Haemolysis as a first sign of thromboembolic event and acute pump thrombosis in patients with the continuous-flow left ventricular assist device HeartMate II. Neth Heart J. 2016;24:134-142. [PMID: 26689927 PMCID: PMC4722006 DOI: 10.1007/s12471-015-0786-2]

Bleeding and thrombotic complications and their impact on mortality in patients supported with left ventricular assist device for cardiogenic shock

INTRODUCTION

Thrombosis and bleeding are major complications in patients supported with left ventricular assist devices (LVADs). We aimed to assess the incidence of bleeding and thrombosis in patients supported with a HeartWare left ventricular assist device (HVAD), their predictive factors and their impact on mortality.

METHODS

A single centre retrospective observational study of patients supported with HVAD over 5 years from January 2015 to October 2020.

RESULTS

A total 139 patients (median age 52.5, 72.1% male) were included for analysis. The probability of 1-year survival was 73.1%. Advanced age (>60 years) and EuroSCORE II score (>20%) were independently associated with reduced survival. Major bleeding and thrombosis occurred in 46.8% and 35.3% respectively. Secondary mechanical circulatory support (MCS) increased likelihood of experiencing major bleeding (HR: 2.76, 95%1.65-4.62, p < 0.0001) whilst patients receiving aspirin were protected from bleeding and thrombosis (HR: 0.34 95% CI 0.19-0.58, p < 0.001). Pre-operative anaemia (HR: 3.02, 95% CI: 1.6-5.7, p = 0.014) and use of a secondary MCS device (HR: 2.78, 95% CI: 1.2-6.3, p = 0.001) were associated with an increased risk of thrombosis. Patients with any major bleeding (with or without thrombosis) had a 7.68-fold (95% CI 3.5-16.8) increased risk of death compared to those without. In contrast, 'thrombosis only' patients had 4.23-fold (95% CI 1.8-10.2) increased risk of death compared to those without thrombosis. The risk of mortality was increased in patients with any thrombosis and the risk of death was highest in patients with major bleeding and thrombosis (HR: 16.49 [95% CI 7.7-35.3]).

CONCLUSIONS

Major bleeding and thrombosis significantly increase the 1-year mortality. Optimal perioperative haemostasis and anticoagulation remains crucial in patients supported with HVAD.

Acute Outflow Graft Occlusion-A Novel Predictable Complication of Lysis Therapy for the Treatment of Left Ventricular Assist Device Intra-Pump Thrombosis

Lysis therapy is an established treatment option for intra-pump thrombosis of left ventricular assist devices (LVADs). In clinical routine, we observed repeated cases of acute outflow graft occlusions (OGO) associated with lysis therapy with need for urgent intervention. The aim of this investigation was to gain understanding of this observation. We screened data of 962 HeartWare ventricular assist device (HVAD) patients. One hundred twenty (13.8%) had intra-pump thromboses; 58 were treated with recombinant tissue-type plasminogen activator (rtPA). Mean age was 53.0 ± 11.1 years; 84.9% were male. In 13 (24.5%) patients, OGO occurred following rtPA-lysis. These patients showed an increase in left ventricular function (18.45% ± 12.62% to 27.73% ± 10.57%; p = 0.056), more frequent 1:1 aortic valve opening (OGO+: +36.4%; OGO-: +7.4%; p = 0.026), a decrease in LVAD pulsatility within 12 months prior intra-pump thrombosis (OGO+: -0.8 L/min [interquartile range {IQR}, -1.4 to -0.4 L/min]; OGO-: -0.3 L/min [IQR, -0.9 to 0.1 L/min]; p = 0.038) and lower HVAD flows at admission (OGO+: 6.7 L/min [IQR, 6.1-7.4 L/min]; OGO-: 8.3 L/min [IQR, 6.9-9.3 L/min]; p = 0.013), indicating a subclinical OGO prior intra-pump thrombosis. There were no differences in implantation techniques, blood parameters, and lysis strategy. Subclinical OGO represented a major risk factor for acute OGO following rtPA lysis therapy. We here propose an algorithm for risk stratification and dealing with patients presenting this first-described complication. Further research is required to confirm our results and decipher the underlying pathomechanism. http://links.lww.com/ASAIO/B97.

Intraoperative pump thrombosis (PT) in HeartMate (HM) III

Pump thrombosis (PT) is a rare and infrequent complication of HeartMate III left ventricular assist device (LVAD). While there are reports of PT in the postoperative period, to our knowledge, there have been no prior reports on PT in the intraoperative period. Here we present a case of a 24-year-old female who required HeartMate III LVAD implantation for progressive heart failure and the intraoperative period was complicated with PT. Managing PT in the intraoperative period is challenging and time-sensitive because of its rare occurrence and paucity of recommendations in diagnosing the PT.

Physical Properties of Blood and their Relationship to Clinical Conditions

It has been long known that blood health heavily influences optimal physiological function. Abnormalities affecting the physical properties of blood have been implicated in the pathogenesis of various disorders, although the exact mechanistic links between hemorheology and clinical disease manifestations remain poorly understood. Often overlooked in current medical practice, perhaps due to the promises offered in the molecular and genetic era, the physical properties of blood which remain a valuable and definitive indicator of circulatory health and disease. Bridging this gap, the current manuscript provides an introduction to hemorheology. It reviews the properties that dictate bulk and microcirculatory flow by systematically dissecting the biomechanics that determine the non-Newtonian behavior of blood. Specifically, the impact of hematocrit, the mechanical properties and tendency of red blood cells to aggregate, and various plasma factors on blood viscosity will be examined. Subsequently, the manner in which the physical properties of blood influence hemodynamics in health and disease is discussed. Special attention is given to disorders such as sickle cell disease, emphasizing the clinical impact of severely abnormal blood rheology. This review expands into concepts that are highly topical; the relation between mechanical stress and intracellular homeostasis is examined through a contemporary cell-signaling lens. Indeed, accumulating evidence demonstrates that nitric oxide is not only transported by erythrocytes, but is locally produced by mechanically-sensitive enzymes, which appears to have intracellular and potentially extracellular effects. Finally, given the importance of shear forces in the developing field of mechanical circulatory support, we review the role of blood rheology in temporary and durable mechanical circulatory support devices, an increasingly utilized method of life support. This review thus provides a comprehensive overview for interested trainees, scientists, and clinicians.

Does infection predispose to thrombosis during long term ventricular assist device support?

BACKGROUND

Infections and thrombotic events remain life-threatening complications in patients with ventricular assist devices (VAD).

METHODS

We describe the relationship between both events in our cohort of patients (n=220) supported with the HeartWare VAD (HVAD). This is a retrospective analysis of patients undergoing HVAD implantation between July 2009 and March 2019 at the Freeman Hospital, Newcastle upon Tyne, United Kingdom.

RESULTS

Infection was the most common adverse event in HVAD patients, with 125 patients (56.8%) experiencing ≥ one infection (n=168, 0.33 event-per-person-year-EPPY), followed by pump thrombosis (PT) in 61 patients (27.7%, 0.16 EPPY). VAD-specific infections were the largest group of infections. Of the 125 patients who had an infection, 66 (53%) had a thrombotic event. Both thrombotic events and infections were related to the duration of support, though there was only limited evidence that infections predispose to thrombosis. Those with higher than median levels of CRP during the infection were more likely to have an ischaemic stroke (IS) (34.5% vs 16.7%, p=0.03), though not PT or a combined thrombotic event (CTE: first PT or IS). However, in multivariate analysis there was no significant effect of infection predisposing to CTE.

CONCLUSIONS

Infection and thrombotic events are significant adverse events related to the duration of support in patients receiving HVADs. Infections do not clearly predispose to thrombotic events.

Early detection of HVAD pump thrombosis based on technical analysis and power consumption measurements

BACKGROUND

Continuous-flow left ventricular assist devices (LVAD) have been extensively used in a strategy of bridge to orthotopic heart transplant and destination therapy. The usage of LVAD, however, is not free from limitations such as device-related adverse events, including pump thrombosis (PT). We aimed to develop an algorithm of early PT detection based on the maintenance parameters monitored by the implanted device.

METHODS

We analyzed log files of 101 patients implanted with HeartWare pump (HVAD) with 18 PT events among them. For signal processing, we used Open-High-Low-Close format transformation and Typical Price (TP) technical analysis indicator. Model parameters were tuned with 5-fold cross-validation and the final performance was measured on a separate group of patients.

RESULTS

Our algorithm achieved 100% sensitivity and 100% specificity of indications. In the final evaluation alarms preceded the clinical acknowledgement of events by 2 days and 20 hours on average. In the worst-case scenario, an alarm was raised 1 day and 8 hours prior to the event.

CONCLUSIONS

Proposed algorithm could be installed to work directly with the device controller and provide clinicians with automatic readings analysis, raising an alarm when there is a high probability of thromboembolism. Early event detection could enable better thrombosis management and improve prognosis in patients implanted with HVAD.

Correlation among Hemolysis Biomarkers in Pediatric Patients Undergoing Extracorporeal Membrane Oxygenation

Hemolysis is a common complication associated with mortality on extracorporeal membrane oxygenation (ECMO). Plasma-free hemoglobin (PFH) is the most commonly used biomarker reported for hemolysis on ECMO. This test is not readily available at all institutions, and other more readily available tests may indicate hemolysis nearly as well or as well as PFH. The purpose of this study was to study the correlation of other biomarkers of hemolysis to PFH on ECMO. All patients younger than 21 years placed on ECMO in a quaternary children's hospital between January 2013 and December 2016 were included in the study; biomarkers (urine hemoglobin [U-Hb], PFH, lactate dehydrogenase [LDH], aspartate aminotransferase [AST], gross hemolysis, and red cell distribution width (RDW)) were collected from the medical record. Descriptive statistics and repeated bivariate analyses were determined using SPSS 22.0. The median age on day 0 of ECMO was 29 days (.08 years) (IQR: 2; 319 days (.005; .875 years)). The median weight was 3.9 kg (IQR: 2.8; 8.6), and the median total duration of the ECMO run was 10.48 days (IQR: 4.25; 14), with 82% of all the patients being on venoarterial ECMO. There was no correlation between hematuria on urinalysis and the level of PFH (p = .338). There was a statistically significant positive correlation between PFH and the following respective biomarkers: gross hemolysis on the routine chemistry studies (p < .01, Rho = .439), AST (p < .01, Rho = .439), RDW (p < .01, Rho = .190), LDH (p < .01, Rho = .584), and AST (when associated elevated alanine transaminase (ALT) levels were censored) (p < .01, Rho = .552). U-Hb correlated poorly with PFH. The serum biomarkers AST (in the absence of ALT elevation) and LDH can be useful surrogates for PFH to quantify hemolysis on ECMO in pediatric patients.

Reviewing the clinical utility of ventricular assist device log files

Background

Ventricular assist devices (VADs) have provided a temporising solution to many individuals with refractory heart failure (HF) while awaiting a suitable donor for heart transplantation which remains the gold standard in treatment. Many of the discussions around VADs involve ongoing morbidity; however, one aspect of VADs that is often overlooked is the utility of their log files. We decided to review the literature for mentions of the clinical utility of VAD log files.

Methods

A keyword search was utilised on PUBMED using the terms 'Ventricular Assist Device' and 'Log files'. Perhaps unsurprisingly, this search only yielded 4 results with further articles being discovered through the bibliography of these publications.

Results

The 4 identified articles provided basic information on log files, particularly with reference to the HVAD. Logs can be categorised into three types-data (pump parameters), events (changes in parameters) and alarms (abnormal function). Using a combination of these logs, we can readily identify abnormal pump operation such as the development and progression of pump thrombosis, suction events and gastrointestinal bleeding. However, the research potential of log files was not discussed in these publications, particularly as it pertains to areas such as studying speed modulation and pulsatility in VADs.

Conclusions

VADs are an important staple in the treatment of patients with refractory HF. Log files provide a treasure-trove of information and knowledge that can be utilised for clinical benefit. Furthermore, log files provide an excellent tool for conducting research into device functionality. Current literature on the clinical utility of log files is sparse with much untapped potential.

Comprehensive review of hemolysis in ventricular assist devices

Ventricular assist devices (VADs) have played an important role in altering the natural history of end-stage heart failure. Low-grade hemolysis has been traditionally described in patients with VADs, indicating effective device functionality. However, clinically significant hemolysis could be crucial in terms of prognosis, calling for prompt therapeutic actions. The absence of solid and widely approved diagnostic criteria for clinically significant hemolysis, render the utilization of hemolysis laboratory markers challenging. Hemolysis incidence varies (5%-18%) depending on definition and among different VAD generations, being slightly higher in continuous-flow devices than in pulsatile devices. Increased shear stress of red blood cells and underlying device thrombosis appear to be the main pathogenetic pathways. No certain algorithm is available for the management of hemolysis in patients with VADs, while close clinical and laboratory monitoring remains the cornerstone of management. Imaging examinations such as echocardiography ramp test or computed tomography scan could play a role in revealing the underlying cause. Treatment should be strictly personalized, including either pharmacological (antithrombotic treatment) or surgical interventions.

Biomarkers in Advanced Heart Failure: Implications for Managing Patients With Mechanical Circulatory Support and Cardiac Transplantation

Biomarkers have a well-defined role in the diagnosis and management of chronic heart failure, but their role in patients with left ventricular assist devices and cardiac transplant is uncertain. In this review, we summarize the available literature in this patient population, with a focus on clinical application. Some ubiquitous biomarkers, for example, natriuretic peptides and cardiac troponin, may assist in the diagnosis of left ventricular assist device complications and transplant rejection. Novel biomarkers focused on specific pathological processes, such as left ventricular assist device thrombosis and profiling of leukocyte activation, continue to be developed and show promise in altering the management of the advanced heart failure patient. Few biomarkers at this time have been assessed with sufficient scrutiny to warrant broad, universal application, but encouraging limited data and large potential for impact should prompt ongoing investigation.

High-speed visualization of ingested, ejected, adherent, and disintegrated thrombus in contemporary ventricular assist devices

Biocompatibility of ventricular assist devices (VADs) has been steadily improving, yet the rate of neurological events remains unacceptably high. Recent speculation for elevated stroke rates centers on ingestion of thrombi originating upstream of the pump, such as in the ventricle or left atrial appendage. These thrombi may be ejected by the VAD or become deposited within the blood flow pathway, presenting serious complications to the patient. This study was performed to visualize and quantify the degree of disruption, adherence, and disintegration of thrombi that are ingested by the three most implanted VADs: the HeartMate II, HeartMate 3, and HVAD. Clot analogs of varying microstructure compositions (red, white) and sizes (0.5, 1, 2 cm³ ) were synthesized in vitro based on clinical explant data. These were introduced individually into an in vitro flow loop with a transparent replica of the HMII, HM3, and HVAD operated at nominal steady flow (2.3-4.0 L/min). High-speed videography (up to 10 000 fps) revealed the ingestion, disruption, ejection, and adherence of thrombus fragments. Thromboemboli of varying compositions and sizes were observed mechanically attaching to components in all 3 VAD models. In some instances, ingested thrombi physically obstructed portions of the blood flow path; 18% (3 of 17 total) of red thrombi adhered to the inflow straightener of the transparent HMII. In the HVAD model, fewer than 4% of clots were adherent or trapped within the pump, irrespective of microstructure or initial volume. In comparison, 100% (4 of 4 total) of 1-cm³ white (fibrin) clots became lodged within the transparent HM3 while, in contrast, less than 5% of macerated red clots (3 of 63 total) of the same volume were adherent inside the pump. A significant proportion of ingested thrombi were macerated into infinitesimal fragments; 84% and 74% of 2-cm³ red thrombi in the HVAD and HM3 models, respectively, were found to have disintegrated upon ingestion. However, large emboli were also discharged from both centrifugal VADs; these fragments, ranging from 0.01 to 0.29 cm³ regardless of microstructure and original volume, may be capable of occluding an intracranial vessel. Therefore, ingested thrombus may explain, in part, elevated stroke rates in contemporary blood pumps in the absence of adherent pump thrombosis.

Telecardiographic measurements for device migration: A useful tool for follow-up

OBJECTIVE

Pump thrombosis in left ventricular assist device (LVAD) patients is an important cause of mortality and morbidity. Inflow cannula migration is a predisposing factor for pump thrombosis. Telecardiographic measurements can be used to follow up apical cannula deviation. In this study, we aimed to evaluate the migration of the inflow cannulas in patients with LVADs using angle measurements on telecardiograms.

METHODS

Twenty-three patients who were implanted left ventricular assist devices in our clinic between February 2013 and April 2016 were included in our study. During the first year of follow-up, changes in angle measurements on postoperative 1^st, 3^rd, 6^th, and 12^th month telecardiograms were compared against the incidence of device thrombus and serum Lactate Dehydrogenase (LDH) levels.

RESULTS

Patients who were diagnosed with device thrombosis had more change in inflow cannula angles than patients without device thrombus (p<0.05 at 6^th and 12^th months). Patients with higher LDH values had more parallel angular changes at all intervals, and the change in angle was statistically significant at 3^rd, 6^th and 12^th months (p<0.05).

CONCLUSION

This study shows that it is possible to track the migration of inflow cannulas in patients with left ventricular heart failure using telecardiograms. The correlation between angle change and LDH levels and embolic events may suggest that telecardiographic follow up of angles may be a useful tool for ventricular assist devices teams for early detection of thrombus.

Clinical implications of LDH isoenzymes in hemolysis and continuous-flow left ventricular assist device-induced thrombosis

Pump-induced thrombosis continues to be a major complication of continuous-flow left ventricular assist devices (CF-LVADs), which increases the risks of thromboembolic stroke, peripheral thromboembolism, reduced pump flow, pump failure, cardiogenic shock, and death. This is confounded by the fact that there is currently no direct measure for a proper diagnosis during pump support. Given the severity of this complication and its required treatment, the ability to accurately differentiate CF-LVAD pump thrombosis from other complications is vital. Hemolysis measured by elevated lactate dehydrogenase (LDH) enzyme levels, when there is clinical suspicion of pump-induced thrombosis, is currently accepted as an important metric used by clinicians for diagnosis; however, LDH is a relatively nonspecific finding. LDH exists as five isoenzymes in the body, each with a unique tissue distribution. CF-LVAD pump thrombosis has been associated with elevated serum LDH-1 and LDH-2, as well as decreased LDH-4 and LDH-5. Herein, we review the various isoenzymes of LDH and their utility in differentiating hemolysis seen in CF-LVAD pump thrombosis from other physiologic and pathologic conditions as reported in the literature.

Early postoperative heparinization reduce hemolysis in patients with HeartMate II devices

Hemolysis is closely related with pump thrombosis and thromboembolic events in patients with continuous flow left ventricular assist devices. We retrospectively investigated the impact of early postoperative heparinization on hemolysis in patients with HeartMate II devices. From April 2013 to August 2017, 83 patients (age 45 ± 12 years; 20 females; body surface area 1.6 ± 0.2 m²) underwent HeartMate II implantation. Postoperative heparinization was started when hemostasis was achieved and continued until full warfarinization. Hemolysis was defined in accordance with the Interagency Registry for Mechanically Assisted Circulatory Support definitions. The average support period was 22 ± 14 months. The 6-, 12-, and 24-month freedoms from hemolysis were 72%, 70%, and 67%, respectively. Pump thrombosis developed in five (6%) patients and four (5%) required pump exchanges. Heparin start time was significantly later in patients with hemolysis (43 ± 23 h after implantation) versus those without (29 ± 14 h after implantation; p = 0.01). Receiver operating characteristic analysis determined the cut-off point of heparin start time as 29 h. The patients were divided into the early group (heparin start time < 29 h; n = 29), and the late group (heparin start time > 29 h; n = 54). The respective 6-, 12-, and 24-month freedoms from hemolysis for the early group (86%, 86%, and 86%, respectively) were significantly higher than those for the late group (49%, 47%, and 44%, respectively; p = 0.002). Being in the late group was an independent risk factor for hemolysis (hazard ratio 4.09). Early postoperative heparinization (within 29 h after implantation) reduces hemolysis in patients with HeartMate II devices.

Methodology for Hemodynamic Assessment of a Three-Dimensional Printed Patient-Specific Vascular Test Device

Assessing hemodynamics in vasculature is important for the development of cardiovascular diagnostic parameters and evaluation of medical devices. Benchtop experiments are a safe and comprehensive preclinical method for testing new diagnostic endpoints and devices within a controlled environment. Recent advances in three-dimensional (3D) printing have enhanced benchtop tests by allowing generation of patient-specific and pathophysiologic conditions. We used 3D printing, coupled with image processing and computer-aided design (CAD), to develop a patient-specific vascular test device from clinical data. The proximal pulmonary artery (PA) tree including the main, left, and right pulmonary arteries, with a stenosis within the left PA was selected as a representative anatomy for developing the vascular test device. Three test devices representing clinically relevant stenosis severities, 90%, 80%, and 70% area stenosis, were evaluated at different cardiac outputs (COs). A mock circulatory loop (MCL) generating pathophysiologic pulmonary pressure and flow was used to evaluate the hemodynamics within the devices. The dimensionless pressure drop–velocity ratio characteristic curves for the three stenosis severities were obtained. At a fixed CO, the dimensionless pressure drop increased nonlinearly with an increase in (a) the velocity ratio for a fixed stenosis severity and (b) the stenosis severity at a specific velocity ratio. The dimensionless pressure drop observed in vivo was similar (within 1%) to that measured in moderate area stenosis of 70% because both flows were viscous dominated. The hemodynamics of the 3D printed test device can be used for evaluating diagnostic endpoints and medical devices in a preclinical setting under realistic conditions.

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.

Speed Modulation of the HeartWare HVAD to Assess In Vitro Hemocompatibility of Pulsatile and Continuous Flow Regimes in a Rotary Blood Pump

Although rotary blood pumps (RBPs) sustain life, blood exposure to continuous supra-physiological shear stress induces adverse effects (e.g., thromboembolism); thus, pulsatile flow in RBPs represents a potential solution. The present study introduced pulsatile flow to the HeartWare HVAD using a custom-built controller and compared hemocompatibility biomarkers (i.e., platelet aggregation, concentrations for ADAMTS13, von Willebrand factor (vWf), and free-hemoglobin in plasma (pfHb), red blood cell (RBC) deformability, and RBC-nitric oxide synthase (NOS) activity) between continuous and pulsatile flow in a blood circulation loop over 5 h. The HeartWare HVAD was operated using a custom-built controller, at continuous speed (3282 rev/min) or in a pulsatile mode (mean speed = 3273 rev/min, amplitude = 430 rev/min, frequency = 1 Hz) to generate a blood flow rate of 5.0 L/min, HVAD differential pressure of 90 mm Hg for continuous flow and 92 mm Hg for pulsatile flow, and systolic and diastolic pressures of 121/80 mm Hg. For both flow regimes, the current study found; (i) ADP- and collagen-induced platelet aggregation, and ADAMTS13 concentration significantly decreased after 5 h (P < 0.01; P < 0.05), (ii) ristocetin-induced platelet aggregation significantly increased after 45 min (P < 0.05), (iii) vWf concentration did not significantly differ at any time point, (iv) pfHb significantly increased after 5 h (P < 0.01), (v) RBC deformability improved during the continuous flow regime (P < 0.05) but not during pulsatile flow, and (vi) RBC-NOS activity significantly increased during continuous flow (15 min), and pulsatile flow (5 h; P < 0.05). The current study demonstrated: (i) speed modulation does not improve hemocompatibility of the HeartWare HVAD based on no observable differences being detected for routine biomarkers, and (ii) the time-course for increased RBC-NOS activity observed during continuous flow may have improved RBC deformability.

Long-Term Mechanical Durability of Left Ventricular Assist Devices: An Urgent Call for Periodic Assessment of Technical Integrity

Long-term durability and incidence of potential mechanical device failure (MDF) are largely unknown. In this study, we investigated the incidence and potential predictors of MDF in continuous flow left ventricular assist device (CF-LVAD) patients. We conducted a retrospective study of all CF-LVADs (type HeartMate II) implanted in our center. MDF was defined as a failure of driveline, inflow-outflow graft, electrical power, drive unit, or motor failure, excluding device failure because of a biologic complication (e.g., device thrombosis, hemolysis, or infections). A total of 69 CF-LVADs were implanted in 59 patients (median support time 344 days [interquartile range {IQR}, 149-712 days], mean age 50.1 ± 10.7 years, 75% male). MDF occurred in 9 (13%) CF-LVAD patients at a median follow-up time of 846 (IQR, 708-1337) days after implantation. Freedom of MDF through the first, second, and third year after LVAD implantation was 100%, 85%, and 64%, respectively. Patients who experienced MDF were significantly longer supported by their LVAD (median 846 [IQR, 708-1337] vs 268 [IQR, 103-481] days; p = 0.001) and were more frequently readmitted because of LVAD-related technical problems (p = 0.002), including a higher rate of LVAD controllers exchange (44% vs 12%, respectively; p = 0.03). The main reason for MDF was a damaged or fractured driveline (n=8, 89%). In 2 patients, sudden death was related to MDF. Patients needing extended CF-LVAD support are at increasing risk for MDF. Various technical problems precede the onset of MDF. Periodical extensive assessment of the technical integrity of the device is urgently needed during long-term LVAD support.