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Difficulty: MediumPhysical Examination Findings

A 26-year-old woman is evaluated in the outpatient clinic for intermittent episodes of palpitations and atypical chest pain. She has no significant past medical history and takes no medications. Her blood pressure is 112/70 mm Hg, and her heart rate is 78/min. Cardiac auscultation reveals a regular rhythm with a normal first heart sound (S1) and second heart sound (S2). A distinct mid-systolic click is heard at the cardiac apex, followed immediately by a high-pitched, late systolic murmur that radiates to the axilla. The physician decides to perform dynamic auscultation to evaluate the hemodynamics of the condition. Which of the following changes in the auscultatory findings is most likely to occur when this patient transitions from a standing to a squatting position?

  1. The click will occur later in systole, moving closer to the second heart sound (S2)Answer
  2. B
    The murmur will become holosystolic and increase in overall duration
  3. C
    The click will occur earlier in systole, moving closer to the first heart sound (S1)
  4. D
    The overall intensity of the systolic murmur will significantly increase
  5. E
    The systolic murmur will disappear and be replaced by a diastolic rumble

Answer

The click will occur later in systole, moving closer to the second heart sound (S2)
The patient's presentation of a mid-systolic click and a late systolic murmur is the classic physical examination finding for mitral valve prolapse (MVP). The timing of these auscultatory features is highly dependent on left ventricular volume. Squatting increases both venous return (preload) and systemic vascular resistance (afterload), which leads to a larger left ventricular end-diastolic volume. This enlarged ventricular chamber keeps the chordae tendineae and redundant mitral leaflets taut for a longer period during ventricular contraction, delaying the backward prolapse of the leaflets into the left atrium. Because the prolapse is delayed, the associated mid-systolic click occurs later in systole (moving closer to S2), and the resulting late systolic murmur becomes shorter in duration.

Step-by-Step Solution

1
Identify the underlying valvular pathology based on baseline physical examination findings.
The presence of a mid-systolic click followed by a late systolic murmur is the classic presentation of Mitral Valve Prolapse (MVP).
Establishing the baseline diagnosis is required to predict how dynamic maneuvers will alter the hemodynamics.
2
Analyze the physiologic effect of the specified dynamic maneuver (squatting).
Squatting forces blood from the lower extremities back to the heart (increasing preload) and compresses femoral arteries (increasing afterload), leading to a significant increase in left ventricular end-diastolic volume.
Understanding the volume changes in the left ventricle is key to determining the timing of the mitral valve prolapse.
3
Determine how increased left ventricular volume affects the mechanical prolapse of the mitral leaflets.
A larger, more filled left ventricle keeps the chordae tendineae and redundant mitral leaflets taut for a longer period during ventricular systole. Therefore, the physical prolapse into the left atrium is delayed.
The timing of the click directly correlates with the exact moment the leaflets prolapse and the chordae suddenly tense.
4
Correlate the mechanical delay with the resulting auscultatory changes.
Because the prolapse is delayed, the click occurs later in systole (closer to S2). Consequently, the murmur that follows the click is shorter in duration.
This directly answers the question regarding the expected physical examination findings.

Key Concept

Dynamic Auscultation of Mitral Valve Prolapse
Estimated Time:1m 15s
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Topics

Physical Examination Findings

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