Aortic stenosis - valve disease

Aortic stenosis

Definition

Aortic stenosis is a pathological narrowing of the aortic valve.

Aetiology

Congenital bicuspid aortic valves can initially open with little obstruction. There is however turbulent flow across these valves, which become thickened and calcified. Severe stenosis may develop over a period of 20–30 years.

Congenital aortic valve narrowing leads to presentation in infancy or childhood.

Rheumatic fever results in progressive cusp adherence, thickening and calcification. It is often associated with aortic incompetence and mitral valve disease.

Sclerotic aortic stenosis is due to degenerative changes in the cusps seen in the elderly. It may lead to thickening and calcification of the aortic valve, which is often mild and asymptomatic.

Pathophysiology

The outflow of the left ventricle is obstructed causing the pressure within the left ventricle to rise. This pressure overload results in left ventricular hypertrophy and a relative ischaemia of the myocardium with associated angina. As the stenosis becomes more severe, reduced coronary artery perfusion exacerbates myocardial ischaemia even if the coronary arteries are normal. Impaired left ventricular emptying is most apparent during times of increased cardiac demand such as exercise. Ischaemia and hypertrophy of the left ventricle may lead to arrhythmias and left ventricular failure.

Clinical features

Patients are asymptomatic until there is severe stenosis when they present with exercise-induced syncope, angina or dyspnoea. Sudden cardiac death may also occur. Late symptoms include orthopnoea and paroxysmal nocturnal dyspnoea.

On examination the pulse is low volume and slow rising. On palpation there may be an aortic systolic thrill felt in the right second intercostal space. The apex is slow and thrusting in nature but not displaced. On auscultation there may be a systolic ejection click, followed by a midsystolic ejection murmur heard best in the right second intercostal space and radiating to carotids. The murmur is best heard with the patient leaning forward with breath held in expiration.

Investigations

Chest X-ray may show a post-stenotic dilation of the ascending aorta and left ventricular hypertrophy.

ECG shows left ventricular strain or hypertrophy related to the degree of stenosis.

Echocardiography is diagnostic, often showing cusp thickening and calcification. Doppler studies quantify the degree of stenosis and can measure left ventricular function.

Cardiac catheterisation can demonstrate the pressure difference between the left ventricle and aorta, and is required to examine the coronary arteries prior to surgery.

Management

Treatment includes management of angina and cardiac failure. Vasodilators such as nitrates must be avoided in severe aortic stenosis as they can cause syncope due to a fall in systolic blood pressure. ACE inhibitors are also relatively contraindicated. Î²-blockers are often the drug of choice.

Severe stenosis (pressure gradient over 60 mmHg) or symptomatic stenosis are indications for surgery. Operative mortality is approximately 2%, but this is increased if coronary artery bypass is also required. Balloon valvuloplasty may be used in patients unfit for surgery or to improve cardiac function prior to surgery.

Prognosis

When symptomatic, death occurs within a few years without surgical intervention.