Bleeding and Thrombosis in Patients With Continuous-Flow Ventricular Assist Devices

Abstract

Because of the obligate intravascular location of contemporary continuous-flow ventricular assist devices (CF-VADs), it is not surprising that bleeding and thrombosis are among the most common and feared complications of this therapy, respectively. Although strides have been made in our understanding of the pathophysiology of continuous flow, intravascular CF-VADs have been widely used only in the last few years, and a great deal remains less well known (or unknown). Outcomes have improved significantly over the past decade, but a deeper understanding of how these devices perturb the delicate intrinsic balance of bleeding and thrombosis is critical to guide therapy and to overcome the current obstacles to achieving a long-term safety profile comparable to that of mechanical prosthetic valves. ### Hematologic Effect of CF-VADs The hematologic effects of CF-VADs are of significant interest and importance and have recently been reviewed in detail elsewhere.1,2 Hemocompatibility refers to the interaction of prosthetic material with blood and can be measured in terms of impact on hematologic, inflammatory, or immunologic parameters, which has been observed clinically as significant and prolonged activation of endothelial and coagulation systems after CF-VAD implantation, including intercellular adhesion molecule, E-selectin, and tissue factor, for example.3 Hemocompatibility has always been a goal in pump design, along with efforts to maximize blood flow without clinically significant hemolysis, areas of stasis, turbulent flow, or retrograde flow. It has been suggested that the major complications of thrombosis, bleeding, and infection could be related to the effects of blood interaction with the VAD surface,4,5 and further optimization of surface coatings presents an appealing strategy for additional exploration.6 A better understanding of the impact of blood–VAD surface interactions with the presently used CF-VAD devices, however, is essential to evaluating the impact of novel designs or materials. A few recent observations have provided some insight …