Supra-annular Prosthesis Anchoring in Bicuspid Aortic Valve: Evidence in Large Annuli Exceeding the Device Sizing Chart Range.

There is still no consensus on the optimal sizing method for prosthesis selection in bicuspid aortic valve (BAV) patients undergoing transcatheter aortic valve implantation (TAVI). Apart from the height (annular vs supra-annular) to choose when performing sizing assessments, it is still debated which is the correct measure to consider (the intercommissural distance rather than the perimeter or others). The LIRA method is based on the measurement of the perimeter at the level of the maximal protrusion of the raphe (the “LIRA plane”), where we speculate that transcatheter heart valve (THV) anchoring occurs in BAV anatomy.1 This perimeter is compared with the virtual basal ring (VBR) perimeter, and the smallest value is chosen for prosthesis sizing. We have recently reported encouraging outcomes on the application of the LIRA method in a cohort of 104 type Sievers type 1 and type 2 BAVs patients undergoing TAVI.2 In this subanalysis we aimed to further investigate the prosthesis anchoring level in BAV anatomy. Our work was approved by the local ethics committee and conducted in accordance with the Declaration of Helsinki. All patients were scheduled for TAVI after heart team discussion. From the original cohort, we selected 19 patients with annular dimensions exceeding the device sizing chart range and thus unsuitable for TAVI with the chosen platform (perimeter > 85 mm in those receiving a Boston Scientific prosthesis and > 94.2 mm in those receiving a Medtronic prosthesis), but with appropriate dimensions at the LIRA plane. The primary endpoint was device success, a composite endpoint that included: technical success; freedom from mortality; freedom from any intervention related to the device; freedom from major vascular or cardiac structural complications; and intended valve performance, defined as a mean gradient < 20 mm Hg, peak velocity < 3 m/s, and less than moderate aortic regurgitation. Secondary endpoints were 30-day safety outcomes. All study endpoints were defined according to the Valve Academic Research Consortium-3 criteria. Patients were predominantly male (n = 18; 94.8%); mean age was 80.10 ± 5.36 years and mean Society of Thoracic Surgeons score was 3.87 ± 3.76%. All patients had a type 1 BAV anatomy according to Sievers classification, with a raphe located between the left and the right cusp. In 10.5% of cases (n = 2) the raphe was purely fibrotic. Mean raphe length was 13.37 ± 3.11 mm. Mean distance between the VBR and the LIRA plane was 7.77 ± 2.15 mm. The VBR perimeter was significantly greater than the LIRA plane perimeter (92.12 ± 5.45 mm vs 81.68 ± 5.20 mm; P < 0.001), confirming a tapered configuration of the aortic valvar complex. Application of the LIRA method led to prosthesis downsizing in all of the patients, allowing TAVI feasibility with the chosen platform for all of them. Specifically, 10 patients received a size L prosthesis (Boston Scientific), 8 patients received a 34-mm prosthesis (Medtronic), and 1 patient received a 29-mm prosthesis (Medtronic). In the 9 patients receiving a Medtronic prosthesis and having extra-large annular measures (median perimeter 96.7 mm, interquartile range 95.75-97.35 mm), relying on virtual basal ring dimensions would have prevented TAVI feasibility not only with the chosen platform but with all current commercially available self-expanding valves. Predilatation was performed in 94.8% (n = 18) of patients (median diameter 23 mm, interquartile range 22-24 mm), whereas postdilatation was required in 5 patients (26.3%). At 30 days, no moderate or greater paravalvular leak was observed and the mean transaortic gradient was 8 ± 2.32 mm Hg. Device success and intended valve performance were observed in all patients. Regarding secondary outcomes no all-cause death, stroke, conversion to surgery, or valve embolization was reported. A permanent pacemaker implantation was required in 1 patient (5.8%), displaying a right bundle branch block on the basal electrocardiogram. The promising results of the LIRA method in this subset of patients with annular dimensions exceeding the limits of the device sizing charts further supports the concept that, in BAV anatomy, the point of maximal constraint of the aortic valvar complex, where prosthesis anchoring occurs, is located at the raphe level (LIRA plane). In our study cohort, no valve embolization nor significant paravalvular leak was observed. Moreover, despite the large size of the prostheses used, the rate of permanent pacemaker implantation was strikingly low. Indeed, the undersized self-expanding valve with supra-annular anchoring will display a reduced interaction with the VBR. Consequently, the valve will exert decreased pressure on the membranous septum and thus on the conduction system (Fig. 1).