AORTIC STENOSIS

AORTIC STENOSIS..Aortic stenosis is very often due to disease of the aortic valve cusps but sometimes other causes may obstruct the left ventricular outflow tract, e.g.

1. Idiopathic hypertrophic subaortic stenosis due hypertrophy of the left ventricular outflow tract involving the interventricular septum.
2. Congenital subvalvar aortic stenosis due to formation of a membranous diaphragm or a fibrous ridge below the aortic valve.
3. Supravalvar aortic stenosis due to constriction of ascending aorta or formation of fibrous diaphragm above the aortic valves. This is associated with hypercalcaemia and mental retardation called William’s syndrome.

AETIOLOGY:

1. Congenital.
2. Rheumatic.
3. Calcific bicuspid valve.
4. Senile degeneration.
5. Bacterial endocarditis.
6. Bicuspid aortic valves c fibrosis.

All these causes lead to valvar aortic stenosis.

AORTIC STENOSIS

HAEMODYNAMICS:

Normal aortic area is 3-4 cm2. Symptoms usually develop when the cross section of the aortic orifice is reduced by 75%, i.e., it becomes 0.8 to 1 cm2. Since flow varies more with the opening than pressure, a large pressure gradient exists across the aortic valve (>50-70 mm of Hg at rest). The resistance is a fixed one. This leads to increased end diastolic pressure,concentric left ventricular hypertrophy, decreased left ventricular compliance and a fixed cardiac output. Left ventricular ischaemia develops and ultimately failure ensues. Left ventricular systolic function is however preserved.

AORTIC STENOSIS

CLINICAL FEATURES:

More than 80% cases are males.

SYMPTOMS:

The triad of symptoms are:

(a) Syncope

This may be due to following reasons:

1. Low cardiac output.
2. Hypotension.
3. Left ventricular failure.
4. Ventricular standstill and heart block.
5. Ventricular tachyarrhythmia.
6. Sinus bradycardia.
7. Decreased cerebral perfusion due to increased blood flow to the exercising muscles.

(b) Anginal pain

This is due to low mean aortic blood pressure and low fixed output so that coronary flow cannot be maintained at a level desired by the overworking left ventricle. Sometimes the cause is undermined. Atypical angina may also be seen.

AORTIC STENOSIS

(c) Breathlessness

This is due to pulmonary oedema from left ventricular failure due to elevated left ventricular end diastolic pressure. It occurs first on effort, afterwards there is paroxysmal nocturnal dyspnoea leading to orthopnoea.

When this triad of symptoms coexist together the aortic valve area is usually reduced to 0.6 to 0.7 cm2.

SINGS:

1. Pulse is low in volume, slow in rise and well sustained. This is called Anadicrotic pulse or Pulsus pervus et tardus or simply Anacrotic Pulse.
2. BP is low, due to low fixed cardiac output.
3. Jugular venous pulse may sometimes show a small ‘a’ wave (Bernheim’s ‘a’ wave due to left ventricular hypertrophy).

EXAMINATION OF THE HEART:

Inspection

Precordial bulging may sometimes be present.

Palpation

Apical impulse is more down than out, forceful and well sustained (heaving in type). Sometimes apex beat is doubled (double kick) due to hypertrophied left atrial impulse. A basal systolic thrill is felt more over the aortic area and also over the carotids and subclavians. It is best felt in full expiration with the patient leaning forwards. This is present only in severe cases.

AORTIC STENOSIS

Auscultation

Over the aortic area second heart sound (A,) is absent or feeble (depending on the degree of stenosis) and sometimes it may be delayed giving rise to reversed splitting of second sound. A harsh mid-systolic ejection murmur (Grade 3-6) is heard which is well conducted upwards along the carotids and subclavians. Sometimes the murmur may be intensified both at Aortic and mitral area and is less intense in between which is called hour glass conduction. Sometimes the murmur may have a musical character. Sometimes the murmur may be preceded by an ejection click (so long the mobility of the valve is preserved). The first sound over the mitral area may be normal or accentuated and may be preceded by SA. Prominent S4 under 40 years is indicative of severe stenosis. A very soft early diastolic murmur may accompany the systolic murmur which is not due to organic aortic regurgitation. Occasionally the murmur of aortic stenosis may be transmitted to the mitral area particularly the high frequency components specially in association with calcific aortic valve (Gallavardin’s phenomenon).

FEATURES OF SUPRAVALAR STENOSIS:

1. Characteristic Elfin facies with both physical and mental retardation.
2. Pulse volume and BP may be high on the right side.
3. Absence of Aortic ejection click.
4. No AR murmur.
5. No post-stenotic dilatation of Aorta in X-ray.

FEATURES OF SUBVALAR STENOSIS:

1. Pulse volume and BP equal on both sides.
2. No ejection click.
3. AR murmur common.

4 X-ray shows no post-stenotic dilatation, ascending aorta not dilated, cardiac size is enlarged.

SPECIAL INVESTIGATIONS:

1. Radiologically chest X-ray shows normal cardiac size in uncomplicated cases with post-stenotic dilatation of the aorta. Sometimes aortic valve calcification may be seen in LAO position. LV enlargement also develops in course of time. Absence of calcification in adults rules out the possibility of severe aortic stenosis. MRI is also helpful.
2. ECG shows left ventricular hypertrophy (Overload syndrome) With conduction disturbances such as first degree A-V block LBBB or left anterior fascicular block. ECG may be normal in 10% cases.
3. Cardiac catheterization shows a pressure gradient of more than 60 mm of Hg across the aortic valve. Left ventricular end diastolic pressure and left atrial pressure are also elevated. Coronary angiography may be required before surgery. Catheter study is required when Echo IS unsatisfactory.
4. Echocardiogram may be helpful for assessing left ventricular function with thickness or calcification of aortic valves and its orifice. Doppler study is helpful for estimating the pressure gradient and detection of other valve defects.

COMPLICATIONS:

1. Angina pectoris.
2. Tachy and bradyarrhythmias, conduction defect.
3. Left ventricular failure.

4. Right sided heart failure.
5. Infective endocarditis.
6. Cerebral insufficiency.
7. Embolisation of small calcific flakes.
8. Sudden death.

DIFFERNTIAL DIAGNOSIS:

Subaortic stenosis

Common in children, ejection click absent, aortic early diastolic murmur is usually common. Angiography reveals a small chamber just under the aortic valve, echocardiogram characteristically shows a mid-systolic closure of aortic valves.

Hypertrophic cardiomyopathy

The carotid pulse is normal or jerky, the systolic murmur is better heard at the apex and left border of the heart rather than at the base or over the carotid. Angiography reveals obliteration of left ventricular cavity in its apical part at end systole and echocardiography shows characteristically the same finding as in subaortic stenosis.

TREATMENT

Medical management has practically prophylactic penicillin, diuretics, salt-poor diet are all very helpful before surgery and when medical complications arise. Operation is indicated in presence of attacks of syncope, progressive left ventricular failure, recurrent anginal pain not due to coronary disease or where the aortic valve area is less than 1 cm2. In presence of both mitral and aortic stenosis, simultaneous correction should be done. Prosthetic or homograft valve is now usually choiced. The mortality for valve replacement is 2%-5% and it increases with age.

Anticoagulation is required for mechanical prostheses but not for bioprostheses. In patients passed 50 years coronay angiography should be done before surgery and if necessy bypass surgery can also be done simultaneously. Recently Balloon valvuloplasty has been started in many centres. However, the mortality is similar tosurgery and restenosis is often seen within I year. So this procedure is mainly done in very poor-risk surgical candidates.

AORTIC STENOSIS