Hypertrophic Cardiomyopathy Family Screening
A 19-year-old competitive footballer attends after his brother died suddenly at 24 and a paternal uncle at 30. He has had 2 episodes of light-headedness and one near-syncope while sprinting. A grade 3 out of 6 systolic murmur at the left lower sternal border becomes louder on standing and during Valsalva, and softer on squatting. There is a fourth heart sound. Which condition should he be screened for?
- A.Congenital long QT syndrome
- B.Hypertrophic cardiomyopathyCorrect
- C.Brugada syndrome
- D.Arrhythmogenic right ventricular cardiomyopathy
Explanation
Hypertrophic cardiomyopathy is an autosomal dominant sarcomeric protein disease and the leading cause of sudden cardiac death in young athletes, so first-degree relatives of a young person who dies suddenly during exertion require systematic screening. The murmur of dynamic left ventricular outflow tract obstruction behaves in a way that is diagnostic at the bedside: manoeuvres that reduce preload or afterload, such as standing from squatting or the strain phase of Valsalva, reduce ventricular cavity size, worsen septal-mitral apposition and make the murmur louder, whereas squatting or handgrip increase preload and afterload and soften it. This is the opposite of aortic stenosis and mitral regurgitation. Exertional presyncope, a forceful apex and a fourth heart sound from a stiff hypertrophied ventricle fit the same diagnosis. Screening begins with electrocardiography, which typically shows left ventricular hypertrophy with deep lateral T-wave inversion, and transthoracic echocardiography showing asymmetric septal hypertrophy of 15 mm or more, with genetic testing and cascade family screening thereafter. Long QT syndrome causes syncope with swimming, startle or emotion, has a normal cardiac examination and is diagnosed on the corrected QT interval. Brugada syndrome causes events during sleep or fever with a coved ST elevation in leads V1 to V2 and no murmur. Arrhythmogenic right ventricular cardiomyopathy causes exertional ventricular arrhythmia with epsilon waves and right precordial T-wave inversion but not a dynamic outflow murmur. Competitive sport is restricted until risk stratification is complete, and an implantable defibrillator is considered for high-risk patients.
Why each option
- A.
- Long QT syndrome has a normal cardiac examination and causes syncope with exertion, emotion or startle, diagnosed by a prolonged corrected QT interval.
- B.
- Correct. Exertional presyncope with a systolic murmur that increases on standing and Valsalva and a family history of sudden death indicates hypertrophic cardiomyopathy.
- C.
- Brugada syndrome causes arrhythmia during rest, sleep or fever with characteristic V1 to V2 ST elevation and no murmur.
- D.
- Arrhythmogenic right ventricular cardiomyopathy causes exertional arrhythmias but not a dynamic outflow tract murmur.
Reference: AHA/ACC Guideline for the Management of Hypertrophic Cardiomyopathy, 2024
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