Hypertrophic cardiomyopathy and ultra-endurance running - two incompatible entities?

Regular physical exercise is associated with physiological increases in cardiac dimensions which may be reflected on the electrocardiogram (ECG). Differentiating a physiological or pathological remodelling mechanism is important, as significant cardiac enlargement may be an expression of underlying cardiac disease, placing the athlete at a greater risk of sudden cardiac death (SCD) [1]. Approximately 80% of non-traumatic sudden deaths in young athletes (< 35 years) are caused by inherited or congenital structural and functional cardiovascular abnormalities, which provide a substrate for arrhythmias predisposing to SCD [2]. Hypertrophic cardiomyopathy (HCM), defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease, etc) sufficient to cause the observed abnormality [3], is the leading cause of SCD in the young and accounts for one third of all sudden cardiac deaths in young competitive athletes [4,5]. However, existing data also demonstrates that a small proportion of athletes (< 2%) exhibit increased left ventricular wall thickness (LVWT) ranging between 13-16 mm [6-8], which overlaps with morphologically mild HCM.Deaths from HCM are predominantly confined to intermittent 'start-stop' sports such as American football, basketball and soccer, with few cases reported in endurance sports. The postulated theory is that individuals with HCM are unable to augment cardiac output sufficiently to participate in intensive and prolonged endurance sports due to a combination of pronounced LVH, a non-compliant LV, exercise-induced LV outflow obstruction and microvascular ischemia. However, we report an ultra-endurance athlete with confirmed HCM capable of performing high-levels of aerobic ultra-endurance activity.A 44 year-old Caucasian male was evaluated in our centre for investigation of a cardiac murmur identified by his primary care physician. The individual was asymptomatic with no past medical h