Aortic Stenosis

Essentials

• Aortic stenosis often remains asymptomatic for a long time. As the stenosis becomes more severe, patients develop dyspnoea and chest pain on exertion. Loss of consciousness associated with heavy exertion is rarer and suggests severe stenosis.
• As some patients unconsciously reduce their physical activity, assessment of symptoms alone may be misleading.
• A systolic murmur heard on both sides of the sternum, often radiating to the neck, may lead towards the correct diagnosis.
• In severe heart failure, the murmur even from a tight aortic stenosis will be attenuated or may disappear completely.
• Aortic stenosis must always be taken into consideration as a possible cause of dyspnoea on exertion and heart failure in elderly people.
• Doppler ultrasound forms the cornerstone of diagnosis and assessment of the severity of stenosis.
• Symptomatic aortic stenosis should be assessed for invasive treatment without an upper age limit if the patient's performance capacity is otherwise well preserved.
• A mechanical valve prosthesis requires permanent, well-executed anticoagulant treatment with warfarin. Direct oral anticoagulants (apixaban, dabigatran, edoxaban, rivaroxaban) must not be used in patients with a mechanical valve prosthesis.

Prevalence and pathogenesis

• Aortic stenosis is the most common valvular defect in adults in the western world (approx. 40% of all valvular defects).
• It becomes more common with age: at the age of 80, one patient in two has mild stiffening and calcification of the aortic valve and 4% have critical stenosis.
• Aortic stenosis must always be excluded as a cause of heart failure in elderly people.
• Most cases are due to gradual degeneration of a normal tricuspid valve.
• A bicuspid aortic valve predisposing to valve degeneration is found in 1% of the population and may lead to aortic stenosis or regurgitation in middle age.
• Aortic stenosis is an active inflammatory process with similarities to atherosclerosis and the same risk factors (age, male gender, cholesterol, hypertension, smoking) affecting its development.

Symptoms

• Symptoms appear late as the stenosis becomes more severe, and they are unspecific.
• Dyspnoea or chest pain on exertion are the most common symptoms. Loss of consciousness associated with sudden exertion is a rarer sign suggesting severe stenosis.
• As some patients unconsciously reduce their physical activity, assessment of symptoms alone may be misleading.
• Stenosis that has become critical may rapidly lead to manifest heart failure and pulmonary oedema in association with an atrial fibrillation episode or other acute illness, for example.
• Sudden death is a rare first symptom, but as symptoms begin to appear on exertion, the risk of sudden death rapidly becomes high (15-20% per year).
• About one patient in five with significant aortic stenosis shows a bleeding tendency particularly in the intestinal area (angiodysplasias). Valve operation will cure such bleeding tendency.

Findings

• Murmur (Picture 1/3; audio sample Aortic Stenosis (Bicuspic Aortic Valve))
  • A harsh ejection-type systolic murmur, usually the louder and the later its peak in systole, the more severe the stenosis.
  • Radiates to the neck and sometimes towards the apex, in which case it may be difficult to differentiate from mitral regurgitation.
  • As the valve becomes stiffer, the closure sound (S2) is attenuated. If there is regurgitation, as well, there will also be a diastolic regurgitation murmur. With the development of hypertrophy, an atrial gallop (S4) may be audible.
  • In severe heart failure, the murmur even from a tight aortic stenosis will be deceptively attenuated or may disappear completely.
  • Pulmonary emphysema and obesity attenuate murmurs.
• Other findings
  • The carotid pulse is usually weak and slow rising, but in elderly, overweight people, the finding may be difficult to assess.
  • The ECG often shows LVH (both QRS criteria and ST changes) Assessment of Ventricular Hypertrophies from an ECG and left atrial overload.
  • Chest x-ray is often normal. The ascending aorta may be dilated, and valvular calcification may be seen in a lateral projection.

Diagnosis

• Doppler echocardiography Echocardiography as an Outpatient Procedure forms the cornerstone of diagnosis and assessment of the severity of aortic stenosis.
• In addition to establishing the diagnosis, echocardiography can normally be used for reliable assessment of valve structure, the resulting blood flow obstruction (valve gradient) and changes to the left ventricular structure and function due to the valve defect.
• Invasive examinations (cardiac catheterization) are normally not necessary for diagnosis.
• For middle-aged or older patients, coronary angiography or computed tomography of the coronary arteries is indicated before invasive treatment.

Follow-up of valve defect

• As significant left ventricular pressure load from valvular stenosis may gradually lead to irreversible left ventricular pumping dysfunction, even asymptomatic patients should be regularly monitored.
• Specialized care should usually arrange monitoring of patients with aortic stenosis who will probably need invasive treatment, providing primary health care with instructions for other monitoring case by case.
• Physical performance is the single most important issue to be monitored. If physical performance decreases or dyspnoea on exertion occurs for the first time, worsening valve status should always be suspected even if auscultation findings are unchanged.
• The most important things to follow up are pulse, cardiac and pulmonary auscultation, blood pressure, venous pressure assessment and ECG.
• The murmur finding must always be interpreted in relation to the structure of the patient's chest (overweight and pulmonary emphysema attenuate murmurs), symptoms (physical performance, symptoms of heart failure) and general condition (fever, dyspnoea, hypotension).
• Natriuretic peptides (BNP/proBNP) should only be tested as necessary to exclude heart failure. Their levels are often slightly elevated even in patients with mild valve defects, and the significance for monitoring of any changes there is unclear.
• Exercise ECG is mainly used to assess concomitant coronary artery disease and for objective assessment of physical performance if there is disparity between findings and symptoms or if the patient does not exert him-/herself under normal conditions.
• In association with checkups, patients should be informed about the symptoms of atrial fibrillation and the importance of seeking treatment, as well as given instructions for what to do if they develop fever of unclear cause.
• Aortic stenosis will become gradually more severe, and mild valvular stenosis confirmed by echocardiography (mean valvular pressure gradient less than 25 mmHg) should be clinically monitored in outpatient care every couple of years.
• The appearance of symptoms, decreased physical performance, a louder systolic murmur, the appearance of a diastolic murmur or ECG changes warrant repeat echocardiography and assessment in specialized care.
• Moderate stenosis (mean gradient 25-40 mmHg) is usually monitored annually in primary health care and less frequently (every 2-3 years) by echocardiography in specialized care, if the patient is operable or fit for invasive treatment. In specialized care, checkups should be done more frequently as the condition becomes more severe or if left ventricular power is suspected of starting to diminish.
• If the mean systolic pressure gradient exceeds 40 mmHg or the aortic valve area is less than 1 cm² , stenosis should be considered severe and the need for and timing of invasive treatment should be considered. As the cardiac pump power begins to fail, even a smaller pressure difference may be a sign of tight stenosis.
• For more details on indications for referral to specialized care, see The Most Common Types of Acquired Adult Valvular Heart Disease and Associated Murmurs.

Treatment

Anticoagulant and antithrombotic treatment after valvotomy and the TAVI procedure

• A mechanical valve prosthesis requires permanent, well-executed anticoagulant treatment with warfarin.
  • With modern aortic valve prostheses, the target INR level is usually 2.0-3.0, if the patient does not have risk factors for prosthetic valve thrombosis.
  • Direct oral anticoagulants (apixaban, dabigatran, edoxaban, rivaroxaban) must not be used in patients with a mechanical valve prosthesis.
• After placing a biological valve prosthesis, warfarin is often given for 3 months, for example. Aspirin is used increasingly often unless there are other indications for anticoagulant treatment. Practices may vary across countries.
  • A biological valve prosthesis is not a contraindication for using direct oral anticoagulants for atrial fibrillation.
• The antithrombotic treatment following the implantation of a TAVI valve has become lighter and varies depending on the patient's individual risk factors.
  • Aspirin alone is usually used as long-term treatment, unless the patient has other indications for anticoagulant therapy or for more effective antithrombotic treatment.
  • Patients with atrial fibrillation are given just anticoagulants, either direct oral anticoagulants or warfarin.

Monitoring after surgery or TAVI procedure

• The first follow-up visit takes place 2-3 months after the procedure usually in specialized care, and further follow-up of patients with no complications can then usually be carried out in primary health care.
• If the patient has a mechanical valve prosthesis, optimal anticoagulant treatment and follow-up are the most important tasks in outpatient care to prevent thrombosis and bleeding complications. See the article Follow-up and complications after heart valve operation Heart Valve Operation: Patient Follow-Up and Complications.
• Other follow-up in primary health care can normally be carried out annually if the patient is feeling well and has no other diseases requiring more frequent monitoring.
• In follow-up, particular attention should be paid to any changes in physical performance capacity or cardiac symptoms, as well as to the murmur finding (see above).
• The ECG should be checked annually and natriuretic peptides (BNP/proBNP) should be tested if there are symptoms suggesting heart failure.
• Biological valve prostheses may gradually degenerate, causing regurgitation or stenosis (murmur, decreased physical performance). If so, the patient should undergo echocardiographic assessment in specialized care.
• Complications (prosthetic valve thrombosis, endocarditis Infective Endocarditis, bleeding complications, atrial fibrillation), often appearing between follow-up visits, should be recognized at an early stage, and the patient should be referred to the appropriate place for treatment.
• Empiric antimicrobial treatment should not be started in a patient with a valve prosthesis and fever, unless the cause of fever is known (see also Heart Valve Operation: Patient Follow-Up and Complications).
• After implantation of a biological valve prosthesis, direct oral anticoagulants can be used to treat atrial fibrillation.
• Endocarditis prophylaxis is indicated in association with high-risk procedures (see the article Prevention of bacterial endocarditis Prevention of Bacterial Endocarditis). Good oral hygiene and regular dental checkups are important for preventing endocarditis.