MS Rate Control in Pregnancy — EECC MCQ

Correct answer: A — Heart rate control with beta-blockers is the cornerstone — maintaining a resting HR <80 bpm prolongs diastolic filling time across the stenotic mitral valve, reducing LA pressure and pulmonary congestion; beta-1 selective agents (metoprolol) are preferred in pregnancy

Mitral stenosis is the valvular lesion most poorly tolerated during pregnancy because: (1) pregnancy increases heart rate (reducing diastolic filling time across the fixed stenotic orifice); (2) pregnancy increases blood volume (raising LA pressure behind the obstruction); (3) tachycardia is the primary driver of symptom worsening. Heart rate control is therefore the cornerstone: (1) beta-1 selective beta-blocker (metoprolol — least placental transfer) to target resting HR <80 bpm; (2) diuretics cautiously if congestion develops (avoid volume depletion — reduced uteroplacental perfusion); (3) AF prevention/rate control is critical. The 2025 ESC CVD in Pregnancy Guidelines classify moderate MS as mWHO II-III. PMBC during pregnancy may be considered for symptomatic severe MS (mWHO III-IV) refractory to medical therapy — ideally in the second trimester with abdominal lead shielding.

Reference: ESC (2025): CVD in Pregnancy Guidelines