A nanobody against the VWF A3 domain detects ADAMTS13-induced proteolysis in congenital and acquired VWD

von Willebrand factor (VWF) is a multimeric protein, the size of which is regulated via ADAMTS13-mediated proteolysis within the A2 domain. We aimed to isolate nanobodies distinguishing between proteolyzed and non-proteolyzed VWF, leading to the identification of a nanobody (designated KB-VWF-D3.1) targeting the A3 domain, the epitope of which overlaps the collagen-binding site. Although KB-VWF-D3.1 binds with similar efficiency to dimeric and multimeric derivatives of VWF, binding to VWF was lost upon proteolysis by ADAMTS13, suggesting that proteolysis in the A2 domain modulates exposure of its epitope in the A3 domain. We therefore used KB-VWF-D3.1 to monitor VWF degradation in plasma samples. Spiking experiments showed that a loss of 10% intact VWF could be detected using this nanobody. By comparing plasma from volunteers to that from congenital von Willebrand disease (VWD) patients, intact-VWF levels were significantly reduced for all VWD types, and most severely in VWD type 2A-group 2, in which mutations promote ADAMTS13-mediated proteolysis. Unexpectedly, we also observed increased proteolysis in some patients with VWD type 1 and VWD type 2M. A significant correlation (r = 0.51, P < .0001) between the relative amount of high-molecular weight multimers and levels of intact VWF was observed. Reduced levels of intact VWF were further found in plasmas from patients with severe aortic stenosis and patients receiving mechanical circulatory support. KB-VWF-D3.1 is thus a nanobody that detects changes in the exposure of its epitope within the collagen-binding site of the A3 domain. In view of its unique characteristics, it has the potential to be used as a diagnostic tool to investigate whether a loss of larger multimers is due to ADAMTS13-mediated proteolysis.

BAlloon expandable vs. SElf expanding transcatheter vaLve for degenerated bioprosthesIs: design and rationale of the BASELINE trial

BACKGROUND

Surgical aortic valve bioprostheses may degenerate over time and require redo intervention. Transcatheter aortic valve replacement (TAVR) is a less invasive alternative to redo surgery. The BAlloon Expandable vs. SElf Expanding Transcatheter VaLve for Degenerated BioprosthesIs (BASELINE) trial was designed to compare the performance of the balloon-expandable SAPIEN-3 Ultra and the self-expanding EVOLUT PRO+ valve systems in symptomatic patients with a failing surgical bioprosthesis.

METHODS

The BASELINE trial is an investigator-initiated, non-funded, prospective, randomized, open-label, superiority trial enrolling a total of 440 patients in up to 50 sites in 12 countries in Europe and North-America. The primary endpoint is device success at 30-days defined by the Valve Academic Research Consortium-3 Criteria as the composite of technical success, freedom from mortality, freedom for surgery or intervention related to the device or to a major vascular or access-related or cardiac structural complication with an intended performance of the valve (mean gradient <20 mmHg and less than moderate aortic regurgitation). The co-primary endpoint at 1 year is defined as the composite of all-cause death, disabling stroke, rehospitalization for heart failure or valve related problems. Independent Core Laboratories will conduct uniform analyses of echocardiography (pre-, post-, 1-year post-procedure), multi-sliced computed tomography (pre-, and if available post-procedure) and cine-fluoroscopy studies.

CONCLUSIONS

The BASELINE trial is a head-to-head comparative trial investigating the 2 most used contemporary transcatheter heart valves for the treatment of a failing surgical aortic bioprosthesis. (ClinicalTrials.gov number NCT04843072).

Outcomes of transfemoral balloon expandable transcatheter aortic valve implantation: Comparison of two subsequent valve generations

BACKGROUND

The SAPIEN 3 (S3) addresses several limitations of the SAPIEN XT (SXT) for the performance of transfemoral (TF-) balloon expandable transcatheter aortic valve implantation (TAVI).

OBJECTIVES

We aimed to determine whether their altered features translate into improved outcomes in a real-world TF-TAVI patient population.

METHODS

Data for 3,314 patients were extracted from the European registries SOURCE-XT and SOURCE-3. Patients were propensity-score (PS) matched (n = 1,169/group).

RESULTS

In the PS matched comparison, device success was higher in the S3 (99.2%) compared to the SXT group (98.2%; p = .04). S3 patients experienced a lower rate of procedural death (0.7 vs. 2.6%; p = .0004), moderate/severe paravalvular leakage (PVL; 1.4 vs. 5.5%; p < .0001), and procedure-related stroke (1.2 vs. 2.4%; p = .04) while higher rates of mean aortic valve gradients ≥20 mmHg, and new permanent pacemaker implantations were seen. At 30 days a lower rate of all-cause mortality was seen (2.1% vs. 4.3%; p = .003), which was preserved after 1 year (10.7% vs. 14.9%; p = .002). A Cox regression predicting 1-year mortality resulted in a hazard ratio of 0.684 in favor of S3 (p = .0026). The same was true of stroke (2.8% vs. 5.7%; p = .0007), and moderate/severe PVL (2.7 vs. 7.3%; p = .0002) at 1 year. The rate of new pacemaker implantations (13.6% vs. 9.5%; p = .001) and NYHA III/IV (12.8 vs. 8.6%; p = .004) was higher with the S3.

CONCLUSIONS

The improved features of the S3 appear to translate into improved survival and reduced rates of adverse complications, with the exception of a higher rate of new pacemaker implantations.

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< 0.0001). In AVWS-patients, VWF-proteolysis was significantly increased in AS- and LVAD-patients compared to controls (p< 0.0001) and not detectable in MGUS-patients. A significant increase in VWF-proteolysis was detected as soon as three hours after LVAD implantation (p< 0.01). 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.

Vascular and Microvascular Endothelial Function in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Assessment of vascular endothelial function lacks consistency, and microvascular endothelial function has been only partly assessed in heart failure with preserved ejection fraction (HFpEF).

METHODS

The study population consisted of 90 patients: 45 had well documented HFpEF, and 45 had hypertension and no history or evidence of heart failure. Patients with hypertension but no heart failure were matched with HFpEF patients for age, sex, and diabetes. They served as control subjects. All patients underwent 2-dimensional Doppler echocardiography and vascular function measurements, including assessment of arterial wave reflections and arterial stiffness, brachial artery flow-mediated dilation (FMD), and forearm cutaneous blood flow with the use of a laser Doppler flow probe at rest and after release of arterial occlusion for 5 minutes.

RESULTS

Brachial artery FMD was lower in HFpEF than in control subjects (median (IQR) 3.6 (0.4-7.4) vs. 7.2 (3.2-17.2)%, P = .001). Forearm cutaneous blood flow at rest was similar in HFpEF and control subjects (P = .68). After release of arterial occlusion, forearm cutaneous peak blood flow was lower in HFpEF than in control subjects (P = .03). Estimated aortic systolic and mean blood pressures were similar in HFpEF and control subjects, whereas pulse pressure and pressure augmentation were greater in HFPEF than in control subjects (both P < .05).

CONCLUSION

Compared with hypertensive control subjects, patients with HFpEF had a depressed endothelial function in the forearm vasculature and microvasculature.

Antibody-based prevention of von Willebrand factor degradation mediated by circulatory assist devices

Haemorrhagic episodes in patients carrying circulatory assist devices represent a severe life-threatening clinical complication. These bleeding episodes may originate from a reduced functionality of von Willebrand factor (VWF), a multimeric protein pertinent to the formation of a haemostatic plug. It has been reported that the reduced functionality is due to increased proteolytic degradation by the enzyme ADAMTS13, a phenomenon that is facilitated by device-induced increases in shear stress to which VWF is exposed. Here, we have tested a series of VWF-derived protein fragments and monoclonal murine anti-VWF antibodies for their capacity to reduce shear stress-dependent degradation of VWF. Via direct binding experiments, we identified an anti-VWF antibody that partially blocked VWF-ADAMTS13 interactions (46 ± 14%). Epitope mapping experiments revealed that the antibody, designated mAb508, is directed against the distal portion of the VWF D4-domain (residues 2134-2301) and recognises a synthetic peptide encompassing residues 2158-2169. Consistent with its partial inhibition of VWF-ADAMTS13 interactions in binding assays, mAb508 reduced ADAMTS13-mediated VWF degradation in a vortex-based degradation assay by 48 ± 10%. In a HeartMateII-based whole blood-perfusion system, mAb508 was able to reduce degradation of high-molecular-weight (HMW)-VWF-multimers dose-dependently, with a maximal inhibition (83 ± 8%) being reached at concentrations of 10 μg/ml or higher. In conclusion, we report that partial inhibition of VWF-ADAMTS13 interactions using an anti-VWF antibody can prevent excessive degradation of HMW-VWF multimers. This strategy may be used for the development of therapeutic options to treat bleeding episodes due to shear stress-dependent VWF degradation, for instance in patients carrying circulatory assist devices.

Transendocardial cell injection is not superior to intracoronary infusion in a porcine model of ischaemic cardiomyopathy: a study on delivery efficiency

Stem cell therapy is a new strategy for chronic ischaemic heart disease in patients. However, no consensus exists on the most optimal delivery strategy. This randomized study was designed to assess cell delivery efficiency of three clinically relevant strategies: intracoronary (IC) and transendocardial (TE) using electromechanical mapping guidance (NOGA) compared to surgical delivery in a chronic pig model of ischaemic cardiomyopathy. Twenty-four animals underwent delivery of 10(7) autologous Indium-oxine-labelled bone marrow-derived mesenchymal stem cells (MSC) 4 weeks after infarction and were randomized to one of three groups (n = 8 each group): IC, TE or surgical delivery (reference group). Primary endpoint was defined as percentage (%) of injected dose per organ and assessed by in vivo gamma-emission counting. In addition, troponin and coronary flow were assessed before and after MSC injection. Blinded endpoint analysis showed no significant difference in efficiency after surgical (16 ± 4%), IC (11 ± 1%) and TE (11 ± 3%) (P = 0.52) injections. IC showed less variability in efficiency compared with TE and surgical injection. Overall, TE injection showed less distribution of MSC to visceral organs compared with other modalities. Troponin rise and IC flow did not differ between the percutaneous groups. This randomized study showed no significant difference in cell delivery efficiency to the myocardium in a clinically relevant ischaemic large animal model between IC and TE delivery. In addition, no differences in safety profile were observed. These results are important in view of the choice of percutaneous cell delivery modality in future clinical stem cell trials.

Aldosterone, atherosclerosis and vascular events in patients with stable coronary artery disease

BACKGROUND AND AIMS

Plasma aldosterone has been associated with all-cause and cardiovascular mortality in high-risk cardiovascular populations, including patients with heart failure, myocardial infarction and high-risk coronary artery disease (CAD) patients. In the present study, we evaluated the association of plasma aldosterone levels with vascular events in a large prospective cohort of stable CAD patients recruited in an outpatient setting. Moreover, we investigated the relationship between aldosterone and atherosclerotic burden.

METHODS AND RESULTS

Baseline plasma aldosterone levels were measured in 2699 subjects with CAD (mean age 60 ± 10 years, 82% male). During a median follow-up of 4.7 years, 308 (11%) patients died, of which 203 were from a vascular cause. Vascular endpoints of myocardial infarction, ischemic stroke or vascular death occurred in 355 (13%) patients. Multivariable Cox regression analysis was performed, adjusting for multiple confounders. Aldosterone (median 96 pg/mL, interquartile range 70-138 pg/mL, normal range 58-362 pg/mL) was independently associated with major vascular events (hazard ratio (HR) 1.56, 95% confidence interval (CI) 1.13-2.15) and vascular mortality (HR 1.95, 95% CI 1.27-3.00). By multivariable regression analysis, aldosterone was also associated with the presence of atherosclerosis in additional vascular territories (cerebrovascular disease and/or peripheral artery disease) (p=0.026).

CONCLUSIONS

In patients with stable coronary artery disease, plasma aldosterone is independently associated with the risk of major vascular events and vascular mortality and with atherosclerotic burden.