A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 39-year-old man seeks an evaluation in the emergency room due to an episode of syncope at work. He says that he has felt increasing shortness of breath while exercising over the past 6 months. He is a well-built man in mild distress. The vital signs include heart rate 98/min, respiratory rate 18/min, temperature 36.5°C (97.7°F), and blood pressure 135/90 mm Hg. The cardiac examination is significant for a harsh systolic ejection murmur at the left lower sternal border which is accentuated by forceful expiration against a closed airway. Palpation of the carotid artery shows 2 closely spaced pulses which occur during systole. Which of the following is most consistent with these findings?
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A
Aortic stenosisIncorrect. Aortic stenosis murmur DECREASES with Valsalva (reduced flow) and has a delayed/diminished carotid upstroke (pulsus parvus et tardus), not a bifid pulse.
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B
Cardiac tamponadeIncorrect. Cardiac tamponade produces hypotension, distended neck veins, muffled heart sounds (Beck's triad), and pulsus paradoxus - not a systolic ejection murmur with bisferiens pulse.
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C
Hypertrophic cardiomyopathyCorrect. HOCM produces a dynamic outflow murmur that augments with reduced preload, plus a bifid carotid pulse from mid-systolic obstruction.
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D
Third-degree heart blockIncorrect. Third-degree heart block presents with bradycardia, cannon A waves, and syncope from prolonged pauses - it does not produce a systolic murmur with bisferiens pulse.
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E
Mitral valve prolapseIncorrect. MVP produces a mid-systolic click followed by a late systolic murmur that increases with reduced preload, but it does not cause a bifid carotid pulse or dynamic outflow obstruction - HOCM is the syndrome that explains both findings.
↑ Tap an answer to reveal the reasoning
Answer: C. A young man with exertional dyspnea, syncope, and a harsh systolic ejection murmur at the left lower sternal border that INCREASES with Valsalva (forceful expiration against a closed airway) plus a bifid carotid pulse (pulsus bisferiens - 'spike-and-dome') has hypertrophic cardiomyopathy (HCM), specifically the obstructive form (HOCM). HCM is an autosomal dominant disease of sarcomere protein genes (most commonly beta-myosin heavy chain MYH7 or myosin-binding protein C MYBPC3), producing asymmetric septal hypertrophy that obstructs left ventricular outflow during systole.
The murmur INCREASES with maneuvers that decrease LV preload or afterload (Valsalva, standing, amyl nitrate) because reduced LV cavity size brings the hypertrophied septum and the systolic anterior motion (SAM) of the mitral leaflet into closer apposition, worsening outflow obstruction. This is the OPPOSITE of aortic stenosis (which decreases with Valsalva because of reduced flow across the valve).
The pulsus bisferiens occurs because of mid-systolic obstruction: the initial brisk upstroke is followed by a pressure drop as obstruction develops, then a second smaller peak. HCM is the leading cause of sudden cardiac death in young athletes. Management includes beta-blockers/verapamil, avoidance of dehydration and vasodilators, septal myectomy or alcohol ablation, and ICDs for high-risk patients.
**Why each option:**
**A.** Aortic stenosis murmur DECREASES with Valsalva (reduced flow) and has a delayed/diminished carotid upstroke (pulsus parvus et tardus), not a bifid pulse.
**B.** Cardiac tamponade produces hypotension, distended neck veins, muffled heart sounds (Beck's triad), and pulsus paradoxus - not a systolic ejection murmur with bisferiens pulse.
**C.** Correct. HOCM produces a dynamic outflow murmur that augments with reduced preload, plus a bifid carotid pulse from mid-systolic obstruction.
**D.** Third-degree heart block presents with bradycardia, cannon A waves, and syncope from prolonged pauses - it does not produce a systolic murmur with bisferiens pulse.