In aortic regurgitation, what is the primary adaptive mechanism that allows the ventricle to handle the large regurgitant volume while maintaining forward stroke volume?

• A Concentric hypertrophy reduces wall stress and increases ejection fraction
• B Tachycardia reduces diastolic filling time, limiting regurgitant volume
• C Eccentric hypertrophy (volume overload pattern) increases end-diastolic volume via sarcomere replication in series, increasing stroke volume by Starling mechanism ✓
• D Peripheral vasodilation reduces systemic resistance, preferentially increasing forward flow

Explanation

Aortic regurgitation imposes chronic volume overload on the LV (it receives normal venous return plus the regurgitant volume). The primary adaptive response is eccentric hypertrophy: sarcomeres replicate in series (lengthening myocytes), increasing LV end-diastolic volume and radius. Per the Frank-Starling mechanism, larger preload generates higher stroke volume, maintaining total (forward + regurgitant) SV. Wall stress is managed by parallel sarcomere addition (some concentric component). The LV in chronic AR becomes the largest ventricle in cardiology — the 'cor bovinum'.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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