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Aortic valve intervention: Indications, timing, and choice of transcatheter aortic valve implantation versus surgical aortic valve replacement


Indications for aortic valve intervention

Aortic stenosis (AS) is the most common heart valve disease that is associated with increased cardiovascular mortality and requires intervention. The prevalence increases with age, and currently 1 in 20 people age 75 and older have moderate or severe AS. As there are no medical therapies that have been shown to attenuate progression of stenosis, aortic valve intervention (transcatheter aortic valve implantation [TAVI] and surgical aortic valve replacement [SAVR]) is the only available treatment for AS that is able to restore quality of life and improve symptoms and prognosis. However, the treatment is invasive and incurs relevant risks, including but not limited to mortality and stroke. Therefore the indication of the treatment must be carefully evaluated and intervention should be performed only when expected benefit outweighs procedural risks, as well as other shortcomings such as the necessity of antithrombotic therapy and the risks of prosthesis-patient mismatch and structural valve deterioration (SVD). Current recommendations for aortic valve intervention published by the American College of Cardiology (ACC)/American Heart Association (AHA) in 2020 ( Fig. 1.1 ) and the European Society of Cardiology (ESC)/European Association for Cardio-Thoracic Surgery (EACTS) in 2021 ( Fig. 1.2 ) are summarized in Table 1.1 .

Fig. 1.1., Timing of Intervention for AS (2020 ACC/AHA Guideline).

Fig. 1.2., Timing of Intervention for AS (2021 ESC/EACTS Guideline).

TABLE 1.1
Guideline Recommendations: Indications for Aortic Valve Intervention
ACC/AHA 2020 ESC/EACTS 2021
Symptomatic severe high-gradient AS I A I B
Asymptomatic severe high-gradient AS
Symptoms on exercise test I A I C
A decrease in blood pressure on exercise test IIa B IIa C
LVEF <50% I B I B
LVEF <55% IIa B
Very severe AS (V max >5.0 m/s a ), low procedural risk IIa B IIa B
Rapid progression (V max progression ≥0.3 m/s/year), low procedural risk IIa B IIa B
Markedly elevated BNP, b low procedural risk IIa B IIa B
Indications for other cardiac surgery I B I C
Symptomatic classic low-flow low-gradient AS
Positive DSE (true AS) I B I B
Without flow reserve, calcium on CT c IIa C
Symptomatic paradoxic low-flow low-gradient AS
Positive on careful confirmation I B IIa C
Moderate AS
Indications for other cardiac surgery IIb C IIa C

Severe AS very likely: men ≥3000; women ≥1600
Severe AS likely: men ≥2000; women ≥1200
Severe AS unlikely: men <1600; women <800
ACC/AHA, American College of Cardiology/American Heart Association; AS, aortic stenosis; BNP, B-type natriuretic peptide; CT, computed tomography; DSE, dobutamine stress echocardiography; ESC/EACTS, European Society of Cardiology/European Association for Cardio-Thoracic Surgery; LVEF, left ventricular ejection fraction; V max , peak transvalvular velocity.
Table References:

  • 1.

    Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2021;143:e72-e227.

  • 2.

    Vahanian A, Beyersdorf F, Praz F, et al. 2021 ESC/EACTS guidelines for the management of valvular heart disease. Eur Heart J. 2022;43(7):561-632.

a Or mean gradient ≥60 mm Hg in ESC/EACTS guideline.

b BNP > threefold age- and sex-corrected normal range confirmed by repeated measurements and without other explanation (ESC/EACTS) or >3 times normal (AHA/ACC).

c Calcium score by CT.

Symptomatic, severe high-gradient AS

In patients with severe high-gradient AS, who develop classic symptoms of angina, syncope, or heart failure, aortic valve intervention is clearly indicated and considered a Class 1 (or strong) recommendation (see Table 1.1 ). This recommendation is based on observational studies demonstrating that symptomatic patients with severe AS suffer from a dismal prognosis with a mortality rate of 20% or more per year if left untreated, whereas successful SAVR provides effective relief of symptoms and improved long-term survival. Furthermore, a 2015 randomized clinical trial (RCT) comparing conservative treatment versus transfemoral TAVI in patients at a prohibitive surgical risk reported that 50.7% of patients allocated to conservative treatment died within 1 year, whereas TAVI reduced mortality rate to 30.7%. The number needed to treat (NNT) to prevent one death in the first year was five (20% absolute risk reduction). At 5 years of follow-up, the risk of mortality was 93.8% in the conservative treatment group compared with 71.8% in the TAVI group. Therefore timely intervention is recommended in all symptomatic patients with severe high-gradient AS except in cases where the prognosis is more likely to be determined by other comorbidities and an estimated life expectancy of less than 1 year.

Asymptomatic, severe high-gradient AS

In general, AS progresses during an asymptomatic or mildly symptomatic phase, and a substantial proportion of patients with severe AS are asymptomatic at the time of initial diagnosis. SAVR is indicated for selected asymptomatic patients who are considered at high risk of adverse cardiac events, as discussed in more detail later in this chapter. In the updated 2020 ACC/AHA and 2021 ESC/EACTS guidelines, TAVI is not recommended for asymptomatic patients with AS unless LV ejection fraction is reduced or an exercise stress test is abnormal (see Figs. 1.1 and 1.2 ).

Exercise testing

Symptom assessment can be very challenging in patients with severe AS, especially in elderly patients with multiple comorbidities or low physical activities. Exercise testing may be helpful to unmask symptoms. Observational studies suggest that an abnormal exercise test may be encountered in 28% to 67% of asymptomatic individuals and has been associated with poor prognosis. Therefore current guidelines recommend aortic valve intervention allocating a Class I recommendation to patients with symptoms during exercise testing and a Class IIa recommendation to patients with abnormal exercise tests (see Table 1.1 ). Although exercise testing should be customized according to local experience and the results should be interpreted on a case-by-case basis by experienced clinicians, most centers use a standard maximal treadmill test with measurement of blood pressure, assessment of exercise capacity, and assessment of provoked symptoms.

LV dysfunction

Pressure overload due to AS causes cardiac remodeling, which initially leads to cardiac hypertrophy and an increased left ventricular ejection fraction (LVEF) (>60%) but ultimately leads to LV systolic dysfunction. Observational studies suggest that the majority of patients will experience improvement of LV function after aortic valve intervention, and that improvement in LV function is associated with improved clinical outcomes. However, irreversible myocardial fibrosis may occur as a result of prolonged excessive overload: at this stage, LV function may not improve even after correction of outflow obstruction. This suggests that early intervention before myocardial fibrosis might improve long-term outcomes after aortic valve intervention. Accordingly, asymptomatic patients with severe AS and LV systolic dysfunction (LVEF <50%) are recommended to undergo aortic valve intervention (Class I) in current guidelines (see Table 1.1 ). More recently, data from the The Heart Valve Clinic International Database (HAVEC) registry indicate that even asymptomatic AS patients with EF between 50% and 59% have worse outcomes than those with LVEF >60%, suggesting that the threshold of LVEF <50% may fail to identify the optimal threshold for intervention before irreversible myocardial damage. Thus in the updated 2021 ESC/EACTS guidelines, aortic valve intervention is considered reasonable (Class IIaB) for asymptomatic patients with severe AS and LVEF <55%. Furthermore, LVEF may constitute a late phenotype of myocardial injury and may not be suitable as a surrogate marker for silent disease progression. LV hypertrophy or global longitudinal strain may be early and effective markers of LV dysfunction that could be integrated into the risk stratification model in future guidelines.

Markedly elevated brain natriuretic peptide

An increased level of b-type natriuretic peptide (BNP) is a marker of disease progression, reflecting prolonged pressure overload caused by severe AS. In a multicenter registry including 387 asymptomatic patients with severe AS who were not referred for SAVR, 5-year rates of AS-related events (mortality or heart failure hospitalization) increased with increasing BNP levels, whereas those with BNP levels <100 pg/mL had an event rate of only 2.1% at 1 year. It should be noted, however, that elevated BNP levels may be attributed to cardiac diseases or comorbidities other than AS. Current guidelines suggest that aortic valve intervention is reasonable (Class IIaB) in asymptomatic patients with a “markedly elevated BNP (3 times normal range)” if the procedural risk is considered low (see Table 1.1 ).

Very severe AS

Peak aortic jet velocity is a marker of disease severity and an important predictor of worse outcomes with increased event rates and symptom onset among asymptomatic patients. In the HAVEC registry, the mean 2-year and 4-year overall survival rates in asymptomatic patients with AS were 93% and 86%, respectively, and aortic velocity of 5.0 m/s and higher was associated with a sixfold increased risk of cardiovascular mortality. Recently an RCT reported improved long-term survival in patients who underwent early SAVR compared with those treated conservatively in asymptomatic patients with very severe AS (very severe AS was defined as aortic valve area [AVA] of ≤0.75 cm 2 with either an aortic jet velocity of ≥4.5 m/s or a mean transaortic gradient of ≥50 mm Hg). Therefore it is reasonable (Class IIaB) to perform aortic valve intervention for asymptomatic patients with very severe AS if the procedural risk is considered low (see Table 1.1 ).

Rapid progression

In case of rapid disease progression defined by an aortic velocity increase of 0.3 m/s/year, 80% of patients underwent surgery or died within 2 years. When serial testing shows a rapid increase in aortic velocity, the risk of watchful waiting may outweigh the risk of early intervention, and SAVR is reasonable (Class IIa) as long as the surgical risk is considered low (see Table 1.1 ).

Indications for other cardiac surgery

If asymptomatic patients with severe AS have an indication for other cardiac surgery, combined SAVR is recommended (Class I). For patients with moderate AS and an indication for other cardiac surgery, combined SAVR is considered reasonable (Class IIa) in the 2021 ESC/EACTS guidelines and may be considered (Class IIb) in the 2020 ACC/AHA guideline. Because AS is a progressive disease, moderate or asymptomatic severe AS may progress and cause symptoms within the next few years after the initial surgery. Conversely, initial combined SAVR may have shortcomings such as the risk of prosthesis-patient mismatch and SVD, as well as the surgical complexity with an increased perioperative risk. In the era of TAVI, patients with moderate AS may undergo nonsurgical aortic valve intervention at a later stage. Therefore the decision should be individualized based on the disease progression rate, specific operative risk, clinical and anatomic factors, and patient preferences, especially in patients with moderate AS.

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