Aortic stenosis: how to diagnose and manage

Aortic stenosis (AS) is one of the most common valvular abnormalities in the older patient. It is a pathological narrowing of the aortic valve which results in restriction of blood flow across the valve.

Aortic sclerosis is where there is calcification of the valve, but often this is not associated with significant limitation of blood flow. Numerous factors can contribute to sclerosis including smoking, hypertension, diabetes and hypercholesterolemia. Valvular degeneration in the elderly and congenital bicuspid valve in younger individuals are other significant causes of AS. Despite being a common cause for aortic stenosis in the past, rheumatic heart disease is very rare in industrialised countries and is more commonly seen in resource-limited tropical settings. Prompt treatment of rheumatic disease can prevent valvular complications.

A Norwegian study into the epidemiology of aortic stenosis put its prevalence at 3.9% in the 70-79 year cohort, compared to 0.2% in the 50-59 year cohort and 1.3% in 60-69 year cohort respectively. The figure dramatically reaches to nearly 10% of the population in people in their eighth decades. However, in patients with congenital bicuspid valves, the condition can manifest earlier than usual. It is therefore important that its diagnosis and management are well understood.

Diagnosis

Aortic stenosis can be classified according to the site of the lesion and this helps with future management plans.

Supra-valvular lesions

Supra-valvular lesions can occur with the genetic condition Williams’ syndrome, a developmental disorder. Signs and symptoms associated with Williams syndrome include, mild to moderate intellectual disability, elfin facies, supravalvular aortic stenosis and occasionally connective tissue abnormalities.

Valvular aortic stenosis

Valvular aortic stenosis this can occur with senile degeneration and often occurs in over 55-year-olds.

Subvalvular aortic stenosis

Subvalvular aortic stenosis is associated with a bicuspid aortic valve. This is where the aortic valve has two leaflets instead of three. This is a congenital abnormality and is occasionally associated with coarctation of the aorta or Turners syndrome.

Aortic stenosis is a common valvular pathology particularly amongst the elderly. Diagnosis consists of a thorough history and clinical examination, imaging is to confirm the diagnosis and degree of stenosis. Symptoms associated with AS may include chest pain, shortness of breath, syncope, palpitations, reduced exercise tolerance. A triad of; shortness of breath, chest pain and syncope may be apparent in severe aortic stenosis.

Anaemia may also be associated with AS. Specifically Heyde’s syndrome, which consists of a triad of AS, acquired coagulapathy and angiodysplasia in the GI tract. The stenosed valve and increased flow of blood through the stenosed valve can lead to shearing of Von Willebrand factor leading to bleeding. The resulting anaemia may worsen any concomitant heart failure. A gastroscopy/colonoscopy may be used to diagnose the angiodyplasia.

If patients present with any of the above symptoms a thorough cardiac exam should be undertaken. Aortic stenosis presents as an ejection systolic murmur heard loudest in the aortic area. Of particular note, the following may be present in severe aortic stenosis:

Ejection systolic murmur radiating to the carotid arteries.
Slow rising pulse.
Narrow pulse pressure.

The amplitude of the murmur does not correlate to the severity of stenosis. Rather, in severe stenosis, the murmur may become quieter. Ejection systolic murmurs without the above signs of severity may represent aortic sclerosis €“ mild calcification of the aortic valve. Regardless of this, in newly diagnosed murmurs, especially if there is a history of shortness of breath, chest pain or syncope an echocardiogram should be undertaken.

Aortic stenosis is categorised as mild, moderate or severe. The following echocardiogram findings categorise the degree of stenosis:

	Mild	Moderate	Severe
Peak Gradient	15-40 mmHg	40-70 mmHg	70-100 mmHg
Aortic valve area	>1.5 cm²	1.5 €“ 1 cm²	<1 cm²

Like any other cardiac abnormalities, an ECG can be done in AS which will not directly confirm AS but will show LVH resulting from pressure load secondary to AS. In some instances, AS can produce conduction abnormalities in ECG. Although echocardiogram is the preferred choice to diagnose AS, cardiac MRI can be used to visualise cardiac anatomy and function in cases where echocardiogram cannot produce conclusive findings. A cardiac workup that can be done in this instance is cardiac catheterisation.

Features of aortic stenosis

Symptoms	Signs
Shortness of breath	Ejection systolic murmur
Chest pain	Slow rising pulse
Syncope	Narrow pulse pressure

Management

The approach to treatment depends on the presence of symptoms, the severity of stenosis and eligibility for surgery. Although there is no direct evidence of medical therapy in AS, statins and angiotensin-converting-enzyme inhibitors are traditionally used to treat coexisting other cardiac comorbidities.

Individuals are often monitored for the severity of the stenosis with six monthly or annual echocardiograms. If however, the symptoms become severe or the echocardiogram reveals moderate to severe aortic stenosis, then valve replacement can be considered. Untreated patients can develop acute congestive heart failure and sudden cardiac death.

There are two options for replacing the valve, the first is surgical aortic valve replacement (SAVR). This involves open heart surgery, placing the patient on a cardiopulmonary bypass machine and replacing the native valve surgically with a mechanical or biological prosthesis.

Mechanical valves are indicated in those aged under 60 and biological valves in those aged over 60. The life of a biological valve is about 15 years and porcine or bovine valves are often used. Individuals with mechanical valves are required to be on Warfarin life long with an INR within the range of 2.5 – 3.5.

Individuals with severe symptomatic aortic stenosis who are not suitable for surgery can be considered for transcatheter aortic valve implantation (TAVI). This procedure involves patients being under general or local anaesthetic. A guidewire is then passed through the femoral or subclavian artery. The aortic valve ring may then be dilated using a balloon, subsequently, the prosthetic valve is placed inside the native aortic valve. Complications such as thrombosis, restenosis and infection of prosthetic valves can be seen in these patients post valve replacement.

Prognosis

Mild to moderate AS patients may experience a decrease in valve area of 0.1 cm2/year and an increase in the gradient of 7mmHg per year. There is a variable rate of progression between individuals and each individual will require personalised close follow up. Those who have AS may go on to develop heart failure, prompt recognition and appropriate monitoring of AS is therefore important.

Conclusion

Aortic stenosis is one of the most common valvular abnormalities. If left untreated individuals can go on to develop heart failure. Appropriate screening of patients, with a thorough cardiovascular exam, should take place with those individuals presenting with a history of shortness of breath, chest pain or syncope. If there is a suspicion of AS an ECG and echocardiogram should be requested and then a referral made to cardiology if the individual is symptomatic or has moderate to severe AS.

Dr Ghalib Kadir Choudhury Specialist Registrar, Geriatric medicine, Stroke medicine and General Internal Medicine, Luton and Dunstable University Hospital, NHS Foundation Trust

Dr Zaw Myo Aung Senior house officer, Stroke Medicine, Luton and Dunstable University Hospital, NHS Foundation Trust

[email protected]

Conflict of interest: none declared

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Zaw Myo Aung

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