Aortic valve obstruction initially permits maintained cardiac output but progressively increases the workload on the left ventricle.
Compensation and myocardial supply
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Cardiac output is initially maintained at the cost of a steadily increasing pressure gradient across the aortic valve.
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Progressive stenosis causes increasing left ventricular hypertrophy. Coronary blood flow may become inadequate for the myocardium, allowing angina to develop even without coexisting coronary artery disease.
Exertional symptoms and ventricular failure
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Fixed outflow obstruction limits the increase in cardiac output required during exercise, which is when symptoms usually first occur.
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Eventually, the left ventricle cannot overcome the obstruction. Left ventricular failure follows and leads to pulmonary oedema.