Flavien Vincent

A novel ELISA-based diagnosis of acquired von Willebrand disease with increased VWF proteolysis

Von Willebrand disease-type 2A (VWD-2A) and acquired von Willebrand syndrome (AVWS) due to aortic stenosis (AS) or left ventricular assist device (LVAD) are associated with an increased proteolysis of von Willebrand factor (VWF). Analysis of VWF multimeric profile is the most sensitive way to assess such increased VWF-proteolysis. However, several technical aspects hamper a large diffusion among routine diagnosis laboratories. This makes early diagnosis and early appropriate care of increased proteolysis challenging. In this context of unmet medical need, we developed a new ELISA aiming a quick, easy and reliable assessment of VWF-proteolysis. This ELISA was assessed successively in a LVAD-model, healthy subjects (n=39), acquired TTP-patients (n=4), VWD-patients (including VWD-2A(IIA), n=22; VWD-2B, n=26; VWD-2A(IIE), n=21; and VWD-1C, n=8) and in AVWS-patients (AS, n=9; LVAD, n=9; and MGUS, n=8). A standard of VWF-proteolysis was specifically developed. Extent of VWF-proteolysis was expressed as relative percentage and as VWF proteolysis/VWF:Ag ratio. A speed-dependent increase in VWF-proteolysis was assessed in the LVAD model whereas no proteolysis was observed in TTP-patients. In VWD-patients, VWF-proteolysis was significantly increased in VWD-2A(IIA) and VWD-2B and significantly decreased in VWD-2A(IIE) versus controls (p<u20090.0001). In AVWS-patients, VWF-proteolysis was significantly increased in AS- and LVAD-patients compared to controls (p<u20090.0001) and not detectable in MGUS-patients. A significant increase in VWF-proteolysis was detected as soon as three hours after LVAD implantation (p<u20090.01). In conclusion, we describe a new ELISA allowing a rapid and accurate diagnosis of VWF-proteolysis validated in three different clinical situations. This assay represents a helpful alternative to electrophoresis-based assay in the diagnosis and management of AVWS with increased VWF-proteolysis.

CT-ADP Point-of-Care Assay Predicts 30-Day Paravalvular Aortic Regurgitation and Bleeding Events following Transcatheter Aortic Valve Replacement

BACKGROUNDnParavalvular aortic regurgitation (PVAR) remains a frequent postprocedural concern following transcatheter aortic valve replacement (TAVR). Persistence of flow turbulence results in the cleavage of high-molecular-weight von Willebrand multimers, primary haemostasis dysfunction and may favour bleedings. Recent data have emphasized the value of a point-of-care measure of von Willebrand factor-dependent platelet function (closure time [CT] adenosine diphosphate [ADP]) in the monitoring of immediate PVAR. This study examined whether CT-ADP could detect PVAR at 30 days and bleeding complications following TAVR.nnnMETHODSnCT-ADP was assessed at baseline and the day after the procedure. At 30 days, significant PVAR was defined as a circumferential extent of regurgitation more than 10% by transthoracic echocardiography. Events at follow-up were assessed according to the Valve Academic Research Consortium-2 consensus classification.nnnRESULTSnSignificant PVAR was diagnosed in 44 out of 219 patients (20.1%). Important reduction of CT-ADP could be found in patients without PVAR, contrasting with the lack of CT-ADP improvement in significant PVAR patients. By multivariate analysis, CT-ADPu2009>u2009180u2009seconds (hazard ratio [HR]: 5.1, 95% confidence interval [CI]: 2.5-10.6; pu2009<u20090.001) and a self-expandable valve were the sole independent predictors of 30-day PVAR. At follow-up, postprocedural CT-ADP >180u2009seconds was identified as an independent predictor of major/life-threatening bleeding (HR: 1.7, 95% CI [1.0-3.1]; pu2009=u20090.049). Major/life-threatening bleedings were at their highest levels in patients with postprocedural CT-ADPu2009>u2009180u2009seconds (35.2 vs. 18.8%; pu2009=u20090.013).nnnCONCLUSIONnPostprocedural CT-ADPu2009>u2009180u2009seconds is an independent predictor of significant PVAR 30 days after TAVR and may independently contribute to major/life-threatening bleedings.

Arterial Pulsatility and Circulating von Willebrand Factor in Patients on Mechanical Circulatory Support

BACKGROUNDnThe main risk factor for bleeding in patients with continuous-flow mechanical circulatory support (CF-MCS) is the acquired von Willebrand factor (VWF) defect related to the high shear-stress forces developed by these devices. Although a higher bleeding rate has been reported in CF-MCS recipients who had reduced pulsatility, the relation between pulsatility and the VWF defect has never been studied.nnnOBJECTIVESnThe purpose of this study was to investigate the relation between pulsatility and VWF under CF-MCS.nnnMETHODSnWe assessed the effect of 2 CF-MCS on VWF multimer degradation in a mock circulatory loop (model 1). Using these devices, we investigated in a dose-effect model (model 2) 3 levels of pulsatility in 3 groups of swine. In a cross-over model (model 3), we studied the effects of sequential changes of pulsatility on VWF. We reported the evolution of VWF multimerization in a patient undergoing serial CF-MCS and/or pulsatile-MCS.nnnRESULTSnWe demonstrated the proteolytic degradation of VWF multimers by high shear CF-MCS in a circulatory loop without pulsatility. We observed both in swine models and in a patient that the magnitude of the VWF degradation is modulated by the pulsatility level in the high shear-stress level condition, and that the restoration of pulsatility is a trigger for the endothelial release of VWF.nnnCONCLUSIONSnWe demonstrated that the VWF defect reflects the balance between degradation induced by the shear stress and the endothelial release of new VWF triggered by the pulsatility. This modulation of VWF levels could explain the relationship between pulsatility and bleeding observed in CF-MCS recipients. Preservation of pulsatility may be a new target to improve clinical outcomes of patients.

Real-Time Monitoring of von Willebrand Factor in the Catheterization Laboratory: The Seatbelt of Mini-Invasive Transcatheter Aortic Valve Replacement?

Significant paravalvular regurgitation (PVR) remains a relatively frequent (4% to 9%) and deleterious complication of transcatheter aortic valve replacement (TAVR), even with the latest generation of bioprosthesis. Although mini-invasive TAVR without general anesthesia or transesophageal echocardiography (TEE) is progressively becoming the predominant approach, identification and grading of PVR in the catheterization laboratory remain an important and challenging clinical issue. The authors discuss how a recently reported blood biomarker reflecting the von Willebrand factor activity, that is, the closure time with adenosine diphosphate, can be successfully applied during the TAVR procedure to detect and monitor PVR in real time, with an excellent negative predictive value. This point-of-care testing performed directly in the catheterization laboratory may improve the diagnosis of PVR and rationalize the decision of whether or not to perform corrective measures. They further discuss how such a test could be a substitute for the multimodal approach combining TEE, hemodynamics, and cine-angiography, and help to secure the transition to the mini-invasive approach and facilitate the expanding indications of less invasive procedures to lower-risk patients without jeopardizing procedural and clinical outcomes.

Outcomes of transcatheter mitral valve replacement for degenerated bioprostheses, failed annuloplasty rings, and mitral annular calcification

AimsnWe sought to evaluate the outcomes of transcatheter mitral valve replacement (TMVR) for patients with degenerated bioprostheses [valve-in-valve (ViV)], failed annuloplasty rings [valve-in-ring (ViR)], and severe mitral annular calcification [valve-in-mitral annular calcification (ViMAC)].nnnMethods and resultsnFrom the TMVR multicentre registry, procedural and clinical outcomes of ViV, ViR, and ViMAC were compared according to Mitral Valve Academic Research Consortium (MVARC) criteria. A total of 521 patients with mean Society of Thoracic Surgeons score of 9.0u2009±u20097.0% underwent TMVR (322 patients with ViV, 141 with ViR, and 58 with ViMAC). Trans-septal access and the Sapien valves were used in 39.5% and 90.0%, respectively. Overall technical success was excellent at 87.1%. However, left ventricular outflow tract obstruction occurred more frequently after ViMAC compared with ViR and ViV (39.7% vs. 5.0% vs. 2.2%; Pu2009<u20090.001), whereas second valve implantation was more frequent in ViR compared with ViMAC and ViV (12.1% vs. 5.2% vs. 2.5%; Pu2009<u20090.001). Accordingly, technical success rate was higher after ViV compared with ViR and ViMAC (94.4% vs. 80.9% vs. 62.1%; Pu2009<u20090.001). Compared with ViMAC and ViV groups, ViR group had more frequent post-procedural mitral regurgitation ≥moderate (18.4% vs. 13.8% vs. 5.6%; Pu2009<u20090.001) and subsequent paravalvular leak closure (7.8% vs. 0.0% vs. 2.2%; Pu2009=u20090.006). All-cause mortality was higher after ViMAC compared with ViR and ViV at 30u2009days (34.5% vs. 9.9% vs. 6.2%; log-rank Pu2009<u20090.001) and 1u2009year (62.8% vs. 30.6% vs. 14.0%; log-rank Pu2009<u20090.001). On multivariable analysis, patients with failed annuloplasty rings and severe MAC were at increased risk of mortality after TMVR [ViR vs. ViV, hazard ratio (HR) 1.99, 95% confidence interval (CI) 1.27-3.12; Pu2009=u20090.003; ViMAC vs. ViV, HR 5.29, 95% CI 3.29-8.51; Pu2009<u20090.001].nnnConclusionnThe TMVR provided excellent outcomes for patients with degenerated bioprostheses despite high surgical risk. However, ViR and ViMAC were associated with higher rates of adverse events and mid-term mortality compared with ViV.

von Willebrand Factor for Aortic Valve Intervention: From Bench to Real-Time Bedside Assessment

VWF (von Willebrand factor ) is a circulating multimeric blood glycoprotein. VWF plays a major role in primary hemostasis by promoting the adhesion of platelets to subendothelial collagen at sites of vascular damage and thereby promoting platelet aggregation. VWF is synthesized in endothelial cells and megakaryocytes. The VWF units dimerize and are transported into the Golgi apparatus, where disulfide bonds are formed leading to formation of VWF multimers. This large subunit combination is required to support its hemostatic function. nnVWF has the unique features to be circulating in an inactive coiled form, hiding binding domains for platelet receptors and subendothelial collagen. At the site of vascular injury, VWF binds to the exposed collagen and unfolds. Once VWF is unfolded, the VWF A1 domain is exposed allowing the binding of platelets via GP Ib (glycoprotein IB) receptor. After platelet activation, GP IIb/IIIa (glycoprotein IIb/IIIa) receptor becomes able to bind VWF C1 domain. The VWF conformation and activity is intimately related to shear conditions and blood flow. At high shear rate (beyond 10–15 pN), it becomes unfolded exposing binding sites but also the cleavage site in VWF A2 domain for ADAMTS13 (adisintegrin-like and metalloprotease thrombospondin) protease that conducts to its proteolysis. Overall, these environmental changes generate the modification of the conformation of VWF …