Hypertrophic cardiomyopathy in the athletic population

Hypertrophic cardiomyopathy (HCM) is a heart condition characterized by excessive thickening of the heart muscles. Left ventricular thickening is usually the most common defining feature of the disease though in some patients right ventricular thickening is also noticed. While heart muscle thickening is also observed in patients with a history of high blood pressure and among those with prolonged athletic training, in HCM the thickening is idiopathic. HCM occurs roughly in around 1 in 500 (600,000 to 1.5 million) people in the U.S. And is the single most common cause for sudden death in young athletes. [Cleveland Clinic] Statistics show that roughly around 35% of sudden deaths among athletes are ascribed to HCM. Statistics also reveal that sudden deaths among joggers, marathon racers, and other forms of athletic sports, stands between 1 in 15,000 or 1 in 50,000. [Maron] Though this is a relatively rare form of cardiac malformation it assumes lot of importance, as the victims are mostly young athletes who are normally viewed as the epitome of the fitness and health. A brief overview of the condition, diagnosis and possible treatment methods would help us better understand the disorder.

HCM Demographics and Diagnosis

As mentioned above, HCM is the most common cause for sudden deaths among young athletes. Sudden death occurs usually after intense athletic training or other form of physical exertion. Around 70% of sudden deaths among athletes in the U.S. were from games such as football and basketball. It is also observed that around 90% of sudden deaths occurred in male athletes suggesting that males are more intense in their training. [Maron] it has been noticed that in almost all of these cases of reported deaths the victims were young, healthy looking, and asymtomatic individuals and death followed a period of intense physical exercise. Identifying potentially at risk HCM patient thus remains the main focus of physical examiners. Factors such as family history of sudden death, genetic testing and the identification of the at risk genotype, electrocardiography using HOLTER monitor to identify ventricular trachycardia, the existence of frequent syncopes and left ventricular Hypertrophy values greater than 30 mm are the important risk factors useful in identifying at risk people. Genetic research has revealed that mutations of at least ten different types of genes, responsible for the development of the cardiac muscles, are observed in HCM patients. In particular, mutations are observed in genes that code for proteins such as beta myosin heavy chain, troponin T, alpha tropomyosin, cardiac myosin binding protein-C, etc., that are involved in the heart muscle contraction process. [CMA]

Though the anterior ventricular septum is the most common site for hypertrophy, thickening of walls is also observed through the whole left ventricle. However, in almost 30% of HCM cases only one segment of the left ventricle develops hypertrophy. The patterns of LV wall thickening is also diverse as is the thickness of the LV, which ranges from anywhere between 21 mm (average) to even 60 mm in some patients. It remains a sad fact that screening programs in the form of preparticipation evaluation based on familial history and electrocardiography does not reveal much. A recent study showed that a preparticipation screening for 115 high school and college athletes who later succumbed to sudden death could identify only 3% of them as at risk. This study also revealed that LVH is very mild and not obvious in adolescents and therefore electrocardiography readings are not diagnostically conclusive. [Maron]

Treatment

Since there is not complete cure for the condition, treatment is purely symptomatic. Typically beta blockers (which reduce ventricular contraction), calcium channel blockers that slow the racing heart and reduce blood pressure and other drugs used in the treatment of arrhythmias are used. In cases that do not respond well to medicine, surgical interventions such as myectomy (removing the thickened region), alcohol septal ablation (to reduce hypertrophy of upper septum) and implantation of dual chamber pace makers are tried based on the individuals condition. [CMA]

Conclusion