Stenosis versus regurgitation as opposite mechanical failures
A stenotic valve fails to open fully, so blood must squeeze through a narrowed orifice. The chamber upstream develops a high pressure gradient to push flow forward, and over time it responds with concentric hypertrophy (thicker walls, similar cavity size). Aortic stenosis is the classic example, where the left ventricle generates a large pressure difference across the valve in systole.
A regurgitant valve fails to close fully, so blood leaks backward. The upstream chamber receives both the normal venous return and the leaked volume, so it dilates over time (eccentric hypertrophy, larger cavity). Mitral regurgitation and aortic regurgitation are volume-overload lesions rather than pressure-overload lesions.
How the four lesions load different chambers
Aortic stenosis pressure-loads the left ventricle. Aortic regurgitation volume-loads the left ventricle in diastole. Mitral stenosis raises left atrial pressure and backs up into the pulmonary circulation, often presenting with breathlessness and atrial fibrillation. Mitral regurgitation volume-loads both the left atrium and ventricle.
On a pressure-volume loop these patterns separate cleanly: stenosis raises systolic pressure for a given volume, while regurgitation widens the loop toward larger volumes. This is general educational information, not medical advice; valve disease evaluation, severity grading, and treatment decisions require echocardiography and a qualified cardiologist.