2.2 / IAGS 2019
Session 2: Structural Session 1 - Aortic
Which Valve for Which Patient and Whether and When to do Bioprosthetic Valve Modification
Problem Presenter: Adam Greenbaum, MD
Statement of the problem or issue
For patients with failing surgical bioprosthetic valves, transcatheter aortic valve replacement (TAVR) has been shown to be a safe and efficacious alternative to repeat surgery for those with significant operative risks. However, a substantial percentage of these patients have a surgical prosthesis of small diameter, often with inadequate sinus widths, placing them at risk for life-threatening coronary obstruction during a valve-in-valve TAVR procedure, as well as patient-prosthesis mismatch, leaflet thrombosis, and premature TAVR-valve deterioration from under-expansion.
Gaps in knowledge
Current commercially available TAVR valves have unique design specifications (ie, skirt length, leaflet location, commissural heights), which may uniquely impact aortic and coronary flow after placement. User-driven, novel, adjunctive techniques have been developed to maximize TAVR valve expansion (such as bioprosthetic valve fracture [BVF]) and maintain flow into the native sinus (bioprosthetic aortic scallop intentional laceration to prevent coronary obstruction [BASILICA]). Small retrospective case series of both, and a recently completed 30-patient, NHLBI-funded, prospective study of BASILICA, showed high technical and clinical success with no signal of safety concern. However, predicting the true risk of coronary obstruction as well as understanding the long-term impact of both higher gradients and optimal flow into the sinus post valve-in-valve TAVR, and therefore the benefit of BVF and BASILICA techniques, remain challenging.
Possible solutions and future directions
Long-term clinical and echocardiographic data from large multicenter trials of transcatheter heart valves, and smaller nested registries specifically investigating their use for valve-in-valve applications, should provide further insight into the implication of residual gradients post TAVR. However, industry is less well suited to help answer questions related to the more novel, and somewhat “off-label” techniques of BVF and BASILICA. One solution could be to capture these data within the Transcatheter Valve Therapies (TVT) registry, in which most centers implanting commercial transcatheter valves in the United States are participating. Yet, this registry may not be nimble enough to incorporate the rapid pace of changes to additional adjunctive procedural techniques, let alone capture their individual nuances, and stakeholders would need to be very proactive to overcome this. Additionally, detailed preprocedural CT imaging results are not captured in the TVT registry. Another solution could be separate, prospective, multicenter registries specifically aimed at techniques such as BVF and BASILICA, which could conceivably also involve core lab analysis of all baseline CT data. But, obstacles to operationalizing these concepts remain. Registries of this nature typically require either institutional review board (IRB) oversight and approval at each center as well as individual patient consent, or agreement to rely on a single IRB and a waiver of patient-consent, both of which can be difficult to obtain. Additionally, questions surrounding benefits to BVF and BASILICA with regard to valve durability and overall survival will likely require large numbers of patients, and long-term follow up. Participation in multiple simultaneous registries can be onerous and costly for often understaffed clinical programs with little institutional gain for participation. Funding for registries of techniques alone is unlikely to come from outside sources. In the meantime, dedicated equipment to simplify and streamline BASILICA is in development and in the end, answers to questions surrounding novel techniques may require equally “out-of-the-box” thinking in terms of proving their long-term benefit.