Aortic regurgitation - valve disease

Aortic regurgitation

Definition

Retrograde blood flow through the aortic valve from the aorta into the left ventricle during diastole.

Aetiology/pathophysiology

Aortic regurgitation is caused by incompetence of the valve in diastole, allowing blood to leak back into the left ventricle. This may result from:

·        Inability of the valve cusps to close properly due to thickening, shrinkage, perforation or a tear in the cusp. Causes include rheumatic heart disease (now rare in the United Kingdom), infective endocarditis occurring on a previously damaged or bicuspid aortic valve, and various arthritides such as Reiter’s syndrome, ankylosing spondylitis or rheumatoid arthritis.

·        Significant dilation of the aortic annulus such that the cusps are separated at the edges. Causes include severe hypertension, dissecting aneurysm and Marfan’s syndrome.

As a result of the volume overload, the left ventricle grad-ually enlarges and the ejection fraction is increased (Starling’s mechanism). It is only when volume overload is excessive and chronic that the left ventricle fails. The first sign of this decompensation is a reduction in the ejection fraction, leading to an increased end systolic volume. There is also reduced coronary artery perfusion with associated increased risk of myocardial ischaemia.

Clinical features

Aortic regurgitation is asymptomatic until left ventricular failure develops. Patients usually present with dyspnoea, a pounding heart beat and angina. On examination there is a large volume pulse, which is collapsing in character. The blood pressure has a wide pulse pressure (high systolic and low diastolic pressure). The apex is displaced laterally and downwards and is heaving in nature. Various signs of the high-velocity blood flow have been described but are rare.

On auscultation there is a high pitched early diastolic murmur running from the aortic component of the second heart sound. There may be an accompanying mid-systolic ejection murmur due to volume overload. An Austin Flint murmur may also be heard. This is a mid-diastolic rumbling murmur due to back flow of blood during diastole causing a partial closure of the mitral valve.

Investigations

Chest X-ray shows an enlarged left ventricle and possibly dilation of the ascending aorta.

ECG may show signs of progressive left ventricular hypertrophy.

Echocardiogram is diagnostic demonstrating abnormal valve movement. Doppler studies demonstrate and quantify the regurgitation. The best way to monitor the clinical effect of the valve lesion is to measure the left ventricular dimension. An end systolic dimension of over 5 cm indicates decompensation.

Management

Any underlying causes such as infective endocarditis should be treated. Antibiotic prophylaxis against infective endocarditis should be administered when appropriate.

Symptomatic relief can be given by treatment of any associated heart failure.

Refractory symptoms with evidence of increasing heart size or diminishing left ventricular function are indications for surgical intervention usually by valve replacement.

Prognosis

Mild or moderate aortic regurgitation has a relatively good prognosis and thus surgical intervention is not required. However, it is important to perform surgical correction before irreversible left ventricular failure develops.