Aortic Stenosis: When A Heart Valve Wears Out

The aortic valve opens and closes with every heartbeat across a lifetime. In a proportion of older adults it stiffens and narrows, and symptoms appear only at a late stage.

What the valve does

The aortic valve sits between the left ventricle and the aorta. It opens to allow ejection and closes to prevent blood returning during filling.

Its leaflets are thin and flexible, and they must seal completely under high pressure while offering minimal resistance when open.

Over decades this amounts to an enormous number of cycles, each involving mechanical stress concentrated at the same points on the leaflets.

Narrowing is an active process, not simple wear

Calcific valve disease was long assumed to be passive deposition. It is now understood as an active process resembling aspects of atherosclerosis and bone formation.

Endothelial injury allows lipids to enter the leaflet, inflammatory cells follow, and some valve cells adopt a bone-forming character that deposits calcium.

The leaflets thicken and become rigid, so the opening area falls progressively. A congenitally two-leaflet valve tends to reach this state considerably earlier.

Why symptoms appear so late

The left ventricle compensates by thickening its wall, which allows it to generate higher pressure and maintain output across the narrowed opening.

This compensation is effective for years, so a substantially narrowed valve can exist without the person noticing any limitation at rest.

Once the ventricle can no longer keep pace, symptoms emerge relatively quickly, which is why the condition is often described as silent until it is not.

The symptoms that matter

The classic triad is breathlessness on exertion, chest tightness with activity, and lightheadedness or blackouts during exertion.

All three are easily attributed to ageing, deconditioning or other conditions, which is a major reason for delayed presentation.

Exertional blackouts in particular are treated as urgent, because they indicate the heart cannot increase output when demand rises, and the outlook changes once symptoms begin.

Many people also adapt without realising it, reducing walking pace or avoiding stairs, so the limitation is discovered only when someone asks what they no longer do.

How it is identified and followed

A murmur heard with a stethoscope usually prompts the first suspicion, and echocardiography then measures flow velocity, pressure difference and valve area.

Mild or moderate narrowing without symptoms is typically monitored with repeat scans at intervals determined by severity and rate of change.

Decisions about intervention depend on severity, symptoms, ventricular function and overall health, and belong firmly with a cardiology team.