What is a TAVI (Transcatheter Aortic Valve Implantation) and in which patients is it indicated?

What is TAVI (Transcatheter Aortic Valve Implantation)?

TAVI is a minimally invasive catheter-based procedure that replaces a severely stenotic aortic valve without open-heart surgery, primarily indicated for patients with severe symptomatic aortic stenosis who are at high or prohibitive surgical risk. 1, 2

Definition and Procedure Overview

• TAVI involves delivering a bioprosthetic valve (bovine pericardial) through a catheter to replace the diseased native aortic valve, avoiding the need for sternotomy and cardiopulmonary bypass. 3, 2

• The procedure was first performed in humans in 2002 by Alain Cribier, initially using an antegrade transseptal approach, which was subsequently replaced by more practical access routes. 3

• Two main valve types are used: balloon-expandable and self-expandable prostheses, each with specific anatomic requirements and deployment characteristics. 4

Access Routes

The transfemoral (retrograde arterial) approach is the preferred and most common access route for TAVI when anatomy permits. 3, 5

Alternative Access Options:

• Transapical access involves direct puncture of the left ventricular apex through a small thoracotomy, providing antegrade valve delivery when femoral access is unsuitable. 3, 5

• Transsubclavian and direct transaortic approaches serve as additional alternatives for patients with prohibitive peripheral vascular disease. 3, 5

Patient Selection Criteria

Primary Indication:

• TAVI is indicated for patients with severe symptomatic aortic stenosis (valve area ≤1.0 cm², mean gradient ≥40 mmHg, or peak velocity ≥4.0 m/sec) who are at high surgical risk (STS score ≥8%) or deemed inoperable. 1, 6

• Patients must have predicted survival >12 months and an estimated ≥50% risk of mortality or irreversible morbidity at 30 days from surgical aortic valve replacement. 1

Multidisciplinary Assessment:

• A Heart Valve Team including interventional cardiologists, cardiac surgeons, imaging specialists, anesthesiologists, and heart failure specialists must evaluate all TAVI candidates. 1

Absolute Contraindications

General Contraindications:

• Aortic annulus <18 mm or >25 mm for balloon-expandable devices, or <20 mm or >27 mm for self-expandable devices. 4

• Bicuspid aortic valves due to risk of incomplete prosthesis deployment. 4

• Asymmetric heavy valvular calcification that may compress coronary arteries during valve deployment. 4

• Aortic root dimension <45 mm at the aorto-tubular junction for self-expandable prostheses. 4

• Presence of left ventricular apical thrombus. 4

Transfemoral Approach Contraindications:

• Iliac arteries with severe calcification, tortuosity, or diameter <6-9 mm (depending on device used). 4

• Severe aortic angulation, severe atheroma of the arch, coarctation, or abdominal aortic aneurysm with protruding mural thrombus. 4

• Bulky atherosclerosis of the ascending aorta and arch detected by transesophageal echocardiography. 4

Transapical Approach Contraindications:

• Previous left ventricular surgery using a patch (e.g., Dor procedure). 4

• Calcified pericardium. 4

• Severe respiratory insufficiency or severe pulmonary hypertension (transapical route only; transfemoral remains permissible). 1

• Non-reachable left ventricular apex. 4

Pre-Procedural Imaging Requirements

• CT angiography of chest, abdomen, and pelvis with ECG-gated thoracic acquisition is required to assess iliofemoral vessel diameter, aortic annulus sizing, coronary ostia height, and calcification distribution. 1

• Transthoracic echocardiography must confirm maximum aortic velocity, mean gradient, aortic valve area, left ventricular ejection fraction, and pulmonary artery pressure. 1

• Transesophageal echocardiography should be performed if borderline annular measurements create doubt about procedural feasibility, as TEE shows larger values than transthoracic echo. 4

Clinical Outcomes

Mortality and Efficacy:

• At 1 year, TAVI reduces all-cause mortality to 30.7% compared to 50.7% with standard therapy in inoperable patients (hazard ratio 0.55, P<0.001). 2

• TAVI significantly reduces the composite endpoint of death or repeat hospitalization to 42.5% versus 71.6% with standard therapy (hazard ratio 0.46, P<0.001). 2

• Among survivors at 1 year, cardiac symptoms (NYHA class III or IV) are reduced to 25.2% with TAVI versus 58.0% with standard therapy (P<0.001). 2

Procedural Complications:

• 30-day mortality ranges from 5-18% depending on patient risk profile and center experience. 4

• Major stroke occurs in 3-9% of patients, with higher rates at 30 days (5.0%) compared to standard therapy (1.1%, P=0.06). 4, 2

• Vascular complications occur in 10-17% and remain a significant cause of morbidity and mortality. 4, 2

• Permanent pacemaker implantation is required in 4-24% of patients, with higher rates for self-expandable devices. 4

• Paravalvular aortic regurgitation (mild-to-moderate) occurs in approximately 50%, though severe regurgitation has decreased to 5% with improved sizing techniques. 4

Special Populations

Severely Reduced LVEF:

• LVEF <20% is a relative contraindication but not absolute, requiring careful individualized evaluation. 1

• LVEF between 20-35% is acceptable for TAVI candidacy. 1

Pulmonary Hypertension:

• Severe pulmonary hypertension is a relative contraindication only for the transapical approach, while transfemoral access remains permissible. 1

• Right-heart catheterization should be considered in TAVI candidates with pulmonary hypertension to characterize severity and mechanism before proceeding. 1

Facility and Team Requirements

• TAVI should be performed only in high-volume centers with both cardiology and cardiac surgery departments, with expertise in structural heart disease intervention and high-risk valvular surgery. 4

• The optimal environment should be spacious, sterile, and feature high-quality imaging equipment with hemodynamic monitoring capabilities—ideally a hybrid suite combining operating room and catheterization laboratory features. 4

• Close cooperation between clinical cardiologists, echocardiographists, interventional cardiologists, cardiac surgeons, and anesthesiologists is mandatory for procedural success. 4

Post-Procedural Follow-Up

• Transthoracic echocardiography immediately post-TAVR must assess maximum aortic velocity, mean gradient, valve area, paravalvular regurgitation severity, and left ventricular function. 1

• Serial echocardiography at specified intervals is required for long-term surveillance to monitor valve function and paravalvular regurgitation progression. 1

• Valve function remains stable at 1-2 years with no deterioration in stenosis or regurgitation on echocardiographic assessment. 4, 2