The aortic valve links the left ventricle (LV) and the aorta. It is normally tricuspid. Impaired aortic valve opening, due to its narrowing, is known as aortic stenosis (AS). It impedes outflow of blood from the LV into the aorta and imposes a pressure load on the LV. Deficient valve closure (aortic regurgitation, AR, incompetence) allows blood to flow back into the LV and thus imposes a volume load on the LV.

Aortic Stenosis

Causes

Senile Calcification 

This is the most common cause. Calcium deposits occur at the base of the cusp, without involvement of the commissures. This is most likely related to prolonged mechanical stress, and is more common in people with congenital bicuspid valves. About 50% of patients aged under 70 with significant AS have bicuspid valves, whereas most older patients with AS have tricuspid valves.

Rheumatic 

AS as a result of rheumatic heart disease is unusual without coexisting mitral valve disease. Male sex, diabetes and hypercholesterolaemia are also risk factors for AS.

Congenital 

A unicuspid aortic valve is usually fatal within 1 year of birth. Bicuspid aortic valves develop progressive fusion of the commissures, and symptoms usually present after 40 years. Infants with atherosclerosis due to lipid disorders may develop AS in conjunction with coronary artery disease (CAD).

Pathophysiology

A slow reduction in aortic valve area requires the LV to pump harder to expel blood into the aorta, which causes left ventricular hypertrophy and eventual myocardial dysfunction, arrhythmias and heart failure (see Chapter 46). ‘Critical’ AS occurs when there is greater than a 75% reduction of valve area, to <0.5 cm²/m² body surface area, and a >50 mmHg gradient between peak systolic LV and aortic pressure at a normal cardiac output. With worsening AS, cardiac output cannot increase adequately during exercise and eventually becomes insufficient at rest. As AS progresses the left ventricle dilates, and LV end-diastolic pressure (EDP) increases to the point where overt LV failure ensues.

Clinical Features

AS is typically associated with a triad of symptoms: angina, syncope and breathlessness. Patients present usually between the ages of 50 and 70 years, most commonly with angina

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