MKSAP: 21-year-old man with a heart murmur

Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 21-year-old man is evaluated during a medical examination for health insurance. The patient is a weight lifter. He has no medical problems and takes no medications or illicit drugs.

On physical examination, blood pressure is 128/73 mm Hg, pulse rate is 56/min, and respiration rate is 16/min; BMI is 30. Increased skeletal muscle mass is noted. There is no jugular venous distention. Carotid upstrokes are brisk. There is a grade 2/6 early systolic murmur along the left lower sternal border that is accentuated by a Valsalva maneuver and decreases with a hand-grip maneuver. An S4 gallop is also noted. Electrocardiogram shows sinus bradycardia and left ventricular hypertrophy by voltage. Echocardiogram shows left ventricular hypertrophy with marked septal hypertrophy and an associated 46 mm Hg outflow tract obstruction, small left ventricular cavity size, normal systolic function with an ejection fraction of 65%, marked left atrial enlargement, and reduced early diastolic filling.

Which of the following is the most likely diagnosis?

A: Dilated cardiomyopathy
B: Hypertensive cardiomyopathy
C: Hypertrophic cardiomyopathy
D: Restrictive cardiomyopathy

MKSAP Answer and Critique

The correct answer is C: Hypertrophic cardiomyopathy.

The most likely diagnosis is hypertrophic cardiomyopathy. The cardiac examination is consistent with a dynamic left ventricular outflow tract obstruction, whereby the systolic murmur is accentuated during maneuvers that decrease preload (Valsalva maneuver) but attenuated by increasing afterload (hand-grip maneuver). Echocardiographic findings confirm left ventricular outflow tract obstruction and asymmetric septal hypertrophy consistent with hypertrophic cardiomyopathy.

The echocardiographic features in hypertrophic cardiomyopathy are diverse and include left ventricular hypertrophy, which may disproportionately involve the septal, anterior, lateral, or apical walls or may be concentric (particularly if marked). Dynamic left ventricular outflow tract or mid-cavity obstruction is a feature of hypertrophic cardiomyopathy, but it is not always seen nor is it a necessary finding to confirm the diagnosis. Additional echocardiographic features include a small left ventricular cavity size and significant left atrial enlargement. Although patients with hypertrophic cardiomyopathy may present with symptoms such as dyspnea, chest pain, or dizziness, many are asymptomatic.

This patient is a weight lifter, a known cause of concentric left ventricular hypertrophy (athlete’s heart). Echocardiography is often useful in differentiating left ventricular hypertrophy associated with hypertrophic cardiomyopathy from that of athlete’s heart. Marked hypertrophy with a small left ventricular cavity is typical of hypertrophic cardiomyopathy, whereas the cavity is often enlarged in athlete’s heart. In addition, marked left atrial enlargement and diastolic dysfunction are not typical features of athlete’s heart.

Dilated cardiomyopathy is easily excluded on the basis of echocardiography, which does not show an enlarged left ventricle with systolic dysfunction (ejection fraction <40%), as would be expected for this diagnosis.

Left ventricular hypertrophy, left atrial enlargement, and impaired early diastolic filling seen on the echocardiogram in this patient could be potentially explained by a hypertensive cardiomyopathy. However, a long-standing history of hypertension would need to be present. In addition, hypertensive cardiomyopathy cannot explain the patient’s systolic murmur that increases in intensity with a Valsalva maneuver.

Restrictive cardiomyopathy could explain left ventricular hypertrophy. However, an accentuated rate of early diastolic filling (restrictive filling) is characteristic of this entity, and not impaired early filling, as is present in this patient. Lack of this pattern of filling virtually excludes restrictive cardiomyopathy.

Key Point

  • Hypertrophic cardiomyopathy is characterized by a dynamic left ventricular outflow tract obstruction evidenced by a systolic murmur that is accentuated during maneuvers that decrease preload (Valsalva maneuver) but attenuated by increasing afterload (hand-grip maneuver).

This content is excerpted from MKSAP 16 with permission from the American College of Physicians (ACP). Use is restricted in the same manner as that defined in the MKSAP 16 Digital license agreement. This material should never be used as a substitute for clinical judgment and does not represent an official position of ACP. All content is licensed to on an “AS IS” basis without any warranty of any nature. The publisher, ACP, shall not be liable for any damage or loss of any kind arising out of or resulting from use of content, regardless of whether such liability is based in tort, contract or otherwise.

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