Chronic In Vivo Testing of the Penn State Infant Ventricular Assist Device

Abstract

The Penn State Infant Ventricular Assist Device is a 12-14 ml stroke volume pneumatically actuated pump, with custom Björk-Shiley monostrut valves, developed under the National Heart, Lung, and Blood Institute (NHLBI) Pediatric Circulatory Support program. In this report we describe the 7 most recent chronic animal studies of the Infant VAD in the juvenile ovine model, with a mean body weight of 23.5 +/- 4.1 kg. The goal of 4-6 weeks survival was achieved in 5 of 7 studies, with support duration ranging from 5 to 41 days; mean 26.1 days. Anticoagulation was accomplished using unfractionated heparin, and study animals were divided into 2 protocol groups: the first based on a target activated partial thromboplastin time of 1.5 to 2 times normal, and a second group using a target thromboelastography R-time of 2 times normal. The second group required significantly less heparin, which was verified by barely detectable heparin activity (anti-Xa). In both groups, there was no evidence of thromboembolism except in one animal with a chronic infection and fever. Device thrombi were minimal, and were further reduced by introduction of the custom valve. These results are consistent with results of adult VAD testing in animals, and are encouraging given the extremely low levels of anticoagulation in the second group.

Assessment of Thrombelastography and Platelet Life Span in Ovines

“…The ovine is a frequently used preclinical animal model for the assessment of cardiovascular device function and biocompatibility . Adult ovines have hearts that are similar in size to the human heart for evaluation of implantable devices such as ventricular assist devices (VAD).…”

“…Limited data exist describing the use of TEG in sheep. TEG was used as one parameter to assess the efficacy of anticoagulation in sheep as well as coagulation status following initiation of mechanical circulatory support . In another report, TEG was used to assess platelet function before and after burn and smoke inhalation injury .…”

Preanesthesia, Anesthesia, Analgesia, and Euthanasia

“…This equipment may not be able to support animals above 100 kg body weight. Very young animals may benefit from breathing 60-70% oxygen to minimize adverse effects on the lungs (Carney et al, 2009;Weiss et al, 2012). High oxygen flow rates (5-10 L/min) are initially used to flush nitrogen from the circuit and animal and promote uptake of the inhalant agent (Abrahamsen, 2009a).…”

“…Used in conjunction with other analgesic drugs such as opioids and NSAIDs, local or regional anesthesia provides an effective regimen of multimodal analgesia (Schauvliege et al, 2006;Carney et al, 2009). Following thoracotomy in sheep and calves, the authors have used a diffusion catheter (Mila International) to deliver bupivacaine (0.25%, 5-12 ml q 8 h) at the thoracotomy incision (Carney et al, 2009;Weiss et al, 2012). Although CRI may be used with this method of drug delivery, intermittent boluses of local anesthetics delivered through a diffusion catheter appear to provide more effective local anesthesia (Hansen et al, 2013).…”

A transapical-to-aorta double lumen cannula-based neonate left ventricular assist device efficiently unloads the left ventricle in neonate lambs

“…6–9 Although these pumps are very small, it is still challenging to implant them into the small neonate body. 10–12 The neonate’s mediastinal cavity is very small and easily leads to conduit kinking/heart compression, which may prevent chest closure. The neonate’s open chest requires continuous sedation/anesthesia and is associated with a greater incidence of bleeding/infection, which makes extubation, mobilization, and oral feeding impossible.…”