Thrombus formation at the inflow cannula of continuous-flow left ventricular assist devices-A systematic analysis.

Abstract

Despite numerous design iterations, thrombus formation at the inflow cannula of continuous-flow left ventricular assist devices remains an unsolved problem. We systematically investigated the impact of cannula surface on thrombus formation. Thrombus appearance was photographically documented in 177 explanted hearts with the polished (N=46) or sintered (N=131) inflow cannula of the Medtronic HeartWare™ HVAD™ System. Thrombus load was compared for both inflow cannula types. Mean thrombus length was correlated with protruding cannula length. Support duration and the extent of thrombus growth were examined. The prevalence of thrombi at the left ventricular entry site and at the sintered-to-polished transition zone was correlated with left ventricular geometry and hemodynamic parameters. Polished inflow cannulas showed a greater percentage and also a greater mean length of thrombus formation at the entry site than sintered cannulas (91.3% [Pol] vs. 36.7% [sTi]; p<0.0001; mean 7.6mm vs. 1.9mm; p<0.0001). A comparison of the early postoperative period (POD1-90) with long-term support (POD>90) showed an increase in thrombus length originating from the transition zone (1.96±3.41mm vs. 3.03±2.91mm; p=0.013). A sintered titanium surface at the entry site is crucial to enable anchoring of myocardial tissue to the cannula. As thrombus growth progresses on polished surfaces, a greater sintered length seems to be beneficial. After an initial three-month healing period, thrombus load appears to decline during prolonged support duration at the sintered entry site but not at the transition zone.