Overview

Number of cusps3 (right, left, non-coronary)

Normal orifice area3–4 cm²

Severe stenosis<1.0 cm²; mean gradient ≥40 mmHg

Bicuspid aortic valve prevalence≈1–2%

Cusps and sinuses. The aortic valve has three semilunar cusps, each with a central nodule and two lunules. Behind each cusp the aortic wall bulges to form an aortic sinus (sinus of Valsalva). The cusps are named after the coronary arteries. The right coronary artery arises from the right sinus and the left main coronary artery from the left sinus. The posterior sinus has no artery and is called the non-coronary sinus.

Coronary filling. Because the coronary ostia lie behind the open cusps, the coronary arteries fill mainly in diastole. At that time the valve is closed and the recoiling aorta drives blood into them.

Position. The aortic valve sits at the centre of the heart, wedged between the mitral and tricuspid orifices and in contact with the central fibrous body and the bundle of His. Its normal orifice area is 3–4 cm².

Sound. Aortic closure (A2) is normally the louder, earlier part of S2. It is best heard in the 2nd right intercostal space, even though the valve itself lies behind the left half of the sternum at the 3rd intercostal space.

Location: Behind the left half of the sternum at the level of the 3rd intercostal space. It is best heard in the 2nd right intercostal space beside the sternum.

Parts & subdivisions

Right coronary cusp
In front of the right aortic sinus, which gives rise to the RCA.
Left coronary cusp
In front of the left aortic sinus, which gives rise to the left main coronary artery.
Non-coronary (posterior) cusp
Has no coronary ostium and lies next to the interatrial septum.
Aortic sinuses (of Valsalva)
Bulges of the aortic root behind the cusps.

Function

Allows the left ventricle to eject into the aorta.
Prevents blood flowing back into the ventricle during diastole, which maintains diastolic pressure and coronary perfusion.

Clinical significance

Aortic stenosis

In older people aortic stenosis is usually due to calcific degeneration. A congenitally bicuspid valve, found in about 1–2% of the population, causes it at a younger age. Rheumatic disease is another cause.

Signs include an ejection systolic crescendo–decrescendo murmur in the 2nd right intercostal space that radiates to the carotids, a slow-rising pulse, a narrow pulse pressure and a soft A2. Symptoms are angina, syncope and breathlessness from heart failure, and once they appear the prognosis is poor without valve replacement.

Stenosis is severe when the valve area is <1.0 cm², the mean gradient is ≥40 mmHg or the peak velocity is ≥4 m/s. Treatment is surgical or transcatheter (TAVI) valve replacement.

Aortic regurgitation

Aortic regurgitation results either from dilatation of the aortic root (hypertension, Marfan syndrome, aortitis) or from disease of the leaflets (bicuspid valve, endocarditis, rheumatic disease). It produces an early diastolic, decrescendo murmur at the left sternal edge, loudest with the patient sitting forward and holding their breath in expiration. The pulse is collapsing ("water-hammer") with a wide pulse pressure. There may also be a mid-diastolic murmur at the apex (Austin Flint murmur).

Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.