A 17-year-old boy is brought to the office for a routine presports physical evaluation. The patient has no symptoms. He plays competitive soccer for his high school. Blood pressure is 120/80 mm Hg, pulse is 62/min, and respirations are 15/min. BMI is 27 kg/m². The patient is well built with increased skeletal muscle mass. Physical examination is unremarkable. ECG demonstrates normal sinus rhythm with T-wave inversion in leads V₅ and V₆. Echocardiography reveals left ventricular hypertrophy with impaired early diastolic filling and mild left atrial enlargement. What is the most likely diagnosis in this patient?

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Explanation: 11ec25c8_d353_bd6f_bc81_451613b38d6b_MD0003_00 This patient with ECG showing repolarization abnormalities (ie, lateral T-wave inversions) and echocardiography revealing diastolic dysfunction and left atrial enlargement most likely has hypertrophic cardiomyopathy (HCM). HCM is an autosomal dominant inherited condition involving mutations in genes that encode proteins of the cardiac sarcomere. The phenotypic manifestations typically begin during adolescence and include the following: Asymmetric left ventricular (LV) hypertrophy, usually primarily affecting the interventricular septum Myocardial disarray Coronary microvascular dysfunction with a poorly developed capillary network Depending on the degree of interventricular septal hypertrophy, many patients with HCM have dynamic LV outflow tract (LVOT) obstruction that can be recognized by a crescendo-decrescendo murmur best heard at the left sternal border. The LVOT obstruction commonly causes exertional symptoms (eg, dyspnea, lightheadedness). However, not all patients have significant LVOT obstruction and the associated murmur. Such patients may be asymptomatic or may still have exertional symptoms (eg, dyspnea, angina) caused by myocardial oxygen supply-demand mismatch. These patients may also still be at increased risk for ventricular tachycardia and sudden cardiac death. (Choice A) Athlete's heart consists of physiologic adaptations that occur in response to intense exercise training. Left ventricular hypertrophy is typically present, but impaired diastolic filling and left atrial enlargement are not expected and suggest HCM. Significant depolarization or repolarization abnormalities on ECG are also not expected (sinus bradycardia, increased QRS voltage, and J point elevation may be seen). exercise training (Choice B) Brugada syndrome follows autosomal dominant inheritance and usually involves mutations affecting cardiac sodium channels. Affected patients have ECG abnormalities (eg, ST elevation in leads V₁ and V₂) and are at increased risk of sudden cardiac death (due to ventricular arrhythmia), but no structural cardiac abnormalities are typically present. ₁ ₂ (Choice D) Prolonged, uncontrolled hypertension (usually for ≥10 years) is the most common cause of LV hypertrophy. This concentric LV hypertrophy commonly leads to impaired diastolic function and left atrial enlargement, but it is highly unlikely in this adolescent patient who currently has normal blood pressure. Educational objective: Patients with hypertrophic cardiomyopathy (HCM) may not have significant left ventricular outflow tract obstruction to cause a murmur. Findings that differentiate HCM from athlete's heart, another potential cause of left ventricular hypertrophy in young patients, include depolarization or repolarization abnormalities on ECG and evidence of diastolic dysfunction or left atrial enlargement on echocardiography. References: Long-term outcome of nonobstructive versus obstructive hypertrophic cardiomyopathy: a systematic review and meta-analysis. (http://www.ncbi.nlm.nih.gov/pubmed/28747036) Hypertrophic cardiomyopathy. (http://www.ncbi.nlm.nih.gov/pubmed/22874472)

A 17-Year-Old Boy Is Brought to the Office for a Routine