Perioperative onset of acquired von Willebrand syndrome: Comparison between HVAD, HeartMate II and on-pump coronary bypass surgery

Knee replacement surgery in a patient with acquired von Willebrand disease: a case study with recommendations for patient management

Introduction and importance

Acquired von Willebrand disease (AvWD) is a rare underdiagnosed bleeding disorder caused by alterations in the levels of the major blood-clotting protein von Willebrand factor (vWF). The clinical and laboratory parameters of AvWD are similar to congenital vWD, but it is found in individuals with no positive family history with no underlying genetic basis. The disease remains multifactorial and incompletely understood. Proposed mechanisms include the development of autoantibodies to vWF, absorption of high molecular weight vWF multimers that impair normal function, shear stress induced vWF cleavage and increased proteolysis.The aetiology of the disease is variable, the most common being hematoproliferation, lymophoproliferation, myeloproliferation and autoimmune and cardiovascular disorders. Consensus and protocols for AvWD patients that require major surgery are currently lacking. Patients with AvWD can experience thrombotic events during surgery as a result of therapeutic interactions with pro-thrombotic risk factors.

Case presentation

Here, the authors report a patient with AvWD requiring a knee prosthesis implantation due to chronic pain, limited range of motion and functional impairment. The patient had a high risk of bleeding during surgery and was at risk of thrombosis due to age and obesity.

Clinical discussion

Perioperative care required a collaborative approach and the management of bleeding. The patient was administered vWF concentrate Willfact lacking Factor VIII to prevent haemorrhage and to minimize the risk of thrombosis.

Conclusion

The treatment was effective and well-tolerated. The authors use this information to provide recommendations for AvWD patients for whom major surgery is indicated.

Patient-specific severity of von Willebrand factor degradation identifies patients with a left ventricular assist device at high risk for bleeding

BACKGROUND

Continuous-flow left ventricular assist devices (LVADs) cause an acquired von Willebrand factor (VWF) deficiency and bleeding. Models to risk-stratify for bleeding are urgently needed. We developed a model of continuous-flow LVAD bleeding risk from patient-specific severity of VWF degradation.

METHODS

In a prospective, longitudinal cohort study, paired blood samples were obtained from patients (n = 67) with a continuous-flow LVAD before and during support. After 640 ± 395 days, patients were categorized as all-cause bleeders, gastrointestinal (GI) bleeders, or nonbleeders. VWF multimers and VWF clotting function were evaluated to determine bleeding risk.

RESULTS

Of 67 patients, 34 (51%) experienced bleeding, 26 (39%) experienced GI bleeding, and 33 (49%) did not bleed. In all patients, LVAD support significantly reduced high-molecular-weight VWF multimers (P < .001). Bleeders exhibited greater loss of high-molecular-weight VWF multimers (mean ± standard deviation, -10 ± 5% vs -7 ± 4%, P = .008) and reduced VWF clotting function versus nonbleeders (median [interquartile range], -12% [-31% to 4%] vs 0% [-9 to 26%], P = .01). A combined metric of VWF multimers and VWF function generated the All-Cause Bleeding Risk Score, which stratified bleeders versus nonbleeders (86 ± 56% vs 41 ± 48%, P < .001) with a positive predictive value of 86% (95% confidence interval, 66%-95%) and diagnostic odds ratio of 11 (95% confidence interval, 2.9-44). A separate GI Bleeding Risk Score stratified GI bleeders versus nonbleeders (202 ± 114 vs 120 ± 86, P = .003) with a positive predictive value of 88% (64%-97%) and diagnostic odds ratio of 18 (3.1-140).

CONCLUSIONS

The severity of loss of VWF multimers and VWF clotting function generated Bleeding Risk Scores with high predictive value for LVAD-associated bleeding. This model may guide personalized antithrombotic therapy and patient surveillance.

von Willebrand Factor and Angiopoietin-2 are Sensitive Biomarkers of Pulsatility in Continuous-Flow Ventricular Assist Device Patients

Nonsurgical bleeding occurs in a significant proportion of patients implanted with continuous-flow ventricular assist devices (CF-VADs) and is associated with nonphysiologic flow with diminished pulsatility. An in vitro vascular pulse perfusion model seeded with adult human aortic endothelial cells (HAECs) was used to identify biomarkers sensitive to changes in pulsatility. Diminished pulsatility resulted in an ~45% decrease in von Willebrand factor (vWF) levels from 9.80 to 5.32 ng/ml (n = 5, p < 0.05) and a threefold increase in angiopoietin-2 (ANGPT-2) levels from 775.29 to 2471.93 pg/ml (n = 5, p < 0.05) in cultured HAECs. These changes are in agreement with evaluation of patient blood samples obtained pre-CF-VAD implant and 30-day postimplant: a decrease in plasma vWF level by 50% from ~45.59 to ~22.49 μg/ml (n = 15, p < 0.01) and a 64% increase in plasma ANGPT-2 level from 7,073 to 11,615 pg/ml (n = 8, p < 0.05). This study identified vWF and ANGPT-2 as highly sensitive to changes in pulsatility, in addition to interleukin-6 (IL-6), IL-8, and tumor necrosis-α (TNF-α). These biomarkers may help determine the optimal level of pulsatility and help identify patients at high risk of nonsurgical bleeding.

Optimization of a Screw Centrifugal Blood Pump Based on Random Forest and Multi-Objective Gray Wolf Optimization Algorithm

The centrifugal blood pump is a commonly used ventricular assist device. It can replace part of the heart function, pumping blood throughout the body in order to maintain normal function. However, the high shear stress caused by the impeller rotating at high speeds can lead to hemolysis and, as a consequence, to stroke and other syndromes. Therefore, reducing the hemolysis level while ensuring adequate pressure generation is key to the optimization of centrifugal blood pumps. In this study, a screw centrifugal blood pump was used as the research object. In addition, pressure generation and the hemolysis level were optimized simultaneously using a coupled algorithm composed of random forest (RF) and multi-objective gray wolf optimization (MOGWO). After verifying the prediction accuracy of the algorithm, three optimized models were selected and compared with the baseline model in terms of pressure cloud, 2D streamline, SSS distribution, HI distribution, and vortex distribution. Finally, via a comprehensive evaluation, the optimized model was selected as the final optimization design, in which the pressure generation increased by 24% and the hemolysis value decreased by 48%.

Association of Oxidative Stress and Platelet Receptor Glycoprotein GPIbα and GPVI Shedding During Nonsurgical Bleeding in Heart Failure Patients With Continuous-Flow Left Ventricular Assist Device Support

Nonsurgical bleeding (NSB) in heart failure (HF) patients with continuous-flow left ventricular assist device (CF-LVAD) support is the most common clinical complication. The aim of this study was to investigate the association between oxidative stress and platelet glycoproteins GPIbα and GPVI shedding on the incidence of NSB in CF-LVAD patients. Fifty-one HF patients undergoing CF-LVAD implantation and 11 healthy volunteers were recruited. Fourteen patients developed NSB (bleeder group) during 1 month follow-up duration, while others were considered nonbleeder group (n = 37). Several biomarkers of oxidative stress were quantified at baseline and weekly intervals in all patients. Surface expression and plasma elements of platelet receptor glycoproteins GPIbα and GPVI were measured. Oxidative stress biomarkers and platelet GPIbα and GPVI receptor-shedding (decreased surface expression and higher plasma levels) were found to be preexisting conditions in baseline samples of both groups of HF patients when compared with healthy volunteers. Significantly elevated oxidative stress biomarkers and platelet glycoprotein receptor shedding were observed in postimplant bleeder group temporarily when compared with nonbleeder group. Strong significant associations between biomarkers of oxidative stress and platelet glycoprotein receptor shedding were observed, suggesting a possible role of oxidative stress in platelet integrin shedding leading to NSB in CF-LVAD patients. Receiver operating characteristic analyses of GPIbα and GPVI indicated that the likelihood of NSB had a predictive power of bleeding complication in CF-LVAD patients. In conclusion, elevated oxidative stress may play a role in GPIbα and GPVI shedding in the event of NSB. Thus, oxidative stress and GPIbα and GPVI shedding may be used as potential biomarkers for bleeding risk stratification in those patients.

Fluid Dynamics in the HeartMate 3: Influence of the Artificial Pulse Feature and Residual Cardiac Pulsation

Ventricular assist devices (VADs), among which the HeartMate 3 (HM3) is the latest clinically approved representative, are often the therapy of choice for patients with end-stage heart failure. Despite advances in the prevention of pump thrombosis, rates of stroke and bleeding remain high. These complications are attributed to the flow field within the VAD, among other factors. One of the HM3's characteristic features is an artificial pulse that changes the rotor speed periodically by 4000 rpm, which is meant to reduce zones of recirculation and stasis. In this study, we investigated the effect of this speed modulation on the flow fields and stresses using high-resolution computational fluid dynamics. To this end, we compared Eulerian and Lagrangian features of the flow fields during constant pump operation, during operation with the artificial pulse feature, and with the effect of the residual native cardiac cycle. We observed good washout in all investigated situations, which may explain the low incidence rates of pump thrombosis. The artificial pulse had no additional benefit on scalar washout performance, but it induced rapid variations in the flow velocity and its gradients. This may be relevant for the removal of deposits in the pump. Overall, we found that viscous stresses in the HM3 were lower than in other current VADs. However, the artificial pulse substantially increased turbulence, and thereby also total stresses, which may contribute to clinically observed issues related to hemocompatibility.

Changes in Von Willebrand factor profile predicts clinical outcomes in patients on mechanical circulatory support

BACKGROUND

The associations between mechanical circulatory support (MCS), acquired von Willebrand syndrome (AvWS), and clinical outcome are incompletely understood.

METHODS

In 128 heart failure patients with pulsatile MCS implants (65 total artificial heart or biventricular assist device implants, 63 left ventricular assist device [LVAD] implants) and 76 patients with continuous flow LVAD implants, we analyzed the von Willebrand factor (vWF) profile before (≤24 h) and 17.5 (standard deviation: 5.1) days after device implant. We determined vWF concentrations, vWF activity, and vWF collagen binding capacity and calculated ratios of vWF activity/binding capacity with vWF concentration. The relation of the vWF profile with clinical outcomes such as stroke, gastrointestinal bleeding, and survival was also evaluated. Events were assessed up to 1 year of device implant.

RESULTS

All entities of vWF were already significantly elevated preoperatively and remained high after MCS implantation. The ratios of vWF activity/concentration (vWF:RCo/Ag) and collagen binding capacity/concentration (vWF:CBA/Ag) were significantly reduced preoperatively and remained low postoperatively, indicating AvWS. The preoperative alterations in the vWF profile were already present in patients without intra-aortic balloon pump and/or extracorporeal circulatory membrane oxygenation implants. The vWF profile was unrelated to postoperative stroke. However, a higher postoperative ratio of vWF:CBA/Ag was independently associated with increased gastrointestinal bleeding. In addition, a postoperative increase in vWF concentrations and activity were independent predictors of increased 1-year mortality.

CONCLUSIONS

Our data indicate that AvWS is present in heart failure patients before device implantation, and is independently associated with clinical outcomes, especially with 1-year mortality.

Clinical overview of the HVAD: a centrifugal continuous-flow ventricular assist device with magnetic and hydrodynamic bearings including lateral implantation strategies

Growing worldwide incidences of end-stage heart failure and declining rates of cardiac transplants have given rise to the need for alternative treatment options, based on mechanical circulatory support (MCS) devices such as left ventricular assist devices (LVADs). Technologically advanced LVADs such as the HVAD^® (HeartWare^®, Medtronic) facilitate safe and efficient treatment of heart failure patients with reduced post-operative complications, which is attributed to their considerably miniaturized size. This also facilitates the development and implementation of novel, minimally-invasive surgical techniques. The HVAD is a centrifugal pump, manufactured by HeartWare Inc., (Framingham, MA, USA) and subsequently by Medtronic Inc., (Minnesota, MN, USA), and has been approved for clinical application after receiving the CE Mark approval in 2008 and the FDA approval in 2012. Current research efforts are focused on further miniaturization alongside optimization of electronic and software controllers as well as implementation of the transcutaneous energy transfer (TET) technology. Salient features of the HVAD pump technology, clinical applications and future optimization strategies have been discussed in this article.