Anticoagulation management of left ventricular assist devices

Common Complications and Cardiopulmonary Resuscitation in Patients with Left Ventricular Assist Devices: A Narrative Review

Heart failure remains a major global burden regarding patients' morbidity and mortality and health system organization, logistics, and costs. Despite continual advances in pharmacological and resynchronization device therapy, it is currently well accepted that heart transplantation and mechanical circulatory support represent a cornerstone in the management of advanced forms of this disease, with the latter becoming an increasingly accepted treatment modality due to the ongoing shortage of available donor hearts in an ever-increasing pool of patients. Mechanical circulatory support strategies have seen tremendous advances in recent years, especially in terms of pump technology improvements, indication for use, surgical techniques for device implantation, exchange and explantation, and postoperative patient management, but not in the field of treatment of critically ill patients and those undergoing cardiac arrest. This contemporary review aims to summarize the collected knowledge of this topic with an emphasis on complications in patients with left ventricular assist devices, their treatment, and establishing a clear-cut algorithm and the latest recommendations regarding out-of-hospital or emergency department management of cardiac arrest in this patient population.

Bivalirudin Experience in a Heterogeneous Ventricular Assist Device Population

Ventricular assist devices (VADs) are an increasingly common therapy for end-stage heart failure across all ages as a bridge to recovery or transplant and more recently as destination therapy. With increasing experience and difficulties with establishing therapeutic heparin levels, we have begun to explore the effectiveness of direct thrombin inhibitors in this patient population. This is a retrospective review of all long-term VAD patients, both adult and pediatric, who were anticoagulated with bivalirudin between January 2009 and January 2016. The starting dose was 0.3 mg/kg/hr, and dose was titrated for a goal partial thromboplastin time (PTT) of 70-100. There were 14 patients (13 males, 5 ≤18 years) with 17 episodes of bivalirudin therapy. The median age on initiation was 45 years (range, 15 days-67 years) with 10 episodes associated with a HeartWare HVAD, five a HeartMate II, and two with a Berlin Heart EXCOR. The predominant indication of bivalirudin therapy was suspected pump thrombosis (13/17). The median time from VAD insertion to initiation of bivalirudin was 116 days (range, 3-1,870) with the median duration of therapy being 21 days (range, 3-113). In patients with pump thrombosis, the mean baseline lactate dehydrogenase (LDH) was 229 ± 64 U/L, peak 690 ± 380 U/L, and decreased to 330 ± 243 U/L when bivalirudin was stopped. The outcomes following suspected pump thrombosis included: transitioned to warfarin (n = 7), death in two destination therapy patients who did not undergo pump exchange, transplantation (n = 2), and pump exchange (n = 2). A major bleeding complication occurred in only one patient. Our experience highlights the potential use of bivalirudin in a heterogenous VAD population. Although these initial results suggest some potential role for direct thrombin inhibitors for use in long-term VADs, larger prospective studies are required to support these preliminary observations and to determine who may benefit from direct thrombin inhibitors (DTIs) and the side effect profile in this patient population.

Hemostatic Challenges in Pediatric Critical Care Medicine-Hemostatic Balance in VAD

Ventricular assist devices (VAD) are used more in children. Safe and effective anticoagulation is required for successful management of children supported with ventricular assist devices. Developmental hemostasis, device hemocompatibility, plastic to body ratio, surgical variable techniques, lack of knowledge on pharmacokinetics of anticoagulants, and wide variability in anticoagulation protocols have all contributed to increased incidence of bleeding and thromboembolic complications. New collaborative learning networks, such as the ACTION network, provide opportunities to define best practices, optimize, and reduce anticoagulation related adverse events. ACTION was established Dec 2017. It consists of expert clinicians in heart failure, as well as researchers, parents, and patients, with goals to improve outcomes, share data, improve education and standard practice for children with heart failure (, n.d). Changes in pediatric VAD anticoagulation strategy from using mainly heparin to DTI such as bivalirudin have helped reduce bleeding and clotting complications.

Prothrombin Complex Concentrate for Warfarin Reversal in Patients with Continuous-Flow Left Ventricular Assist Devices: A Narrative Review

Durable left ventricular assist device (LVAD) recipients require long-term anticoagulation to prevent thromboembolic complications. Their management is complicated by the risk of bleeding, which may require rapid anticoagulation reversal. We conducted a narrative review of data published from January 2007 to September 2018, analyzing anticoagulation reversal strategies in patients with durable, continuous-flow LVADs. The aim of this review is to provide guidance for reversal strategies in patients with LVADs experiencing bleeding complications or needing urgent surgical procedures, incorporating four-factor prothrombin complex concentrate (4F-PCC). Most data were from small, retrospective studies. Data for 4F-PCC use were more robust for heart transplant than for other surgical procedures or bleeding management. In patients undergoing heart transplant, 4F-PCC reversed warfarin more rapidly and reduced total blood product use versus other reversal strategies. Most surgical procedures were conducted without excess bleeding when utilizing 4F-PCCs. Time to warfarin reversal was shorter when managing intracranial hemorrhage with 4F-PCC. No differences in thromboembolic rates between 4F-PCC and control groups were observed. Overall, the use of 4F-PCC resulted in more rapid and predictable warfarin reversal in LVAD patients with no apparent risk of thromboembolism. Well-designed, larger prospective trials are required to better define 4F-PCC use in patients with LVADs.

Hemostatic complications associated with ventricular assist devices

Hemostatic complications are common in patients with ventricular assist devices. The pathophysiologic mechanisms that lead to dysregulated hemostasis involve complex interactions between device surface, sheer stress, and blood flow. These factors lead to various manifestations that require a thorough understanding of the interplay among platelets, coagulation factors, and red cells. In this article, we review the pathophysiology of hematologic complications (bleeding, acquired von Willebrand disease, heparin-induced thrombocytopenia, hemolysis, stroke and pump thrombosis), the clinical manifestations, and the management of each. We summarize the evidence available for management of these entities and provide a pragmatic clinical review.

Anticoagulation management following left ventricular assist device implantation is similar across all provider strategies

OBJECTIVES

Thromboembolic and bleeding events are potential complications following left ventricular assist device implantation. A tight control of the international normalized ratio (INR) is believed to be crucial in the reduction of postimplant complications. There is significant variability among institutions as to whether a device implanting centre should be managing the INR. In this study, we evaluated the effect of INR management strategies in maintaining a therapeutic INR.

METHODS

A retrospective review was utilized to identify patients implanted with either the HeartMate II or the HeartWare HVAD between January 2011 and February 2016. Patients were stratified into 4 groups based on the post-discharge INR management strategy: outside hospital system anticoagulation clinic, outside hospital primary care provider, implanting centre anticoagulation clinic or implanting centre ventricular assist device office. The INR data were collected and analysed for both the early (discharge, 7, 14, 21 and 30 days) and late (3, 6, 9 and 12 months) postoperative periods.

RESULTS

There were 163 patients identified during the study period who met the study inclusion criteria: 49 (30%) patients were managed by an outside hospital system anticoagulation clinic, 59 (36.2%) patients by an outside hospital physician/primary care provider, 22 (13.5%) patients by the implanting centre anticoagulation clinic and 33 (20.2%) patients by the implanting centre ventricular assist device office. There were no statistically significant differences found between management strategies across all time points.

CONCLUSIONS

There was no statistically significant difference found between the management strategies examined. Regardless of the chosen INR management strategy, patients have similar INR values and postoperative outcomes.

Pediatric Acquired von Willebrand Disease With Berlin Heart Excor Ventricular Assist Device Support

BACKGROUND

The balance of hemostasis and anticoagulation is a concern for patients dependent upon ventricular assist devices (VADs). Bleeding is a common complication with both short- and long-term use of these devices. A better understanding of the risk factors and etiologies of bleeding associated with these devices is needed and could improve the overall results. We sought to determine the relationship of mechanical circulatory assist device use with acquired von Willebrand disease (avWD) in children.

METHODS

Data were analyzed retrospectively via review of the medical record of 19 consecutive patients who were supported with the Berlin EXCOR VAD for greater than 24 hours. Laboratory testing for avWD was performed at the discretion of the clinical team, often in association with clinical bleeding.

RESULTS

Of 19 pediatric patients, 10 (52.6%) had laboratory testing consistent with avWD. Median time to detection of avWD was 35 days postimplantation of device (range 0-310 days). Both minor mucosal bleeding and bleeding requiring intervention were highly prevalent in patients in whom avWD was identified (10/10 [100%] and 7/10 [70%]). The mean age of all patients was 3.3 years, but patients found to have avWD tended to be older (mean 5.3 years) and supported with larger volume VADs.

CONCLUSIONS

This experience demonstrates a high prevalence of avWD following EXCOR implantation. Bleeding, older age, and larger VAD size may be associated with avWD. These results should stimulate critical evaluation of individualized anticoagulation regimens in pediatric VAD patients.

Singularity now: using the ventricular assist device as a model for future human-robotic physiology

In our 21^st century world, human-robotic interactions are far more complicated than Asimov predicted in 1942. The future of human-robotic interactions includes human-robotic machine hybrids with an integrated physiology, working together to achieve an enhanced level of baseline human physiological performance. This achievement can be described as a biological Singularity. I argue that this time of Singularity cannot be met by current biological technologies, and that human-robotic physiology must be integrated for the Singularity to occur. In order to conquer the challenges we face regarding human-robotic physiology, we first need to identify a working model in today's world. Once identified, this model can form the basis for the study, creation, expansion, and optimization of human-robotic hybrid physiology. In this paper, I present and defend the line of argument that currently this kind of model (proposed to be named "IshBot") can best be studied in ventricular assist devices - VAD.