In a 66-year-old man with a diastolic murmur best heard at the left sternal edge and an outwardly displaced apex beat, which condition most typically presents with these findings?

Aortic Regurgitation (Answer: B)

The clinical presentation of a diastolic murmur best heard at the left sternal edge combined with a laterally displaced apex beat is pathognomonic for aortic regurgitation. 1, 2

Clinical Reasoning

The combination of findings in this patient creates a highly specific diagnostic pattern:

The Diastolic Murmur

• Diastolic murmurs at the left sternal edge are characteristic of aortic regurgitation, representing the high-pitched, decrescendo sound of blood flowing backward from the aorta into the left ventricle during diastole 1
• The ACC/AHA guidelines explicitly state that the diagnosis of chronic severe AR can usually be made on the basis of the diastolic murmur and displaced LV impulse 1
• When AR results from aortic root dilatation, the murmur may be louder at the right sternal border, but the left sternal edge remains the classic location 1, 2

The Displaced Apex Beat

• A laterally displaced apex beat indicates left ventricular volume overload and dilatation, which is the hallmark hemodynamic consequence of chronic aortic regurgitation 1, 3
• Chronic severe AR causes combined LV volume and pressure overload, leading to progressive LV dilation that physically displaces the apex beat outward and downward 3
• This finding is so specific that it is listed as one of the key diagnostic features in major guidelines 1

Why the Other Options Are Incorrect

Coarctation of the Aorta (Option A)

• Produces a systolic murmur (not diastolic) best heard over the back between the scapulae 1
• Does not typically cause a displaced apex beat unless there is severe long-standing hypertension with secondary LV hypertrophy 1

Mitral Regurgitation (Option C)

• Produces a holosystolic murmur (not diastolic) best heard at the apex with radiation to the axilla 1
• While it can cause a displaced apex beat due to LV volume overload, the absence of a systolic murmur and presence of a diastolic murmur excludes this diagnosis 1

Aortic Stenosis (Option D)

• Produces a crescendo-decrescendo systolic ejection murmur (not diastolic) best heard at the right upper sternal border with radiation to the carotids 4
• Typically causes LV hypertrophy rather than dilation, so the apex beat may be forceful but is not usually displaced laterally 4

Clinical Pitfalls to Avoid

• Do not dismiss mild-sounding murmurs: The intensity of the diastolic murmur correlates poorly with AR severity in chronic regurgitation—even a soft murmur can indicate severe disease 2
• Always assess additional physical findings: Look for wide pulse pressure, bounding peripheral pulses, and other signs of chronic AR to confirm the diagnosis 1, 3
• Consider the patient's age: At 66 years, this patient's presentation is consistent with chronic degenerative AR, which is common in this age group 1