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Difficulty: HardPhysical Examination Findings

A 3434-year-old man with a history of Marfan syndrome is brought to the emergency department after the sudden onset of severe, tearing chest pain radiating to his back. He appears pale, diaphoretic, and in acute respiratory distress. His blood pressure is 90/50 mmHg90/50 \text{ mmHg}, heart rate is 122 /min122 \text{ /min}, and respiratory rate is 26 /min26 \text{ /min}. A bedside echocardiogram reveals an ascending aortic intimal flap and a new, severe regurgitant jet across the aortic valve. Which of the following physical examination findings are most likely to be present in this patient? (Select all that apply)

  1. A soft or absent first heart sound (S1S_1)Answer
  2. B
    Bounding, high-amplitude peripheral pulses
  3. A short, early diastolic murmur at the left sternal borderAnswer
  4. D
    A laterally displaced, hyperdynamic apical impulse
  5. E
    A widened arterial pulse pressure of greater than 60 mmHg60 \text{ mmHg}

Answer

The expected physical examination findings are a soft or absent first heart sound (S1S_1) and a short, early diastolic murmur at the left sternal border.
This patient has acute severe aortic regurgitation due to a proximal aortic dissection. In acute aortic regurgitation, a large volume of regurgitant blood rapidly enters a normal-sized, non-compliant left ventricle. This causes an abrupt and massive increase in left ventricular end-diastolic pressure. The highly elevated left ventricular pressure exceeds left atrial pressure early in diastole, forcing the mitral valve to close prematurely, which manifests as a soft or absent first heart sound (S1S_1). Furthermore, the rapid equilibration of pressures between the aorta and the left ventricle during diastole causes the characteristic decrescendo diastolic murmur of aortic regurgitation to be notably short and lower-pitched compared to the prolonged, high-pitched murmur seen in chronic aortic regurgitation.

Step-by-Step Solution

1
Identify the primary pathophysiological event.
The patient is experiencing acute severe aortic regurgitation secondary to an ascending aortic dissection.
An intimal flap and new regurgitant jet in a patient with Marfan syndrome and tearing chest pain confirms this diagnosis.
2
Analyze the hemodynamic consequences of acute aortic regurgitation.
A sudden influx of regurgitant blood into a normal-sized, non-compliant left ventricle causes a rapid and massive rise in left ventricular end-diastolic pressure.
The left ventricle has not had time to undergo the eccentric hypertrophy and dilation that occurs in chronic aortic regurgitation.
3
Correlate the altered hemodynamics with physical examination findings.
The highly elevated left ventricular diastolic pressure causes premature closure of the mitral valve (producing a soft or absent S1S_1) and a rapid pressure equilibration between the aorta and left ventricle (producing a short, low-pitched diastolic murmur).
These signs reflect the acute failure of the heart to accommodate the regurgitant volume, fundamentally distinguishing it from the clinical presentation of chronic aortic regurgitation.

Key Concept

Physical examination findings in acute aortic regurgitation differ significantly from chronic aortic regurgitation; acute aortic regurgitation is characterized by a soft or absent S1S_1, a short early diastolic murmur, a narrow pulse pressure, and an undisplaced apical impulse due to the lack of ventricular compensation.
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Physical Examination Findings

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