Anatomy and causes of aortic stenosis
The aortic valve normally consists of three cusps: the left coronary, right coronary, and non-coronary cusps. Aortic stenosis is the narrowing of this valve orifice, caused by three main reasons.
- Acute rheumatic fever causes commissural fusion with thickening and fibrosing of the cusps, resulting in the formation of a triangular aortic valve orifice.
- Degenerative calcification begins at the base of the cusps and extends toward their edges, while the commissures remain open.
- Bicuspid aortic valve is a congenital condition in which only two cusps function instead of three. The load on each cusp increases, causing the valve to wear out and calcify faster than a tricuspid one.
Clinical symptom triad
Aortic stenosis is characterized by an independent triad of symptoms, each having its own prognostic value.
- Angina pectoris occurs because the narrowed valve orifice forces the left ventricle to contract with greater force to eject the required volume of blood. Eccentric left ventricular hypertrophy develops, myocardial oxygen demand increases, causing burning retrosternal pain radiating to the left arm and lower jaw. Once angina appears, the patient's average life expectancy is about 5 years.
- Dyspnea is a consequence of left heart overload: the ventricle fails to pump out all the blood in time, and pressure rises in the pulmonary circulation. The prognosis for this symptom is an average of 2 years of life.
- Syncope (fainting) is the result of inadequate cerebral perfusion, as the left ventricle is unable to push the required volume of blood through the narrowed orifice. The average life expectancy after the onset of syncope is 3 years.
Diagnostics
The main diagnostic method is echocardiography (transthoracic echocardiogram). The image shows a narrowed aortic valve and an enlarged left ventricle. This is a key method for evaluating both stenosis and heart valve regurgitation.
Classification by severity
Aortic stenosis is classified by valve area, transaortic blood flow velocity, and mean pressure gradient.
- Stage A (mild stenosis): valve area 3–4 cm², velocity less than 2 m/s, mean pressure gradient less than 10 mm Hg.
- Stage B (progressive, moderate stenosis): area 1.5–3 cm², velocity 2–3 m/s, increasing pressure gradient.
- Stage C1 (severe, asymptomatic): valve area less than 1 cm², mean gradient greater than 40 mm Hg, velocity greater than 4.0 m/s, but no clinical manifestations, left ventricular ejection fraction is preserved.
- Stage C2: similar severe hemodynamic parameters in the absence of symptoms, but ejection fraction less than 50%.
- Stage D (severe, symptomatic): severe stenosis with clinical manifestations — angina, dyspnea, syncope.
Indications for surgical intervention
The decision for surgery is made taking into account the class of indications.
- Class IA — severe symptomatic aortic stenosis.
- Class IB — severe stenosis in a patient scheduled for another cardiac surgery (coronary artery bypass grafting, mitral valve intervention, thoracic aorta surgery).
- Class IC — severe stenosis with left ventricular dysfunction (ejection fraction less than 50%).
- Class IIA — moderate stenosis in a patient scheduled for bypass surgery, mitral valve intervention, or thoracic aorta surgery; the decision is made collectively by a surgical team (Heart Team) involving cardiologists, cardiac surgeons, and other specialists, sometimes directly during open-heart surgery.
Choice of valve prosthesis and TAVI technique
In severe stenosis, calcified cusps are removed and replaced with a prosthesis — mechanical or biological.
- Mechanical valves are chosen for younger patients, last on average 25 years or longer, but require lifelong warfarin therapy with INR monitoring (target range usually 2–3) to prevent cusp thrombosis.
- Biological valves are made from porcine, bovine, or other animal pericardium with the removal of immune cells; the average lifespan is 10–15 years. They are chosen for patients older than 65–70 years (lower risk of reoperation), pregnant women (due to warfarin teratogenicity, although a combination of warfarin with low-molecular-weight heparin by trimesters is now possible), and cancer patients, since warfarin is poorly compatible with chemotherapy.
In addition to open surgery (sternotomy with cardiopulmonary bypass), there is the TAVI technique (transcatheter aortic valve implantation), used since 2002. The main access is via the femoral artery under transesophageal echocardiographic guidance; transfemoral, transapical, transaortic, and subclavian approaches also exist. To prevent embolization of calcium fragments into cerebral vessels, special embolic protection devices protecting the brachiocephalic branches can be used.
The choice between open surgery and TAVI is made collectively by the Heart Team, taking into account age and risk scores EuroSCORE and STS-PROM. Patients under 75 years of age with low risk (EuroSCORE less than 3–4%) are indicated for open surgery; patients older than 75 years with high risk (EuroSCORE greater than 8%) are preferred for TAVI.
Key points
- Main causes of aortic stenosis: rheumatic fever, degenerative calcification, bicuspid aortic valve.
- The classic symptom triad — angina, dyspnea, syncope — has different survival prognoses (5, 2, and 3 years, respectively).
- The main diagnostic method is echocardiography.
- The severity of stenosis is assessed by valve area, flow velocity, and pressure gradient (stages A, B, C1, C2, D).
- Indications for surgery are determined by classes (IA-IIA) considering symptoms, ejection fraction, and concomitant cardiac surgeries.
- A mechanical valve is durable but requires lifelong warfarin; a biological valve does not require anticoagulants but wears out faster.
- TAVI is a minimally invasive alternative to open surgery, used primarily in elderly patients with high surgical risk.
- The treatment strategy decision is made collectively by the surgical team (Heart Team).