Background:
Aortic stenosis (AS) is driven by progressive inflammatory and fibro-calcific processes. While presence of AS has been associated with an increased prevalence of cardiac amyloidosis, localized amyloid deposits within the aortic valve (AV) tissue have been ascribed to chronic damage, old thrombotic material, and scarring via external stimuli in calcifying forms of AS. However, morphological AV phenotyping regarding amyloid deposits, mineralization and inflammation has not been investigated thoroughly.

Methods:
We retrospectively analyzed 118 consecutive patients with symptomatic AS undergoing AV replacement. Patients were stratified by positive amyloid deposition into two groups of amyloid+ (n=78) and amyloid- (n=40) patients. The primary combined endpoint was defined as all-cause death, stroke, myocardial infarction, and heart-failure related hospitalization during one year follow up (FU).

Results:
Histological analysis of AVs revealed positive amyloid deposition in 78 patients. We found typical distribution patterns of calcification, which were significantly different between both groups (p<0.05). Most interestingly, amyloid+ deposition was typically found at the edge of calcifying nodules with a thickness > 1mm. 91% of amyloid+ patients showed large calcification areas affecting more than 50% of the AV cusps (p<0.05). Only 35% of amyloid- patients showed calcifying areas with a thickness >1 mm. Patients without amyloid deposition showed significantly higher amounts of valve resident cells and enhanced infiltrating inflammatory cells within the AV (p<0.05). Degree of calcification and amyloid+ area correlated significantly (r=0.591, p < 0.0001) in our patient cohort. Amyloid+ patients were significantly more often on ASA therapy at baseline (p=0.004) and had significantly more often concomitant coronary artery disease (p=0.018). Furthermore, calcification and amyloid+ area were associated with AVA (r=0.396, p=0.041). 18/118 patients reached the combined endpoint during one year FU. Interestingly, all-cause mortality was significantly associated with absence of amyloid deposition within AV tissue. Elevated CRP levels, an increased Euro Score II, impaired LVEF, and hypercholesterolemia were also significantly associated with mortality during FU. 5 out of 6 patients who died during FU belonged to the amyloid- group (p=0.009). Kaplan-Meier estimates revealed that amyloid- patients showed a significantly higher mortality (log rank 10.398, p=0.001), while there was no difference regarding the combined endpoint in both groups. Furthermore, Kaplan Meier estimates also showed that there was a significant association of the occurrence of all-cause mortality in relation to presence of coronary artery disease in combination with valvular amyloid+ deposition (log rank 10.528, p=0.015). Interestingly, absence of amyloid deposition remained independently associated with adverse outcome in cox regression analysis.

Conclusion:
Our findings suggest that amyloid deposition within AV tissue is associated with degree of calcification of the affected AV indicating a chronically calcifying valvular phenotype rather than a rapid progressive inflammatory valvular phenotype. Absence of amyloid deposition within AVs is associated with increased valvular cellularity, which might mirror an inflammatory, accelerated AV phenotype. Further studies are needed to elucidate underlying mechanisms of amyloid deposition and its prognostic impact.