Hypertrophic Cardiomyopathy (HCM)

I received an email inquiry yesterday from a reader who was interested in hypertrophic cardiomyopathy (HCM), a newly-diagnosed condition which had sidelined him from the sport that he loves. I thought I’d share some information about HCM that I shared with him yesterday. This is an uncommon problem, but it is a potentially lethal problem for athletes in sports with high cardiovascular demands.
What is HCM?
We use the terms hypertrophic cardiomyopathy (HCM) when there is thickening (that we call hypertrophy) of the ventricular (lower heart chamber) walls, if there is no other explanation. This disorder has been known by several other names in recent years, including hypertrophic obstructive cardiomyopathy (HOCM) and idiopathic hypertrophic subaortic stenosis. There are several patterns, but in the most common situation the septum (that divides the left and right ventricles) enlarges to >1.3 cm, while the other ventricular walls remain

In approximately 35% of cases of HCM, there is also obstruction to the flow of blood as it leaves the heart. This obstruction can be due to the thickening of the ventricular septum or to a condition known as systolic anterior motion of the mitral valve (SAM). With SAM, the mitral valve moves forward and gets in the way of blood that is heading toward the aortic valve to leave the heart.
Many individuals with HCM will have no symptoms at all. Some patients report instances of chest pain, with or without exertion, shortness of breath, palpitations, or syncope (blacking out), either during exertion or afterwards.
Role in Sudden Death
In the United States, HCM is probably the leading cause of death among athletes with sudden cardiac death. In most reports, HCM is found at autopsy in as many as 40% of young athletes with sudden death. Unfortunately, sudden death in individuals with HCM tends to occur in young people with no previous warning signs, who are engaged in moderate to strenuous physical activity.
The diagnosis of HCM is established with an echocardiogram (an evaluation of the heart’s structure using ultrasound). The echocardiogram makes detailed pictures of the various heart walls and heart valves and the thickness of the various heart walls can be measured. The echocardiogram can also be used to estimate the degree of obstruction to blood flow exiting the heart.
The treatment for HCM will depend on many variables that are specific to the individual patient. In general, treatment is designed to: 1) treat (or prevent) heart failure that may arise and 2) prevent sudden death. Potential treatments include medications, surgery (to remove some of the thickened heart wall or to replace the mitral valve), injection of alcohol into the heart wall (alcohol ablation) to cause it to shrink, insertion of a pacemaker, or insertion of a defibrillator (that delivers a shock to restart the heart in the event of sudden death).
Distinguishing from “Athlete’s Heart”
For athletes, there can sometimes be confusion about the diagnosis of HCM. This stems from the fact that well-trained athletes often have thickening of the ventricular walls that is simply a physiologic consequence of training. The distinction between HCM and athlete’s heart can be particularly problematic for individuals with ventricular wall thickness between 1.0 and 1.5 cm. Athletes in this situation would be well-served by consultation with a cardiologist with particular expertise in this area. Features that would favor athlete’s heart over HCM include: left ventricular cavity size >55 mm in diameter, and decrease in wall thickness with deconditioning. Features that would favor HCM include: family history of HCM, abnormal ECG, left ventricular cavity

Recommendations for Athletes
Consensus panels have convened to make recommendations for athletes with HCM. Athletes with HCM who are younger than 30 years old should not participate in sports with high cardiovascular demands. Athletes with HCM who are older than 30 years old should not participate in such sports if they have any other worrisome features of the disease: ventricular arrhythmias, syncope (blacking out spells), moderate or worse obstruction to ventricular outflow (such as with systolic anterior motion of the mitral valve), intermittent atrial arrhythmias, or enlarged left atrium. Older athletes HCM who do not have these features should consult with their cardiologist about continued participation.
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