1 INTRODUCTION

Coronary obstruction (CO) may complicate transcatheter aortic valve replacement (TAVR) as native or bioprosthetic aortic valve leaflets are displaced toward the coronary artery ostia during transcatheter valve deployment.¹ This is a rare but potentially life-threatening complication with an incidence of <1% and 30-day mortality of 41%.² Risk factors for CO include female gender, low coronary height, small sinus of Valsalva, those receiving balloon-expandable valves (BEV), and those with previous surgical aortic bioprostheses (SAVR).^{2, 3}

Prophylactic strategies have been described to mitigate CO risk. These include coronary wire protection,⁴ prophylactic chimney-snorkel stenting^{5, 6} and novel transcatheter electrosurgical leaflet modification techniques, specifically BASILICA (Bioprosthetic or Native Aortic Scallop Intentional Laceration to Prevent Iatrogenic Coronary Artery Obstruction)¹ and UNICORN (Undermining Iatrogenic CO with Radiofrequency Needle).⁷ The premise of the electrosurgical approaches is to modify and splay aortic leaflets to preserve coronary artery flow post TAVR.⁸ Both BEV and self-expanding (SEV) transcatheter heart valves (THV) have been used for BASILICA facilitated TAVR.⁹ The developers of the UNICORN technique have mandated the use of BEV as SEV platforms were considered to have insufficient radial strength to splay the leaflet after initial ballooning. However, in many patients where UNICORN may be efficacious including for TAVR-in-SAVR and TAVR-in-TAVR, there is a significant risk of patient-prosthesis mismatch (PPM) with BEV owing to small original prosthesis size.¹⁰ Further, TAVR-in-TAVR with BEV may have suboptimal performance if there is supra-annular leaflet overhang from the original SEV.¹¹ Via iterative modifications to the UNICORN technique for BEV, we describe our consecutive case experience of using sequential leaflet modification measures to facilitate safe use of SEV in these settings. To allow for this distinction this modified technique has been labeled LLAMACORN (Leaflet Laceration with bAlloon Mediated Annihilation to prevent CO with Radiofrequency Needle).

2 CASE PRESENTATIONS

2.1 Patients

We present a case series of five patients. Their clinical presentations and imaging findings are summarized in Table 1 and Figure 1. One patient was a TAVR-in-TAVR and the remaining four cases were TAVR-in-SAVR into Trifecta (Abbott) or Mitroflow (Sorin) prostheses (externally mounted bioprosthetic leaflets). Owing to their various comorbidities, all five patients were deemed high to prohibitive risk for open surgery at multidisciplinary heart team assessment.

Table 1. Patient clinical presentations and imaging findings.

Case #	Age/sex	Case presentation	Echocardiogram	Cardiac Computed Tomography
1	69/ F	NYHA IV; early failure of 29 mm Evolut Pro+ (Medtronic) implanted into a 23 mm native aortic annulus at another center.	4+ transvalvular AR, LVEF 65%, DVI 0.58.	HALT likely due to a constrained valve with leaflet pinwheeling and altered flow dynamics. Persistence of findings despite three months of anticoagulation. High risk of LMCA CO from leaflet obstruction and sinus sequestration.
2	83/ F	NYHA III dyspnea and CCS III angina; degenerative 21 mm Trifecta (Abbott) aortic prosthesis.	Severe AS, LVEF 65%, mAVG 48 mmHg, DVI 0.20, 2D planimetry of bioprosthetic aortic valve orifice 0.41cm2.	LMCA height 6.4 mm, VTC 3.1 mm.
3	84/ F	NYHA III; degenerative 19 mm Trifecta (Abbott) aortic prosthesis.	Severe AS, LVEF 58%, mAVG 36 mmHg, DVI 0.2, EOA 0.5cm2; 3+ transvalvular AR.	LMCA height 8.8 mm, VTC 3.8 mm.
4	87/ M	NYHA IV; degenerative 25 mm Mitroflow (Sorin) aortic prosthesis.	4+ transvalvular AR, LVEF 45%, DVI 0.52.	LMCA height 10.0 mm, VTC 3.2 mm.
5	84/ M	NYHA III dyspnoea; degenerative 21 mm Trifecta (Abbott) aortic prosthesis.	4+ transvalvular AR, LVEF 60%, DVI 0.40.	LMCA height 8.5 mm, VTC 3.0 mm.

• Abbreviations: AR, aortic regurgitation; AS, aortic stenosis; CCS, Canadian Cardiovascular Society; DVI, dimensionless velocity index; HALT, hypoattenuation with leaflet thickening; LMCA, left main coronary artery; NYHA, New York Heart Association.

2.4 Valve deployment and procedural outcome

The THV was deployed under controlled ventricular pacing at 120–140 bpm and postdilatation performed in all cases under rapid ventricular pacing to 180 bpm. Angiography confirmed patency of coronary arteries, with TEE and hemodynamic assessment confirming no to trivial aortic regurgitation (see Figures 2-6).

3 DISCUSSION

This case series illustrates the potential for LLAMACORN to allow for TAVR-in-SAVR or TAVR-in-TAVR with SEV prostheses at high risk for CO. In case 1, there were two issues to contend with for a TAVR-in-TAVR procedure. First, it has been suggested that BASILICA for a degenerative SEV may not provide adequate leaflet splaying to prevent CO.¹² Second, UNICORN would normally have mandated the use of BEV, and inside a large supra-annular SEV there was concern for potential leaflet overhang from the SEV. In cases 2 to 5 the failed aortic bioprostheses had externally mounted leaflets which are associated with higher risk of CO. The use of SEV for these cases was to try and minimize the likelihood of PPM, which would be more likely to arise with a BEV into the small SAVR prostheses.^{13, 14} LLAMACORN allowed for the successful management of these issues in all cases with satisfactory clinical and hemodynamic findings at follow-up.

4 CONCLUSION

LLAMACORN represents a potential alternative as a modification of UNICORN to facilitate the use of SEV for valve in valve procedures. Further investigation of LLAMACORN appears warranted.

CONFLICT OF INTEREST STATEMENT

Anthony C. Camuglia and Christopher M. W. Cole are clinical proctors for Edwards Lifesciences. A. C. C. M., Christopher M. W. Cole, Samual M. Hayman and Stephen V. Cox are clinical proctors for Abbott. All authors work for institutions who have received research support from Abbott, Medtronic and Boston Scientific. The remaining authors declare no conflicts of interest.