What are the indications for transcatheter aortic valve replacement (TAVR) in patients with severe aortic stenosis?

Indications for TAVR

TAVR is now recommended for symptomatic severe aortic stenosis across all surgical risk categories (low, intermediate, high, and prohibitive) when aortic and vascular anatomy is suitable, representing a paradigm shift from earlier risk-stratified approaches. 1, 2

Core Diagnostic Criteria for Severe Aortic Stenosis

TAVR requires echocardiographic confirmation of severe aortic stenosis using these thresholds 2:

• High-gradient severe AS: Aortic valve area (AVA) ≤1.0 cm² with peak velocity ≥4 m/s or mean gradient ≥40 mmHg 2
• Very severe AS: Peak velocity ≥5 m/s or mean gradient ≥60 mmHg 2
• Extremely severe AS: AVA ≤0.6 cm², mean gradient ≥50 mmHg, or jet velocity ≥5 m/s 2
• Low-flow, low-gradient severe AS: AVA ≤1.0 cm² with peak velocity <4 m/s or mean gradient <40 mmHg 2

Symptomatic Patients (Primary Indication)

Any symptoms attributable to aortic stenosis constitute an indication for TAVR regardless of surgical risk when anatomy is suitable. 1, 2 This includes:

• Classic symptoms: dyspnea, angina, syncope, or heart failure 2
• Left ventricular systolic dysfunction (LVEF <50%) not due to another cause 2
• Patients requiring concurrent cardiac surgery (CABG, ascending aorta surgery, or other valve surgery) 2

Asymptomatic Patients (Selected Indications)

Asymptomatic severe AS may warrant TAVR in specific scenarios 3:

• LVEF <50% with Vmax 4.0-4.9 m/s: Appropriate for AVR (TAVR or SAVR) across all risk levels 3
• Abnormal exercise stress test showing symptoms clearly related to AS 2
• High-risk profession or lifestyle (airline pilot, competitive athlete) or anticipated prolonged time away from medical supervision with low surgical risk 3
• ≥1 predictor of rapid progression: ΔVmax >0.3 m/s/year, severe valve calcification, elevated BNP, or excessive LV hypertrophy without hypertension 3

Important caveat: For asymptomatic patients with preserved LVEF (≥50%), Vmax 4.0-4.9 m/s, negative exercise test, and no predictors of rapid progression, observation is appropriate and intervention is only "may be appropriate" even in high/intermediate risk patients. 3

Risk Stratification Framework

The American College of Cardiology defines surgical risk categories as 3:

• Low risk: STS-PROM <3% 3
• Intermediate risk: STS-PROM 4-8% 3
• High risk: STS-PROM ≥8% or ≥50% risk of mortality/irreversible morbidity at 30 days from SAVR 4
• Prohibitive risk: Predicted survival <12 months or severe comorbidities precluding surgery 4

Critical consideration: While FDA approval expanded TAVR to low-risk patients in 2019 based on PARTNER 3 and Evolut Low Risk trials, the evidence base in low-risk patients is substantially smaller than in higher-risk cohorts, with only 62 total deaths or disabling strokes at 1 year across both trials. 3 The Evolut LR trial had only 9.8% of patients complete 2-year follow-up, requiring extensive statistical imputation. 3

Anatomic Requirements

Mandatory pre-procedural imaging 1, 4:

• CT angiography (chest/abdomen/pelvis with ECG-gated thoracic acquisition) to assess iliofemoral vessel diameter and calcification, aortic annulus sizing, coronary ostia height, and aortic root calcification distribution 1, 4
• Transthoracic echocardiography for valve gradients, LVEF, pulmonary pressures, and mitral valve assessment 4
• Coronary angiography on all candidates, with PCI consideration for significant left main or proximal CAD before TAVR 1

Suitable anatomy means adequate vascular access (typically transfemoral), appropriate annular size for available valve sizes, and absence of anatomic contraindications. 1, 2

Special Populations and Expanded Indications

Bicuspid aortic valve: FDA and European Conformity have approved TAVR for low-risk patients regardless of valve anatomy, though international guidelines still recommend surgical replacement for BAV. 5 Approximately 10% of current TAVR patients have BAV, representing at least 25% of patients ≥80 years referred for AVR. 5

Severely reduced LVEF: LVEF 20-35% is not a contraindication; LVEF <20% is only a relative contraindication requiring careful evaluation. 4

Severe pulmonary hypertension: This is a relative contraindication only for trans-apical TAVR approach; transfemoral access remains permissible. 4 Right-heart catheterization should be considered in TAVR candidates with PH to characterize severity and mechanism. 4

Contraindications and Futility

TAVR should not be performed when 4:

• Expected benefit is less than expected risk 4
• Multiple organ system failure present 4
• Severe frailty or advanced cognitive impairment 4
• Life expectancy <12 months from non-cardiac causes 4
• Patient goals incompatible with realistic procedural outcomes 4

Mandatory Multidisciplinary Evaluation

Every TAVR candidate must be evaluated by a Heart Valve Team including interventional cardiologists, cardiac surgeons, imaging specialists, cardiovascular anesthesiologists, and heart failure specialists. 1, 4, 2 This team-based approach is foundational given the complex technology and multiple procedural considerations. 2

Age Considerations

TAVR is proposed as first-line option for patients >74 years old, though median age in low-risk trials was 74 years and systematic investigation in young low-risk patients remains lacking. 6 For younger patients requiring valve durability considerations, those needing concurrent surgical procedures, or when mechanical valve is preferred, SAVR remains the preferred option. 1