Expansion
Stenosis creates a pressure load; regurgitation creates a volume load
Expansion
| Lesion | Load | Ventricular response |
|---|---|---|
| Aortic stenosis | Pressure on the left ventricle | Concentric hypertrophy |
| Aortic regurgitation | Volume and pressure on the left ventricle | Eccentric hypertrophy, marked dilatation |
| Mitral stenosis | Pressure on the left atrium and pulmonary circulation | Left atrial dilatation, pulmonary hypertension; the left ventricle is spared |
| Mitral regurgitation | Volume on the left ventricle and atrium | Eccentric hypertrophy |
Two points are commonly tested. Mitral stenosis is the one left-sided lesion that does not load the left ventricle, so it presents with atrial fibrillation, haemoptysis and pulmonary hypertension rather than left ventricular failure.
And in mitral regurgitation the ventricle ejects into the low-pressure atrium, so afterload is reduced and ejection fraction is deceptively well preserved; a “normal” ejection fraction of 55 per cent already indicates significant impairment, which is why surgery is considered before it falls further.