Mount Sinai Hospital

Gilbert H. L. Tang

Valvular heart disease affects 2-3 percent of the U.S. population and is responsible for approximately 25,000 deaths annually. While the majority of patients may benefit from surgical interventions, these procedures are not without risk. This is especially true in older patients who tend to also present with more comorbidities. In the recent past, transcatheter valve therapies have evolved as viable alternatives to open-heart surgery. A few of these notable technologies in the realms of aortic and mitral valve disease are briefly discussed next.

Aortic Valve Disease

Severe and symptomatic calcific aortic stenosis (AS), the most prevalent disease of the aortic valve, has historically been treated with surgical aortic valve replacement (SAVR). While the first catheter-based approach of treating AS was performed in 1985 (balloon aortic valvuloplasty) as an alternative to SAVR in inoperable patients, the modern era of transcatheter valve therapies was ushered in by the advent of transcatheter aortic valve replacement (TAVR) in 2002. Since then, numerous clinical trials have validated the clinical use of TAVR in a variety of patient settings, and TAVR has now become the standard of care for patients with symptomatic heart disease due to severe native calcific AS across the surgical risk spectrum. However, a number of issues continue to impact outcomes, including a lack of data on long-term valve durability and hemodynamics (particularly in low surgical risk patients), prosthesis-patient mismatch (PPM), risk of stroke and new persistent conduction abnormalities, vascular access complications, coronary reaccess and the risk of coronary occlusion, the feasibility of valve-in-valve TAVR, and the use of TAVR in patients with bicuspid aortic valve disease.

There are several devices available to TAVR operators. The U.S. Food and Drug Administration (FDA)-approved current-generation transcatheter heart valves (THVs) include the SAPIEN 3, SAPIEN 3 Ultra (Edwards Lifesciences LLC), and Evolut PRO+ (Medtronic Inc) devices. THVs under clinical investigation include the ACURATE neo2 (Boston Scientific), Portico(Abbott), JenaValve, and J-valve systems. These devices differ with regards to their mode of expansion (balloon-expandable versus self-expanding), leaflet position (intra- or supra-annular), frame material, ability to be repositioned, leaflet tissue material, and delivery sheath sizes. Factors to consider when choosing the optimal TAVR device include expected post-procedural hemodynamic parameters (e.g., supra-annular self-expanding devices are generally associated with lower mean gradients and larger effective orifice areas), annular size, and anatomy (e.g., supra-annular THVs may be advantageous in patients with small annuli), the degree of the aortic valve and root calcification, the expected risk of a conduction abnormality (e.g., device implantation depth may need to be adjusted for patients with shorter membranous septal lengths), and the risk of coronary occlusion. Ultimately, a thorough review of each patient’s anatomic suitability for TAVR by the Heart Team is mandatory for successful outcomes.

“In the recent past, transcatheter valve therapies have evolved as viable alternatives to open-heart surgery.”

In recent years, the role of TAVR, specifically valve-in-valve TAVR, in young- and middle-aged patients with aortic valve disease has been questioned. These patients represent a challenging population given their higher cumulative lifetime risk of valve-related complications. Despite limited valve durability owing to structural valve degeneration (SVD) and the inevitable need for reoperative AVR (redo-AVR), there has been a significant increase in the use of bioprosthetic SAVR in these patients. Compared to AVR for native aortic valve disease, redo-AVR is associated with higher morbidity and mortality. While valve-in-valve TAVR may appear to be an attractive solution, the long-term durability of this technology has not been determined. Other serious limitations include high residual valve gradients, severe PPM, and coronary artery obstruction. Thus, a prospective strategy in which younger patients at low surgical risk are advised to undergo bioprosthetic SAVR with the anticipation of then performing valve-in-valve TAVR is not currently recommended.

Mitral Valve Disease

Over the last two decades, the development of new technologies has expanded the number of patients who can potentially benefit from the treatment of mitral regurgitation (MR). Nevertheless, MR remains underdiagnosed and undertreated. Given the various etiologies, lesions, and pathophysiological abnormalities underlying MR, a proper understanding of the characteristics of this disease is essential to plan the correct treatment. This is often aided by novel and sophisticated multimodality imaging that allows an accurate evaluation of the mitral valve complex, thus guiding the diagnosis, timing of intervention, and treatment with surgical techniques or percutaneous technologies. In contemporary practice, given the vast array of therapeutic options, offering each patient the most appropriate and tailored treatment strategy according to disease etiology and surgical risk is imperative.

Transcatheter mitral valve repair (TMVr) interventions currently in clinical use include transcatheter edge-to-edge repair (TEER) with the MitraClip (Abbott) system and PASCAL (Edwards Lifesciences)system (latter CE marked in Europe), chordal implantation with the HARPOON and NeoChord DS1000 systems (both under clinical investigation), and direct annuloplasty with the Cardioband mitral system (CE marked). While surgical mitral valve repair (MVr) remains the standard of care for patients with primary degenerative MR, TEER with MitraClip has been shown to consistently reduce MR and hospitalizations for heart failure, and is associated with significant reductions in NYHA functional class and increased quality of life. The role of the MitraClip system in patients with heart failure and severe secondary MR has also been clarified by two recent randomized trials. In the current era, the MitraClip procedure is indicated only for patients with disproportionately severe MR meeting the COAPT trial criteria. As with TAVR, several anatomic features may limit the use of TEER, including severe annular and/or leaflet calcification, prolapse of multiple scallops, large intercommissural extension of the regurgitant jet, severe asymmetric tethering, and commissural lesions.

In the last ten years, numerous transcatheter mitral valve replacement (TMVR) devices have also been developed, but this procedure remains in its infancy. Obstacles include the complex anatomy of the MV apparatus, proper anchoring, and sealing of currently-available prostheses, bulky devices, and the risk of protrusion into the left ventricular outflow tract. Nevertheless, several encouraging clinical experiences have been obtained with the use of TMVR in meticulously selected patients.

Conclusion

As our understanding of valvular heart disease continues to evolve, newer transcatheter technologies will undoubtedly emerge, including updated designs from currently-approved systems. With a plethora of percutaneous therapies available on the market, interventional surgeons have to be well-versed with the various patient-, anatomy-, and device-specific factors that ultimately lead to optimal device selection.