Pseudointima in inflow and outflow conduits of a left ventricular assist system: Possible role in clinical outcome

Activation of blood coagulation and thromboemboli have been shown to presen t significant clinical risks in patients supported with an left ventricular assist system (LVAS). The interaction of pseudointima (PI) with blood in t he conduits of the device could be involved in these clinical complications . Our aim was to study the morphology of the PI verses duration of circulat ory support. Novacor N 100 PC LVASs were explanted from 10 men and 2 women after a mean of 209 days (range 23-560 days) of circulatory assistance. PI in the inflow and outflow conduits were investigated with immunohistochemic al assays. In the inflow conduits, a loosely adherent PI had built up from collagen type I and III fibers growing into and between fibrin deposits. Di sorganized collagenous matrix and longitudinally oriented collagen fibers i ncluded alpha -smooth muscle actin positive cells with random orientation. Macrophages were concentrated in the fibrin and were dispersed throughout t he extracellular matrix. In the outflow conduits, a thin, adherent PI was c omposed of regular collagen type I and III layers. Collagen type I fibers h ad grown into the woven Dacron and cu-smooth muscle actin positive cells we re oriented in the axis of the blood flow. Macrophages were concentrated in the Dacron and reached the inner collagen layers. Venous blood flow in the inflow conduits allows the development of a non endothelialized irregular collagenous matrix intermingled with fibrin and invaded by macrophages. The se persistent structural features progress with duration of circulatory ass istance and reflect matrix degradation and remodeling. The potential to rel ease thromboembolic fragments from the non stable, thrombogenic PI may be i nvolved in the thromboembolic or neurologic complications sustained by 5 of 12 patients who were on circulatory support for as long as 200 days.