Heart Valves

Four one-way valves keep blood moving in the right direction through the heart. The mitral and tricuspid valves guard the entrances to the ventricles and are anchored by cords to prevent them blowing backwards; the aortic and pulmonary valves, with three half-moon cusps each, guard the exits. Their snapping shut produces the familiar 'lub-dub' heart sounds.

Key facts

There are four valves: mitral, tricuspid, aortic and pulmonary.
The mitral is the only valve with two cusps instead of three.
Valves have no muscle of their own — pressure differences open and close them.
Fine cords (chordae tendineae) tether the mitral and tricuspid valves to the ventricle walls.
Heart murmurs are the sounds of turbulent flow, often at a narrowed or leaking valve.

What can go wrong

Valves can narrow (stenosis) or leak (regurgitation) through wear and calcification with age, congenital differences (such as a two-cusp aortic valve), infection (endocarditis) or stretching of the heart. Significant valve disease makes the heart work harder and can cause breathlessness, chest pain, palpitations or fainting.

Related conditions

Hypertension

Related procedures & tests

Related symptoms

Watch: related videos

▶ WatchHeart valves

Frequently asked questions

What makes the 'lub-dub' sound?

The closing of the valves. 'Lub' is the mitral and tricuspid valves shutting at the start of contraction; 'dub' is the aortic and pulmonary valves shutting as the ventricles relax.

Can a leaking valve be harmless?

Yes — tiny leaks are common and often found incidentally on scans in healthy hearts. It is the severity of the leak or narrowing, and its effect on the heart's size and function, that decides whether treatment is needed.

Educational information only. This atlas explains normal anatomy and describes conditions in general terms; it is not medical advice and does not replace assessment by a qualified clinician. If you have symptoms that worry you, seek medical care.