Abstract 17311: How You “Place It” Matters: The Impact of Inflow and Outflow VAD Cannulation Orientation on Overall System Thrombogenicity
Purpose: VADs are burdened with an incidence of thromboembolic events. Limited surgical guidance exists as to optimized orientation of VADs during surgical implantation as to radial orientation of the inflow cannula (ICA), and the anastomosis angle (AOA) of the outflow graft to the aorta. Further, limited data exists with regard to the effect of ICA and the reintroduction of blood flow from the VAD into the aorta. The direction of swirling flow (SWD) generated by the VAD when reentering the aorta may affect flow-induced stresses. The thrombogenic potential (TP) of two VADs, HeartMate II (HMII) and HeartAssist 5 (HA5), were compared using Device Thrombogenicity Emulation (DTE) - developed by our group (Plos One 7(3): e32463. doi:10.1371, 2012), and 36 thrombus-formation-patterns (TFP) were predicted, and compared to the effects of cannulation angles and the SWD of these VADs.
Methods: 1. Human-purified-platelets were recirculated in flow-loop with VADs operating at physiological condition (10000 and 9000 rpm for HMII and HA5, @4 L/min). Platelet-activation was measured. 2. Advanced-CFD was conducted. ~30,000 platelets flowed through both VADs and the corresponding stress accumulations (SA) computed along flow trajectories. The recirculation zones (RZ) and stagnant platelet trajectories (SPT) were computed by MATLAB. Four radial orientation angles were studied for the ICA (0°, 15°, 30° and 60°). The SWD in HMII-clockwise and HA5-counterclockwise were studied with 60° and 90° OAA.
Results: Platelets flowing through the HMII have higher TP. The Platelet-activity-rate (PAR) of the HA5 was 2.5-fold lower than HMII (p<0.05). Simulations of HMII depicted RZ and SPT downstream of the flow-straightener-fins with SPT at the entry of the impeller-fins. The RZ and SPT matched TFP clinically observed in explanted-HMIIs. 60° ICA had the lowest TP. Counterclockwise-SWD (HA5) had lower TP than clockwise (HM II). The 90° AOA had higher TP than 60°.
Conclusions: Factors such as orientation angle of the inflow cannula as well as the angle of anastomosis of the outflow graft to the aorta have significant impact on overall VAD system thrombogenicity. System modeling using DTE can provide optimized surgical implantation guidance for a given VAD enhancing safety and efficacy.
- © 2013 by American Heart Association, Inc.