Characteristics and outcomes of patients with eccentric aortic valve calcification undergoing transcatheter aortic valve implantation

Background: Transcatheter aortic valve implantation (TAVI) has become the standard therapy for most patients with aortic valve stenosis. Eccentric aortic valve calcification may pose a challenge during TAVI by interfering with precise valve implantation and full valve expansion. This study aims to compare definitions for eccentric aortic valve calcification and to evaluate the impact of these on the clinical characteristics and outcomes of patients undergoing TAVI.

Methods: 501 patients who underwent transfemoral TAVI between February 2017 and June 2023 with a tricuspid aortic valve were included in the analysis. All patients had severe and symptomatic aortic stenosis. We analysed preprocedural cCT-scans using 3mensio Structural Heart software (3mensio Medical Imaging BV) and measured the calcium volume of each individual aortic valve cusp. We compared ∆ Calcium Score (CS) (Nakajima et al. 2021), Eccentricity Index (EI) (Li et al. 2021) and developed a new definition to combine the strengths of the two tested scores.

Results: Comparing CS and EI we found that EI mainly classified patients with overall low total calcium as eccentric. Since CS only considered the most and the lowest calcified cusp it included lots of patients where two of the cusps were heavily calcified. The EI eccentric group had greater aortic valve areas (AVA) and lower valve gradients (AVG) in baseline characteristics compared to the symmetric group (AVG median 30.5 vs. 36 mmHg, p = 0.001; AVA ø 0.83 cm vs. 0.71 cm, p = 0.005). The CS eccentric group was younger (ø age 82.56 a vs. 81.63 a, p = 0.037), had less procedural atrial fibrillation (34 % vs. 52 %, p < 0.001), less CAD and less dyslipidaemia. The observed differences in AVA and AVG for EI were not significant for CS. The EI groups had no differences in the outcome. We found a better survival (1-year survival 91 % vs. 85 %, p = 0.003) and higher rates of vascular complications and bleeding for CS. To overcome the disadvantages of the CS and EI we propose a definition that considers the total level of calcification and the distribution based on a graph drawn through the visualised data. We defined a function for a cut-off that marked patients over f(x) = 1/(0.005*x+1.5) +0.34 as eccentric. (x = calcium amount most calcified cusp/ total calcium amount). In baseline characteristics we found less preprocedural atrial fibrillation for the eccentric group (34% vs. 46%, p = 0.024). Despite the procedural outcome revealed a higher rate of new conduction disturbances and arrhythmias (50 % vs. 39 %, p = 0.034), the eccentric group had a better survival rate (1- year survival 95 % vs. 85 %, p = 0.046). We found no significant differences in permanent pacemaker implantations or paravalvular leakage.

Conclusion: CS and EI take heterogenous patient groups into account. The EI excludes patients with higher total calcium while CS considers them especially by not respecting a second heavily calcified cusp. Both scores do not consider the total calcification of the valve.  We propose a new definition to increase the importance of a high total calcium volume and exclude patients with overall low calcium. Our results indicate that eccentric aortic valve calcification may be a risk factor for new conduction disturbances and arrythmias after TAVI. However, the 1-year survival of these patients was better. Eccentric calcification is most likely a common finding in aortic valve stenosis with low impact on the outcome after TAVI.