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Pregnancy Haemodynamic Changes — EECC MCQ

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ModerateGeneral CardiologyPregnancy Haemodynamic ChangesEECC

A 45-year-old woman with MS and a mechanical mitral valve develops dyspnoea at 28 weeks gestation. Echocardiography shows a well-functioning prosthesis with normal gradients. Her heart rate is 105 bpm and haemoglobin is 95 g/L. What physiological change of pregnancy explains her symptoms?

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Correct answer: A — Pregnancy causes a 30-50% increase in blood volume and cardiac output peaking at 28-34 weeks, which unmasks limited cardiac reserve in patients with mechanical valves and fixed valve areas — physiological anaemia and tachycardia compound the problem

Pregnancy induces profound cardiovascular changes: (1) blood volume increases 30-50% (peaking 28-34 weeks); (2) cardiac output increases 30-50% (through increased stroke volume and heart rate); (3) SVR decreases 20-30% (vasodilation from progesterone and prostacyclin); (4) physiological anaemia (haemodilution — haemoglobin falls to ~100-110 g/L); (5) hypercoagulable state. These changes peak in the late second/early third trimester. In patients with fixed cardiac output limitation (mechanical valves, severe stenotic lesions, severe PH), the increased volume load cannot be accommodated, unmasking symptoms. The 2025 ESC CVD in Pregnancy Guidelines use mWHO classification to stratify pregnancy risk: mechanical valves = mWHO III (significant risk requiring specialist care throughout pregnancy).

Reference: ESC (2025): Guidelines for CVD in Pregnancy