Antithrombotic therapies in children on durable Ventricular Assist Devices: A literature review

Introduction: Ventricular Assist Devices (VADs) are increasingly utilised in children with end-stage heart failure, and experience high bleeding and clotting rates. In particular, pediatric VAD patients are more challenging than adults to anticoagulate due to developmental hemostasis, lack of suitable drug preparations, and difficult anticoagulation monitoring often due to poor vascular access; in addition to difficulties of VAD design in smaller children. This review aims to summarize the current evidence related to antithrombotic therapy in pediatric VAD patients. Materials and methods: A search of 2 databases across a 17-year period of time was undertaken using key words selected a priori. Identified publications were then categorized according to VAD types utilised and the anticoagulation protocols described. Results: 27 articles were identified consistent with the inclusion criteria developed for this review. Devices included in the cohort were Berlin Heart EXCOR, Thoratec, Medos, Novacor, HeartMate II and HeartWare HVAD. Most studies reported the use of unfractionated heparin post-operatively with a transition to low molecular weight heparin and warfarin. Antiplatelet regimens most commonly included aspirin and dipyridamole. Definition of bleeding and clotting events differed between cohorts. The incidence of bleeding overall was 37% (209/558; range of 0 to 89%) and 26% (143/554; range of 8.3 to 100%) for thromboembolism events. All studies reported had significant methodological limitations. Conclusions: The clinical use of antithrombotic therapies - including dosages, timing and monitoring - varies considerably. This review highlights the further research required to improve understanding of hemostasis in the pediatric VAD field.