Invited Commentary

Abstract

Left ventricular assist devices (LVADs) continue to be an important therapy for patients with end-stage heart failure. While survival with a LVAD is superior to medical therapy alone, device-related complications are unfortunately common. Nonsurgical bleeding is a particularly serious challenge, as it negatively affects a large percentage of patients receiving LVAD therapy. This phenomenon is thought, in part, to result from the mechanical interface of the device with patient blood. Supraphysiologic shear stress is notable in the newer generation of nonpulsatile LVADs and can induce degradation of important clotting factors, including von Willebrand Factor (vWF). In this article, the authors [1Bartoli C.R. Kang J. Zhang D. et al.Left ventricular assist device design reduces von Willebrand factor degradation: a comparative study between the HeartMate II and the EVAHEART left ventricular assist system.Ann Thorac Surg. 2017; 103: 1239-1245Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar] use a mock circulatory loop to compare two devices: the axial flow HeartMate II and the centrifugal pump EVAHEART LVAS. Whole blood was run through each of the mock loops, and levels of vWF and its degradation products were measured at 6-hour intervals. This study found a significant increase in the breakdown of vWF with the axial flow device compared with the centrifugal pump. While they acknowledge that other design features might affect their results, the authors attribute less breakdown of vWF with the centrifugal pump to the relatively larger blood gaps and lower revolutions per minute associated with the device. This study is an important demonstration of how pump mechanics can dramatically affect the components of circulating blood. The bench model does not account for endothelial function or other physiologic parameters found in vivo. However, the purity of design enables researchers to examine directly how a change in pump properties can help to minimize blood trauma. Ultimately, more patients are now living longer with mechanical circulatory support. To minimize device-related complications, such as nonsurgical bleeding, it is important to understand the effects of design features. Studies such as these will help to inform the next generation of devices. Left Ventricular Assist Device Design Reduces von Willebrand Factor Degradation: A Comparative Study Between the HeartMate II and the EVAHEART Left Ventricular Assist SystemThe Annals of Thoracic SurgeryVol. 103Issue 4PreviewSupraphysiologic shear stress from continuous-flow left ventricular assist devices (LVADs) accelerates von Willebrand factor (vWF) degradation and predisposes patients to nonsurgical bleeding. It is unknown whether unique design characteristics of LVADs differentially affect vWF degradation. We tested the hypothesis that the centrifugal-flow EVAHEART (Evaheart, Houston, TX) left ventricular assist system (LVAS), which was designed to minimize shear stress (low operational revolutions per minute [rpm], larger flow gaps, low shear stress, flat H-Q curve), reduced vWF degradation versus the axial-flow HeartMate II (Thoratec, Pleasanton, CA) LVAD. Full-Text PDF