As with other cardiac conditions, ACC/AHA guidelines divide aortic stenosis also into stages A to D. In stage A there are conditions which can lead on to aortic stenosis like bicuspid aortic valve or aortic valve sclerosis. Stage B is that of progressive mild – moderate aortic stenosis with leaflet calcification, fibrosis or commissural fusion. Stage C is asymptomatic severe aortic stenosis, which is subdivided into C1 without left ventricular systolic dysfunction and C2 with left ventricular systolic dysfunction with left ventricular ejection fraction (LVEF) <50%. Severe aortic stenosis has valve area ≤1.0 cm2 , mean pressure gradient ≥40 mm Hg or aortic Vmax ≥4 m/s. Very severe AS has aortic Vmax ≥5 m/s or mean pressure gradient ≥60 mm Hg. Stage D symptomatic severe aortic stenosis is subdivided into D1, D2 and D3. D1 is the high gradient aortic stenosis with aortic Vmax ≥4 m/s or mean pressure gradient ≥40 mm Hg and aortic valve area ≤1.0 cm2. In D2, aortic valve area is ≤1.0 cm2 with resting aortic Vmax <4 m/s or mean pressure gradient <40 mm Hg. But dobutamine stress echocardiography shows AVA <1.0 cm2 with Vmax ≥4 m/s at any flow rate. LVEF is <50%. This is low-flow, low-gradient aortic stenosis. D3 is paradoxical low-flow severe aortic stenosis with LVEF ≥50% and stroke volume index <35 mL/m2. Aortic valve area is ≤1.0 cm2 with an aortic Vmax <4 m/s or mean pressure gradient <40 mm Hg as in stage D2 .
Aortic valve replacement, either surgical or percutaneous, is indicated in those with symptomatic high gradient severe aortic stenosis (D1). In asymptomatic patients it is indicated if LVEF is less than 50% (C2). Those with stage C1, asymptomatic severe AS with normal LVEF, valve replacement is indicated along with other cardiac surgery if indicated. Aortic valve replacement is also recommended in symptomatic patients with low-flow low-gradient severe AS with reduced LVEF (D2). In stage D3, symptomatic patients with low-flow low-gradient severe AS with normal LVEF, aortic valve replacement is considered if aortic stenosis is the most likely cause of symptoms. All these are Class I indications. In summary, Class I indications are for stage C2 and D. C1 is considered along with other cardiac surgery. In addition there are several class IIa and IIb indications as well. Basically class IIa indications are in stage C1. A common denominator for these situations is a low surgical risk. In stage B, there is a class IIb indication along with other cardiac surgery.
While considering the choice between a bioprosthetic valve and a mechanical prosthesis, age below 50 years is the cut off for preferring mechanical prosthesis and age above 65 years is the cut off for bioprosthesis. 50-65 years is the grey zone. Bioprosthetic valves have a higher and earlier deterioration in younger age group. Those in whom long term anticoagulation is not feasible, bioprosthesis is considered. Choice is based on a shared decision making process in most situations.
The choice between surgical aortic valve replacement (SAVR) and transcatheter aortic valve implantation (TAVI, also known as TAVR) is mainly for those in whom bioprosthetic valves are indicated. For those below the age of 65 years or a life expectancy more than 20 years, SAVR is preferred. In the 65-80 years age range, either SAVR or transfemoral TAVI can be considered after a shared decision making process. TAVI will be recommended in those above 80 years and in younger patients with a life expectancy less than 10 years. In all these situations, there should be no contraindications for transfemoral TAVI as it is the recommended option. When vascular or valve anatomy is not suitable for TAVI, SAVR is considered. If the surgical risk is high or prohibitive, TAVI is considered if survival beyond 12 months with reasonable quality of life is expected. Discussion so far is based on ACC/AHA guidelines, 2020 .
ESC/EACTS guidelines for management of valvular heart disease were published in 2017 . The guideline mentions that data on TAVI are limited for patients below 75 years and for low surgical risk patients. Hence SAVR was preferred in those patients. On this aspect, the more recent ACC/AHA guidelines incorporate more recent evidence. In ESC/EACTS guidelines, SAVR is preferred if STS/EuroSCORE II is less than 4% and TAVI if it is more than or equal to 4%. TAVI is preferred in those with severe comorbidity, previous cardiac surgery, frailty, and restricted mobility. SAVR is preferred if there is a suspicion of endocarditis.