Transcatheter Aortic Valve Replacement (TAVR) is a minimally invasive procedure that replaces a diseased aortic valve. This technique involves threading a new valve through a catheter, typically inserted via the femoral artery, and implanting it within the patient’s native valve without open-heart surgery. TAVR has revolutionized the treatment of aortic stenosis, offering a life-saving option for many patients who are not candidates for traditional surgery. As TAVR is increasingly performed in younger individuals, the question arises: what happens when the replacement valve eventually wears out and a second intervention is needed?
Understanding Valve Lifespan and Deterioration
The valves used in TAVR are bioprosthetic, constructed from animal tissue, usually bovine or porcine pericardium. Like any biological material, these valves have a finite lifespan, which becomes relevant as patients live longer after the initial procedure. Bioprosthetic valves typically show signs of deterioration between 10 and 15 years after implantation.
The necessity for a repeat procedure stems from bioprosthetic valve dysfunction. The primary cause is Structural Valve Deterioration (SVD), where the valve leaflets stiffen and calcify over time. This stiffening leads to the valve narrowing (stenosis) or failing to close properly (regurgitation), impeding efficient blood flow from the heart. Other reasons for failure include valve thrombosis or infection.
The Valve-in-Valve Solution
Yes, TAVR can be repeated using a technique called Valve-in-Valve (ViV) TAVR. This procedure involves implanting a second transcatheter heart valve directly inside the frame of the previously implanted, failing TAVR device. The new valve is delivered via a catheter, usually through the femoral artery, without requiring a major surgical incision.
During ViV TAVR, the new valve is expanded, pushing the leaflets and frame of the old valve outward to restore proper function and blood flow. ViV TAVR offers a significantly less invasive option than undergoing a second open-heart surgery, especially for patients who are frail or have multiple health issues. This approach is the preferred re-intervention strategy due to its lower immediate risk profile and faster recovery time compared to redo-surgery.
Specific Considerations for Repeat TAVR
Technical Challenges and Coronary Risk
Repeating a TAVR procedure using the ViV technique introduces unique technical challenges that require meticulous planning. A major concern is the risk of obstructing the coronary arteries, which sit just above the aortic valve. When the new valve is deployed, the old valve’s leaflets are compressed and pinned against the aortic wall, potentially blocking blood flow to the coronary arteries.
Specialized pre-procedural imaging, often using Computed Tomography (CT) scans, calculates the predicted distance between the new valve and the coronary artery openings. This measurement, known as the virtual valve-to-coronary distance, determines the safety of the ViV procedure. A distance less than four millimeters is considered a strong predictor of coronary obstruction risk, often requiring alternative strategies.
Patient-Prosthesis Mismatch
A second valve placed inside the first can create a smaller effective opening for blood flow, leading to a higher residual pressure gradient across the valve. This interaction between the two valve frames is known as patient-prosthesis mismatch (PPM). Clinicians must carefully select the size and type of the new valve to optimize blood flow and reduce the risk of future deterioration. Assessing the original vascular access site is also necessary, ensuring the femoral arteries are suitable for catheter delivery.
When Redo TAVR is Not an Option
Despite the success of the ViV technique, a second TAVR is not always the safest choice for every patient. Anatomical factors, particularly a high risk of coronary obstruction identified during planning, can make a redo-TAVR procedure too dangerous. In these high-risk scenarios, a redo Surgical Aortic Valve Replacement (redo SAVR) may be considered the primary treatment.
Redo SAVR involves an open-heart operation to physically remove the failed transcatheter valve and implant a new surgical valve. Although more invasive with a longer recovery than ViV TAVR, redo SAVR addresses coronary obstruction risk by removing the old valve entirely. Redo SAVR is also favored for specific failure types, such as active infection (endocarditis) or severe patient-prosthesis mismatch. For patients too frail for either ViV TAVR or redo SAVR, medical management or palliative care may be the only remaining course of action.