Antoine Rauch

Von Willebrand Factor Multimers during Transcatheter Aortic-Valve Replacement

BACKGROUND Postprocedural aortic regurgitation occurs in 10 to 20% of patients undergoing transcatheter aortic-valve replacement (TAVR) for aortic stenosis. We hypothesized that assessment of defects in high-molecular-weight (HMW) multimers of von Willebrand factor or point-of-care assessment of hemostasis could be used to monitor aortic regurgitation during TAVR. METHODS We enrolled 183 patients undergoing TAVR. Patients with aortic regurgitation after the initial implantation, as identified by means of transesophageal echocardiography, underwent additional balloon dilation to correct aortic regurgitation. HMW multimers and the closure time with adenosine diphosphate (CT-ADP), a point-of-care measure of hemostasis, were assessed at baseline and 5 minutes after each step of the procedure. Mortality was evaluated at 1 year. A second cohort (201 patients) was studied to validate the use of CT-ADP in order to identify patients with aortic regurgitation. RESULTS After the initial implantation, HMW multimers normalized in patients without aortic regurgitation (137 patients). Among the 46 patients with aortic regurgitation, normalization occurred in 20 patients in whom additional balloon dilation was successful but did not occur in the 26 patients with persistent aortic regurgitation. A similar sequence of changes was observed with CT-ADP. A CT-ADP value of more than 180 seconds had sensitivity, specificity, and negative predictive value of 92.3%, 92.4%, and 98.6%, respectively, for aortic regurgitation, with similar results in the validation cohort. Multivariable analyses showed that the values for HMW multimers and CT-ADP at the end of TAVR were each associated with mortality at 1 year. CONCLUSIONS The presence of HMW-multimer defects and a high value for a point-of-care hemostatic test, the CT-ADP, were each predictive of the presence of aortic regurgitation after TAVR and were associated with higher mortality 1 year after the procedure. (Funded by Lille 2 University and others; ClinicalTrials.gov number, NCT02628509.).

von Willebrand Factor as a Biological Sensor of Blood Flow to Monitor Percutaneous Aortic Valve Interventions

RATIONALE Percutaneous aortic valve procedures are a major breakthrough in the management of patients with aortic stenosis. Residual gradient and residual aortic regurgitation are major predictors of midterm and long-term outcome after percutaneous aortic valve procedures. We hypothesized that (1) induction/recovery of high molecular weight (HMW) multimers of von Willebrand factor defect could be instantaneous after acute changes in blood flow, (2) a bedside point-of-care assay (platelet function analyzer-closure time adenine DI-phosphate [PFA-CADP]), reflecting HMW multimers changes, could be used to monitor in real-time percutaneous aortic valve procedures. OBJECTIVE To investigate the time course of HMW multimers changes in models and patients with instantaneous induction/reversal of pathological high shear and its related bedside assessment. METHODS AND RESULTS We investigated the time course of the induction/recovery of HMW multimers defects under instantaneous changes in shear stress in an aortic stenosis rabbit model and in patients undergoing implantation of a continuous flow left ventricular assist device. We further investigated the recovery of HMW multimers and monitored these changes with PFA-CADP in aortic stenosis patients undergoing transcatheter aortic valve implantation or balloon valvuloplasty. Experiments in the aortic stenosis rabbit model and in left ventricular assist device patients demonstrated that induction/recovery of HMW multimers occurs within 5 minutes. Transcatheter aortic valve implantation patients experienced an acute decrease in shear stress and a recovery of HMW multimers within minutes of implantation which was sustained overtime. In patients with residual high shear or with residual aortic regurgitation, no recovery of HMW multimers was observed. PFA-CADP profiles mimicked HMW multimers recovery both in transcatheter aortic valve implantation patients without aortic regurgitation (correction) and transcatheter aortic valve implantation patients with aortic regurgitation or balloon valvuloplasty patients (no correction). CONCLUSIONS These results demonstrate that variations in von Willebrand factor multimeric pattern are highly dynamic, occurring within minutes after changes in blood flow. It also demonstrates that PFA-CADP can evaluate in real time the results of transcatheter aortic valve procedures.

M1 and M2 macrophage proteolytic and angiogenic profile analysis in atherosclerotic patients reveals a distinctive profile in type 2 diabetes

This study aimed to investigate atherosclerotic mediators’ expression levels in M1 and M2 macrophages and to focus on the influence of diabetes on M1/M2 profiles. Macrophages from 36 atherosclerotic patients (19 diabetics and 17 non-diabetics) were cultured with interleukin-1β (IL-1β) or IL-4 to induce M1 or M2 phenotype, respectively. The atherosclerotic mediators’ expression was evaluated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). The results showed that M1 and M2 macrophages differentially expressed mediators involved in proteolysis and angiogenesis processes. The proteolytic balance (matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1), MMP-9/plasminogen activator inhibitor-1 (PAI-1) and MMP-9/tissue factor pathway inhibitor-2 (TFPI-2) ratios) was higher in M1 versus M2, whereas M2 macrophages presented higher angiogenesis properties (increased vascular endothelial growth factor/TFPI-2 and tissue factor/TFPI-2 ratios). Moreover, M1 macrophages from diabetics displayed more important proangiogenic and proteolytic activities than non-diabetics. This study reveals that M1 and M2 macrophages could differentially modulate major atherosclerosis-related pathological processes. Moreover, M1 macrophages from diabetics display a deleterious phenotype that could explain the higher plaque vulnerability observed in these subjects.

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

BACKGROUND Paravalvular 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. METHODS CT-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. RESULTS Significant 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-ADP > 180 seconds (hazard ratio [HR]: 5.1, 95% confidence interval [CI]: 2.5-10.6; p < 0.001) and a self-expandable valve were the sole independent predictors of 30-day PVAR. At follow-up, postprocedural CT-ADP >180 seconds was identified as an independent predictor of major/life-threatening bleeding (HR: 1.7, 95% CI [1.0-3.1]; p = 0.049). Major/life-threatening bleedings were at their highest levels in patients with postprocedural CT-ADP > 180 seconds (35.2 vs. 18.8%; p = 0.013). CONCLUSION Postprocedural CT-ADP > 180 seconds 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

BACKGROUND The 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. OBJECTIVES The purpose of this study was to investigate the relation between pulsatility and VWF under CF-MCS. METHODS We 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. RESULTS We 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. CONCLUSIONS We 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.

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. VWF 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 …

Subacute right heart failure revealing three simultaneous causes of post-embolic pulmonary hypertension in metastatic dissemination of breast cancer

A 72‐year‐old woman with history of breast cancer only treated surgically was referred to our department for pulmonary hypertension (PH) suspicion. Echocardiogram revealed elevated right ventricular systolic pressure. Computed tomography (CT) angiogram showed no pulmonary embolism (PE), but lung scan revealed two ventilation‐perfusion mismatch areas. Right cardiac catheterization established precapillary PH. Despite treatment with PH specific therapy (sildenafil, ambrisentan, and epoprostenol), her condition worsened rapidly with acute right heart failure (RHF). She died 22 days after admission. Post‐mortem microscopic examination showed a rare combination of PH etiologies consistent with metastasis of breast cancer in pulmonary vasculature including the rare pulmonary tumour thrombotic microangiopathy (PTTM).

Facteur von Willebrand et maladie de Willebrand : nouvelles approches

Resume Le facteur von Willebrand (VWF) est une glycoproteine multimerique qui joue un role essentiel dans la formation du thrombus plaquettaire en presence de forces de cisaillement elevees. La maladie de Willebrand (MW) est une pathologie hemorragique, d’origine constitutionnelle ou acquise, resultant d’un deficit quantitatif ou qualitatif en VWF, et qui se caracterise par une grande heterogeneite clinique et biologique, temoignant de la physiologie complexe du VWF. Si de nombreux progres ont ete realises concernant la comprehension des mecanismes physiopathologiques sous-jacents a la MW, son diagnostic reste difficile et justifie un avis specialise. Au-dela de son role dans l’hemostase, le VWF pourrait jouer un role actif dans l’inflammation, l’angiogenese, l’apoptose et la proliferation cellulaire.