Impact of Nodular Calcifications in the Aortic Annulus and Left Ventricular Outflow Tract on TAVI Outcome with New-Generation Devices

Abstract

Background: The impact of nodular calcifications in left ventricular outlow tract (LVOT) and aortic annulus on the procedural outcome of transcatheter aortic valve implantation (TAVI) with new-generation devices is yet to be elucidated. Similarly, computational simulations may provide a novel insight into the biomechanical features of TAVI devices and their interaction with nodular calcifications.

Methods: This retrospective single-center study included 232 patients submitted to TAVI with Evolut-R (53.4%), Portico (33.6%) and Lotus (13.0%) devices with available preoperative computed tomography (CT) angiography and evidence of nodular calcifications in aortic annulus and/or LVOT. Calcification severity was defined $\ge$ moderate in presence of at least two nodules or one nodule $\le$ 5 mm. Three virtual simulation models of aortic root presenting a nodular calcification of increasing size were implemented. Stress distribution, stent-root contact area and paravalvular orifice area were computed.

Results: At least moderate calcifications were found in 123 (53.0%) patients, with no sex differences. Among the $\ge$ moderate calcification group, lower device success rate was evident (87.8% vs. 95.4%; p = 0.039). Higher rates of $\ge$ moderate paravalvular leak (PVL) (11.4% vs. 3.7%; p = 0.028) and vascular complications (9.8% vs. 2.8%; p = 0.030) were also observed. Among the Evolut-R group, higher rates of at $\ge$ moderate PVL (12.1%) were observed compared to Portico (3.8%; p = 0.045) and Lotus (0.0%; p = 0.044) groups. Calcification of both annulus and LVOT (odds ratio [OR] 0.105; p = 0.023) were independent predictors of device success. On computational simulations, Portico exhibited homogeneous stress distribution by increasing calfications and overall a larger paravalvular orifice areas compared to Evolut-R and Lotus. Evolut-R showed higher values of average stress than Portico, although with a more dishomogeneous distribution leading to greater paravalvular orifice areas by severe calcifications. Lotus showed overall small paravalvular orifice areas, with no significant increase across the three models.

Conclusions: At least moderate nodular calcifications in the annulus/LVOT region significantly affected TAVI outcome, as they were independent predictors of device success. Lotus and Portico seemed to perform better than Evolut-R as for device success and $\ge$ moderate PVL. Computational simulations revealed unique biomechanical features of the investigated devices in terms of stent compliance and radial force.

Keywords: computational simulation; device success; nodular calcification; paravalvular leak; transcatheter aortic valve implantation.

Fig. 1.

Evaluation of calcification severity at CT angiography. Mild calcification severity: a calcified nodule (max diameter 2.25 mm) in the annulus (A); LVOT is free from calcifications (C); $\ge$moderate calcification severity: two nodular calcifications with a max diameter of 7.5 mm and of 6 mm respectively are present at the annulus (B) and LVOT (D).

Fig. 2.

Nodular calcification model. Example of TAVI simulation with Lotus valve in a 0.25 IE aortic root having nodular calcifications of increasing size (maximum diameter: mild 8 mm, moderate 12 mm, severe 14 mm).

Fig. 3.

Stent-rott interaction model. (A) Stent-root interaction area: contact area between the stent and the internal surface of the aortic root. (B) Von Mises stress map: distribution of stress values in the inner aortic root. (C) Paravalvular orifice area: definition of a cutting plane $\mathrm{\Omega }$ passing through the sino-tubular junction and cross-section of the model at the level of the plane to identify paravalvular orifices.

Fig. 4.

In-hospital outcomes. Differences between Evolut-R, Portico and Lotus valves groups by $\ge$moderate PVL (A) and by device success (B) rate. Higher rates of $\ge$moderate PVL were observed in the Evolut-R group, compared both to Portico and Lotus patients (A). On the other hand, Evolut-R group showed lower device success rates compared to the Lotus group (p = 0.043), but did not reach statistical significancy with the Portico group (p = 0.072) (B).

Fig. 5.

Simulation analysis. (A) Stent-root contact area, (B) average stress, (C) stress distribution and (D) paravalvular orifice area in relation to nodular calcific burden and valve type.