Aortic valve disease

Cardiology Lectures Dr. Ahmed Moyed Hussein

Aortic Valve Disease
Aortic Stenosis (AS)

Aetiology and pathophysiology:

The likely aetiology depends on the age of the patient

Cardiac output is initially maintained at the cost of a steadily increasing pressure gradient across the aortic valve. The LV becomes increasingly hypertrophied and coronary blood flow may then be inadequate; patients may therefore develop angina, even in the absence of
concomitant coronary disease. The fixed outflow obstruction limits the increase in cardiac output required on exercise. Eventually, the LV can no longer overcome the outflow tract obstruction and pulmonary oedema
supervenes.

Clinical features:

Aortic stenosis is commonly picked up in asymptomatic patients at routine clinical examination but the three cardinal symptoms are angina, breathlessness and syncope. The characteristic clinical signs of severe aortic stenosis are A harsh ejection systolic murmur radiates to the neck, with a soft second heart sound, particularly in those with calcific valves. The murmur is often likened to a saw cutting wood and may (especially in older patients) have a musical quality like the ‘mew’ of a seagull.

Investigations:

In advanced cases, ECG features of LV hypertrophy are often gross , and down-sloping ST segments and T inversion (‘strain pattern’) are seen. Echocardiography demonstrates restricted valve opening and Doppler assessment permits calculation of the systolic gradient across the aortic valve, from which the severity of stenosis can be assessed.
CT and MRI are useful in assessing the degree of valve calcification and
stenosis, respectively, but are rarely necessary.


Management:
Irrespective of the severity of valve stenosis, patients with asymptomatic aortic stenosis have a good immediate prognosis and conservative management is appropriate. Such patients should be kept under review, as the development of angina, syncope, symptoms of low
cardiac output or heart failure has a poor prognosis and is an indication for prompt surgery. In practice, patients with moderate or severe stenosis are evaluated every 1–2 years with Doppler echocardiography to detect progression in severity; this is more rapid in older patients with heavily calcified valves.
Patients with symptomatic severe aortic stenosis should have prompt aortic valve replacement. Aortic balloon valvuloplasty is useful in congenital aortic stenosis but is of no value in older patients with calcific aortic stenosis.

Aortic Regurgitation(AR)

Aetiology and pathophysiology:
This condition is due to disease of the aortic valve cusps or dilatation of the aortic root.

The LV dilates and hypertrophies to compensate for the regurgitation. The stroke volume of the LV may eventually be doubled or trebled, and the major arteries are then conspicuously pulsatile. As the disease progresses, left ventricular diastolic pressure rises and breathlessness develops.

Clinical features:

Until the onset of breathlessness, the only symptom may be an awareness of the heart beat, particularly when lying on the left side, which results from the increased stroke volume. Paroxysmal nocturnal dyspnea is sometimes the first symptom, and peripheral oedema or angina may occur. The characteristic murmur is early diastolic murmur best heard to the left of the sternum during held expiration; a thrill is rare. The regurgitant jet cause fluttering of the mitral valve and, if severe, causes partial closure of the anterior mitral leaflet, leading to functional mitral stenosis and a soft mid-diastolic (Austin Flint) murmur.

Investigations:

Regurgitation is detected by Doppler echocardiography. In severe acute aortic regurgitation, the rapid rise in left ventricular diastolic pressure may cause premature mitral valve closure. Cardiac catheterization and aortography can help in assessing the severity of regurgitation, and dilatation of the aorta and the presence of coexisting coronary artery disease. MRI is useful in assessing the degree and extent of aortic dilatation.
Management:
Aortic valve replacement is indicated if aortic regurgitation causes symptoms, Asymptomatic patients should be followed up annually with echocardiography for evidence of increasing ventricular size, then aortic valve replacement should be undertaken.
Systolic BP should be controlled with vasodilating drugs, such as nifedipine or ACE inhibitors. When aortic root dilatation is the cause of aortic regurgitation (e.g. Marfan’s syndrome), aortic root replacement is usually necessary.

Tricuspid valve disease

Tricuspid stenosis
Aetiology:
Tricuspid stenosis is usually rheumatic in origin and is rare in developed countries. Tricuspid disease occurs in fewer than 5% of patients with rheumatic heart disease and then nearly always in association with mitral and aortic valve disease. Tricuspid stenosis and regurgitation are features of the carcinoid syndrome.
Clinical features and investigations:
Tricuspid stenosis may cause symptoms of right heart failure, including hepatic discomfort and peripheral oedema.
The main clinical feature is a raised JVP with a prominent a wave, and a slow y descent due to the loss of normal rapid right ventricular filling. There is also a mid-diastolic murmur, best heard at the lower left or right sternal edge. This is generally higher-pitched than the murmur of mitral stenosis and is increased by inspiration. Right heart failure causes hepatomegaly with pre-systolic pulsation (large a wave), ascites and peripheral oedema. On Doppler echocardiography, the valve has similar appearances to those of rheumatic mitral stenosis.
Management:
In patients who require surgery to other valves, either the tricuspid valve is replaced or valvotomy is performed at surgery.


Tricuspid regurgitation
Aetiology, clinical features and investigations:
Tricuspid regurgitation is common, and is most frequently ‘functional’ as a result of right ventricular dilatation.
Symptoms are usually non-specific, with tiredness related to reduced forward flow, and oedema and hepatic enlargement due to venous congestion. The most prominent sign is a ‘giant’ v wave in the jugular
venous pulse (a cv wave replaces the normal x descent).
Other features include a pansystolic murmur at the left sternal edge and a pulsatile liver. Echocardiography may reveal dilatation of the RV. If the valve has been affected by rheumatic disease, the leaflets will appear
thickened and, in endocarditis, vegetations may be seen.
Management:
Tricuspid regurgitation due to right ventricular dilatation often improves when the cause of right ventricular overload is corrected, with diuretic and vasodilator treatment of congestive cardiac failure. Patients undergoing mitral valve replacement, who have tricuspid regurgitation
due to marked dilatation of the tricuspid annulus, benefit from valve repair with an annuloplasty ring to bring the leaflets closer together. Those with rheumatic damage may require tricuspid valve replacement.

Pulmonary valve disease

Pulmonary stenosis
This can occur in the carcinoid syndrome but is usually congenital, in which case it may be isolated or associated with other abnormalities, such as Fallot’s tetralogy.
The principal finding on examination is an ejection systolic murmur, loudest at the left upper sternum and radiating towards the left shoulder. There may be a thrill, best felt when the patient leans forward and breathes out. The murmur is often preceded by an ejection sound (click). Delay in right ventricular ejection may cause wide splitting of the second heart sound.
ECG evidence of right ventricular hypertrophy, and post-stenotic dilatation in the pulmonary artery on the chest X-ray. Doppler echocardiography is the definitive investigation.
Mild to moderate isolated pulmonary stenosis is relatively common and does not usually progress or require treatment. Severe pulmonary stenosis (resting gradient > 50 mmHg with a normal cardiac output) is treated by
percutaneous pulmonary balloon valvuloplasty or, if this is not available, by surgical valvotomy.

Pulmonary regurgitation

This is rare in isolation and is usually associated with pulmonary artery dilatation due to pulmonary hypertension.
It may complicate mitral stenosis, producing an early diastolic decrescendo murmur at the left sternal edge that is difficult to distinguish from aortic regurgitation (Graham Steell murmur). The pulmonary hypertension may be secondary to other disease of the left side of the heart, primary pulmonary vascular disease or Eisenmenger’s syndrome. Trivial pulmonary regurgitation is a frequent finding in normal individuals and has no clinical significance.


Valve replacement surgery:
Diseased heart valves can be replaced with mechanical or biological prostheses. Prosthetic valve generate prosthetic sounds or clicks on auscultation, while biological valve generate normal heart sounds.
All mechanical valves require long-term anticoagulation with warfarin because they can cause systemic thromboembolism or may develop valve thrombosis or obstruction.