AORTIC STENOSIS

SALIENT FEATURES

History

· Asymptomatic (many patients do not have symptoms).

· Fatigue.

· Angina (in -70% of adults average survival after onset of angina is 5 years).

· Syncope (in 25% of patients, during or immediately after exercise; average survival after onset of

syncope ix 3 years).

· Dyspnoea is a common presenting symptom (suggests left ventricular dys-function; heart failure reduces

life expectancy to less than 2 years).

Examination

Pulse

· Low volume pulse. It is reduced in volume with a delayed upstroke (pulsus parvus et tardus). This is due

to a reduction in systolic pressure and a gradual decline in diastolic pressure.

· Normal pulse in mild aortic stenosis when the gradient is <50 mmHg.

· Slow rise with diminished volume, sometimes with a notch on the upstroke, is an 'anacrotic pulse',

suggesting severe aortic stenosis. When aortic stenosis is associated with aortic regurgitation, a double

or 'bisferious' pulse may be felt.

Heart

· Apex beat is heaving in nature but ix not displaced. (A displaced apex beat indicates left ventricular

dilatation and severe disease.)

· Palpable systolic vibrations over the primary aortic area, with the patient in the sitting position during full

expiration (often correlates with a gradient of more than 40 mmHg).

· Systolic thrill over the aortic area and the carotids.

· Soft second heart sound.

· EJection click heard 0.1 s after first heart sound, along the left sternal border (indicates valvular

stenosis). An ejection sound that moves with respiration is not aortic in origin.

· An atrial (S4) sound may be heard.

· Ejection systolic murmur at the base of the heart conducted to the carotids and the right clavicle.

(Listen carefully for an early diastolic murmur as mild aortic regurgitation often accompanies aortic

stenosis.)

· Third heart sound: in patients with aortic stenosis, third heart sounds are uncommon but usually

indicate the presence of systolic dysfunction and raised filling pressures.

General examination

· Check the blood pressure, keeping in mind that the pulse pressure is low in moderate to severe

stenosis.

DIAGNOSIS

This patient has pure aortic stenosis (lesion) which may be due to rheumatic' aetiology or a bicuspid

aortic valve (aetiology); he has severe aortic stenosis as he gives a history of recurrent syncope

(functional status).

QUESTIONS

How would you differentiate aortic stenosis from aortic sclerosis?

Aortic sclerosis is seen in the elderly; the pulse is normal volume, the apex beat is not shifted and the

murmur is localized.

Mention some causes of aortic stenosis.

· Under the age of 60 years: rheumatic, congenital.

· Between 60 and 75 years: calcified bicuspid aortic valve, especially in men.

· Over the age of 75 years: degenerative calcification.

What does the second heart sound tell us in this condition?

· A soft second heart sound indicates valvular stenosis (except in calcific stenosis of the elderly, where

the margins of the leaflets usually maintain their mobility).

· A single second heart sound may be heard when there is fibrosis and fusion of the valve leaflets.

· Reversed splitting of the second sound indicates mechanical or electrical pro-longation of ventricular

systole.

· A perfectly normal second heart sound (i.e. normal splitting with A2 of normal intensity) is strong

evidence against the presence of critical aortic stenosis.

What do you understand by the term ejection systolic murmur?

It is a crescendo-decrescendo murmur which begins after the first heart sound (or after the ejection click

when present), peaks in mid or late systole and ends before the second heart sound. This peak is

delayed with increasing severity of aortic stenosis.

ADVANCED-LEVEL QUESTIONS

Does the loudness of the murmur reflect the severity of the aortic stenosis ?

No, the loudness of the murmur is related more to the cardiac output and the systolic turbulence

surrounding the valve than to the severity of the stenosis. Thus, a loud murmur may be associated with

trivial stenosis and, in severe heart failure, the mur-mur may be soft because of decreased flow across

the valve from the diminished cardiac output.

Mention other causes of ejection systolic murmur at the base of the heart.

· Pulmonary stenosis.

· Hypertrophic obstructive cardiomyopathy.

· Supravalvular aortic stenosis.

What is the prevalence of aortic stenosis in the elderly?

According to the Helsinki Ageing Study, almost 3%, of individuals aged between 75 and 86 years have

critical aortic stenosis (J Am Coil Cardiol 1993; 21: 1220-5).

What is the mechanism of syncope in aortic stenosis?

· The left ventricle is suddenly unable to contract (transient electro-mechanical dissociation) against

the stenosed valve.

· Cardiac arrhythmias (bradycardia, ventricular tachycardia or fibrillation).

· Marked peripheral vasodilatation without a concomitant increase in cardiac out-put. particularly after

exercise.

What investigations would you perform?

ECG

ECG usually shows left ventricular hypertrophy, ST-T changes, possibly left axis deviation, later left atrial

hypertrophy (negative P waves in V1), conduction abnormalities due to calcification of conducting tissues

(first-degree heart block, left bundle branch block).

Chest radiograph

May show cardiac enlargement, post-stenotic dilatation of aorta (a bicuspid valve should be suspected if

the proximal aorta is greatly enlarged), calcification of aortic valve (particularly in older patients).

Echoeardiography is' useful in:

· The diagnosis and assessment of severity of aortic stenosis: estimates valve gradient, normal valve

appearance excludes significant aortic stenosis in adults; also helps to define the level of obstruction

(i.e. valvar, supravalvar, subvalvar); calcified valves can be identified.

· The assessment of left ventricular size, function and/or haemodynamics.

· The re-evaluation of patients with known AS with changing symptoms and signs.

· The re-evaluation of asymptomatic patients with severe AS and the assessment of patients with

known AS during pregnancy.

Note. The degree of aortic stenosis is graded as: mild (valve area >1.5 cm2), moderate (area >1.0 to 1.5

cm2) or severe (area <? 1.0 em2).

Exercise testing

Exercise testmg tn adults with AS has been discouraged largely because of safety: it should not be

performed in symptomatic patients as it may be fatal: in asymptomatic patients an abnormal

haemodynamic response (e.g. hypotension) is sufficient to consider AVR. In selected patients it may be

useful to provide a basis for advice about physical activity.

Cardiac catheterization

This is done to assess the coronary circulation and to confirm or clarify the diagnosis. When the

echocardiogram is inadequate, cardiac haemodynamics using both left and right heart catheterization is

indicated and requires: ( 1 ) measurement of transvalvular flow, (2) determination of transvalvular

pressure gradient and (3) calculation of the effective valve area.

What are the complications of aortic stenosis?

· Left ventricular failure indicates poor prognosis unless the valve is replaced.

· Sudden death occurs in 10-20% of adults and I% of children. It has been rarely documented to occur

without prior symptoms. It is an uncommon event -probably <1% per year.

· Arrhythmias and conduction abnormalities include ventricular arrhythmias (more common than

supraventricular arrhythmias) and heart block (may occur because of calcification of conducting tissues).

· Systemic embolization is caused by disintegration of the aortic valve apparatus or by concomitant aortic

atheroma.

· Infective endocarditis (in 10% of cases) should be considered when these patients present with

unexplained illness.

· Haemolytic anaemia.

What are the clinical signs of severity of aortic stenosis?

· Narrow pulse pressure.

· Soft second sound.

· Narrow or reverse split second sound.

· Systolic thrill and heaving apex beat.

· Fourth heart sound.

· Cardiac failure.

How would you manage this patient?

If the patient is asymptomatic and the valvular gradient is less than 50 mmHg, then observe the patient.

Surgery is not recommended in asymptomatic patients.

Valve replacement in the following circumstances:

· The patient is symptomaticor the valvular gradient is more than 50 mmHg. Surgery is mandatory in

symptomatic patients.

· Valve replacement should be considered in asymptomatic patients with severe aortic stenosis

(peak-to-peak gradient >50 mmHg) particularly when any one or more of the following features is present:

left ventricular systolic dysfunction: abnormal response to exercise (e.g. hypotension), ventricular

tachycardia; marked excessive left ventricular hypertrophy (> 15 mm); valve area <0.6 cra:.

· In asymptomatic patients with moderate AS it is generally acceptable to perform aortic valve

replacement in those who are undergoing mitral valve or aortic root surgery or coronary artery bypass

surgery.

· Severe aortic stenosis with low mean systolic aortic valve gradient (< 30 mmHg) and severe LV

dysfunction (Circulation 2000; 101: 1940-6).

· Valve area less than 0.8 cm2 (normal area 2.5-3.0 cra2). Patients with severe aortic stenosis should

have valve replacement early to avoid deterioration.

· Patients with severe AS, with or without symptoms, who are undergoing coronary artery bypass

surgery, surgery on the aorta or other heart valves should undergo AVR at the time of their surgery.

· Patients often require coronary artery bypass grafts during aortic valve replacement.

Balloon valvuloplasty should be limited to moribund patients requiring emergency intervention or

those with a very poor life expectancy due to other pathology. In one study, although in-hospital mortality

rates were similar to those following conventional surgical replacement, there were more deaths in the

valvuloplasty group in the subsequent follow-up period (d Am Coil Cardiol 1992; 20:796-801 ).

If a young person presents with signs and symptoms of aortic stenosis but the aortic valve is

normal on echocardiography which condition would you suspect?

Supravalvular or subvalvular aortic stenosis.

What are the genetics of supravalvular stenosis?

Studies suggest that mutation in the elastin gene causes supravalvular stenosis (Cell 1993; 73: 159).

If this patient had bleeding per rectum what unusual cause would come to mind?

Angiodysplasia of the colon (Radiology 1974: 113:11).

If the patient was icteric and had haemolytic anaemia, what would the mechanism be?

Microangiopathic haemolysis has been described in severe calcified aortic stenosis manifesting with

anaemia and icterus (Semin Hemato/ 1969; 6: 133).

What do you understand by the term 'Gallavardin phenomenon'?

The high-frequency components of the ejection systolic murmur may radiate to the apex, falsely

suggesting mitral regurgitation. This is known as the Gallavardin phenomenon (Lyons Med 1925; 135:

523).

Williams' syndrome is characterized by elfin facies, supravalvular aortic stenosis and hypercalcaemia

(J.C.R Williams, New Zealand physician).