ULTRASTRUCTURAL ANALYSES OF BLOOD-INTERFACING LININGS FORMED WITHIN PARTIAL ARTIFICIAL HEARTS OR ABDOMINAL LEFT...

Following each of 21 clinical trials with the partial artificial heart or abdominal left ventricular assist device (ALVAD), we have examined the blood-interfacing human pseudoneointimal (PNI) linings formed on the fibril-flocked pumping surface by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The salient results of these ultrastructural analyses can be summarized: (1) early PNI accretion kinetics (< 24 hrs) involve plasma protein adsorption, entrapment of erythrocytes, platelets, lymphocytes, numerous neutrophils and macrophages, and the deposition of fibrin within fibril flock interstices (TEM); (2) the surface (< 24 hrs) consists of interconnected fibrin strands (SEM); (3) later PNI accretion kinetics (1-6 days) involve the formation of alternating cellular and fibrin layers (TEM); (4) the surface (1-6 days) consists of cellular aggregates (inter-membrane distances of 340 A) simulating an endothelial interface (SEM, TEM). Based on these analyses, a plausible sequence of events for human PNI accretion kinetics can be advanced, i.e., 0-24 hrs: (a) maximal foreign body response of blood in contact with Dacron fibrils, (b) cellular lysis and fibrin compaction; 1-6 days: (c) accretion and lysis of cellular aggregates (neutrophils, macrophages) 3-4micro thick, (d) accretion of linear fibrin aggregates, 8-10micro thick, and (e) cyclic replication (up to six) of phases c and d.