Aortic stenosis

What is aortic stenosis?

Aortic stenosis is a common valvular disorder causing left ventricular outflow obstruction. The normal aortic valve is composed of three thin cusps that project from the wall at the origin of the aorta.

Aortic sclerosis is thickening and calcification of the valve without impacting on blood flow.

Who gets aortic stenosis? (Epidemiology)¹²

• Aortic stenosis has become the most frequent type of valvular heart disease in Europe and North America.

• The prevalence of aortic sclerosis is 1-2% in adults under the age of 65 and 29% of people over 65, whereas the prevalence of aortic stenosis is between 2 and 9% in adults over the age of 75.

• Aortic stenosis occurs in almost 10% of adults over the age of 80 years, with a mortality rate of about 50% at two years unless outflow obstruction is relieved.

• Age related calcific aortic stenosis is the most common cause in the Western world whilst rheumatic heart disease remains the most common cause in LEDCs.

• It is expected that the prevalence of aortic stenosis will double over the next decades due to the increase in age of the population.

Aortic stenosis risk factors

A congenital bicuspid valve predisposes to aortic stenosis and is the commonest cause in people under 70 in the MEDCs.³

Presentation of aortic stenosis (symptoms)¹

See also the separate Heart auscultation and Heart murmurs in children articles.

• Symptoms typically begin between the ages of 50 and 70 in adults with a bicuspid aortic valve and over the age of 70 in those with a calcified tricuspid aortic valve.

• Aortic stenosis symptoms include a gradual development of shortness of breath on exertion, fatigue, and dizziness.

• Severe exertional dyspnoea, paroxysmal nocturnal dyspnoea, orthopnoea, and pulmonary oedema can result from progressive pulmonary venous hypertension.

• Angina occurs due to a combination of an increased oxygen requirement in hypertrophied myocardium and reduction of oxygen delivery because of the excessive compression of coronary vessels.

• Syncope during exertion is caused by the decrease in cerebral perfusion occurring. The baroreceptor mechanism can also malfunction.

• Gastrointestinal (GI) bleeding can occur due to angiodysplasia or other vascular malformations, along with platelet aggregation due to stress.

• Cerebral emboli can occur due to microthrombi formation on thickened bicuspid valves.

• The risk of infective endocarditis increases in patients with aortic valve disease, especially those with a bicuspid valve.

• The characteristic murmur may occasionally be faint and so the patient may present as having heart failure of unknown cause.

• The disappearance of the second aortic sound is specific to severe AS, although not a sensitive sign.

Signs of aortic stenosis

• Examination of the pulse in significant AS reveals a slow-rising, flat character called pulsus parvus et tardus.

• Blood pressure shows a narrow pulse pressure. In the elderly, a rigid aorta may make this sign less obvious.

• The second heart sound may lack a split and can be heard as a single sound during inspiration.

• Aortic stenosis murmur:

  • A2 is soft in AS. In aortic sclerosis, A2 is normal or loud.

  • Both conditions are associated with an harsh ejection systolic murmur that is transmitted to the carotids. A similar murmur may occur without stenosis if turbulence is due to aortic aneurysm causing dilation of the proximal aorta. Such pathology may cause leakage from the valve too and with it an early diastolic murmur.

  • The typical murmur of AS is a crescendo-decrescendo systolic ejection murmur shortly after the first heart sound that ends just before the second heart sound. It is a rough, low-pitched sound that is loudest at the base of the heart and most commonly heard in the second right intercostal space.

  • In congestive heart failure leading to a fall in cardiac output, the murmur will be quieter.

  • An ejection click may be present, especially with bicuspid valves. Ejection sounds are more obvious in children in whom the valves are more mobile than in older people.

  • A fourth heart sound indicates left ventricular hypertrophy (LVH) in severe AS. If the left ventricle dilates and fails, a third heart sound may be heard.

Differential diagnosis of aortic stenosis

Other causes of murmurs that are, or appear to be, from the aortic valve include:

• Aortic sclerosis.

• Aortic regurgitation.

• Subacute bacterial endocarditis.

• Dilatation of the root of the aorta (may also lead to a leaking valve).

• Flow murmurs (turbulence from high cardiac output in anaemia, thyrotoxicosis, and marked aortic regurgitation).

• Murmurs originating from the pulmonary valve with disease of that valve or atrial septal defect (the pulmonary and aortic areas are very close).

NB: flow murmurs can be normal in children and in neonates. Interpretation of cardiac sounds in children can be very difficult. Aortic valve disease is often not detected until the child is about 2 years old.

Referral for adults with aortic stenosis⁴

Refer to cardiologists should be offered to:

• Adults with moderate or severe valve disease of any type.

• Adults with bicuspid aortic valve disease of any severity (including mild valve disease).

Pregnant women and women considering pregnancy

Women with valve disease can have a pregnancy without complications.

Refer pregnant women or women who are considering a pregnancy to a cardiologist with expertise in the care of pregnant women, if they have any of the following:

• Moderate or severe valve disease.

• Bicuspid aortic valve disease of any severity (including mild disease) and associated aortopathy.

• A prosthetic valve. Refer whether they have symptoms or not.

Investigating aortic stenosis¹

• Echocardiography:

  • Is the key diagnostic tool. It confirms the presence of AS, assesses the degree of valve calcification, left ventricular function and wall thickness, detects the presence of other associated valve disease or aortic pathology and provides prognostic information.

  • Trans-oesophageal echocardiography should be considered when transthoracic echocardiography is of insufficient quality.

  • Doppler echocardiography is the preferred technique for assessing AS severity.

• Exercise testing:

  • Is contra-indicated in symptomatic patients with AS but it is recommended in physically active patients for unmasking symptoms and in the risk stratification of asymptomatic patients with severe AS.

  • Exercise testing is safe in asymptomatic patients, provided it is performed under the supervision of an experienced physician while monitoring for the presence of symptoms, changes in blood pressure, and/or ECG changes.

• Cardiac computed tomography (CT) use is expanding in patients with calcific aortic valve disease.

  • It is only needed when other tests are inconclusive.

• Cardiac magnetic resonance imaging (MRI) can assess LV mass, function, and volume when echocardiography is no available.

Aortic stenosis treatment and management^{56 78}

See also the separate Prevention of infective endocarditis article.

Medical therapy¹

• Surgical management is superior to medical management of aortic stenosis itself; however, medical management of some of the conditions associated with aortic stenosis is recommended

• Modification of atherosclerotic risk factors is strongly recommended. Aortic sclerosis and stenosis in the older age group, should be seen as a strong risk for coronary heart disease and appropriate steps should be taken.

• Co-existing hypertension should be treated. However, treatment should be carefully titrated to avoid hypotension and patients should be re-evaluated frequently. ACE inhibitors and ARBs are the first-line anti-hypertensives of choice.

• Maintenance of sinus rhythm is important, using anti-arrhythmic drugs as indicated.

• Patients who are unsuitable candidates for surgery or TAVI, or who are currently awaiting a surgical or TAVI procedure, may be treated with the appropriate medication for their symptoms (eg, heart failure medication).

Symptomatic aortic stenosis

• Symptomatic severe aortic stenosis has a poor prognosis and early surgical intervention (aortic valve replacement) is strongly recommended in all patients.

• The only exceptions are for those in whom intervention is unlikely to improve quality of life or survival due to severe comorbidities, or for those with concomitant conditions associated with survival less than 1 year.

• Surgery is recommended in all symptomatic patients, even where their symptoms are mild.

Asymptomatic aortic stenosis

• Intervention is recommended in asymptomatic patients with severe aortic stenosis and:

  • Impaired LV function (LV ejection fraction < 50%).

  • Who are undergoing any other cardiac surgery, eg CABG.

  • An abnormal exercise ECG.

  • A peak velocity greater than 5 m/sec and mean pressure gradient greater than 60.

  • Annual progression of peak velocity of greater than 0.3 m/s/year.

Aortic valve replacement

Aortic valve replacement is the treatment of choice for aortic stenosis.

Aortic valve replacement can be via transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR). TAVI has been shown to be superior to SAVR in high- and medium-risk patients. The operative mortality in surgical AVR is about 3.2% in patients undergoing isolated AVR but is less than 1% in patients aged less than 70 with minimal comorbidities.

The choice between proceeding with surgical AVR or transcatheter AVR depends on multiple factors, including frailty. Currently surgical AVR is still usually offered to younger patients as the long term effects of TAVI have not yet been established.

Balloon aortic valvuloplasty may be considered as a bridge to TAVI or SAVR in patients with decompensated aortic stenosis and (when feasible) in those with severe aortic stenosis who require urgent high-risk non-cardiac surgery. The procedure carries a significant risk of complications.

Monitoring when no current need for intervention¹

• In asymptomatic patients, repeat imaging is typically performed every 3 to 5 years for mild, 1 to 2 years for moderate, and 6 to 12 months for severe aortic stenosis unless surgery is recommended.

NICE guidance

For adults with aortic valve disease, NICE recommends the following:⁴

• Echocardiogram should be offered to all adults with a murmur.

• Referral should be made for all patients with evidence of aortic stenosis.

• Any decision about monitoring patients with aortic stenosis should be made by cardiologists. Ongoing echocardiography monitoring should be done by cardiologists.

• Surgery should be offered as first-line intervention for adults with severe aortic stenosis.

• Surgical AVR should be offered to those who are low or intermediate surgical risk as TAVI is not cost effective for people at low or intermediate surgical risk at the current list price.

• TAVI should be offered, if suitable, to adults with non-bicuspid severe aortic stenosis who are at high surgical risk or if surgery is unsuitable.

• Anticoagulation should not be offered after surgical biological valve replacement unless there are other indications for anticoagulation. Aspirin, or clopidogrel if aspirin is not tolerated, should be offered after TAVI.

Aortic stenosis prognosis¹⁶⁹

• The rate of progression of aortic stenosis is highly variable. Older age, severe leaflet calcification, hypertension, obesity, smoking, hyperlipidaemia, renal insufficiency, and metabolic syndrome are associated with rapid hemodynamic regression.

• Doppler aortic jet velocity is the strongest predictor of symptom progression in asymptomatic patients.

• The role of BNP in disease progression has not yet been fully defined.

• Survival is poor in symptomatic patients, even while the symptoms are mild, unless the outflow obstruction is relieved. Average survival without AVR is only about 1 to 3 years after the symptom onset.

• Women with aortic stenosis have higher mortality than men, resulting from late diagnosis and initial specialist assessment followed by less frequent and delayed referral for intervention.

• Sudden cardiac death is a frequent cause of death in symptomatic patients but appears to be rare in truly asymptomatic patients, even in very severe AS.

• In asymptomatic patients with severe AS, reported average event-free survival at two years ranges from 20% to more than 50%.

• As soon as symptoms occur, the prognosis of severe AS is very poor, with survival rates of only 15-50% at five years.

• After successful AVR, symptoms and quality of life are in general greatly improved.

• Long-term survival may be close to the age-matched general population in older patients.