Bivalirudin for left ventricular assist device thrombosis

Bivalirudin Monitoring in Pediatric Ventricular Assist Device and Extracorporeal Membrane Oxygenation: Analysis of Single-Center Retrospective Cohort Data 2018-2022

OBJECTIVES

The activated partial thromboplastin time (aPTT) is the most frequently used monitoring assay for bivalirudin in children and young adults on mechanical circulatory support including ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO). However, intrinsic variability of the aPTT complicates management and risks bleeding or thrombotic complications. We evaluated the utility and reliability of a bivalirudin-calibrated dilute thrombin time (Bival dTT) assay for bivalirudin monitoring in this population.

DESIGN

Retrospective analysis of clinical data (including aPTT, dilute thrombin time [dTT]) and results of residual plasma samples from VAD patients were assessed in two drug-calibrated experimental assays. One assay (Bival dTT) was validated for clinical use in VAD patients, and subsequently used by clinicians in ECMO patients. Pearson correlation and simple linear regression were used to determine R2 correlation coefficients between the different laboratory parameters using Statistical Package for Social Sciences (Armonk, NY).

SETTING

ICUs at Cincinnati Children's Hospital Medical Center.

SUBJECTS

Children on VAD or ECMO support anticoagulated with bivalirudin.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred fifteen plasma samples from 11 VAD patients were analyzed. Both drug-calibrated experimental assays (anti-IIa and Bival dTT) showed excellent correlation with each other (R2 = 0.94) and with the dTT (R2 = 0.87), but poor correlation with aPTT (R2 = 0.1). Bival dTT was selected for validation in VAD patients. Subsequently, clinically ordered results (105) from 11 ECMO patients demonstrated excellent correlation between the Bival dTT and the standard dTT (R2 = 0.86) but very poor correlation with aPTT (R2 = 0.004).

CONCLUSIONS

APTT is unreliable and correlates poorly with bivalirudin's anticoagulant effect in ECMO and VAD patients. A drug-calibrated Bival dTT offers superior reliability and opportunity to standardize results across institutions. Additional studies are needed to determine an appropriate therapeutic range and correlation with clinical outcomes.

Guidance on the management of left ventricular assist device (LVAD) supported patients for the non-LVAD specialist healthcare provider: executive summary

The accepted use of left ventricular assist device (LVAD) technology as a good alternative for the treatment of patients with advanced heart failure together with the improved survival of patients on the device and the scarcity of donor hearts has significantly increased the population of LVAD supported patients. Device-related, and patient-device interaction complications impose a significant burden on the medical system exceeding the capacity of LVAD implanting centres. The probability of an LVAD supported patient presenting with medical emergency to a local ambulance team, emergency department medical team and internal or surgical wards in a non-LVAD implanting centre is increasing. The purpose of this paper is to supply the immediate tools needed by the non-LVAD specialized physician - ambulance clinicians, emergency ward physicians, general cardiologists, and internists - to comply with the medical needs of this fast-growing population of LVAD supported patients. The different issues discussed will follow the patient's pathway from the ambulance to the emergency department, and from the emergency department to the internal or surgical wards and eventually back to the general practitioner.

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.