In life insurance underwriting, it is important to recognize the differences between hypertrophic cardiomyopathy (HCM) and the benign heart enlargement of an athlete. Both conditions increase left ventricular (LV) mass; however, HCM causes the LV wall to thicken whereas athletic heart syndrome causes the cavity to enlarge. Because similar EKG changes can occur with both conditions, an echocardiogram is the primary determinate and often the only underwriting evidence available to differentiate between the two.

What Is Hypertrophic Cardiomyopathy?

• HCM is a cardiovascular disease characterized by an abnormal thickening of the walls of the heart that can significantly impair heart function, cause heart rhythm disturbance and, in extreme cases, result in sudden cardiac death.
• Cause - HCM is usually caused by a mutation in some of the genes of the heart muscle. Approximately 60% of patients with HCM have a currently identifiable gene abnormality. Familial HCM is the most common genetic cardiovascular disease and is autosomal dominant, which means a person with a gene mutation for HCM has a 50% chance of passing the gene to his or her child. Not all people with the gene will develop the disease, however.
• Prevalence - The prevalence of HCM in the general population is approximately 1 out of every 500 adults (or 0.2%).
• Presentation is variable. Some people with severe disease are completely asymptomatic, while others with milder disease can have symptoms that significantly impair quality of life. Regardless of symptom severity, all individuals with HCM are at an increased risk for sudden death.
• Mortality - Approximately 1% of all adults with HCM die annually.
• HCM is the leading cause of sudden cardiac death in athletes and young people, accounting for roughly a quarter of deaths.

What Is Athletic Heart Syndrome?

• In competitive athletes, particularly those in endurance sports such as distance running, cycling and swimming, the heart will enlarge on its own in response to an increase in cardiac exertion.
• An athletic heart requires a professional level of engagement (many hours of strenuous activity per week for several weeks). Casual participation in endurance sports will not cause heart enlargement.
• It is not a disease but a normal physiological response to extreme exercise.
• It is a non-pathological condition in an otherwise healthy individual.
• The heart enlargement is most pronounced in the left ventricle, resulting in a benign form of left ventricular hypertrophy (LVH).
• The LVH is usually symmetric and less than 13 mm.
• Once the athlete stops the intense training, there is regression of LVH to a normal heart size.

The chart below outlines key differences, which are particularly evident on an echocardiogram. However, sometimes the heart enlargement falls in a "gray area" where the two conditions can overlap. In these cases it is important to look at other factors, such as family history and clinical presentation, to try to distinguish between the conditions.