Bleeding and thrombosis associated with ventricular assist device therapy

Design and Rationale for the Direct Oral Anticoagulant Apixaban in Left Ventricular Assist Devices (DOAC LVAD) Study

Implantable left ventricular assist device (LVAD) therapy is used to improve quality of life, alleviate symptoms and extend survival rates in patients with advanced heart failure. Patients with LVADs require chronic anticoagulation to reduce the risk of thromboembolic complications, and they commonly experience bleeding events. Apixaban is a direct oral anticoagulant that has become first-line therapy for patients with nonvalvular atrial fibrillation and venous thromboembolism; however, its safety in patients with LVADs has not been well characterized. The evaluation of the hemocompatibility in the DOAC LVAD (Direct Oral Anti-Coagulant apixaban in Left Ventricular Assist Devices) trial is a phase 2, open-label trial of patients with LVADs who were randomized to either apixaban or warfarin therapy. Patients randomized to apixaban will be started on a dosage of 5 mg twice daily, whereas those randomized to warfarin will be managed at an International Normalized Ratio goal of 2.0-2.5. All patients will be treated with aspirin at 81 mg daily. We plan to randomize and follow as many as 40 patients for 24 weeks to evaluate the primary outcomes of freedom from death or hemocompatibility-related adverse events (stroke, device thrombosis, bleeding, aortic root thrombus, and arterial non-CNS thromboembolism). The DOAC LVAD trial will establish the feasibility of apixaban anticoagulant therapy in patients with LVADs. Clinicaltrials.gov: NCT04865978.

Evaluation of the Hemocompatibility of the Direct Oral Anticoagulant Apixaban in Left Ventricular Assist Devices: The DOAC LVAD Study

BACKGROUND

Patients receiving left ventricular assist device (LVAD) support require long-term anticoagulation to reduce the risk of thromboembolic complications. Apixaban is a direct oral anticoagulant that has become first-line therapy; however, its safety in LVAD recipients has not been well described.

OBJECTIVES

This study sought to investigate whether, in patients with a fully magnetically levitated LVAD, treatment with apixaban would be feasible and comparable with respect to safety and freedom from the primary composite outcome of death or major hemocompatibility-related adverse events (HRAEs) (stroke, device thrombosis, major bleeding, aortic root thrombus, and arterial non-central nervous system thromboembolism) as compared with treatment with warfarin.

METHODS

The DOAC LVAD (Evaluation of the Hemocompatibility of the Direct Oral Anti-Coagulant Apixaban in Left Ventricular Assist Devices) trial was a phase 2, open label trial of LVAD recipients randomized 1:1 to either apixaban 5 mg twice daily or warfarin therapy. All patients were required to take low-dose aspirin. Patients were followed up for 24 weeks to evaluate the primary composite outcome.

RESULTS

A total of 30 patients were randomized: 14 patients to warfarin and 16 patients to apixaban. The median patient age was 60 years (Q1-Q3: 52-71 years), and 47% were Black patients. The median time from LVAD implantation to randomization was 115 days (Q1-Q3: 56-859 days). At 24 weeks, the primary composite outcome occurred in no patients receiving apixaban and in 2 patients (14%) receiving warfarin (P = 0.12); these 2 patients experienced major bleeding from gastrointestinal sources.

CONCLUSIONS

Anticoagulation with apixaban was feasible in patients with an LVAD without an excess of HRAEs or deaths. This study informs future pivotal clinical trials evaluating the safety and efficacy of apixaban in LVAD recipients. (Evaluation of the Hemocompatibility of the Direct Oral Anti-Coagulant Apixaban in Left Ventricular Assist Devices [DOAC LVAD]; NCT04865978).

Investigation of the role of von Willebrand factor in shear-induced platelet activation and functional alteration under high non-physiological shear stress

BACKGROUND

von Willebrand factor (vWF) plays a crucial role in physiological hemostasis through platelet and subendothelial collagen adhesion. However, its role in shear-induced platelet activation and functional alteration under non-physiological conditions common to blood-contacting medical devices (BCMDs) is not well investigated.

METHODS

Fresh healthy human blood was treated with an anti-vWF antibody to block vWF-GPIbα interaction. Untreated blood was used as a control. They were exposed to three levels of non-physiological shear stress (NPSS) (75, 125, and 175 Pa) through a shearing device with an exposure time of 0.5 s to mimic typical shear conditions in BCMDs. Flow cytometric assays were used to measure the expression levels of PAC-1 and P-Selectin and platelet aggregates for platelet activation and the expression levels of GPIbα, GPIIb/IIIa, and GPVI for receptor shedding. Collagen/ristocetin-induced platelet aggregation capacity was characterized by aggregometry.

RESULTS

The levels of platelet activation and aggregates increased with increasing NPSS in the untreated blood. More receptors were lost with increasing NPSS, resulting in a decreased capacity of collagen/ristocetin-induced platelet aggregation. In contrast, the increase in platelet activation and aggregates after exposure to NPSS, even at the highest level of NPSS, was significantly lower in treated blood. Nevertheless, there was no notable difference in receptor shedding, especially for GPIIb/IIIa and GPVI, between the two blood groups at the same level of NPSS. The block of vWF exacerbated the decreased capacity of collagen/ristocetin-induced platelet aggregation.

CONCLUSIONS

High NPSS activates platelets mainly by enhancing the vWF-GPIbα interaction. Platelet activation and receptor shedding induced by high NPSS likely occur through different pathways.

Advanced Heart Failure: Therapeutic Options and Challenges in the Evolving Field of Left Ventricular Assist Devices

Heart Failure is a chronic and progressively deteriorating syndrome that has reached epidemic proportions worldwide. Improved outcomes have been achieved with novel drugs and devices. However, the number of patients refractory to conventional medical therapy is growing. These advanced heart failure patients suffer from severe symptoms and frequent hospitalizations and have a dismal prognosis, with a significant socioeconomic burden in health care systems. Patients in this group may be eligible for advanced heart failure therapies, including heart transplantation and chronic mechanical circulatory support with left ventricular assist devices (LVADs). Heart transplantation remains the treatment of choice for eligible candidates, but the number of transplants worldwide has reached a plateau and is limited by the shortage of donor organs and prolonged wait times. Therefore, LVADs have emerged as an effective and durable form of therapy, and they are currently being used as a bridge to heart transplant, destination lifetime therapy, and cardiac recovery in selected patients. Although this field is evolving rapidly, LVADs are not free of complications, making appropriate patient selection and management by experienced centers imperative for successful therapy. Here, we review current LVAD technology, indications for durable MCS therapy, and strategies for timely referral to advanced heart failure centers before irreversible end-organ abnormalities.

PERSUADE Survey-PERioperative AnestheSia and Intensive Care Management of Left VentricUlar Assist DevicE Implantation in Europe and the United States

OBJECTIVE

To comprehensively assess relevant institutional variations in anesthesia and intensive care management during left ventricular assist device (LVAD) implantation.

DESIGN

The authors used a prospective data analysis.

SETTING

This was an online survey.

PARTICIPANTS

Participants were from LVAD centers in Europe and the US.

INTERVENTIONS

After investigating initial interest, 91 of 202 European and 93 of 195 US centers received a link to the survey targeting institutional organization and experience, perioperative hemodynamic monitoring, medical management, and postoperative intensive care aspects.

MEASUREMENTS AND MAIN RESULTS

The survey was completed by 73 (36.1%) European and 60 (30.8%) US centers. Although most LVAD implantations were performed in university hospitals (>5 years of experience), significant differences were observed in the composition of the preoperative multidisciplinary team and provision of intraoperative care. No significant differences in monitoring or induction agents were observed. Propofol was used more often for maintenance in Europe (p < 0.001). The choice for inotropes changed significantly from preoperatively (more levosimendan in Europe) to intraoperatively (more use of epinephrine in both Europe and the US). The use of quantitative methods for defining right ventricular (RV) function was reported more often from European centers than from US centers (p < 0.05). Temporary mechanical circulatory support for the treatment of RV failure was more often used in Europe. Nitric oxide appeared to play a major role only intraoperatively. There were no significant differences in early postoperative complications reported from European versus US centers.

CONCLUSIONS

Although the perioperative practice of care for patients undergoing LVAD implantation differs in several aspects between Europe and the US, there were no perceived differences in early postoperative complications.

Aspirin and Hemocompatibility Events With a Left Ventricular Assist Device in Advanced Heart Failure: The ARIES-HM3 Randomized Clinical Trial

IMPORTANCE

Left ventricular assist devices (LVADs) enhance quality and duration of life in advanced heart failure. The burden of nonsurgical bleeding events is a leading morbidity. Aspirin as an antiplatelet agent is mandated along with vitamin K antagonists (VKAs) with continuous-flow LVADs without conclusive evidence of efficacy and safety.

OBJECTIVE

To determine whether excluding aspirin as part of the antithrombotic regimen with a fully magnetically levitated LVAD is safe and decreases bleeding.

DESIGN, SETTING, and PARTICIPANTS

This international, randomized, double-blind, placebo-controlled study of aspirin (100 mg/d) vs placebo with VKA therapy in patients with advanced heart failure with an LVAD was conducted across 51 centers with expertise in treating patients with advanced heart failure across 9 countries. The randomized population included 628 patients with advanced heart failure implanted with a fully magnetically levitated LVAD (314 in the placebo group and 314 in the aspirin group), of whom 296 patients in the placebo group and 293 in the aspirin group were in the primary analysis population, which informed the primary end point analysis. The study enrolled patients from July 2020 to September 2022; median follow-up was 14 months.

Intervention

Patients were randomized in a 1:1 ratio to receive aspirin (100 mg/d) or placebo in addition to an antithrombotic regimen.

MAIN OUTCOMES AND MEASURES

The composite primary end point, assessed for noninferiority (-10% margin) of placebo, was survival free of a major nonsurgical (>14 days after implant) hemocompatibility-related adverse events (including stroke, pump thrombosis, major bleeding, or arterial peripheral thromboembolism) at 12 months. The principal secondary end point was nonsurgical bleeding events.

RESULTS

Of the 589 analyzed patients, 77% were men; one-third were Black and 61% were White. More patients were alive and free of hemocompatibility events at 12 months in the placebo group (74%) vs those taking aspirin (68%). Noninferiority of placebo was demonstrated (absolute between-group difference, 6.0% improvement in event-free survival with placebo [lower 1-sided 97.5% CI, -1.6%]; P < .001). Aspirin avoidance was associated with reduced nonsurgical bleeding events (relative risk, 0.66 [95% confidence limit, 0.51-0.85]; P = .002) with no increase in stroke or other thromboembolic events, a finding consistent among diverse subgroups of patient characteristics.

CONCLUSIONS AND RELEVANCE

In patients with advanced heart failure treated with a fully magnetically levitated LVAD, avoidance of aspirin as part of an antithrombotic regimen, which includes VKA, is not inferior to a regimen containing aspirin, does not increase thromboembolism risk, and is associated with a reduction in bleeding events.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04069156.

Kinetic and Dynamic Effects on Degradation of von Willebrand Factor

The loss of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in aortic stenosis (AS) and continuous-flow left ventricular assist devices (cf-LVADs) is believed to be associated with high turbulent blood shear. The objective of this study is to understand the degradation mechanism of HMWM in terms of exposure time (kinetic) and flow regime (dynamics) within clinically relevant pathophysiologic conditions. A custom high-shear rotary device capable of creating fully controlled exposure times and flows was used. The system was set so that human platelet-poor plasma flowed through at 1.75 ml/sec, 0.76 ml/sec, or 0.38 ml/sec resulting in the exposure time ( texp ) of 22, 50, or 100 ms, respectively. The flow was characterized by the Reynolds number (Re). The device was run under laminar (Re = 1,500), transitional (Re = 3,000; Re = 3,500), and turbulent (Re = 4,500) conditions at a given texp followed by multimer analysis. No degradation was observed at laminar flow at all given texp . Degradation of HMWM at a given texp increases with the Re. Re ( p < 0.0001) and texp ( p = 0.0034) are significant factors in the degradation of HMWM. Interaction between Re and texp , however, is not always significant ( p = 0.73).

Prophylactic negative pressure wound therapy is not effective for preventing driveline infection following left ventricular assist device implantation

BACKGROUND

Driveline infection (DLI) following left ventricular assist device (LVAD) implantation remains an unresolved problem. Negative pressure wound therapy (NPWT) promotes wound healing by applying negative pressure on the surface of the wound. Recently, the prophylactic application of NPWT to closed surgical incisions has decreased surgical site infections in various postsurgical settings. Therefore, we evaluated the efficacy and safety of prophylactic NPWT for preventing DLI in patients with LVAD implantation.

METHODS

Prophylactic NPWT was provided to 50 patients who received continuous-flow LVADs as bridge-to-transplant therapy at our institution between May 2018 and October 2020 (NPWT group). The negative pressure dressing was applied immediately after surgery and retained on the driveline exit site for 7 days with a continuous application of -125 mm Hg negative pressure. The primary outcome was DLI within 1 year of LVAD implantation. We compared the rate of DLI incidence in the NPWT group with that in the historical control cohort (50 patients) treated with the standard dressing (SD) who received LVAD implantation between July 2015 and April 2018 (SD group).

RESULTS

No severe complications were associated with the NPWT. During the follow-up period, DLI was diagnosed in 16 participants (32%) in the NPWT group and 21 participants (42%) in the SD group. The rates of DLI incidence and freedom from DLI did not differ between groups (p = 0.30 and p = 0.63).

CONCLUSIONS

Prophylactic NPWT at the driveline exit site was safe following LVAD implantation. However, it did not significantly reduce the risk of DLI.

Enhanced Thrombin Formation in Patients With Ventricular Assist Devices Experiencing Bleeding: Insights From the Multicenter PREVENT Study

The aim of this investigation was to characterize the hemostatic status of heart failure patients with implanted left ventricular assist devices (LVADs) to propose a mechanism associated with bleeding. Patients (n = 300) from 23 US hospitals were enrolled in the PREVENtion of HeartMate II Pump Thrombosis through Clinical Management (PREVENT) study. A biobank was established with serum and plasma samples prospectively collected from a cohort of 175 patients preimplant baseline (BL) and 3 months (3M) postimplant. Outcomes were collected for 6 months. Thrombin (prothrombin fragment 1.2 [F1.2], functional thrombin generation [TG]) and fibrinolytic activity (D-dimer, plasminogen activator inhibitor-1 [PAI-1]), but not contact activation (complement C5a), were elevated in heart failure patients at BL. F1.2, TG, and PAI-1 levels decreased 3M after LVAD implantation ( p < 0.01) but did not revert to normal in all patients; conversely, D-dimer increased BL to 3M ( p < 0.01). Compared with patients without events, thrombin activity (F1.2) was increased in patients with late bleeding (3-4 months postimplant) ( p = 0.06) and in those with late gastrointestinal (GI) bleeding ( p = 0.01). Patients with 3M F1.2 levels above the cohort mean had a higher incidence of bleeding ( p < 0.001) and GI bleeding ( p < 0.001) compared with those with below mean F1.2. Patients experiencing multiple bleeding events were more likely to have 3M F1.2 greater than the cohort mean. Despite anticoagulation with aspirin and warfarin, LVAD implanted patients exhibit hemostatic activation. Excess thrombin formation, particularly shown by increased F1.2, was demonstrated in association with bleeding in LVAD implanted patients.

Comparing left ventricular assist device inflow cannula angle between median sternotomy and thoracotomy using 3D reconstructions

BACKGROUND

Left ventricular assist device (LVAD) implantation via thoracotomy has many potential advantages compared to conventional sternotomy, including improved inflow cannula (IFC) positioning. We compared the difference in IFC angles, postoperative, and long-term outcomes for patients with LVADs implanted via thoracotomy and sternotomy.

METHODS

A single-center, retrospective analysis of 14 patients who underwent thoracotomy implantation was performed and matched with 28 patients who underwent sternotomy LVAD implantations for a total of 42 patients. Inclusion required a minimum LVAD support duration of 30 days and excluded concomitant procedures. A postoperative CT-chest was used to measure the angle the between the IFC and mitral valve in two-dimensions and results were compared with three-dimensional reconstruction using the same CT chest. Outcome data were extracted from medical records.

RESULTS

There was no significant difference in gender, INTERMACS score, BMI, or age between the two groups. Median cardiopulmonary bypass time was longer in the thoracotomy group compared to the sternotomy group, 107 min (86-122) versus 76 min (56-93), p < 0.01. 3D reconstructions revealed less deviation of the IFC away from the mitral valve in devices implanted via thoracotomy compared to sternotomy, median (IQR) angle 16.3° (13.9°-21.0°) versus 23.2° (17.9°-26.4°), p < 0.01. Rates of pump thrombosis, stroke, and gastrointestinal bleeding were not significantly different.

CONCLUSIONS

Devices implanted via thoracotomy demonstrated less deviation away from mitral valve. However, there was no difference in morbidity between the two approaches. 3D reconstruction of the heart is an innovative technique to measure angulation and is clinically advantageous when compared to 2D imaging.

Multi-indicator analysis of mechanical blood damage with five clinical ventricular assist devices

PURPOSE

Device-induced blood damage contributes the hemolysis, thrombosis and bleeding complications in patients supported with ventricular assist device (VAD). This study aims to use a multi-indicator method to understand how devices causes blood damage and identify the "hot spots" of blood trauma within VADs.

METHODS

Computational fluid dynamics (CFD) methods were chosen to investigate the hemodynamic features of five clinical VADs (Impella 5.0, UltraMag, CHVAD, HVAD, and HeartMate II) under the same clinical support condition (flow rate of 4.5L/min, pressure head around 75 mmHg). A comprehensive multi-indicator evaluation method including hemodynamic parameters, hemolysis model, thrombotic potential model and bleeding probability model was used to analyze blood damage and assess the hemodynamic performance and hemocompatibility of these VADs.

RESULTS

Simulation results show that shear stress from 50 Pa to 100 Pa plays a major role in blood damage in Impella 5.0, UltraMag and CHVAD, while blood damage in HVAD and HeartMate II is mainly caused by shear stress greater than 100 Pa. Residence time was not the main factor for blood damage in Impella 5.0, and also makes a limited contribution to blood trauma in UltraMag and CHVAD, while it takes a critical role in elevating thrombotic potential in HVAD and HeartMate II. The distribution of regions of high hemolysis risk and high bleeding probability was similar for all these VADs and partially overlapped for high thrombotic potential regions. For Impella 5.0, regions with high hemolysis and bleeding risk were found mainly in the blade tip clearance and diffuser domains, high thrombotic potential regions were almost absent. For UltraMag, regions with high hemolysis, bleeding and thrombosis potential were found in two corners of the inlet pipe, the secondary flow passage, and the impeller eye. For CHVAD, the high-risk regions for hemolysis, bleeding and thrombosis are mainly in the inner side of the secondary flow passage and the middle region of the impeller passage. The narrow hydrodynamic clearance and impeller passage had a high risk of hemolysis and bleeding, and the clearance between the rotor and guide cone and the hydrodynamic clearance had high thrombotic potential. For HeartMate II, regions of high hemolysis risk and bleeding probability were found in the near-wall region of the straightener, the blade tip clearance and the diffuser domain. The corners of the inlet and outlet pipe and the straightener and diffuser regions had high thrombotic potential.

CONCLUSION

The risk of hemolysis, bleeding and thrombosis for these five VADs, in increasing order, was Impella 5.0, UltraMag, CHVAD, HVAD, and HeartMate II. Flow losses caused by the rotor mechanical movement, chaotic flow and narrow clearances increase the blood damage for all these VADs. The multi-indicator analysis can comprehensively evaluate the VAD performance with improved assessment accuracy of CFD.

Antithrombotic therapy for durable left ventricular assist devices - current strategies and future directions

Left ventricular assist devices (LVADs) improve survival and quality of life for patients with advanced heart failure but are associated with high rates of thromboembolic and hemorrhagic complications. Antithrombotic therapy is required following LVAD implantation, though practices vary. Identifying a therapeutic strategy that minimizes the risks of thromboembolic and hemorrhagic complications is critical to optimizing patient outcomes and is an area of active investigation. This paper reviews strategies for initiating and maintaining antithrombotic therapy in durable LVAD recipients, focusing on those with centrifugal-flow devices.

Decreased Platelet Specific Receptor Expression of P-Selectin and GPIIb/IIIa Predict Future Non-Surgical Bleeding in Patients after Left Ventricular Assist Device Implantation

Non-surgical bleeding (NSB) is one of the major clinical complications in patients under continuous-flow left ventricular assist device (LVAD) support. The increased shear stress leads to an altered platelet receptor composition. Whether these changes increase the risk for NSB is unclear. Thus, we compared the platelet receptor composition of patients with (bleeder group, n = 18) and without NSB (non-bleeder group, n = 18) prior to LVAD implantation. Blood samples were obtained prior to LVAD implantation and after bleeding complications in the post-implant period. Platelet receptor expression of GPIbα, GPIIb/IIIa, P-selectin and CD63 as well as intra-platelet oxidative stress levels were quantified by flow cytometry. Bleeders and non-bleeders were comparable regarding clinical characteristics, von Willebrand factor diagnostics and the aggregation capacity before and after LVAD implantation (p > 0.05). LVAD patients in the bleeder group suffered from gastrointestinal bleeding (33%; n = 6), epistaxis (22%; n = 4), hematuria or hematoma (17%; n = 3, respectively) and cerebral bleeding (11%; n = 2). Prior to LVAD implantation, a restricted surface expression of the platelet receptors P-selectin and GPIIb/IIIa was observed in the bleeder group (P-selectin: 7.2 ± 2.6%; GPIIb/IIIa: 26,900 ± 13,608 U) compared to non-bleeders (P-selectin: 12.4 ± 8.1%, p = 0.02; GPIIb/IIIa: 36,259 ± 9914 U; p = 0.02). We hypothesized that the reduced platelet receptor expression of P-selectin and GPIIb/IIIa prior to LVAD implantation may be linked to LVAD-related NSB.

Physiologic Data-Driven Iterative Learning Control for Left Ventricular Assist Devices

Continuous flow ventricular assist devices (cfVADs) constitute a viable and increasingly used therapy for end-stage heart failure patients. However, they are still operating at a fixed-speed mode that precludes physiological cfVAD response and it is often related to adverse events of cfVAD therapy. To ameliorate this, various physiological controllers have been proposed, however, the majority of these controllers do not account for the lack of pulsatility in the cfVAD operation, which is supposed to be beneficial for the physiological function of the cardiovascular system. In this study, we present a physiological data-driven iterative learning controller (PDD-ILC) that accurately tracks predefined pump flow trajectories, aiming to achieve physiological, pulsatile, and treatment-driven response of cfVADs. The controller has been extensively tested in an in-silico environment under various physiological conditions, and compared with a physiologic pump flow proportional-integral-derivative controller (PF-PIDC) developed in this study as well as the constant speed (CS) control that is the current state of the art in clinical practice. Additionally, two treatment objectives were investigated to achieve pulsatility maximization and left ventricular stroke work (LVSW) minimization by implementing copulsation and counterpulsation pump modes, respectively. Under all experimental conditions, the PDD-ILC as well as the PF-PIDC demonstrated highly accurate tracking of the reference pump flow trajectories, outperforming existing model-based iterative learning control approaches. Additionally, the developed controllers achieved the predefined treatment objectives and resulted in improved hemodynamics and preload sensitivities compared to the CS support.

Preoperative and intraoperative risk factors of postoperative stroke in total aortic arch replacement and stent elephant trunk implantation

BACKGROUND

Acute type A aortic dissection (AAAD) is a disease with high mortality, for which total aortic arch replacement (TAAR) combined with stent elephant implantation (SETI) is a reliable surgical treatment; however, it is associated with a high incidence of postoperative stroke. This retrospective study aimed to find preoperative and postoperative risk factors for postoperative stroke in patients with TAAR combined with SETI, and to provide predictive models and single-factor threshold suggestions.

METHODS

From October 2019 to March 2021, 229 AAAD patients who underwent TAAR and SETI were selected. Patients were divided into stroke group (n = 23) and non-stroke group (n = 206), and preoperative/intraoperative factors were evaluated by independent-samples T-test/ Mann-Whitney U test/Chi-Square test and odds ratio (OR) analysis. The Logistic regression equation and decision tree were used to construct the prediction model of the probability of postoperative stroke. Bayesian-learning model and 2-order derivation were used to calculate the inflection points of the continuous variables.

FINDINGS

Platelet count (PLT), International normalised ratio (INR) value, presence of diabetic history, and cardiopulmonary bypass (CPB) time were independent predictors of postoperative stroke (P-value < 0.05), and the above four factors were used to construct the Logistic regression equation. As for the decision-tree model, a radical model with higher accuracy in stroke predicting was chosen. Three inflection points for the effect of continuous variables (PLT count = 60 × 10^9/L; INR value = 1.82; CPB time = 300 min) on postoperative stroke were found by 2-order derivation.

INTERPRETATION

PLT count, INR value, presence of diabetic history, and CPB time were significant preoperative and intraoperative risk factors for postoperative stroke, and the identification and modeling of these factors can help us to take more active brain protection measures in high-risk patients.

FUNDING

YS was funded by the National Natural Science Foundation of China (Grant ID 81671942).

Advancements in left ventricular assist devices to prevent pump thrombosis and blood coagulopathy

Mechanical circulatory support (MCS) devices, such as left ventricular assist devices (LVADs) are very useful in improving outcomes in patients with advanced-stage heart failure. Despite recent advances in LVAD development, pump thrombosis is one of the most severe adverse events caused by LVADs. The contact of blood with artificial materials of LVAD pumps and cannulas triggers the coagulation cascade. Heat spots, for example, produced by mechanical bearings are often subjected to thrombus build-up when low-flow situations impair washout and thus the necessary cooling does not happen. The formation of thrombus in an LVAD may compromise its function, causing a drop in flow and pumping power leading to failure of the LVAD, if left unattended. If a clot becomes dislodged and circulates in the bloodstream, it may disturb the flow or occlude the blood vessels in vital organs and cause internal damage that could be fatal, for example, ischemic stroke. That is why patients with LVADs are on anti-coagulant medication. However, the anti-coagulants can cause a set of issues for the patient-an example of gastrointestinal (GI) bleeding is given in illustration. On account of this, these devices are only used as a last resort in clinical practice. It is, therefore, necessary to develop devices with better mechanics of blood flow, performance and hemocompatibility. This paper discusses the development of LVADs through landmark clinical trials in detail and describes the evolution of device design to reduce the risk of pump thrombosis and achieve better hemocompatibility. Whilst driveline infection, right heart failure and arrhythmias have been recognised as LVAD-related complications, this paper focuses on complications related to pump thrombosis, especially blood coagulopathy in detail and potential strategies to mitigate this complication. Furthermore, it also discusses the LVAD implantation techniques and their anatomical challenges.

Severe Pulmonary Bleeding after Assist Device Implantation: Incidence, Risk Factors and Prognostic Impact

Background: Continuous flow left ventricular assist devices (CF-LVAD) improve survival in patients with advanced heart failure but confer risk of bleeding complications. Whereas pathophysiology and risk factors for many bleeding complications are well investigated, the literature lacks reports about pulmonary bleeding. Therefore, it was the aim of the present study to assess incidence, risk factors, and clinical relevance of pulmonary bleeding episodes after LVAD implantation. Methods: We retrospectively analyzed our institutional database of 125 consecutive patients who underwent LVAD implantation between 2008 and 2017. Demographic and clinical variables related to bleeding were collected. The primary endpoint was incidence of severe pulmonary bleeding (SPB). Results: Nine out of 125 patients suffered from SPB during the postoperative course (7.2%) 11 days after surgery in the median. None of them had a known history of lung disease or bleeding disorder. History of prior myocardial infarction (0% vWD. 42.2%, p = 0.012) and ischemic cardiomyopathy (25.0% vs. 50.0%, p = 0.046) were less frequent in the SBP group. Concomitant aortic valve replacement was more common in the group with SPB (33.3% versus 7.0%, p = 0.034). Surgical (blood loss 9950 vs. 3800 mL, p = 0.012) as well as ear-nose-throat (ENT) bleedings (33% vs. 4.6%, p = 0.015) were observed more frequently in patients with SPB. SPB was associated with a complicated postoperative course with a higher incidence of acute kidney failure (100% versus 36.7%, p = 0.001) and delirium (44.4% versus 14.8%, p = 0.045); a higher need for red blood cell (26 packs versus 7, p < 0.001), fresh frozen plasma (18 units versus 6, p = 0.002), and platelet transfusion (8 pools versus 1, p = 0.001); longer ventilation time (1206 versus 171 h, p = 0.001); longer ICU-stay (58 versus 13 days, p = 0.002); and higher hospital mortality (66.7% vs. 29%, p = 0.029). Conclusion: SPB is a rare but serious complication after LVAD implantation and is significantly associated with higher morbidity and mortality. The pathophysiology and potential risk factors are unknown but may include coagulation disorders and frequent suctioning or empiric bronchoscopy causing airway irritation.

Individual Variability in von Willebrand Factor Fragility in Response to Shear Stress: A Possible Clue for Predicting Bleeding Risk

Acquired von Willebrand syndrome (AVWS), characterized by reduced von Willebrand factor (VWF) large multimers, has recently been implicated as the principal mechanism underlying bleeding in patients implanted with left ventricular assist devices (LVADs). Hematological severity of AVWS varies among patients, even if an identical device is implanted. We investigated whether this diversity in hematological severity is due to individual variability in VWF fragility, according to responses to incremental shear stress. Whole-blood samples were sheared at 20,000-40,000 s-1 shear rate, an index of shear stress, using a custom-made shear stressor that could generate shear stress compatible with that produced by an LVAD. The degree of VWF large multimers degradation was evaluated using the VWF large multimer index. A significant inverse correlation was observed between the VWF large multimer index and LVAD-compatible magnitudes of shear stress: the VWF large multimer indices were 68.5 ± 18.3, 48.0 ± 13.9, 33.9 ± 12.1, 23.7 ± 7.9, and 18.7% ± 8.7% at 20,000, 25,000, 30,000, 35,000, and 40,000 s-1 of shear rates, respectively (P < 0.0001). Furthermore, experimental VWF large multimer index values were compatible with those derived from patients with implanted LVADs (median; 28.9%). Finally, reduction in the VWF large multimer index corresponding to shear stress showed individual variation. We demonstrated that the combined use of a novel high shear stress loading device and quantitative evaluation of VWF large multimers may predict risk of bleeding before LVAD implantation.

Evolution of Late Right Heart Failure With Left Ventricular Assist Devices and Association With Outcomes

BACKGROUND

A revised definition of right heart failure (RHF) for the Society of Thoracic Surgeons Intermacs database of left ventricular assist devices (LVADs) was introduced in June 2014.

OBJECTIVES

The purpose of this study was to determine the prevalence and severity of RHF over time and the association of RHF status at 3 months with 12-month outcomes after LVAD.

METHODS

All patients in Society of Thoracic Surgeons Intermacs with follow-up and supported at least 3 months with a continuous flow LVAD implanted between June 2, 2014 and March 31, 2017 without a simultaneous RVAD. RHF was defined as both documentation and manifestations of elevated central venous pressures.

RESULTS

There were 6,118 patients included with an incidence of RHF at 3, 6, and 12 months postimplant categorized as mild in 5%, 6%, and 6% and moderate in 5%, 3%, and 3%, respectively. For those with no RHF at 3 months, there was a low incidence of subsequent RHF at 6 and 12 months. The lack of RHF at 3 months, compared with mild and moderate RHF, was associated with a lower 12-month cumulative incidence of mortality (6.9% vs 16.7% vs 28.1%; P < 0.0001) and a lower 12-month cumulative incidence of stroke (7.4% vs 9.5% vs 11.0%; P = 0.0095), gastrointestinal bleeding (14.8% vs 24.2% vs 23.6%; P < 0.0001), and rehospitalization (65.2% vs 73.2% vs 71.2%; P < 0.0001).

CONCLUSIONS

In patients surviving 3 months with LVAD support alone, mild or moderate RHF occurred in nearly 1 of 10 patients at 12 months. Patients with late RHF had worse survival and a higher cumulative incidence of major adverse events.

A data mining-based cross-industry process for predicting major bleeding in mechanical circulatory support

Aims

Over a third of patients, treated with mechanical circulatory support (MCS) for end-stage heart failure, experience major bleeding. Currently, the prediction of a major bleeding in the near future is difficult because of many contributing factors. Predictive analytics using data mining could help calculating the risk of bleeding; however, its application is generally reserved for experienced researchers on this subject. We propose an easily applicable data mining tool to predict major bleeding in MCS patients.

Methods and results

All data of electronic health records of MCS patients in the University Medical Centre Utrecht were included. Based on the cross-industry standard process for data mining (CRISP-DM) methodology, an application named Auto-Crisp was developed. Auto-Crisp was used to evaluate the predictive models for a major bleeding in the next 3, 7, and 30 days after the first 30 days post-operatively following MCS implantation. The performance of the predictive models is investigated by the area under the curve (AUC) evaluation measure. In 25.6% of 273 patients, a total of 142 major bleedings occurred during a median follow-up period of 542 [interquartile range (IQR) 205-1044] days. The best predictive models assessed by Auto-Crisp had AUC values of 0.792, 0.788, and 0.776 for bleedings in the next 3, 7, and 30 days, respectively.

Conclusion

The Auto-Crisp-based predictive model created in this study had an acceptable performance to predict major bleeding in MCS patients in the near future. However, further validation of the application is needed to evaluate Auto-Crisp in other research projects.

The role of viscoelastic testing in assessing peri-interventional platelet function and coagulation

We carried out a literature search in MEDLINE (PubMed) and EMBASE literature databases to provide a concise review of the role of viscoelastic testing in assessing peri-interventional platelet function and coagulation. The search identified 130 articles that were relevant for the review, covering the basic science of VHA and VHA in clinical settings including cardiac surgery, cardiology, neurology, trauma, non-cardiac surgery, obstetrics, liver disease, and COVID-19. Evidence from these articles is used to describe the important role of VHAs and platelet function testing in various peri-interventional setups. VHAs can help us to comprehensively assess the contribution of platelets and coagulation dynamics to clotting at the site-of-care much faster than standard laboratory measures. In addition to standard coagulation tests, VHAs are beneficial in reducing allogeneic transfusion requirements and bleeding, in predicting ischemic events, and improving outcomes in several peri-interventional care settings. Further focused studies are needed to confirm their utility in the peri-interventional case.

Aspirin and left ventricular assist devices: rationale and design for the international randomized, placebo-controlled, non-inferiority ARIES HM3 trial

AIMS

Over decades, left ventricular assist device (LVAD) technology has transitioned from less durable bulky pumps to smaller continuous-flow pumps which have substantially improved long-term outcomes and quality of life. Contemporary LVAD therapy is beleaguered by haemocompatibility-related adverse events including thrombosis, stroke and bleeding. A fully magnetically levitated pump, the HeartMate 3 (HM3, Abbott, USA) LVAD, has been shown to be superior to the older HeartMate II (HMII, Abbott, USA) pump by improving haemocompatibility. Experience with the HM3 LVAD suggests near elimination of de-novo pump thrombosis, a marked reduction in stroke rates, and only a modest decrease in bleeding complications. Since the advent of continuous-flow LVAD therapy, patients have been prescribed a combination of aspirin and anticoagulation therapy on the presumption that platelet activation and perturbations to the haemostatic axis determine their necessity. Observational studies in patients implanted with the HM3 LVAD who suffer bleeding have suggested a signal of reduced subsequent bleeding events with withdrawal of aspirin. The notion of whether antiplatelet therapy can be avoided in an effort to reduce bleeding complications has now been advanced.

METHODS

To evaluate this hypothesis and its clinical benefits, the Antiplatelet Removal and Hemocompatibility Events with the HeartMate 3 Pump (ARIES HM3) has been introduced as the first-ever international prospective, randomized, double-blind and placebo-controlled, non-inferiority trial in a patient population implanted with a LVAD.

CONCLUSION

This paper reviews the biological and clinical role of aspirin (100 mg) with LVADs and discusses the rationale and design of the ARIES HM3 trial.

On the Optimization of a Centrifugal Maglev Blood Pump Through Design Variations

Centrifugal blood pumps are usually designed with secondary flow paths to avoid flow dead zones and reduce the risk of thrombosis. Due to the secondary flow path, the intensity of secondary flows and turbulence in centrifugal blood pumps is generally very high. Conventional design theory is no longer applicable to centrifugal blood pumps with a secondary flow path. Empirical relationships between design variables and performance metrics generally do not exist for this type of blood pump. To date, little scientific study has been published concerning optimization and experimental validation of centrifugal blood pumps with secondary flow paths. Moreover, current hemolysis models are inadequate in an accurate prediction of hemolysis in turbulence. The purpose of this study is to optimize the hydraulic and hemolytic performance of an inhouse centrifugal maglev blood pump with a secondary flow path through variation of major design variables, with a focus on bringing down intensity of turbulence and secondary flows. Starting from a baseline design, through changing design variables such as blade angles, blade thickness, and position of splitter blades. Turbulent intensities have been greatly reduced, the hydraulic and hemolytic performance of the pump model was considerably improved. Computational fluid dynamics (CFD) combined with hemolysis models were mainly used for the evaluation of pump performance. A hydraulic test was conducted to validate the CFD regarding the hydraulic performance. Collectively, these results shed light on the impact of major design variables on the performance of modern centrifugal blood pumps with a secondary flow path.

Dynamics of Blood Flows in Aortic Stenosis: Mild, Moderate, and Severe

Supraphysiologic high shear stresses created in calcific aortic stenosis (AS) are known to cause hemostatic abnormalities, however, the relationship between the complex blood flows over the severity of AS and hemostatic abnormalities still remains unclear. This study systematically characterized the blood flow in mild, moderate, and severe AS. A series of large eddy simulations (LES) validated by particle image velocimetry were performed on physiologically representative AS models with a peak physiologic flow condition of 18 liter per minute. Time-accurate velocity fields, transvalvular pressure gradient, and laminar viscous-and turbulent (or Reynolds) shear stresses (RSSmax) were evaluated for each degree of severity. The peak velocities of mild, moderate, and severe AS were on the order of 2.0, 4.0, and 8.0 m/s, respectively. Jet velocity in severe AS was highly skewed with extremely high velocity (as high as 8 m/s) and mainly traveled through the posterior aortic wall up to the aortic arch while still carrying a relatively high velocity, that is, >4 m/s. The mean laminar viscous wall shear stresses (WSS) for mild, moderate, and severe AS were on the order of 40, 100, and 180 Pa, respectively. The RSSmax were on the order of 260, 490, and 2,500 Pa for mild, moderate, and severe AS, respectively. This study may provide a link between altered flows in AS and hemostatic abnormalities such as acquired von Willebrand syndrome and hemolysis, thus, help diagnosing and timing of the treatment.

Thromboembolic Events in Patients With Left Ventricular Assist Devices Are Related to Microparticle-Induced Coagulation

Thromboembolic events (TEs) are a feared complication in patients supported by a continuous-flow left ventricular assist device (LVAD). The aim of the study was to analyze the role of circulating microparticles (MPs) in activating the coagulation system in LVAD patients, which might contribute to the occurrence of TEs. First, we analyzed the effect of LVAD support on endothelial function, on the levels of endothelial MPs (EMPs) and platelet MPs (PMPs), and on the procoagulative activity of circulating MPs (measured as MP-induced thrombin formation) before LVAD implantation, post-implantation, and at a 3 month follow-up (n = 15). Second, these parameters were analyzed in 43 patients with ongoing LVAD support who were followed up for the occurrence of TEs in the following 12 months. In patients undergoing LVAD implantation, the levels of PMPs and MP-induced thrombin formation increased post-LVAD implantation. The flow-mediated vasodilation (FMD) decreased, while the levels of EMPs increased post-LVAD implantation. TEs occurred in eight patients with ongoing LVAD support despite adequate coagulation. The levels of PMPs and MP-induced thrombin formation were higher in LVAD patients with TEs than in LVAD patients without TEs and were independent predictors for the risk of TEs under LVAD support. As conclusion, implantation of LVAD enhanced MP-induced coagulation, which was independently associated with the occurrence of TEs. These parameters may serve in risk stratification for early transplantation and individualized modification of standard LVAD therapy.

Characterization of the competing role of surface-contact and shear stress on platelet activation in the setting of blood contacting devices

Supraphysiological shear stress and surface-contact are recognized as driving mechanisms of platelet activation (PA) in blood contacting devices (BCDs). However, the competing role of these mechanisms in triggering thrombogenic events is poorly understood. Here, we characterized the dynamics of PA in response to the combined effect of shear stress and material exposure. Human platelets were stimulated with different levels of shear stress (500, 750, 1000 dynes/cm²) over a range of exposure times (10, 20, and 30 min) within capillary tubes made of various polymeric materials. Polyethylene (PE), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), and polyether ether ketone (PEEK), used for BCDs fabrication, were investigated as compared to glass and thromboresistant Sigma™-coated glass. PA was quantified using the Platelet Activity State assay. Our results indicate that mechanical stimulation and polymer surface-contact both significantly contribute to PA. Notably, the contribution of the mechanical stimulus ranges between +36% and +43%, while that associated with polymer surface-contact ranges from +48% to +59%, depending on the exposure time. In more detail, our results indicate that: (i) PA increases with increasing shear stress magnitude; (ii) PA has a non-linear, time-dependent relationship to exposure time; (iii) PA is largely influenced by biomaterials, with PE and PEEK having respectively the lowest and highest prothrombotic potential; (iv) the effects of polymer surface-contact and shear stress are not correlated and can be studied separately. Our results suggest the importance of incorporating the evaluation of platelet activation driven by the combined effect of shear stress and polymer surface-contact for the comprehensive assessment, and eventually minimization, of BCDs thrombogenic potential.

Prospects of Therapeutic Target and Directions for Ischemic Stroke

Stroke is a serious, adverse neurological event and the third leading cause of death and disability worldwide. Most strokes are caused by a block in cerebral blood flow, resulting in neurological deficits through the death of brain tissue. Recombinant tissue plasminogen activator (rt-PA) is currently the only immediate treatment medication for stroke. The goal of rt-PA administration is to reduce the thrombus and/or embolism via thrombolysis; however, the administration of rt-PA must occur within a very short therapeutic timeframe (3 h to 6 h) after symptom onset. Components of the pathological mechanisms involved in ischemic stroke can be used as potential biomarkers in current treatment. However, none are currently under investigation in clinical trials; thus, further studies investigating biomarkers are needed. After ischemic stroke, microglial cells can be activated and release inflammatory cytokines. These cytokines lead to severe neurotoxicity via the overactivation of microglia in prolonged and lasting insults such as stroke. Thus, the balanced regulation of microglial activation may be necessary for therapy. Stem cell therapy is a promising clinical treatment strategy for ischemic stroke. Stem cells can increase the functional recovery of damaged tissue after post-ischemic stroke through various mechanisms including the secretion of neurotrophic factors, immunomodulation, the stimulation of endogenous neurogenesis, and neovascularization. To investigate the use of stem cell therapy for neurological diseases in preclinical studies, however, it is important to develop imaging technologies that are able to evaluate disease progression and to “chase” (i.e., track or monitor) transplanted stem cells in recipients. Imaging technology development is rapidly advancing, and more sensitive techniques, such as the invasive and non-invasive multimodal techniques, are under development. Here, we summarize the potential risk factors and biomarker treatment strategies, stem cell-based therapy and emerging multimodal imaging techniques in the context of stroke. This current review provides a conceptual framework for considering the therapeutic targets and directions for the treatment of brain dysfunctions, with a particular focus on ischemic stroke.

Carotid artery structure and hemodynamics and their association with adverse vascular events in left ventricular assist device patients

Left ventricular assist devices (LVADs) are associated with major vascular complications including stroke and gastrointestinal bleeding (GIB). These adverse vascular events may be the result of widespread vascular dysfunction resulting from pre-LVAD abnormalities or continuous flow during LVAD therapy. We hypothesized that pre-existing large artery atherosclerosis and/or abnormal blood flow as measured in carotid arteries using ultrasonography are associated with a post-implantation composite adverse outcome including stroke, GIB, or death. We retrospectively studied 141 adult HeartMate II patients who had carotid ultrasound duplex exams performed before and/or after LVAD surgery. Structural parameters examined included plaque burden and stenosis. Hemodynamic parameters included peak-systolic, end-diastolic, and mean velocity as well as pulsatility index. We examined the association of these measures with the composite outcome as well as individual subcomponents such as stroke. After adjusting for established risk factors, the composite adverse outcome was associated with pre-operative moderate-to-severe carotid plaque (OR 5.08, 95% CI 1.67-15.52) as well as pre-operative internal carotid artery stenosis (OR 9.02, 95% CI 1.06-76.56). In contrast, altered hemodynamics during LVAD support were not associated with the composite outcome. Our findings suggest that pre-existing atherosclerosis possibly in combination with LVAD hemodynamics may be an important contributor to adverse vascular events during mechanical support. This encourages greater awareness of carotid morphology pre-operatively and further study of the interaction between hemodynamics, pulsatility, and structural arterial disease during LVAD support.

Risk factors of readmission to acute care hospital among individuals with heart failure and left ventricular assist device (LVAD) at inpatient rehabilitation setting (STROBE compliant article)

In post-acute care hospital setting, the heart failure (HF) individuals with left ventricular assist device (LVAD) have about 30% of transfer to acute care hospitals which requires readmission. There is relative increase in cost and mortality due to the readmission.The goal of this study is to identify possible risk factors at Inpatient Rehabilitation Unit (IRU) to decrease the rate of readmission to acute care hospitals.This study is retrospective study at the Inpatient Rehabilitation Unit (IRU)Twenty one individuals with HF and LVAD were admitted to IRU. We determined 2 subgroups. One is the readmission group (Readmission) and the other is the control group (Control). Readmission (n = 6) is the individuals who were transferred to acute care hospital, and Control (n = 15) is the individuals who were discharged.To compare Readmission group with Control group and evaluate demographic, laboratory, and functional outcome parameters. Main Outcome Measures are Body Mass Index (BMI), International Normalized Ratio (INR), and Functional independence measure (FIM).At admission, INR in Readmission group was 3.4 ± 1.2 and in Control group was 2.2 ± 0.5 with a statistically significant p value (P = .004) and FIM score in Readmission group was 81.2 ± 15.9 and in Control group was 96.3 ± 11.5 with a statistically significant p value (P = .023).The study showed the individuals with HF and LVAD at IRU had high INR and low FIM which may be the cause for readmission and need more attentive care. This data can help identify the factors causing readmission and help reduce the rate of readmission. Further evaluation is necessary to determine the cause for readmission.

A two-phase flow approach for modeling blood stasis and estimating the thrombosis potential of a ventricular assist device

Thrombosis and its related events have become a major concern during the development and optimization of ventricular assist devices (VADs, also called blood pumps), and limit their clinical use and economic benefits. Attempts have been made to model the thrombosis formation, considering hemodynamic and biochemical processes. However, the complexities and computational expenses are prohibitive. Blood stasis is one of the key factors which may lead to the formation of thrombosis and excessive thromboembolic risks for patients. This study proposed a novel approach for modeling blood stasis, based on a two-phase flow principle. The locations of blood residual can be tracked over time, so that regions of blood stasis can be identified. The blood stasis in an axial blood pump is simulated under various working conditions, the results agree well with the experimental results. In contrast, conventional hemodynamic metrics such as velocity, time-averaged wall shear stress (TAWSS), and relative residence time (RRT), were contradictory in judging risk of blood stasis and thrombosis, and inconsistent with experimental results. We also found that the pump operating at the designed rotational speed is less prone to blood stasis. The model provides an efficient and fast alternative for evaluating blood stasis and thrombosis potential in blood pumps, and will be a valuable addition to the tools to support the design and improvement of VADs.

Nanomaterials for Cardiac Tissue Engineering

End stage heart failure is a major cause of death in the US. At present, organ transplant and left-ventricular assist devices remain the only viable treatments for these patients. Cardiac tissue engineering presents the possibility of a new option. Nanomaterials such as gold nanorods (AuNRs) and carbon nanotubes (CNTs) present unique properties that are beneficial for cardiac tissue engineering approaches. In particular, these nanomaterials can modulate electrical conductivity, hardness, and roughness of bulk materials to improve tissue functionality. Moreover, they can deliver bioactive cargo to affect cell phenotypes. This review covers recent advances in the use of nanomaterials for cardiac tissue engineering.

Left Ventricular Assist Device-Related Complications

Left ventricular assist device (LVAD) has emerged as a safe, durable, and revolutionary therapy for end-stage heart failure patients. Despite the appearance of newer-generation devices that have improved patient outcomes, the burden of adverse events remains significant. Although the survival rate for patients with LVAD is appreciated to be 81% at 1 year and 70% at 2 years, the incidence of adverse events is also high. Over time, both early and late postimplant complications have diminished in terms of prevalence and impact; however, complications, such as infections, bleeding, right heart failure, pump thrombosis, aortic insufficiency, or stroke, continue to represent a challenge for the practitioner. Therefore, the aim of this review is to highlight the most recent data regarding the current use of LVAD in the treatment of end-stage heart failure, with a specific focus on LVAD-related complications, in order to improve device-related outcomes. It will also revise how to mitigate the risk and how to approach specific adverse events. Withal, understanding the predisposing risk factors associated with postimplant complications, early recognition and appropriate treatment help to significantly improve the prognosis for patients with end-stage heart failure.

Acquired von Willebrand syndrome in paediatric patients during mechanical circulatory support

OBJECTIVES

Bleeding signs can become life-threatening complications in patients on mechanical circulatory support (MCS). Clinical phenotyping and comprehensive analyses of the cause of bleeding are, therefore, essential, especially when risk-stratifying patients during MCS workup. We conducted coagulation analyses and determined von Willebrand factor (VWF) parameters in a paediatric cohort on temporary extracorporeal life support, extracorporeal membrane oxygenation or long-term ventricular assist device support.

METHODS

We carried out an observational single-centre study including 30 children with MCS (extracorporeal life support, n = 13; extracorporeal membrane oxygenation, n = 5; and ventricular assist device, n = 12). We also assessed the acquired von Willebrand parameters of each study participant: collagen binding capacity (VWF:CB), the ratio of collagen-binding capacity to VWF antigen (VWF:CB/VWF:Ag) and high-molecular-weight VWF multimers. We also documented bleeding events, transfusion requirement, haemolysis parameters and surgical interventions.

RESULTS

All children developed AVWS (acquired von Willebrand syndrome) during MCS, usually during the early postoperative course. They presented no AVWS after device explantation. We detected a loss of high-molecular-weight VWF multimers, decreased VWF:CB/VWF:Ag ratios and reduced VWF:CB levels. Twenty of the 30 patients experienced bleeding complications; approximately 53% of them required surgical revision. There were no deaths due to bleeding during support.

CONCLUSIONS

The AVWS prevalence in paediatric patients on MCS is 100% regardless of the types of devices tested in this study. The bleeding propensity of AVWS patients widely varies.

Association between splenic volume and pulsatility index in patients with left ventricular assist devices

The spleen serves as a blood volume reservoir for systemic volume regulation in heart failure (HF) patients. Changes are seen in spleen size in advanced HF patients after left ventricular assist device (LVAD) implantation. The pulsatility index (PI) is an indicator of native heart contractility with hemodynamic changes in patients using LVAD. We hypothesized that the splenic volume was associated with the PI, reflecting the hemodynamics in advanced HF patients with LVADs. Herein, we investigated the relationship between splenic volume and PI in these patients. Forty-four patients with advanced HF underwent implantation of HeartMate II^® (Abbott, Chicago, IL, USA) as a bridge to heart transplantation at the Nagoya University Hospital between October 2013 and June 2019. The data of 27 patients (21 men, median age 46 years) were analyzed retrospectively. All patients underwent blood tests, echocardiography, right heart catheterization, and computed tomography (CT). Spleen size was measured via CT volumetry; the splenic volume (median: 190 mL) correlated with right arterial pressure (r = 0.431, p = 0.025) and pulmonary capillary wedge pressure (r = 0.384, p = 0.048). On multivariate linear regression analysis, the heart rate (β = -0.452, p = 0.003), pump power (β = -0.325, p = 0.023), and splenic volume (β = 0.299, p = 0.038) were independent determinants of PI. The splenic volume was associated with PI, reflecting the cardiac preload in advanced HF patients with LVADs. Thus, spleen measurement using CT may help estimate the systemic volume status and understand the hemodynamic conditions in LVAD patients.

The role of long-term mechanical circulatory support in patients with advanced heart failure

In patients with end-stage heart failure, advanced therapies such as heart transplantation and long-term mechanical circulatory support (MCS) with a left ventricular assist device (LVAD) have to be considered. LVADs can be implanted as a bridge to transplantation or as an alternative to heart transplantation: destination therapy. In the Netherlands, long-term LVAD therapy is gaining importance as a result of increased prevalence of heart failure together with a low number of heart transplantations due to shortage of donor hearts. As a result, the difference between bridge to transplantation and destination therapy is becoming more artificial since, at present, most patients initially implanted as bridge to transplantation end up receiving extended LVAD therapy. Following LVAD implantation, survival after 1, 2 and 3 years is 83%, 76% and 70%, respectively. Quality of life improves substantially despite important adverse events such as device-related infection, stroke, major bleeding and right heart failure. Early referral of potential candidates for long-term MCS is of utmost importance and positively influences outcome. In this review, an overview of the indications, contraindications, patient selection, clinical outcome and optimal time of referral for long-term MCS is given.

Continuous-flow left ventricular assist devices: Management in the emergency department

With an increasing number of left ventricular assist devices (LVADs) being placed every year, emergency clinicians are increasingly likely to encounter them in their practice. Patients may present to the emergency department (ED) with significant hemodynamic perturbations with an LVAD and it is imperative that emergency clinicians are able to assess and treat conditions contributing to low cardiac output states. This review describes the important aspects of the third generation of LVADs and their complications as well as common management approaches for the emergency physician.

Outcomes of left ventricular assist device implantation in hypercoagulable patients

BACKGROUND

The aim of this study was to evaluate outcomes of left ventricular assist devices (LVADs) in patients who tested positive for hypercoagulable hematologic disorders.

METHODS

Adults undergoing continuous-flow LVAD implantation with preoperative hypercoagulability testing between 2004 and 2018 at a single center were reviewed. Hypercoagulability was defined as testing positive for antiphospholipid antibody, anticardiolipin antibody, lupus anticoagulant, protein C, protein S, factor V Leiden, and/or heparin-induced thrombocytopenia. The primary outcome was survival on the original LVAD. Secondary outcomes included rates of thromboembolic complications and readmission for intravenous heparin treatment.

RESULTS

A total of 270 LVAD patients with pre-implant hypercoagulability testing were included, and 157 (58%) tested positive for a hypercoagulable disorder. Of those testing positive, 10 (6.4%) had a clinical pre-LVAD history of thromboembolic events. Survival was comparable between hypercoagulable and non-hypercoagulable patients (1 year: 73.3% vs 78.9%, P = .2195, 2-year: 60.7% vs 62.8%, P = .3627). Rates of pump thrombosis (14.0% vs 13.3%, P = .8618), hemolysis (4.5% vs 3.5%, P = .3536), stroke (18.5% vs 14.2%, P = .3483) and readmission for IV heparin therapy (87.3% (n = 137) vs 77.9% (n = 88), P = .7560) were similar. Outcomes were comparable in patients with positive hypercoagulable tests when stratified by pre-implant clinical history of hypercoagulability as well as stratified by recent preoperative exposure to heparin or warfarin.

CONCLUSIONS

In this series, positive laboratory tests for hypercoagulability were common amongst patients undergoing LVAD implantation although few had positive clinical histories. Survival and freedom from thromboembolic complications were comparable to non-hypercoagulable patients. Hypercoagulability alone should therefore not serve as a contraindication to LVAD implantation.

Spleen size improvement in advanced heart failure patients using a left ventricular assist device

The spleen has been recognized as an important organ that holds a reserve of 20% to 30% of the total blood volume. Spleen contraction and splenic volume reduction occur in patients with hypovolemic shock. However, the change in the spleen volume and the association between spleen size and hemodynamic parameters remain unclear in patients with advanced heart failure (HF) who need left ventricular assist device (LVAD) support. This study was performed to investigate the change in spleen size and the relationship between spleen size and hemodynamic parameters before and after LVAD implantation in patients with advanced HF. We enrolled 20 patients with advanced HF on LVAD support. All patients underwent right heart catheterization and computed tomography before and after LVAD implantation. The spleen size was measured by computed tomography volumetry. We excluded patients with a mean right atrial pressure (RAP) of <5 mm Hg because of the possibility of hypovolemia and those with a cardiac index of >2.2 L/min/m² before LVAD implantation. The splenic volume significantly increased from 160.6 ± 46.9 mL before LVAD implantation to 224.6 ± 73.5 mL after LVAD implantation (P < .001). Before LVAD implantation, there was a significant negative correlation between spleen volume and systemic vascular resistance (SVR). After LVAD implantation, however, there were significant correlations between spleen volume and the cardiac index, RAP, and pulmonary capillary wedge pressure despite the absence of a significant correlation between spleen volume and SVR. Furthermore, one patient developed reworsening HF because of LVAD failure due to pump thrombosis. In this case, the splenic volume was 212 mL before LVAD implantation and increased to 418 mL after LVAD implantation, although it decreased to 227 mL after LVAD failure. The spleen size may change depending on hemodynamics in patients with advanced HF with LVAD support, reflecting sympathetic nerve activity and the systemic volume status.

Remote monitoring for better management of LVAD patients: the potential benefits of CardioMEMS

Left ventricular assist devices (LVAD) are frequently used in the treatment of end-stage heart failure (HF), and due to the shortage of heart donors and destination programs, it is likely to keep on growing. Still, LVAD therapy is not without complications and morbidity and rehospitalization rates are high. New ways to improve LVAD care both from the side of the patient and the physician are warranted. Remote monitoring could be a tool to tailor treatment in these patients, as no feedback exists at all about patient functioning on top of the static pump parameters. We aim to provide an overview and evaluation of the novel remote monitoring strategies to optimize LVAD management and elaborate on the opportunities of remote hemodynamic monitoring with CardioMEMS, at home in these patients as the next step to improve care.

Anesthetic management of a patient with a continuous-flow left ventricular assist device for video-assisted thoracoscopic surgery: a case report

Background

As patients with left ventricular assist device (LVAD) have long expected survival, the incidence of noncardiac surgery in this patient population is increasing. Here, we present the anesthetic management of a patient with a continuous-flow LVAD who underwent video-assisted thoracic surgery (VATS).

Case presentation

A 37-year-old man with LVAD was scheduled to undergo VATS because of repeated spontaneous pneumothorax. Generally, patients with these devices have marginal right heart function; therefore, it is important to avoid factors that worsen pulmonary vascular resistance (PVR). However, VATS requires one-lung ventilation (OLV) and it tends to cause increase in PVR, leading to right heart failure.

In the present case, when the patient was set in a lateral decubitus position and progressive hypoxia was observed during OLV, transesophageal echocardiography demonstrated a dilated right ventricle and a temporally flattened interventricular septum, and the central venous pressure increased to approximately 20 mmHg. Because we anticipated deterioration of right heart function, dobutamine and milrinone were administered and/or respirator settings were changed to decrease PVR for maintaining LVAD performance. Finally, resection of a bulla was completed, and the patient was discharged in stable condition on postoperative day 37.

Conclusions

The anesthetic management of a patient with LVAD during VATS is challenging because the possible hemodynamic changes induced by hypoxia associated with OLV affect LVAD performance and right heart function. In our experience, VATS that requires OLV will be well tolerated in a patient with LVAD with preserved right heart function, and a multidisciplinary approach to maintain right heart function will be needed.

The Predicament of Gastrointestinal Bleeding in Patients With a Continuous-Flow Left Ventricular Assist Device: Pathophysiology, Evaluation, and Management

Heart failure affects over 5 million Americans, with numbers expected to rise. While heart transplantation is the most effective long-term strategy for end-stage heart failure, there is a limited cardiac donor pool, and these organs are often unavailable at the time of need. Left ventricular assist devices, therefore, continue to be used to bridge this gap. Originally implanted as a bridge to transplant, these devices are now additionally utilized as destination therapy for patients ineligible for transplant. With the widespread applicability of these devices for not just temporary measures, but also for prolonged use, the short- and long-term impact on other organ systems has become more evident. For example, gastrointestinal (GI) bleeding, with an incidence approaching 30%, is one such complication post-continuous-flow left ventricular assist device implantation. This high incidence of GI bleeding is thought to stem from a combination of factors, including the need for concomitant anticoagulant and antiplatelet therapy, and intrinsic device-related properties resulting in acquired Von Willebrand disease and arteriovenous malformations. Due to the significant morbidity associated with these GI bleeding events, a standardized protocol optimizing medical and endoscopic management, alongside close coordination between the gastroenterology and cardiology services, should be advocated for and ultimately employed.

Longitudinal assessment of the platelet transcriptome in advanced heart failure patients following mechanical unloading

Patients with heart failure (HF) and left ventricular assist devices (LVAD) have dysregulated thrombo-inflammatory responses, mediated in part by platelets. While studies of platelet activation have been undertaken in HF, changes in the platelet transcriptome in HF patients following mechanical unloading with an LVAD have not been investigated. We prospectively enrolled and longitudinally followed advanced HF patients (n = 32) for a mean of 57 months post-LVAD implantation. For comparison, healthy donors were also enrolled (n = 20). Platelets were hyperactive in HF, as evidenced by significantly increased formation of circulating platelet-monocyte aggregate formation. Platelet transcriptome interrogation by next-generation RNA-sequencing identified that the expression of numerous genes (n = 588) was significantly (FDR < 0.05) altered in HF patients prior to LVAD implantation. Differentially expressed genes were predicted to have roles in angiogenesis, immune and inflammatory responses, apoptosis, and cardiac muscle contraction. 90 days following LVAD implantation, the majority (80%) of differentially expressed genes in HF patients normalized, as compared to the platelet transcriptomes of healthy donors. In conclusion, advanced HF is associated with marked alterations in the platelet transcriptome. While LVAD implantation to off load the failing heart results in resolution in the majority of differentially expressed genes, a subset of the platelet transcriptome remains persistently altered.

Platelet deposition estimation: A novel method for emulating the pump thrombosis potential of blood pumps

Pump thrombosis potential exists in most blood pumps and limits their clinical use. To improve the pump thrombosis performance of blood pumps, a method for emulating the platelet deposition on the flow passage component surfaces inside blood pumps was presented and tested. The method emulates the blood platelet deposition, employing laser-induced fluorescence tracing technology. The blood pump was rotated in a mock circulation loop with deionized water filled with fluorescent particles. The component surfaces were then explored via laser. The fluorescent particles were induced by laser and imaged in a charge-coupled device (CCD) camera to show the distribution of fluorescent particles gathering on the blood pump component surfaces. The activated platelet deposition was emulated by fluorescent particle gathering. The experiment showed obvious particle gathering on the interface surfaces and cross-sectional surface (perpendicular to the flow). This platelet deposition estimation (PDE) method can be easily incorporated in the in vitro testing phase to analyze and decrease a pump's thrombosis potential before animal experimentation, thereby reducing the cost of blood pump development. This methodology of emulating blood platelet deposition indicates its potential for improving flow passage component structure and reducing device thrombosis of blood pumps.

Sequential Pattern Mining of Longitudinal Adverse Events After Left Ventricular Assist Device Implant

Left ventricular assist devices (LVADs) are an increasingly common therapy for patients with advanced heart failure. However, implantation of the LVAD increases the risk of stroke, infection, bleeding, and other serious adverse events (AEs). Most post-LVAD AEs studies have focused on individual AEs in isolation, neglecting the possible interrelation, or causality between AEs. This study is the first to conduct an exploratory analysis to discover common sequential chains of AEs following LVAD implantation that are correlated with important clinical outcomes. This analysis was derived from 58,575 recorded AEs for 13,192 patients in International Registry for Mechanical Circulatory Support (INTERMACS) who received a continuous-flow LVAD between 2006 and 2015. The pattern mining procedure involved three main steps: (1) creating a bank of AE sequences by converting the AEs for each patient into a single, chronologically sequenced record, (2) grouping patients with similar AE sequences using hierarchical clustering, and (3) extracting temporal chains of AEs for each group of patients using Markov modeling. The mined results indicate the existence of seven groups of sequential chains of AEs, characterized by common types of AEs that occurred in a unique order. The groups were identified as: GRP1: Recurrent bleeding, GRP2: Trajectory of device malfunction & explant, GRP3: Infection, GRP4: Trajectories to transplant, GRP5: Cardiac arrhythmia, GRP6: Trajectory of neurological dysfunction & death, and GRP7: Trajectory of respiratory failure, renal dysfunction & death. These patterns of sequential post-LVAD AEs disclose potential interdependence between AEs and may aid prediction, and prevention, of subsequent AEs in future studies.