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Difficulty: MediumPhysical Examination Findings

A 19-year-old collegiate athlete is evaluated in the clinic for pre-participation sports clearance. He is entirely asymptomatic and reports excellent exercise tolerance during rigorous training. His family history is highly notable for the sudden, unexplained death of his older brother at age 22 during a basketball game. The patient's temperature is 37.0°C (98.6°F), blood pressure is 112/68 mm Hg, and pulse is 62/min. Cardiac auscultation reveals a regular rate and rhythm with a grade 3/6 harsh, crescendo-decrescendo systolic murmur heard best at the left lower sternal border. The murmur does not radiate to the carotid arteries.

Which of the following dynamic physical examination maneuvers would most likely result in an INCREASE in the intensity of this patient's murmur?

  1. A
    Sustained isometric handgrip exercise
  2. B
    Rapid assumption of a squatting position
  3. C
    Passive elevation of the lower extremities
  4. Transitioning from a supine to a standing positionAnswer
  5. E
    Application of firm pressure to the carotid sinus

Answer

Transitioning from a supine to a standing position
The patient's clinical presentation—a harsh systolic murmur at the lower left sternal border and a family history of sudden cardiac death—strongly suggests hypertrophic cardiomyopathy (HCM). The murmur of HCM is caused by dynamic left ventricular outflow tract (LVOT) obstruction. Maneuvers that decrease left ventricular volume (by decreasing preload or afterload) exacerbate this obstruction and increase the murmur's intensity. Transitioning from a supine to a standing position causes venous pooling in the lower extremities, thereby decreasing venous return (preload). The reduced left ventricular end-diastolic volume brings the anterior leaflet of the mitral valve closer to the hypertrophied interventricular septum, worsening the LVOT obstruction and making the murmur louder.

Step-by-Step Solution

1
Identify the most likely diagnosis based on the clinical vignette.
The patient has hypertrophic cardiomyopathy (HCM), indicated by a harsh systolic murmur at the lower left sternal border and a family history of sudden cardiac death in a young relative.
A precise anatomical diagnosis is required to predict the physiological response to dynamic maneuvers.
2
Determine the pathophysiology of the murmur in the identified condition.
The murmur in HCM results from dynamic left ventricular outflow tract (LVOT) obstruction. The obstruction worsens when the left ventricular cavity volume is reduced.
Understanding the structural mechanism is key to evaluating how changes in hemodynamics affect the intensity of the murmur.
3
Evaluate the physiological effect of the maneuvers listed in the options.
Standing decreases venous return (preload), leading to a smaller left ventricular cavity. This exacerbates the LVOT obstruction, making the murmur louder.
Connecting the maneuver's hemodynamic effect to the underlying pathophysiology identifies which specific action will increase the murmur's intensity.

Key Concept

Dynamic auscultation and physiological maneuvers in the evaluation of hypertrophic cardiomyopathy.
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Topics

Physical Examination Findings

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