Non-vitamin K antagonist oral anticoagulants (NOACs) attenuate valvular calcification in patients with severe aortic stenosis

Abstract

Abstract Background In vitro studies has demonstrated that non-vitamin K antagonist oral anticoagulants (NOACs) down-regulated the expression of proteins responsible for valve calcification and inflammation in valve interstitial cells (VICs) cultures. Aims Our goal was to evaluate whether long-term anticoagulation with NOACs, including dabigatran (thrombin inhibitor), rivaroxaban and apixaban (FXa inhibitors) can impair the valvular calcification and inflammation in patients with severe AS. Methods We enrolled 38 patients with severe AS aged 70±5.9 years (mean gradient - PGmean: 50mmHg, max gradient - PGmax: 80mmHg), including 18 individuals with AS and concomitant atrial fibrillation taking NOACs for at least 3 years (51±10 months) (AS-NOACs group). Stenotic aortic valves were obtained during valve replacement surgery. Valvular calcification was estimated ex vivo using micro-computed tomography (micro-CT). Total volume of each calcification (bone volume - BV), the distribution of clods sizes of calcification parts (trabecular thickness -Tbth) and the volume of the hardest / most calcified part (hard CT) of each valve were assessed. Valvular expression of bone morphogenetic protein 2 (BMP-2) and NFκB was evaluated by immunostaining. The fluorescence intensity (FI) was computed as the ratio (%) of positively and negatively stained areas. Results AS patients did not differ from AS-NOACs participants with regard to demographic or risk factors. Micro-CT analysis showed 65.5% lower BV in AS-NOACs valves compared to patients not taking NOACs (87±47 mm3 vs. 252±146 mm3, p=0.0017). Of note, in AS-NOACs patients Tbth showed strong association with transvalvular pressure gradients (PGmean: r=0.76, p=0.033; PGmax: r=0.77, p=0.01), as clinical measures of the AS severity. The duration of anticoagulation was associated with the lower Tbth (from 0.35 mm for 60 months to 0.51 mm for 36 months, p<0.01), which suggests that long NOACs treatment changed the pattern of valvular calcification, leading to formation of calcium deposits with reduced volume. Moreover, in AS-NOACs patients BV correlated with hard CT (r=−0.69, p=0.027), suggesting that the lesions increase their volume but do not ossify. Valvular expression of BMP-2 and NFκB was 44% and 33% decreased in AS-NOACs patients, compared to those without such treatment and the expression of both proteins was positively associated (r=0.34, p=0.001). Moreover, in AS-NOACs patients the expression of BMP-2 and NFκB was observed mainly in the fibrosa layer of the leaflets, but not in the deeper layers of tissue, as in AS patients without NOACs treatment. Conclusions NOACs can inhibit the increase of valvular calcium volume and its ossification via suppressed NFkB expression. Our study may suggest that long-term anticoagulation with NOACs could slow down the rate of AS progression, at least in patients with an indication for anticoagulant therapy. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Polish National Science Centre