A 17-year-old boy is evaluated due to left-sided chest discomfort for the past week. It is exacerbated by left arm movement and deep inspiration. The patient plays competitive soccer for his high school and has been practicing almost daily. His mother is worried that he has a heart condition because his maternal uncle died from a "massive heart attack" at age 35. Blood pressure is 125/80 mm Hg, pulse is 56/min, and respirations are 15/min. BMI is 27 kg/m². The patient is well built with increased skeletal muscle mass. There is no jugular venous distension. Physical examination is unremarkable. ECG demonstrates sinus bradycardia with T-wave inversion in lead V₁. Echocardiography reveals slightly enlarged left ventricular cavity size, mild left ventricular wall thickening, and no left atrial enlargement. What is the most likely cause of this patient's cardiac findings?

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Explanation: 11ec25c8_d354_80c0_bc81_41846650fa8f_MD0003_00 Differentiating the physiologic changes of athlete's heart from serious underlying pathology that can increase the risk of sudden cardiac death (eg, hypertrophic cardiomyopathy) is highly important. This young athlete, who has undergone intensive endurance training, has the characteristic findings of athlete's heart. These include the following: characteristic findings Eccentric left ventricular (LV) hypertrophy with enlarged LV cavity size and slightly (and uniformly) increased LV wall thickness Enlarged right ventricular cavity size Increased stroke volume with unchanged LV ejection fraction Absence of left atrial enlargement Sinus bradycardia at rest, often with low-grade atrioventricular block (ie, first degree or Mobitz type I second degree), resulting from increased resting vagal tone. Additional ECG findings that can be seen include increased QRS voltage and J point elevation; isolated T-wave inversion in V₁ is relatively common in the general population, including in athletes. In contrast, characteristic echocardiographic findings of hypertrophic cardiomyopathy include asymmetric LV wall thickening that favors the interventricular septum, with resultant reduced LV cavity size and left atrial enlargement (possibly compensating for LV diastolic dysfunction). ECG often demonstrates abnormalities in depolarization (eg, prominent Q waves) and repolarization (eg, T-wave inversions in 2 contiguous leads) (Choice D). (Choice B) Cardiac amyloidosis typically affects older patients (eg, age >60), causing LV wall thickening and restrictive cardiomyopathy. Left atrial dilation is typically present secondary to LV diastolic dysfunction. (Choice C) Fabry disease is a rare, X-linked inherited disorder involving deficiency of lysosomal hydrolase alpha-galactosidase A that leads to lysosomal accumulation of glycosphingolipids (specifically globotriaosylceramide [Gb3]). Affected patients typically develop neurologic manifestations (eg, paresthesias) during adolescence with cardiac manifestations including concentric LV hypertrophy, myocardial fibrosis, and heart failure developing at age >30. (Choice E) Masked hypertension is the term given to chronic hypertension that fluctuates throughout the day, making it difficult to diagnose at clinic visits; blood pressure is often normal at clinic visits but mean pressure over 24 hours is elevated. It is uncommon in adolescents and would be expected to cause concentric LV wall thickening with reduced LV cavity size rather than LV cavity enlargement. Educational objective: Athlete's heart resulting from intensive endurance training is characterized by enlarged left ventricular (LV) cavity size with slightly increased LV wall thickness and normal left atrial size. It is important to differentiate athlete's heart from pathologic causes of left ventricular hypertrophy, namely hypertrophic cardiomyopathy characterized by reduced LV cavity size, left atrial enlargement, and asymmetric LV wall thickening that favors the interventricular septum.

A 17-Year-Old Boy Is Evaluated Due to Left-Sided Chest Discomfort