Abstract 14760: Evaluation of High Molecular Weight von Willebrand Factor Multimer Levels in Patients Undergoing Transcatheter Aortic Valve Replacement

Introduction: Abnormal levels of circulating high molecular weight von Willebrand Factor multimers (HMWFm) are observed in patients with severe aortic stenosis (AS). Evidence suggests factor recovery after successful valve replacement. We aim to confirm factor recovery after transcatheter aortic valve replacement (TAVR), to determine the post-implantation time point when patients first demonstrate factor recovery and to observe association between degree of para-aortic regurgitation (PAR) and factor recovery. We also aim to evaluate correlation between HMWFm assay using traditional means (immunoblot) and a novel enzyme-linked immunosorbent collagen binding assay (CBA). Methods: Fifteen patients with severe AS underwent TAVR. Plasma was collected at multiple time points: pre-TAVR (T1), immediately after valve deployment (T2), post-operative day one (T3) and prior to discharge (T4). Levels of HMWFm were analyzed using immunoblot and CBA. PAR was assessed using vena contracta area (VCA) and longitudinal jet length methods. Results: Mean population age was 82.6 years. Baseline mean transvalvular gradient/aortic valve area (AVA) was 38.5 mmHg/0.88 cm2 respectively. After TAVR, mean gradient/AVA was 5.6 mmHg/2.7 cm2 respectively. PAR was classified as moderate in 4/14 and severe in 2/14 patients. Kappa statistic for agreement between both methods of PAR assessment was 0.32. HMWFm levels initially decreased at T2, but increased by T3. Using Immunoblot, HMWFm levels were significantly higher at T4 compared to T1. Using CBA, levels were significantly higher at T3 and T4 compared to T1. Stratification by degree of PAR demonstrated a trend towards greater HMWFm recovery in patients without PAR versus those with PAR. Post-TAVR NYHA symptoms did not significantly effect levels. Conclusions: We confirm that HMWFm levels improve after successful TAVR. Unlike a recent study by Belle et al (Circulation, 2016), we do not demonstrate immediate HMWFm recovery, rather only by post-operative day one. We demonstrate feasibility of CBA as a faster substitute to immunoblot method for factor analysis. We demonstrate intriguing differences in factor recovery between PAR strata, suggesting that levels of factor recovery are influenced by degree of PAR.