Pathologic analysis of 34 explanted symbion ventricular assist devices and 10 explanted Jarvik-7 total artificial...

Thirty-four Symbion ventricular assist devices and 10 Jarvik-7 total artificial hearts that had been in clinical use for 1 to 164 days (assist devices) and 1 to 176 days (artificial hearts) were analyzed using a detailed protocol for pathological analysis. The major finding was thrombus formation in 85% of the assist devices and 75% of the artificial hearts. Thrombi were generally small and in only one case interfered with pump function. The number of distinct thrombi per device was 2.5 mean (range 0-5) for assist devices and 2.6 mean (range 0-6) for artificial hearts. Major sites of thrombus formation in the assist devices were valves, valve connections, diaphragm, and the inner surface of the deairing port. Artificial heart thrombi were predominantly paravalvular. In order to relate sites of diaphragmatic thrombi to specific design features of the assist device, the pattern was analyzed quantitatively using a polar coordinate mapping technique to measure the average radial thrombus length around the circumference of each diaphragm. The concentration of thrombus was highest between the valve orifices and lateral to the outflow valve. This identified areas particularly susceptible to thrombus formation and thereby targets specific pump features for redesign. Intraluminal infection was seen in 1 assist device and 1 artificial heart (outflow grafts); extraluminal infection was seen in two artificial hearts (infected hematomas around the outflow grafts). Neither device mineralization for mechanical defects were noted. Thus thrombus formation related to (and potential thromboemboli from) valves, their connectors, and the pumping diaphragms represents the major device-associated complication of pneumatic Symbion assist devices and Jarvik-7 artificial hearts. Thrombi associated with other sites and both intra- and extraluminal infection occur less frequently.