Question

A patient is diagnosed with acute mitral regurgitation (MR). Which of the following statements about this condition is true?

• A. Normal JVP
• B. Short systolic murmur before S2
• C. Displaced apex
• D. (Dummy option) Early diastolic murmur present

Hint:

Differentiating Acute vs. Chronic MR clinically:
Acute MR: Sudden pulmonary edema, normal heart size on CXR, normal apex beat, early systolic decrescendo murmur.
Chronic MR: Exertional dyspnea, massively enlarged heart on CXR (cardiomegaly), displaced apex, holosystolic murmur.

Answer 1

The Correct Option is B

Concept:
Acute Mitral Regurgitation (MR) occurs suddenly, typically secondary to complications like papillary muscle rupture (post-MI), chordae tendineae rupture, or infective endocarditis.
The acute pathophysiology fundamentally differs from chronic MR because the cardiac chambers have not had time to adapt to the volume overload.
Explanation:
• In chronic MR, the left atrium is massively dilated and highly compliant, meaning it can absorb the regurgitant volume without a massive spike in pressure. The murmur is typically holosystolic, lasting all the way to S2.

• In contrast, in acute MR, the left atrium is of normal size and relatively non-compliant (stiff).

• When a large volume of blood is suddenly ejected backwards into this small, stiff atrium during systole, the left atrial pressure rises rapidly and massively (forming a giant 'v' wave).

• Because the pressure in the left atrium rises so quickly, it rapidly equalizes with the declining left ventricular pressure in late systole.

• Once the pressure gradient between the LV and LA disappears, the regurgitant flow stops. Thus, the murmur of acute MR is typically an early or decrescendo systolic murmur that cuts off and ends before the second heart sound (S2).

• Option (A) is incorrect. The massive backup of pressure from the non-compliant LA translates instantly into the pulmonary venous system, causing acute pulmonary edema, pulmonary hypertension, and acute right heart strain, which leads to an elevated Jugular Venous Pressure (JVP).

• Option (C) is incorrect. The Left Ventricle has not yet undergone the slow, eccentric hypertrophy and dilation seen in chronic MR, so the apex beat remains in its normal, non-displaced position.

• Option (D) is incorrect. Mitral regurgitation is a systolic phenomenon; an early diastolic murmur is characteristic of Aortic Regurgitation.
Final answer:
The rapid equalization of pressures between the left ventricle and a non-compliant left atrium causes a short systolic murmur that terminates before S2.