Aortic Valve Calcium Score Spectrum Identifies Bimodal Outcomes for Transcatheter Aortic Valve Implantation: Insights From the AMTRAC Registry

BACKGROUND: Degenerative calcification is the primary mechanism underlying severe aortic stenosis; however, some patients with hemodynamically severe aortic stenosis have low aortic valve calcium scores (AVCS), suggesting heterogeneous disease processes. This study aimed to evaluate the clinical characteristics and outcomes across the spectrum of AVCS. METHODS: We performed a retrospective analysis of the AMTRAC (Aortic+Mitral Transcatheter Valve) registry, including 3766 patients with severe aortic stenosis who underwent transcatheter aortic valve implantation across 16 centers mainly in Europe (2013–2024). Patients were stratified into three groups of low, high, or very high based on their AVCS. The primary end point was 3-year mortality. Secondary end points included periprocedural outcomes (Valve Academic Research Consortium-3) and posttranscatheter aortic valve implantation hemodynamics. RESULTS: Patients with low AVCS more frequently presented with low-gradient aortic stenosis and advanced New York Heart Association classes. At 3 years, mortality displayed a bimodal pattern in association with AVCS spectrum: 30.5% in the low, 26.5% in the high, and 31.3% in the very-high AVCS group (P<0.05). Paravalvular leak greater than moderate increased with AVCS severity (0.5%, 0.9%, 1.9%, for low, high, and very-high AVCS, respectively; P<0.01). The risk for stroke and permanent pacemaker implantation were also higher in the very-high AVCS group compared with the low/high AVCS groups (stroke: 4.1%, 1.4%, 2.4%; permanent pacemaker: 21.2%, 14.7%, 14.2%; for very-high, low, high, respectively; P<0.05 for both). CONCLUSIONS: Low AVCS defines a unique phenotype marked by predominant fibrosis, advanced symptoms, and increased mortality despite fewer procedural complications. In contrast, very-high AVCS is linked to higher procedural risk, more bicuspid valves, and increased mortality. These insights challenge calcification-based criteria and support incorporating fibrosis assessment into treatment strategies.