Introduced in 2002, TAVR has revolutionized the management of aortic stenosis (AS), providing a minimally invasive alternative to surgical aortic valve replacement (SAVR). TAVR is now established as a safe and effective treatment option for patients with varying surgical risk profiles—from those deemed inoperable to low-risk patients
Types of Valves Used for TAVR
- Balloon-Expandable Valves: The SAPIEN 3 and SAPIEN 3 Ultra (Edwards Lifesciences) are FDA-approved balloon-expandable TAVR devices. These valves feature a trileaflet bovine pericardial valve mounted in a cobalt-chromium frame designed to minimize paravalvular leaks (PVL). However, they are non-repositionable, requiring precise implantation on the first attempt. India made valve Myvalv is a popular valve similar to SAPIEN valve with non-inferior short-term outcomes in the LANDMARK trial.
- Self-Expanding Valves: The Evolut PRO+ (Medtronic) represents the FDA-approved self-expanding valve category. With a supra-annular design, these valves often achieve lower gradients and larger effective orifice areas compared to balloon-expandable valves. They allow for repositioning, enhancing procedural flexibility, though their increased frame height can complicate coronary reaccess.
| Factors to Consider in Choosing a Valve for TAVR | |
|---|---|
| May Favor BEV | May Favor SEV |
| Short or narrow sinus of Valsalva (feasibility of future TAV-in-TAV) | Small annulus (lower TAVR gradients) |
| RBBB or other high-grade conduction disease (lower risk of pacemaker implantation) | Severe LVOT calcification (less risk of annular trauma) |
| Need for future PCI ( easier coronary re-access) | |
| BES = balloon-expandable valve; LVOT = left ventricular outflow tract; PCI = percuteneous coronary inter-vention; RBBB = right bundle branch block; SEV = self-expanding valve; TAV = transcather aortic valve; TAVR = transcatherter aortic valve replacement |
Which Factors Should be Considered While Selecting Device for TAVR?
Selecting the optimal TAVR device depends on various patient and anatomical factors:
- Annular Size and Shape: Proper valve sizing is critical to prevent complications such as PVL or valve embolization. Balloon-expandable valves are generally preferred for smaller annuli, while self-expanding valves may be advantageous in larger or irregularly shaped annuli due to their flexible design. In the recent SMART trial published in April 2024, among patients with severe aortic stenosis and a small aortic annulus who underwent TAVR, a self-expanding supra-annular valve was noninferior to a balloon-expandable valve with respect to clinical outcomes and was superior with respect to bioprosthetic-valve dysfunction through 12 months.
- Risk of Conduction Abnormalities: The need for permanent pacemaker implantation (PPI) varies with the type of TAVR device and implantation technique. Self-expanding and mechanically expandable valves are associated with a higher risk of PPI due to continuous radial force exerted on the conduction system.
- Coronary Reaccess and Obstruction: Valves with taller frames, such as self-expanding designs, may complicate coronary reaccess post-TAVR, posing challenges for future coronary interventions. Balloon-expandable valves, with their lower profiles, generally facilitate easier coronary re-access.
What Should be The Properties of an Ideal Transcatheter Aortic Valve Prosthesis
- Minimal vascular access size
- Optimal effective orifice area
- Minimal paravalvular leak
- Suitable for wide range of annulus sizes
- Repositionable and retrievable
- Durable long-term
- Low risk of permanent pacemaker implant and/or new permanent conduction abnormalities
- Easy coronary re-access
- Consistent commissural alignment
- Minimal need of contrast dye use
- Simple-to-use delivery system
- Suitable for use in patients with low
- Suitable for different aortic valve pathologies
Patient Scenarios that Favor Particular Valve Types
| Balloon-expandable valve | Self-expanding valve |
|---|---|
| Extremely large annulus beyond manufacturer recommendations | Dense annular/sub-annular calcium |
| Horizontal aorta (>70°) | Intolerant to rapid pacing (eg, low EF) |
| High preprocedural risk of permanent pacemaker implantation | Small or challenging ileo-femoral artery access |
| Extensive coronary artery disease and high likelihood of future percutaneous coronary intervention | TAVR-in-SAVR (for supra-annular designs)
Avoid severe prosthesis-patient mismatch |
What are the Long-Term Outcomes and Durability Factor related to TAVR?
The hemodynamic outcomes of TAVR prostheses are generally favourable, with self-expanding valves showing lower gradients and larger effective orifice areas compared to balloon-expandable valves. However, the clinical significance of these differences, particularly over the long term, remains uncertain.
While TAVR devices have demonstrated promising mid-term durability, long-term data, especially for newer generations of devices, are still limited. Ongoing trials such as the PARTNER 3 and Evolut Low Risk studies are expected to provide valuable insights into the durability of TAVR prostheses up to 10 years post-implantation
What are the Challenges and Future Directions in TAVR?
- Managing Paravalvular Leak (PVL) remains a significant challenge in TAVR, linked to gaps between the native valve and the implanted prosthesis. Advances in valve design, including improved sealing cuffs and skirts, have reduced the incidence of moderate to severe PVL in newer-generation devices.
- Patients with bicuspid aortic valves (BAV), characterized by leaflet asymmetry and raphe, pose unique challenges for TAVR. The asymmetric anatomy complicates valve positioning and expansion, necessitating specialized device designs and careful procedural planning.
- Persistent conduction abnormalities, such as new-onset left bundle branch block, are common after TAVR and can negatively impact patient outcomes. Strategies to minimize these risks include optimizing valve positioning and selecting devices with lower radial forces.
- Acute or delayed coronary obstruction, though rare, is a severe complication of TAVR. Preventive measures, including the use of retrievable valves and coronary protection techniques, are crucial in high-risk patients.
