Clinical Scenario:
A 9-year-old boy is referred because of exertional chest pain and two episodes of near-syncope during exercise. His father died suddenly at 35 years of age. On examination, there is a harsh systolic murmur at the left sternal edge that becomes louder when he stands and softer when he squats.
ECG shows left ventricular hypertrophy with deep, narrow Q waves in the lateral leads. Echocardiography demonstrates marked asymmetric interventricular septal hypertrophy and systolic anterior motion of the mitral valve.
What is the most likely diagnosis?
A. Aortic stenosis
B. Dilated cardiomyopathy
C. Hypertrophic cardiomyopathy
D. Myocarditis
E. Pulmonary stenosis
Correct answer & Explanation:
Answer: C. Hypertrophic cardiomyopathy
Explanation
The combination of exertional syncope/chest pain, family history of sudden cardiac death, LV hypertrophy, asymmetric septal hypertrophy and systolic anterior motion of the mitral valve is characteristic of hypertrophic cardiomyopathy (HCM). Dynamic LV outflow tract obstruction explains why the murmur becomes louder with standing and softer with squatting.
- A. Aortic stenosis: Can cause exertional symptoms and a systolic murmur, but the echocardiographic finding of asymmetric septal hypertrophy with systolic anterior motion of the mitral valve supports HCM.
- B. Dilated cardiomyopathy: Characterized by ventricular dilation and systolic dysfunction rather than asymmetric septal hypertrophy.
- D. Myocarditis: May cause chest pain and ventricular dysfunction but does not typically produce this characteristic phenotype or family history.
- E. Pulmonary stenosis: Produces an ejection systolic murmur at the upper left sternal border and RV rather than LV hypertrophy.
MRCPCH clue:
Exertional syncope + family history of sudden death + asymmetric septal hypertrophy + systolic anterior motion of mitral valve → HCM.
Reference:
Kliegman RM, St Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 22nd ed. Elsevier. Chapter on Cardiomyopathies.
