ARTIFICIAL CIRCULATORY SUPPORT WITH TEXTURED INTERIOR SURFACES - A COUNTERINTUITIVE APPROACH TO MINIMIZING THROMBOEMBOLISM

Background Although numerous left ventricular assist devices (LVADs) h ave been used clinically, frequent thromboembolic complications have b een reported despite the smooth interior LVAD surfaces and systemic an ticoagulant medication. In contrast, the Thermo Cardiosystems HeartMat e 1000 IP LVAD has textured interior surfaces that are promptly covere d by a densely adherent neointimal. We hypothesize that elimination of a direct interface between prosthetic material and blood elements red uces the risk of peripheral embolization and minimizes the necessity f or systemic anticoagulant medication. This report defines the thromboe mbolic risk of this type of LVAD and characterizes the nature and effe ctiveness of the various anticoagulation regimens that were tested dur ing the initial clinical trial with this device. Methods and Results A ll values are reported as mean+/-SD. Fifty-four males and three female s with an average age of 47+/-11 years were supported with the HeartMa te 1000 IP LVAD for an average of 62+/-76 days at 11 clinical centers in the United States. Patients were prospectively evaluated for thromb oembolic complications. Five different anticoagulation regimens were u sed during the first 4 postoperative weeks: no anticoagulants, low-mol ecular-weight dextran, heparin, dipyridamole plus aspirin, or miscella neous agents. After the first 4 weeks, the patients were treated with aspirin plus dipyridamole or miscellaneous agents. Prothrombin time (P T), partial thromboplastin time (PTT), and fibrinogen values for the p atients were measured at 0.1, 1, 2, 4, 8, 12, 16, 20, 24, 32; and 46 w eeks during support. Two patients (3.5%) suffered thromboembolic cereb rovascular complications, an incidence of 0.2 episodes per patient-yea r of observation. One episode was due to fungal vegetation developing on the device and the other was due to embolization from a previously placed native mechanical aortic valve prosthesis. In the absence of in fection, there were no device-related thromboembolic complications. Me an prothrombin time for all groups was 13.3+/-0.5 seconds with no sign ificant intergroup differences. Mean partial thromboplastin time durin g the first 4 weeks for the heparin-treated group was 53.3+/-6.6 secon ds, which was significantly longer than for all other groups, but fell to control values after heparin was discontinued at 4 weeks. Mean fib rinogen level for all groups was 370+/-48 mg/dL, with no intergroup di fferences. Conclusions The HeartMate 1000 IP LVAD provides adequate ci rculatory support with a low risk of thromboembolism despite minimal s ystemic anticoagulation. The use of textured surfaces may be an import ant factor contributing to the low observed risk of thromboembolic com plications.