Activation of endothelial and coagulation systems in left ventricular assist device recipients

The Role of Coagulation in Heart Failure: A Literature Review

PURPOSE OF REVIEW

This article summarizes the role of coagulation factors in the pathophysiology of heart failure including D-dimer, fibrinogen and fibrin, prothrombin, p-selectin, tissue factor, tissue plasminogen activator, von Willebrand factor, β-thromboglobulin, Factor XI, tissue thromboplastin, plasminogen activator inhibitor-1 (PAI-1), thrombomodulin, soluble urokinase-type plasminogen activator receptor (suPAR) and stuart-prower factor.

RECENT FINDINGS

The D-dimer, P-selectin, prothrombin, von Willebrand factor, tissue plasminogen activator, fibrinogen, suPAR, tissue factor, thrombomodulin and Factor XI play significant roles the pathophysiology of heart failure. However, no associations were found between β-thromboglobulin, tissue thromboplastin, PAI-1 and stuart-prower factor in the context of heart failure. Coagulation factors play significant role in the pathophysiology of heart failure. Consequently, the underlying pathophysiological mechanisms that explain changes in the cascade are closely related to the diagnostic, prognostic and therapeutic roles of coagulation cascade factors, which help physicians identify and treat heart failure.

The Impact of Acute Exercise on Hemostasis and Angiogenesis Mediators in Patients With Continuous-Flow Left Ventricular Assist Devices: A Prospective Observational Pilot Study

Impaired primary hemostasis and dysregulated angiogenesis, known as a two-hit hypothesis, are associated with gastrointestinal (GI) bleeding in patients with continuous-flow left ventricular assist devices (CF-LVADs). Exercise is known to influence hemostasis and angiogenesis in healthy individuals; however, little is known about the effect in patients with CF-LVADs. The objective of this prospective observational study was to determine whether acute exercise modulates two-hit hypothesis mediators associated with GI bleeding in patients with a CF-LVAD. Twenty-two patients with CF-LVADs performed acute exercise either on a cycle ergometer for approximately 10 minutes or on a treadmill for 30 minutes. Blood samples were taken pre- and post-exercise to analyze hemostatic and angiogenic biomarkers. Acute exercise resulted in an increased platelet count (p < 0.00001) and platelet function (induced by adenosine diphosphate, p = 0.0087; TRAP-6, p = 0.0005; ristocetin, p = 0.0009). Additionally, high-molecular-weight vWF multimers (p < 0.00001), vWF collagen-binding activity (p = 0.0012), factor VIII (p = 0.034), angiopoietin-1 (p = 0.0026), and vascular endothelial growth factor (p = 0.0041) all increased after acute exercise. This pilot work demonstrates that acute exercise modulated two-hit hypothesis mediators associated with GI bleeding in patients with CF-LVADs.

Vasoplegic syndrome during heart transplantation: A systematic review and meta-analysis

BACKGROUND

Vasoplegic syndrome (VS) is a common occurrence during heart transplantation (HT). It currently lacks a uniform definition between transplant centers, and its pathophysiology and treatment remain enigmatic. This systematic review summarizes the available published clinical data regarding VS during HT.

METHODS

We searched databases for all published reports on VS during HT. Data collected included the incidence of VS in the HT population, patient and intraoperative characteristics, and postoperative outcomes.

RESULTS

Twenty-two publications were included in this review. The prevalence of VS during HT was 28.72% (95% confidence interval: 27.37%, 30.10%). Factors associated with VS included male sex, higher body mass index, hypothyroidism, pre-HT left ventricular assist device or venoarterial extracorporeal membrane oxygenation (VA-ECMO), pre-HT calcium channel blocker or amiodarone usage, longer cardiopulmonary bypass time, and higher blood product transfusion requirement. Patients who developed VS were more likely to require postoperative VA-ECMO support, renal replacement therapy, reoperation for bleeding, longer mechanical ventilation, and a greater 30-day and 1-year mortality.

CONCLUSIONS

The results of our systematic review are an initial step for providing clinicians with data that can help identify high-risk patients and avenues for potential risk mitigation. Establishing guidelines that officially define VS will aid in the precise diagnosis of these patients during HT and guide treatment. Future studies of treatment strategies for refractory VS are needed in this high-risk patient population.

Stroke and Mechanical Circulatory Support in Adults

PURPOSE OF THE REVIEW

Short-term and durable mechanical circulatory support (MCS) devices represent life-saving interventions for patients with cardiogenic shock and end-stage heart failure. This review will cover the epidemiology, risk factors, and treatment of stroke in this patient population.

RECENT FINDINGS

Short-term devices such as intra-aortic balloon pump, Impella, TandemHeart, and Venoatrial Extracorporal Membrane Oxygenation, as well as durable continuous-flow left ventricular assist devices (LVADs), improve cardiac output and blood flow to the vital organs. However, MCS use is associated with high rates of complications, including ischemic and hemorrhagic strokes which carry a high risk for death and disability. Improvements in MCS technology have reduced but not eliminated the risk of stroke. Mitigation strategies focus on careful management of anti-thrombotic therapies. While data on therapeutic options for stroke are limited, several case series reported favorable outcomes with thrombectomy for ischemic stroke patients with large vessel occlusions, as well as with reversal of anticoagulation for those with hemorrhagic stroke. Stroke in patients treated with MCS is associated with high morbidity and mortality. Preventive strategies are targeted based on the specific form of MCS. Improvements in the design of the newest generation device have reduced the risk of ischemic stroke, though hemorrhagic stroke remains a serious complication.

Insights in the Prothrombotic Changes After Implantation of a Left Ventricular Assist Device in Patients With End-Stage Heart Failure: A Longitudinal Observational Study

Thrombus formation is a common complication during left ventricular assist device (LVAD) therapy, despite anticoagulation with vitamin K antagonists (VKA) and a platelet inhibitor. Plasma levels of markers for primary and secondary hemostasis and contact activation were determined before LVAD implantation and 6 and 12 months thereafter in 37 adults with end-stage heart failure. Twelve patients received a HeartMate 3, 7 patients received a HeartWare, and 18 patients received a HeartMate II. At baseline, patients had elevated plasma levels of the platelet protein upon activation, β-thromboglobulin, and active von Willebrand factor in thrombogenic state (VWFa), which remained high after LVAD implantation. Von Willebrand factor levels and VWF activity were elevated at baseline but normalized 12 months after LVAD implantation. High D -dimer plasma levels, at baseline, remained elevated after 12 months. This was associated with an increase in plasma thrombin-antithrombin-complex levels and plasma levels of contact activation marker-cleaved H-kininogen after LVAD implantation. Considering these results it could be concluded that LVAD patients show significant coagulation activation despite antithrombotic therapy, which could explain why patients are at high risk for LVAD-induced thrombosis. Continuous low-grade systemic platelet activation and contact activation may contribute to prothrombotic effects of LVAD.

The endogenous thrombin potential in patients with left ventricular assist device or heart transplant

Background

The Heartmate 3 (HM 3) is a left ventricular assist device featuring less shear stress, milder acquired von Willebrand syndrome, and fewer bleeding incidences than its predecessor the Heartmate II (HM II). The novel surface coating of the HM 3 suggests less contact activation of plasmatic coagulation. We hypothesized that patients with HM 3 exhibit fewer aberrations in their thrombin potential than patients with HM II. We compared these results with the thrombin potential of patients with heart transplantation (HTX).

Methods

Thrombin generation in plasma samples of patients with HM II (n = 16), HM 3 (n = 20), and HTX (n = 13) was analyzed 3 days after implantation/transplantation and after long-term support (3-24 months) with HM II (n = 16) or HM 3 (n = 12) using calibrated automated thrombography. Heparin in postoperative samples was antagonized with polybrene.

Results

Three days postoperatively HM II patients exhibited a lower endogenous thrombin potential (ETP) than HM 3 and HTX patients (HM II: 947 ± 291 nM*min; HM 3: 1231 ± 176 nM*min; HTX: 1376 ± 162 nM*min, p < 0.001) and a lower velocity index of thrombin generation (HM II: 18.74 ± 10.90 nM/min; HM 3: 32.41 ± 9.51 nM/min; HTX: 37.65 ± 9.41 nM/min, p < 0.01). Subtle differences in the thrombin generation profiles remained in HM II and HM 3 patients under long-term support (Velocity Index: HM II: 38.70 ± 28.46 nM/min; HM 3: 73.32 ± 32.83 nM/min, p < 0.05). Prothrombin fragments 1 + 2 were higher in HM II than in HM 3 patients (HM II: 377.7 ± 208.4 pM; HM 3: 202.1 ± 87.7 pM, p < 0.05) and correlated inversely with the ETP (r = -0.584, p < 0.05).

Conclusion

We observed a more aberrant thrombin generation in HM II than in HM 3 despite comparable anticoagulation and routine parameters. A trend toward lower values was still observable in HM 3 compared to HTX patients. Calibrated automated thrombography may be a good tool to monitor the coagulation state of these patients and guide anticoagulation in the future.

The Effect of Artificial Pulsatility on the Peripheral Vasculature in Patients with A Continuous-Flow Ventricular Assist Device

BACKGROUND

Implantation of left ventricular assist systems (LVASs) has become the standard of care for advanced heart failure (HF). The absence of pulsatility in previous devices contributes to vascular and endothelial dysfunction, related to atherosclerotic or vascular complications. We hypothesized that the artificial pulsatility provided by the HeartMate 3 (HM3) LVAS would exert a favorable effect on the vasculature.

METHODS

In 32 patients implanted with HM3 (5 females; mean age 55±13.6 years), the reactive hyperemia index (RHI) and peripheral augmentation index (AI), markers of endothelial function and arterial stiffness, were measured with an Endo-PAT2000 prior to and in the 3^rd and 6^th months after implantation. RHI and AI data from 30 HeartMate II (HM II) recipients in the 3^rd and 6^th months after implantation, from 15 advanced HF patients without LVASs, and from 13 healthy volunteers were also analyzed.

RESULTS

In HM3 recipients, the mean RHI significantly decreased at 3^rd and 6^th months after implantation. The RHI was substantially lower at baseline than that of healthy or HF reference group. Increasing AI values, indicating worsening arterial stiffness, were also observed. Similar trends were observed in HM II recipients between the 3^rd and 6^th months, but with higher absolute values of RHI and AI.

CONCLUSIONS

We detected impaired vascular function in HM3 patients and provided additional evidence on the negative effect of low pulsatility on vascular function after LVAS implantation. The results suggest that the artificial pulsatility of the HM3 does not avert the progression of endothelial dysfunction.

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.

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.

Endothelial Function in Patients With Continuous-Flow Left Ventricular Assist Devices

The endothelium plays a crucial role in maintaining cardiovascular homeostasis. Shear stress generated by flowing blood regulates the release of substances that provide adequate tissue perfusion. The extent of damage to endothelial cells depends on locally disturbed shear stress caused by the deteriorated flow. Patients with heart failure have reduced cardiac output, which results in reduced blood flow and negative shear stress. Reduced shear stress also affects microcirculation and reduces tissue perfusion. Consequently, the production of free oxygen radicals is increased and bioavailability of nitric oxide is additionally decreased. Therefore, endothelial dysfunction is involved in the progression of heart failure and cardiovascular events. Left ventricular assist devices (LVAD) are used for the treatment of patients with advanced heart failure. Older pulsatile flow LVADs were mostly substituted by continuous-flow LVADs (cf-LVADs). Despite the advantages of the cf-LVADs, the loss of pulsatility leads to different complications on the micro- and macrovascular levels. One of the pathogenetic mechanisms of cardiovascular complications with cf-LVADs may be endothelial dysfunction, which after the implantation of the device does not improve and may even deteriorate. In contrast, the pulsatile pattern of LVADs on blood flow could preserve endothelial function.

Proteomic Signatures During Treatment in Different Stages of Heart Failure

Background:

Proteomics have already provided novel insights into the pathophysiology of heart failure (HF) with reduced ejection fraction. Previous studies have evaluated cross-sectional protein signatures of HF, but few have characterized proteomic changes following HF with reduced ejection fraction treatment with ARNI (angiotensin receptor/neprilysin inhibitor) therapy or left ventricular assist devices.

Methods:

In this retrospective omics study, we performed targeted proteomics (N=625) of whole blood sera from patients with American College of Cardiology/American Heart Association stage D (N=29) and stage C (N=12) HF using proximity extension assays. Samples were obtained before and after (median=82 days) left ventricular assist device implantation (stage D; primary analysis) and ARNI therapy initiation (stage C; matched reference). Oblique principal component analysis and point biserial correlations were used for feature extraction and selection; standardized mean differences were used to assess within and between-group differences; and enrichment analysis was used to generate and cluster Gene Ontology terms.

Results:

Core sets of proteins were identified for stage C (N=9 proteins) and stage D (N=18) HF; additionally, a core set of 5 shared HF proteins (NT-proBNP [N-terminal pro-B type natriuretic peptide], ESM [endothelial cell-specific molecule]-1, cathepsin L1, osteopontin, and MCSF-1) was also identified. For patients with stage D HF, moderate (δ, 0.40–0.60) and moderate-to-large (δ, 0.60–0.80) sized differences were observed in 8 of their 18 core proteins after left ventricular assist devices implantation. Additionally, specific protein groups reached concentration levels equivalent ( g <0.10) to stage C HF after initiation on ARNI therapy.

Conclusions:

HF with reduced ejection fraction severity associates with distinct proteomic signatures that reflect underlying disease attributes; these core signatures may be useful for monitoring changes in cardiac function following initiation on ARNI or left ventricular assist device implantation.

Magnetic Resonance Imaging Based Flow Field and Lagrangian Particle Tracking From a Left Ventricular Assist Device

This study explores the optimal left ventricular assist device (LVAD) cannula outflow configuration in a patient-specific replica of the aorta. The volumetric velocity field is measured using phase-contrast magnetic resonance imaging (PC-MRI) under a physiologically relevant steady flow. The effect of the LVAD outflow graft insertion site and anastomosis angle on the transport of embolic particles to cranial vessels is studied by solving the particle equation of motion for spheres in the range of 0.1-1.0 mm using the measured three-dimensional (3D) velocity field. Results show that for a given aorta anatomy, it is possible to design the cannula graft location and terminal curvature so that the probability of embolic transport to the cranial vessels is significantly minimized. This is particularly important since the complex flow pattern in each cannula case affects the embolic trajectories differently, and hence the common assumption that particles distribute by the volumetric flow division does not hold.

Medical Management of Left Ventricular Assist Device Patients: A Practical Guide for the Nonexpert Clinician

Left ventricular assist devices (LVADs) provide short- or long-term circulatory support to improve survival and reduce morbidity in selected patients with advanced heart failure. LVADs are being used increasingly and now have expanded indications. Health care providers across specialties will therefore not only encounter LVAD patients but play an integral role in their care. To accomplish that, they need to understand the elements of LVAD function, physiology and clinical use. This article provides a concise overview of the medical management of LVAD patients for nonexpert clinicians. Our presentation includes the basics of LVAD physiology, design, and operation, patient selection and assessment, medical management, adverse event identification and management, multidisciplinary care, and management of special circumstances, such as noncardiac surgery, cardiac arrest, and end-of-life care. The clinical examination of LVAD patients is unique in terms of blood pressure and heart rate assessment, LVAD "hum" auscultation, driveline and insertion site inspection, and device parameter recording. Important potential device-related adverse events include stroke, gastrointestinal bleeding, hematologic disorders, device infection, LVAD dysfunction, arrhythmias, and heart failure. Special considerations include the approach to the unconscious or pulseless patient, noncardiac surgery, and palliative care. An understanding of the principles presented in this paper will enable the nonexpert clinician to be effective in collaborating with an LVAD center in the assessment, medical management, and follow-up of LVAD patients. Future opportunities and challenges include the improvement of device designs, greater application of minimally invasive surgical implantation techniques, and management of health economics in cost-constrained systems like those of Canada and many other jurisdictions.

Clinical and In Vitro Evidence That Left Ventricular Assist Device-Induced von Willebrand Factor Degradation Alters Angiogenesis

Background Gastrointestinal bleeding from angiodysplasia is a major problem in continuous-flow left ventricular assist device (LVAD) patients. LVAD shear stress causes pathologic degradation of VWF (von Willebrand factor). A mechanistic relationship between VWF degradation and angiodysplasia has not been explored. We tested 2 novel hypotheses: (1) clinical hypothesis: VWF fragments are elevated in LVAD patients that develop angiodysplasia and (2) in vitro hypothesis: VWF fragments generated during LVAD support alter angiogenesis, which may contribute to angiodysplasia. Methods and Results Clinical study: Paired blood samples were collected from continuous-flow LVAD patients (n=35). VWF was quantified with immunoblotting. In vitro experiments: (1) To investigate whether LVAD support alters angiogenesis, human endothelial cells were cultured with LVAD patient plasma (n=11). To investigate mechanism, endothelial cells were cultured with VWF fragments produced by exposing human VWF and ADAMTS-13 (VWF protease) to LVAD-like shear stress (175 dyne/cm², n=8). Clinical study results: in all patients (n=35, mean support 666±430 days), LVAD support degraded high-molecular-weight VWF multimers ( P<0.0001) into low-molecular-weight VWF multimers ( P<0.0001) and VWF fragments ( P<0.0001). In patients with gastrointestinal bleeding from angiodysplasia (n=7), VWF fragments were elevated ( P=0.02) versus nonbleeders. In contrast, in patients with gastrointestinal bleeding without angiodysplasia, VWF fragments were not elevated versus nonbleeders ( P=0.96). In vitro experiments results: LVAD patient plasma caused abnormal angiogenesis with reduced tubule length ( P=0.04) and migration ( P=0.05). Similarly, endothelial cells grown with VWF degradation fragments exhibited reduced tubule length ( P<0.001) and migration ( P=0.01). Conclusions LVAD patients who bled from angiodysplasia had higher levels of VWF fragments than nonbleeders and gastrointestinal bleeders without angiodysplasia. VWF fragments caused abnormal angiogenesis in vitro. These findings suggest that VWF fragments may be a mechanistic link between LVAD support, abnormal angiogenesis, angiodysplasia, and gastrointestinal bleeding.

Meta-Analysis of the Effect of Preoperative Atrial Fibrillation on Outcomes After Left Ventricular Assist Device Implantation

The effect of preoperative atrial fibrillation (AF) on clinical outcomes after left ventricular assist device (LVAD) implantation remains uncertain. We sought to conduct a meta-analysis to assess the safety and efficacy of LVAD implantation in AF patients. Medline and Scopus were searched for studies that assessed the effect of preoperative AF on clinical outcomes in patients who underwent LVAD implantation. Outcomes of interest included all-cause mortality, thromboembolic events, and bleeding. Estimates were combined using random effects model to calculate risk ratios (RRs) with 95% confidence intervals. In this meta-analysis of 7 studies including 5,658 patients, preoperative AF was not associated with increased risk of all-cause mortality at 30 days (RR = 0.84 [0.51, 1.37]; p = 0.49; I² = 0%), 6 months (RR = 1.17 [0.96, 1.14]; p = 0.11; I² = 21%), 1 year (RR = 1.16 [0.84, 1.60]; p = 0.37; I² = 53%) and 2 years (RR = 1.14 [0.96, 1.36]; p = 0.12; I² = 23%). Preoperative AF did not increase the risk of thromboembolism (RR = 0.86 [0.38, 1.92]; p = 0.71; I² = 26%), pump thrombosis (RR = 1.22 [0.88, 1.68]; p = 0.23; I² = 49%), stroke (RR = 1.02 [0.87, 1.19]; p = 0.79; I² = 11%), or major bleeding (RR = 0.86 [0.38, 1.92]; p = 0.71; I² = 26%) after LVAD implantation. However, AF was associated with significantly increased risk of gastro-intestinal bleeding in patients receiving LVADs (RR = 1.27 [1.05, 1.55]; p = 0.014; I² = 0%). In conclusion, this meta-analysis reports a significantly increased risk of gastrointestinal (GI) bleeding in LVADs recipients having concomitant AF. However, AF had no significant effect on all-cause mortality, stroke, or thromboembolic events in these patients. Further well-conducted studies are needed to validate these results.

Device-induced platelet dysfunction in mechanically assisted circulation increases the risks of thrombosis and bleeding

Thrombotic and bleeding complications are the major obstacles for expanding mechanical circulatory support (MCS) beyond the current use. While providing the needed hemodynamic support, those devices can induce damage to blood, particularly to platelets. In this study, we investigated device-induced alteration of three major platelet surface receptors, von Willebrand factor (VWF) and associated hemostatic functions relevant to thrombosis and bleeding. Fresh human whole blood was circulated in an extracorporeal circuit with a clinical rotary blood pump (CentriMag, Abbott, Chicago, IL, USA) under the clinically relevant operating condition for 4 hours. Blood samples were examined every hour for glycoprotein (GP) IIb/IIIa activation and receptor loss of GPVI and GPIbα on the platelet surface with flow cytometry. Soluble P-selectin in hourly collected blood samples was measured by enzyme linked immunosorbent assay to characterize platelet activation. Adhesion of device-injured platelets to fibrinogen, collagen, and VWF was quantified with fluorescent microscopy. Device-induced damage to VWF was characterized with western blotting. The CentriMag blood pump induced progressive platelet activation with blood circulating time. Particularly, GPIIb/IIIa activation increased from 1.1% (Base) to 11% (4 hours) and soluble P-selectin concentration increased from 14.1 ng/mL (Base) to 26.5 ng/mL (4 hours). Those device-activated platelets exhibited increased adhesion capacity to fibrinogen. Concurrently, the CentriMag blood pump caused progressive platelet receptor loss (GPVI and GPIbα) with blood circulating time. Specifically, MFI of the GPVI and GPIbα receptors decreased by 17.2% and 16.1% for the 4-hours sample compared to the baseline samples, respectively. The device-injured platelets exhibited reduced adhesion capacities to collagen and VWF. The high molecular weight multimers (HMWM) of VWF in the blood disappeared within the first hour of the circulation. Thereafter the multimeric patterns of VWF were stable. The change in the VWF multimeric pattern was different from the progressive structural and functional changes of platelets with the circulation time. This study suggested that the CentriMag blood pump could induce two opposite effects on platelets and associated hemostatic functions under a clinically relevant operating condition. The device-altered hemostatic function may contribute to thrombosis and bleeding simultaneously as occurring in patients supported by a rotary blood pump. Device-induced damage of platelets may be an important cause for bleeding in patients supported with rotary blood pump MCS systems relative to device-induced loss of HMWM-VWF.

Ventricular Assist Device Patients Have Different Clinical Outcomes and Altered Patterns of Bleeding with Intracranial Hemorrhage

Intracranial hemorrhage (ICH) is one of the most feared complications of left ventricular assist device (LVAD) support. However, outcomes in this group have not been well described. We therefore sought to examine clinical outcomes in this patient population in comparison to those with heart failure (HF) and no LVAD, as well as those without HF or LVAD. The National Inpatient Sample database, years 2002-2012, was queried to classify patients into 3 groups: any ICH (group 1), any HF with any ICH (group 2), and any LVAD with any ICH (group 3). Clinical outcomes, hemorrhage type, neurosurgical intervention rates, and hospital factors were collected and analyzed. Group 1 consisted of 419,264 patients, group 2 had 41,186, and group 3 had 118 patients. Group 3 patients were more likely to be in large, academic medical centers, with longer length of stay and higher hospital charges. Inpatient mortality was highest in this group at 39%; however, 46.2% were ultimately discharged to home. Patients in group 3 were more likely to have a subarachnoid or intracerebral hemorrhage versus a subdural or epidural hemorrhage. Neurosurgical intervention rates did not differ between the groups. Although LVAD patients with ICH have worse clinical outcomes, the majority survived their event and nearly half were able to be discharged home. Left ventricular assist device patients also have a distinct pattern of bleeding with ICH. Additional study is required to understand risk factors for the development of ICH in this population and ideal management strategies.

Early Gastrointestinal Complications From Ventricular Assist Devices is Increased by Non-Pulsatile Flow

BACKGROUND

Measurements of organ flow and perfusion during cardiopulmonary bypass suggest that perfusion of the splanchnic bed can be impaired by non-pulsatile flow. We postulated that non-pulsatile flow from centrifugal ventricular assist devices might also compromise splanchnic blood flow and cause bowel ischaemia especially in the period of circulatory instability early post-implant. The aim of the present studies was to compare the incidence of gastrointestinal (GI) complications in patients having a non-pulsatile device with the incidence in those having a pulsatile device.

METHODS

In a pilot study, the initial 12 patients who received the Ventrassist (Ventracor, Sydney, NSW, Australia) centrifugal, non-pulsatile device during the period from June 2003 to September 2005 at the Alfred Hospital, Melbourne were compared with 11 patients who received a Thoratec (Thoratec, Pleasanton, CA, USA), pulsatile, positive displacement device and the incidence was recorded of GI complications requiring an intervention either surgical, endoscopic or by interventional radiology. This was followed by a larger (full) study of a second cohort of similar ventricular assist device (VAD) patients from January 1992 until December 2012 comparing 53 patients having non-pulsatile devices and 110 having pulsatile devices.

RESULTS

In the pilot study, the overall incidence of complications in the non-pulsatile group (67%) was almost double that in the pulsatile group (36%) but the difference was not statistically significant (p = 0.15) because of the small number (n = 23) of participants. In the full study, all GI complications with either device occurred within the first 3 weeks post-implant. In the non-pulsatile patients, there was a higher incidence of GI bleeding, 23% vs 4% (p = 0.002), endoscopies, 24% vs 12% (p = 0.049). More patients with a non-pulsatile flow device had delayed absorption of nasogastric feeds than their pulsatile counterparts, 35% vs 7% (p < 0.0001). Patients with a non-pulsatile flow device had a higher overall rate of gastrointestinal complications than patients had with a pulsatile flow device, 56% vs 20% (p < 0.0001). After correcting for the other predictors, the odds of developing a gastrointestinal complication in the pulsatile group was significantly lower (odds ratio 0.07) than in the non-pulsatile device group (p < 0.0001).

CONCLUSIONS

We conclude that the use of non-pulsatile centrifugal VADs compared with pulsatile positive displacement VADs is associated with a higher incidence of both haemorrhagic and ischaemic complications in the gastro-intestinal system especially in the very early post-implant period. Whether these complications could be reduced in centrifugal devices by increasing their pulsatility is not clear and merits further research.

Prothrombotic activity of cytokine-activated endothelial cells and shear-activated platelets in the setting of ventricular assist device support

BACKGROUND

We systematically analyzed the synergistic effect of: (i) cytokine-mediated inflammatory activation of endothelial cells (ECs) with and (ii) shear-mediated platelet activation (SMPA) as a potential contributory mechanism to intraventricular thrombus formation in the setting of left ventricular assist device (LVAD) support.

METHODS

Intact and shear-activated human platelets were exposed to non-activated and cytokine-activated ECs. To modulate the level of LVAD-related shear activation, platelets were exposed to shear stress patterns of varying magnitude (30, 50, and 70 dynes/cm², 10 minutes) via a hemodynamic shearing device. ECs were activated via exposure to inflammatory tumor necrosis factor-α (TNF-α 10 and 100 ng/ml, 24 hours), consistent with inflammatory activation recorded in patients on LVAD circulatory support.

RESULTS

Adhesivity of shear-activated platelets to ECs was significantly higher than that of intact/unactivated platelets, regardless of the initial activation level (70 dynes/cm² shear-activated platelets vs intact platelets: +80%, p < 0.001). Importantly, inflammatory activation of ECs amplified platelet prothrombinase activity progressively with increasing shear stress magnitude and TNF-α concentration: thrombin generation of 70 dynes/cm² shear-activated platelets was 2.6-fold higher after exposure and adhesion to 100 ng/ml TNF-α‒activated ECs (p < 0.0001).

CONCLUSIONS

We demonstrated synergistic effect of SMPA and cytokine-mediated EC inflammatory activation to enhance EC‒platelet adhesion and platelet prothrombotic function. These mechanisms may contribute to intraventricular thrombosis in the setting of mechanical circulatory support.

Large-vessel occlusion stroke after cardiothoracic surgery: Expanding time windows offer new salvage opportunities

OBJECTIVES

Ischemic stroke due to large-vessel occlusion (LVO) is a complication after cardiothoracic surgery (CTS). Recently published endovascular stroke trials have major implications for treating LVO strokes; we evaluated our experience in patients undergoing CTS.

METHODS

Our prospective institutional CTS database was reviewed between July 2013 and April 2018 for ischemic strokes. Patients with LVO were identified and their course and outcomes analyzed.

RESULTS

A total of 5947 patients were reviewed; 148 (2.48%) had a cerebrovascular complication; 92.5% were ischemic. Of these 10.9% had an LVO. Prolonged aortic crossclamp was associated with LVO (odds ratio, 1.012 for every minute of prolonged aortic crossclamp time; confidence interval, 1.001-1.023) and remained significant in patients with ejection fraction >45%; prolonged cardiac bypass time was only associated with LVO in patients with ejection fraction >45% (odds ratio, 1.012 for every minute of prolonged cardiac bypass time; confidence interval, 1.003-1.021). Patients fell into 2 categories: detection of neurologic deficit in the stable postoperative patient or detection of deficit on emergence from anesthesia. Seven patients met criteria for emergent revascularization, with median National Institutes of Health Stroke Scale score 15, and shorter times from last seen well to deficit detection compared with patients not meeting criteria (P = .032). Median National Institutes of Health Stroke Scale day 7 score improved to 5. There was a trend toward better modified Rankin Scale scores at 3 months in patients who underwent thrombectomy.

CONCLUSIONS

LVO complicates a small proportion of patients after CTS and may be more likely with prolonged aortic crossclamp and cardiac bypass times. Both early and late window endovascular stroke treatment has the potential to positively modify the complication profile of CTS. Greater awareness of this treatment option is needed.

Antithrombotic Strategies and Device Thrombosis

Despite improvements in left ventricular assist device (LVAD) technology, bleeding and thrombotic complications are major concerns that adversely influence morbidity and mortality. Current antithrombotic therapy recommendations for LVAD thrombosis prophylaxis are largely derived from clinical device trials that implement a one-size-fits-all strategy. Objective serial laboratory-based assessment of thrombogenicity is needed to balance the risk of bleeding and thrombotic complications. Finally, the newest-generation device, the HeartMate 3, has been associated with lower levels of shear and reduced hemolysis that may mitigate thrombotic event occurrences.

Effects of vitamin K epoxide reductase complex 1 gene polymorphisms on warfarin control in Japanese patients with left ventricular assist devices (LVAD)

PURPOSE

This study aimed to investigate relationships between times in therapeutic range (TTR) or warfarin sensitivity indexes (WSI) and VKORC1-1639G>A and CYP2C9 polymorphisms in patients with left ventricular assist devices (LVAD).

METHODS

Severe heart failure patients who received LVAD from January 1, 2013 to October 31, 2017 were recruited. Relationships between TTR or WSI and VKORC1-1639G>A and CYP2C9 gene polymorphisms were investigated immediately after LVAD implantation (period 1) and immediately prior to hospital discharge (period 2).

RESULTS

Among 54 patients, 31 (72.1%) had VKORC1-1639AA and CYP2C9*1/*1 (AA group) polymorphisms and 12 (27.9%) had VKORC1-1639GA and CYP2C9*1/*1 (GA group) polymorphisms. During period 1, mean prothrombin time-international normalized ratio (PT-INR) values were significantly higher in the AA group than in the GA group (2.21 vs. 2.05, p < 0.0001). Mean WSI values were 1.68-fold greater in the AA group than in the GA group (1.14 vs. 0.68, p < 0.0001). In addition, times below the therapeutic range (TBTR) in the GA group were significantly greater than in the AA group during period 1 (39.8 vs. 28.3%, p = 0.032), and insufficient PT-INR was more frequent in the GA group than in the AA group. However, mean PT-INR values during period 2 did not differ and no significant differences in TTR, TATR, and TBTR values were identified. In subsequent multivariable logistic regression analyses, the VKORC1-1639GA allele was significantly associated with insufficient anticoagulation.

CONCLUSION

Patients with the VKORC1-1639GA and CYP2C9*1/*1 alleles may receive insufficient anticoagulation therapy during the early stages after implantation of LVAD, and VKORC1-1639G>A and CYP2C9 genotyping may contribute to more appropriate anticoagulant therapy after implantation of LVAD.

Identification of Novel Hemostatic Biomarkers of Adverse Clinical Events in Patients Implanted With a Continuous-Flow Left Ventricular Assist Device

Heart failure affects over 5 million people in the United States. Its rising prevalence and the limited supply of donor hearts is increasing the use of mechanical cardiac support with the implantation of continuous-flow ventricular assist devices (CF-VAD). Patients with CF-VAD implants are at risk of complications, specifically adverse hemostatic events such as nonsurgical bleeding and thrombosis. Development of a pump thrombus requires clinical intervention and/or surgical replacement significantly increasing the risk of patient morbidity and mortality. Identification of biomarkers for these events could improve current risk assessment models, subsequent treatment, and quality of life prognoses for VAD-implanted patients. The standard means for identifying thrombus in VAD patients is currently limited to monitoring levels of lactate dehydrogenase (>2× upper limit of normal), which is incapable of predicting a future event, but describes the risk of a present thrombus. Surface-enhanced laser desorption ionization time-of-flight mass spectrometry is a technique used to identify biomarkers. In this study, 3 groups of unique peaks were identified in plasma from patients with left ventricular assist devices: 8.1-kDa, 11.7-kDa, and a 15.2-/16.1-kDa pair. Unique correlations were found for each peak, respectively, with microparticles (MPs) and MP procoagulant activity, C-reactive protein, and MP-tissue factor. Furthermore, the use of 8.1-kDa peaks may be able to differentiate thrombotic events from other hemostatic events.

Treatment of Left Ventricular Assist Device Thrombosis: Single-Center Experience

Heart failure is the one of the biggest health problem in the world. Because of limited donors for heart transplant procedures, the ventricular assist device has become a solution for heart failure therapy. With the increase in number of ventricular assist devices, the incidence of complications has also increased. One of the most important life-threatening complications is ventricular assist device thrombosis. Medical therapy and changes in the ventricular assist device are the main therapy methods for ventricular assist device thrombosis. In this study, we showed our clinical experience with treatment of ventricular assist device thrombosis.

Trends, predictors and outcomes of ischemic stroke and intracranial hemorrhage in patients with a left ventricular assist device

Background

Patients with a left ventricular assist device (LVAD) are at a higher risk of ischemic stroke (IS) and intracranial hemorrhage (ICH). There is limited data available on risk factors and outcomes associated with IS and ICH in LVAD patients.

Methods

All patients >18 years of age with an LVAD were identified based on the U.S. Nationwide Inpatient Sample (NIS) database from the year 2007 to 2011. Patients with a discharge diagnosis of IS were compared to those without IS. In a separate analysis, patients with a discharge diagnosis of ICH were compared to patients without ICH. Trends, predictors and outcomes of IS and ICH were analyzed using a multivariate regression model.

Results

Out of 17,323 discharges with a primary diagnosis of heart failure with LVAD, 624 (3.6%) patients had a co-diagnosis of IS and 387 (2.2%) had a co-diagnosis of ICH. From 2007 to 2011, the discharge diagnosis of heart failure with LVAD increased from 946 to 5,540, but the proportion of patients with IS remained about 3.4%, while the incidence of ICH decreased from 3.8% in 2007 to a plateau of around 2.2% in the following years. After adjusting for potential confounders, increasing Charlson Comorbidity Index (CCI) score was an independent predictor of IS and ICH. In-hospital mortality was four-fold higher in the IS group (odds ratio: 4.2; 95% CI: 2.3-7.6; P<0.0001) and 18-fold higher in the ICH group (OR: 18; 95% CI: 9-34, P<0.0001). Renal disease (OR: 5.3; CI: 1.3-22.1; P=0.02), liver disease (OR: 4.9; CI: 1.1-21.2; P=0.03) and abnormal coagulation profile (OR: 4.8; CI: 1.6-14.4; P=0.01) were independent predictors of mortality in LVAD patients with IS. Presence of diabetes mellitus (OR 4.3, P=0.1) and liver disease (or 2.8, P=0.2) showed trends towards predicting mortality in LVAD patients with ICH but did not reach statistical significance.

Conclusions

Increasing comorbidity burden significantly increases the risk of both IS and ICH with LVAD. In our cohort, the incidence of IS and ICH increases the mortality 4- and 18-fold, respectively. Renal disease, liver disease and abnormal coagulation profile were independent predictors of mortality in LVAD patients with IS.

Left Ventricular Assist Device in Older Adults

Left ventricular assist devices (LVADs) are an effective therapy for a growing and aging population in the background of limited donor supply. Selecting the proper patient involves assessment of indications, risk factors, scores for overall outcomes, assessment for right ventricular failure, and optimal timing of implantation. LVAD complications have a 5% to 10% perioperative mortality and complications of bleeding, thrombosis, stroke, infection, right ventricular failure, and device failure. As LVAD engineering technology evolves, so will the risk-prediction scores. Hence, more large-scale prospective data from multicenters will continually be required to aid in patient selection, reduce complications, and improve long-term outcomes.

CT Imaging of Complications Associated with Continuous-Flow Left Ventricular Assist Devices (LVADs)

Heart failure is becoming increasingly prevalent, and more patients are being treated with left ventricular assist devices (LVADs), either as a bridge to transplant or as destination therapy. The use of continuous-flow LVADs is on the rise. LVAD therapy is associated with several classes of complications, including bleeding, thrombosis, and infection. CT imaging can be used effectively to diagnose LVAD complications, including mediastinal hematomas and pericardial, abdominal wall, and retroperitoneal hemorrhage, inflow and outflow graft and aortic thrombi, and driveline and pump pocket infections. CT can also be helpful in cases of device malfunction and can detect outflow graft kinking and inflow cannula misalignment. When interpreting CT scans in patients with LVADs, accessory materials implanted with the device should not be mistaken for hemorrhage or calcification. With training in recognizing LVAD complications, radiologists can play an important role in the evaluation of patients with heart failure.

Bleeding with the artificial heart: Gastrointestinal hemorrhage in CF-LVAD patients

Continuous-flow left ventricular assist devices (CF-LVADs) have significantly improved outcomes for patients with end-stage heart failure when used as a bridge to cardiac transplantation or, more recently, as destination therapy. However, its implantations carries a risk of complications including infection, device malfunction, arrhythmias, right ventricular failure, thromboembolic disease, postoperative and nonsurgical bleeding. A significant number of left ventricular assist devices (LVAD) recipients may experience recurrent gastrointestinal hemorrhage, mainly due to combination of antiplatelet and vitamin K antagonist therapy, activation of fibrinolytic pathway, acquired von Willebrand factor deficiency, and tendency to develop small intestinal angiodysplasias due to increased rotary speed of the pump. Gastrointestinal bleeding in LVAD patients remains a source of increased morbidity including the need for blood transfusions, extended hospital stays, multiple readmissions, and overall mortality. Management of gastrointestinal bleeding in LVAD patients involves multidisciplinary approach in stabilizing the patients, addressing risk factors and performing structured endoluminal evaluation with focus on upper gastrointestinal tract including jejunum to find and eradicate culprit lesion. Medical and procedural intervention is largely successful and universal bleeding cessation occurs in transplanted patients.

Tumor necrosis factor-α levels and non-surgical bleeding in continuous-flow left ventricular assist devices

BACKGROUND

Non-surgical bleeding (NSB) due to angiodysplasia is common in left ventricular assist device (LVAD) patients. Thrombin-induced angiopoietin-2 (Ang-2) expression in LVAD patients leads to altered angiogenesis and is associated with lower angiopoietin-1 (Ang-1) and increased NSB. However, the mechanism for decreased Ang-1, made by pericytes, is unknown and the origin of thrombin in LVAD patients is unclear. We hypothesized that high tumor necrosis factor-α (TNF-α) levels in LVAD patients induce pericyte apoptosis, tissue factor (TF) expression and vascular instability.

METHODS

We incubated cultured pericytes with serum from patients with heart failure (HF), LVAD or orthotopic heart transplantation (OHT), with or without TNF-α blockade. We performed several measurements: Ang-1 expression was assessed by reverse transcript-polymerase chain reaction (RT-PCR) and pericyte death fluorescently; TF expression was assessed by RT-PCR in cultured endothelial cells incubated with patient plasma with or without TNF-α blockade; and TF expression was assessed in endothelial biopsy samples from these patients by immunofluorescence. We incubated cultured endothelial cells on Matrigel with patient serum with or without TNF-α blockade and determined tube formation by microscopy.

RESULTS

Serum from LVAD patients had higher levels of TNF-α, suppressed Ang-1 expression in pericytes, and induced pericyte death, and there was accelerated endothelial tube formation compared with serum from patients without LVADs. TF was higher in both plasma and endothelial cells from LVAD patients, and plasma from LVAD patients induced more endothelial TF expression. All of these effects were reversed or reduced with TNF-α blockade. High levels of TNF-α were associated with increased risk of NSB.

CONCLUSIONS

Elevated TNF-α in LVAD patients is a central regulator of altered angiogenesis, pericyte apoptosis and expression of TF and Ang-1.

Ventricular assist device elicits serum natural IgG that correlates with the development of primary graft dysfunction following heart transplantation

BACKGROUND

Pre-transplant sensitization is a limiting factor in solid-organ transplantation. In heart transplants, ventricular assist device (VAD) implantation has been associated with sensitization to human leukocyte antigens (HLA). The effect of VAD on non-HLA antibodies is unclear. We have previously shown that polyreactive natural antibodies (Nabs) contribute to pre-sensitization in kidney allograft recipients. Here we assessed generation of Nabs after VAD implantation in pre-transplant sera and examined their contribution to cardiac allograft outcome.

METHODS

IgM and IgG Nabs were tested in pre-transplant serum samples collected from 206 orthotopic heart transplant recipients, including 128 patients with VAD (VAD patients) and 78 patients without VAD (no-VAD patients). Nabs were assessed by testing serum reactivity to apoptotic cells by flow cytometry and to the generic oxidized epitope, malondialdehyde, by enzyme-linked immunosorbent assay.

RESULTS

No difference was observed in serum levels of IgM Nabs between VAD and no-VAD patients. However, serum IgG Nabs levels were significantly increased in VAD compared with no-VAD patients. This increase was likely due to the presence of the VAD, as revealed by lower serum IgG Nabs levels before implantation. Elevated pre-transplant IgG Nabs level was associated with development of primary graft dysfunction (PGD).

CONCLUSIONS

Our study demonstrates that VAD support elicits IgG Nabs reactive to apoptotic cells and oxidized epitopes. These findings further support broad and non-specific B-cell activation by VAD, resulting in IgG sensitization. Moreover, the association of serum IgG Nabs levels with development of PGD suggests a possible role for these antibodies in the inflammatory reaction accompanying this complication.

Bleeding and thrombosis in chronic ventricular assist device therapy: focus on platelets

PURPOSE OF REVIEW

Left ventricular assist devices (LVADs) have markedly improved the survival for patients with advanced heart failure but are plagued with significant morbidity, including pump thrombosis and bleeding. Better understanding of the platelet, and its role in the balance of bleeding and thrombosis, stands to impact the frequency and treatment of these significant complications.

RECENT FINDINGS

In patients with LVADs, there is little consistency linking traditional biomarkers of platelet activation and clinical events. A number of innovative methods of assessing platelet functionality, including shedding of platelet receptors and formation of microparticle complexes as well as measuring mitochondrial membrane potentials, exist and appear to be clinically relevant. Acquired von Willebrand syndrome, while not explaining all bleeding events, is a central feature of mechanical support and offers a target for innovative therapies.

SUMMARY

Although the platelet is only one component of impacting thrombosis and bleeding in patients supported with LVADs, it plays a central role in mediating these two opposing forces. Innovations in understanding platelet physiology as well as manipulating genomic and receptor interactions for an individual patient will be critical if we are to decrease these serious adverse events in the future.

Blood cell microparticles as biomarkers of hemostatic abnormalities in patients with implanted cardiac assist devices

For heart failure patients unable to undergo cardiac transplantation, mechanical circulatory support with left ventricular assist devices can be utilized. These devices improve quality of life and prolong life expectancy, but they are associated with bleeding and thrombotic complications impacting patient survival. Little is known of the relevant mechanisms of these hemostatic issues, hindering identification of a clinically useful biomarker. However, there is suggestive evidence that blood cell-derived microparticles may fulfill this unmet clinical need. Recent publications have shown an association of up regulated microparticle production with implanted left ventricular assist devices and the potential to use this as a biomarker to predict thrombosis (and perhaps other adverse events) with an onset time earlier than currently used clinical indicators.

Monitoring hemostasis parameters in left ventricular assist device recipients - a preliminary report

Introduction

Mechanical circulatory support (MCS) therapy is associated with the improvement of long-term prognosis in patients with end-stage heart failure. For years it has been used as a bridge to transplant. However, more recently it is even being used as a destination therapy. Recently, clinicians have identified common MCS therapy-associated complications: pump thrombosis, bleeding, and hemolysis. These complications are very challenging with regard to both diagnosis and management.

Aim

To determine time-dependant changes of selected hemostasis/coagulation parameters in patients with end-stage heart failure treated with MCS and antithrombotic therapy.

Material and methods

Sixteen patients with end-stage heart failure on left ventricular assist device (LVAD) were followed for 6 weeks (six blood samples for each patient). Every week an extended hemostasis panel was assessed, including activated partial thromboplastin time, prothrombin time, international normalized ratio, von Willebrand factor (vWF) activity, factor VIII activity, fibrinogen level, D-dimer, platelet response to arachidonic acid (ASPI test) and adenosine diphosphate (ADP test), thrombin receptor activating peptide-6 (TRAP test) and collagen (COL test).

Results

The study population comprised 16 men. The median time from LVAD implantation was 120 days (100–150 days). During the study period the D-dimer and fibrinogen concentrations were elevated but remained similar throughout all six measurements. Meanwhile factor VIII and vWF activities were elevated in the first two measurements and then subsequently declined. Inhibition of platelet aggregation was greater early after LVAD implantation. During subsequent weeks the inhibition of platelet aggregation was less pronounced. No patient developed any bleeding or thrombo-embolic event during the study period.

Conclusions

Patients on MCS therapy demonstrate significant time-dependant changes in hemostasis parameters (both in the coagulation system and platelet aggregation).

Elevated Angiopoietin-2 Level in Patients With Continuous-Flow Left Ventricular Assist Devices Leads to Altered Angiogenesis and Is Associated With Higher Nonsurgical Bleeding

BACKGROUND

Nonsurgical bleeding is the most common adverse event in patients with continuous-flow left ventricular assist devices (LVADs) and is caused by arteriovenous malformations. We hypothesized that deregulation of an angiogenic factor, angiopoietin-2 (Ang-2), in patients with LVADs leads to increased angiogenesis and higher nonsurgical bleeding.

METHODS

Ang-2 and thrombin levels were measured by ELISA and Western blotting, respectively, in blood samples from 101 patients with heart failure, LVAD, or orthotopic heart transplantation. Ang-2 expression in endothelial biopsy was quantified by immunofluorescence. Angiogenesis was determined by in vitro tube formation from serum from each patient with or without Ang-2-blocking antibody. Ang-2 gene expression was measured by reverse transcription-polymerase chain reaction in endothelial cells incubated with plasma from each patient with or without the thrombin receptor blocker vorapaxar.

RESULTS

Compared with patients with heart failure or those with orthotopic heart transplantation, serum levels and endothelial expression of Ang-2 were higher in LVAD patients (P=0.001 and P<0.001, respectively). This corresponded to an increased angiogenic potential of serum from patients with LVADs (P<0.001), which was normalized with Ang-2 blockade. Furthermore, plasma from LVAD patients contained higher amounts of thrombin (P=0.003), which was associated with activation of the contact coagulation system. Plasma from LVAD patients induced more Ang-2 gene expression in endothelial cells (P<0.001), which was reduced with thrombin receptor blockade (P=0.013). LVAD patients with Ang-2 levels above the mean (12.32 ng/mL) had more nonsurgical bleeding events compared with patients with Ang-2 levels below the mean (P=0.003).

CONCLUSIONS

Our findings indicate that thrombin-induced Ang-2 expression in LVAD patients leads to increased angiogenesis in vitro and may be associated with higher nonsurgical bleeding events. Ang-2 therefore may contribute to arteriovenous malformation formation and subsequent bleeding in LVAD patients.

New therapy, new challenges: The effects of long-term continuous flow left ventricular assist device on inflammation

Surgically implanted continuous flow left ventricular assist devices (CF-LVADs) are currently used in patients with end-stage heart failure (HF). However, CF-LVAD therapy introduces a new set of complications and adverse events in these patients. Major adverse events with the CF-LVAD include right heart failure, vascular dysfunction, stroke, hepatic failure, and multi-organ failure, complications that may have inflammation as a common etiology. Our aim was to review the current evidence showing a relationship between these adverse events and elevated levels of inflammatory biomarkers in CF-LVAD recipients.

Thrombolytics in VAD management - A single-center experience

Background

With continued increase in the use of mechanical circulatory support, the incidence of device thrombus remains a challenge. This study is a retrospective analysis of data at a single center to assess the safety and efficacy of thrombolytic use in durable mechanical assist devices.

Methods

Data was analyzed retrospectively from 154 patients who underwent left ventricular assist device (LVAD) implantation from 1/1/2005 to 6/30/2014. The HMII device was implanted in 131 patients while 23 received the HVAD. LVAD thrombus was diagnosed when lactate dehydrogenase levels exceeded 1000 units/l accompanied by clinical signs of hemolysis and heart failure, echocardiographic data and surges in pump power. TPA (tissue plasminogen activator) protocol consisted of a 5 mg intravenous bolus followed by 3 mg/h infusion in normal saline for 10 h. If symptoms persisted another cycle of TPA at 1 mg/h was continued up to 48 h.

Results

The TPA group had a 70% success rate. Success was defined as complete resolution of hemolysis and clinical symptoms with no requirement for LVAD exchange at 30 days. 95% survival was noted at 30 days and 90% were free of a hemorrhagic stroke in the TPA group. The rates of hemorrhagic strokes in the TPA group and the control group were not different (OR = 0.92).

Conclusion

The TPA protocol described here was successful consistently. Though this study is limited by its size and retrospective nature it leads the way for larger studies to generate more robust comparisons between different types of mechanical assist devices as well as the tailored use of thrombolytics in this patient population.

Management of anticoagulation and antiplatelet therapy in patients with left ventricular assist devices

Left ventricular assist devices (LVADs) have increased the survival of patients with advanced heart failure fourfold. Despite these advances, significant bleeding and thrombotic complications occur. Hemorrhage requiring surgery has been reported in up to 30% of adults and 50% of children after LVAD placement. LVAD thrombosis and embolic stroke lead to significant long-term morbidity. Adults are treated with antithrombotic therapy to prevent thrombotic complications, but the amount and intensity of treatment differs between institutions. The goal international normalized ratio for warfarin therapy varies from 1.5 to 3.0. Some physicians manage adult LVAD patients without antiplatelet medication, whereas other adults are treated with aspirin as a single agent or combined with dipyridamole. In contrast, physicians typically manage children with LVADs using the Edmonton Anticoagulation and Platelet Inhibition Protocol, a detailed algorithm for anticoagulation and antiplatelet treatment modified based on thromboelastography results. LVAD implantation causes consumption of coagulation proteins, activation of fibrinolysis, and loss of high molecular weight von Willebrand protein multimers. How these changes in the coagulation system influence the risk of hemorrhage and initiation of thrombosis is unknown. Prospective, controlled studies are needed to determine the antithrombotic regimen that most effectively balances bleeding and thrombosis in LVAD patients.

Device-Related Thrombosis in Continuous-Flow Left Ventricular Assist Device Support

Advanced heart failure therapy has been revolutionized with the advent of continuous-flow ventricular assist devices (CF-LVADs) which have improved both survival and quality of life. Despite this, support with CF-LVADs is frequently complicated, with 70% of recipients experiencing a major complication in the first year of durable support. The most concerning of these complications to emerge is device-related thrombosis, which is associated with increased morbidity and mortality. Pathophysiology and diagnosis are multifaceted and complex, with pump-specific and patient-specific factors to be considered. Incidence estimates are evolving with increases seen in the past 2 years compared with earlier implant data. Evidence for treatment is limited to case series and reports, which are subject to significant publication bias. Finally, appropriate primary and secondary prophylaxis is imprecise with multiple antiplatelet and antithrombotic strategies described. This review seeks to summarize the current literature surrounding the pathophysiology, diagnosis, and management of thrombosis in CF-LVAD recipients.