UNICORN and the Evolution of Coronary Protection in the Redo-TAVR Era

Corresponding Author

The landscape of transcatheter aortic valve replacement (TAVR) has fundamentally shifted. As first-generation transcatheter heart valves approach their second decade of implantation and younger patients increasingly receive TAVR, the inevitability of valve-in-valve (ViV) procedures has transformed from theoretical concern to clinical reality.¹ In this issue of JACC: Asia, Wong et al² present the Undermining Iatrogenic Coronary Obstruction With Radiofrequency Needle(UNICORN) Hong Kong Registry, offering valuable real-world insights into a novel leaflet modification technique that addresses one of the most feared complications in ViV-TAVR: iatrogenic coronary obstruction.

The specter of coronary obstruction looms particularly large in Asian populations, where smaller annular dimensions, lower coronary heights, and predominance of smaller surgical bioprostheses create a perfect storm for coronary compromise.³ The VIVID (Valve-in-Valve International Data) registry reported coronary obstruction rates of 2.3% in ViV-TAVR, with mortality rate exceeding 50% when obstruction occurs.⁴ Traditional approaches—from chimney stenting to the more elegant BASILICA (Bioprosthetic or native Aortic Scallop Intentional Laceration to prevent Iatrogenic Coronary Artery obstruction) technique—have provided solutions, but each carries limitations.⁵ BASILICA, while demonstrating safety and efficacy in both multicenter registries and prospective trials, requires specialized equipment, prolongs procedural times, and creates an obligatory period of acute aortic regurgitation that may be poorly tolerated in hemodynamically fragile patients.⁶

The UNICORN technique, first described by Chan et al⁷ in 2022, represents a conceptual shift in leaflet modification. Unlike BASILICA’s electrosurgical laceration approach, UNICORN uses mechanical force to create a controlled fenestration through which the transcatheter valve is deployed, theoretically minimizing hemodynamic compromise while maintaining continuous annular contact to shield the coronary ostia. The Hong Kong Registry’s 100% procedural success rate across 17 high-risk patients—including both balloon-expandable and self-expanding valves—provides encouraging evidence for this approach.

Particularly noteworthy is the authors’ innovation with the recrossing technique for self-expanding valves. Recognizing that these valves lack the radial force to simultaneously lacerate and expand through a fenestration, the side-by-side positioning of balloon and valve represents elegant problem-solving that minimizes the vulnerable period between leaflet disruption and valve deployment. The single case requiring bileaflet modification with combined UNICORN and BASILICA techniques further demonstrates the procedural versatility required in complex coronary anatomy—a hybrid approach recently termed “BABICORN” (Bileaflet Alteration with BASILICA and Iatrogenic Cusp Obliteration Using Radiofrequency Needle), by Ghoneem et al.⁸

The proliferation of acronyms in this space—BASILICA, UNICORN, LLAMACORN (Leaflet Laceration with Balloon Mediated Annihilation to prevent Coronary Obstruction with Radiofrequency Needle), and CLEVE (CLEveland Valve Electrosurgery)—reflects the structural heart community’s recognition that no single technique will address all anatomies.^9,10 Each represents a variation on the theme of transcatheter electrosurgery, a technology that has revolutionized our approach to leaflet modification beyond simple balloon valvuloplasty.

However, several questions merit consideration. The relatively small cohort size and single-center experience, although understandable for a novel technique, limit generalizability. The absence of standardized balloon sizing algorithms—acknowledged by the authors—raises concerns about reproducibility across centers. Most critically, longer-term outcomes remain unknown. Will mechanically disrupted leaflets behave differently from electrosurgically lacerated ones? Could incomplete leaflet opening lead to delayed complications?

The UNICORN Hong Kong Registry represents more than a technical achievement; it exemplifies the innovative spirit required to address the emerging challenges of lifetime TAVR management. As we enter an era where patients may undergo multiple valve interventions across decades, techniques that preserve coronary access while minimizing procedural risk will prove invaluable. The authors have provided the structural heart community with another tool in our armamentarium—one that may prove particularly valuable in anatomies and clinical scenarios where traditional approaches fall short.

The future of ViV-TAVR will likely involve personalized selection from a menu of coronary protection strategies, with computed tomography–based planning algorithms guiding technique selection. Multicenter registries and eventual randomized comparisons will help define optimal patient selection for UNICORN vs BASILICA vs newer techniques yet to be developed. Until then, Wong et al² deserve recognition for advancing the field and providing hope for patients who might otherwise face prohibitive procedural risk.

Funding Support and Author Disclosures

The author has reported that he has no relationships relevant to the contents of this paper to disclose.