillator to try to prevent sudden death), medicines (to treat heart failure or heart rhythm problems), and surgery or catheter based treatment (to relieve severe blockage to blood flow out of the heart [a problem in some patients with HCM].
The guidelines recommend that patients diagnosed with HCM by echocardiogram undergo genetic testing to determine which gene or genes is causing the individual’s HCM (eight genes have been characterized but there are other genes for HCM that have not yet been characterized).
Patients with HCM, for risk stratification, may require an exercise stress test, an exercise stress echocardiogram, a Holter Monitor (a 24 heart monitor to detect dangerous heart rhythms), and uncommonly a test for coronary artery disease (CT angiogram or cardiac perfusion imaging).
“A minority of clinically recognized patients with HCM are judged to be at increased risk for SCD, with a rate of about 1% per year (53,55,386–389)*(2).”
A 2010 Circulation article (3) states that “[While] HCM occurs at a frequency of 1 of 500 in the general population,17 affecting an estimated 600 000 people in the United States. However, only a small proportion of such individuals are recognized clinically. Because a truly general unselected HCM population is not available for study, the precise proportion of all HCM patients with a significant SD risk remains elusive.” And further “Reports over the last 15 years from less selected regional or community-based cohorts placed HCM mortality rates at a much more realistic ≤1% annually.2,3,19,20**” [Note that this article suggests a much smaller risk than (2), altho both seem to agree that we really have little data on the risk of SCD in unselected HCM patients.]
The implantable cardiac defibrillator is the only treatment that can prevent sudden death in HCM but the decision as to which patient will benefit from one is difficult (See section 6.3.2—Selection of Patients for ICDs (2)).
And ICDs have significant side effects (See section 6.3.3—Complications of ICDs in HCM) (2)). Patients have died from ICD malfunctions.
So, after all of the above, should we screen asymptomatic high school and college athletes for HCM to try to prevent sudden cardiac death?
The 2007 AHA Preparticipation Screening recommendations (1) recommend against screening asymptomatic athletes for sudden cardiac death with electrocardiogram and/or echocardiogram (although mostly on the grounds that it would cost too much).
And after reviewing the 20ll HCM guidelines and the other references (1-3), I believe that, based on the data available at this time, screening the asymptomatic would do more harm than good (even if cost was no object).
* These are the footnotes of reference (2) below.
**These are the footnotes of reference (3) below.
(1) Recommendations and Considerations Related to Preparticipation Screening for Cardiovascular Abnormalities in Competitive Athletes: 2007 Update. A Scientific Statement From the American Heart Association Council on Nutrition, Physical Activity, and Metabolism. Circulation. 2007;115:1643-1655.
(2) 2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy. Circulation. 2011;124:e783-e831.
(3) Contemporary Insights and Strategies for Risk Stratification and Prevention of Sudden Death in Hypertrophic Cardiomyopathy. Circulation. 2010; 121: 445-456.