The Thermo Cardiosystems Inc (Woburn, MA) HeartMate 1000 IP left ventricular assist device (LVAD) has been evaluated as a bridge to transplantation in 34 patients for up to 324 days at seven clinical centers in the United States. Sixty-five percent of the patients underwent transplantation, 80% of whom were discharged from the hospital. Six additional control patients, transplant candidates who met the entrance criteria but who did not receive the device, were also included in the study. Although 3 (50%) of the control patients received transplants, all 6 died within 77 days of having met the LVAD inclusion criteria (100% mortality). Complications resulting from use of the device were comparable with those previously reported for all ventricular assist devices, except for thromboembolic events: bleeding, 39%; infection, 25%; and right heart failure, 21%. No device-related thromboembolic events occurred, although 1 patient experienced an event related to a mechanical aortic valve in the native heart. None of the complications had a significant negative association with outcome of the patient except for right heart failure. All survivors had a significant improvement in hepatic function before transplantation. Total bilirubin values were reduced by 60% during LVAD support. No significant differences were observed when total bilirubin values were compared at 30 and 60 days after LVAD support and at 30 and 60 days after transplantation in a cohort of 15 patients (p greater than 0.05). The improvement in renal function was less predictable than that of hepatic function. Creatinine values decreased significantly before transplantation; however, the values measured at 30 and 60 days after transplantation were higher than those measured at the same intervals after LVAD support had been initiated, and this increase is presumably related to the immunosuppressive drugs. In conclusion, the HeartMate 1000 IP LVAD has been shown to be effective in supporting end-stage cardiomyopathy patients to transplantation. Thromboembolism, previously regarded as a serious complication with such devices, has not been a problem with this device. Additional patients are being enrolled into the study to further document the safety and effectiveness of this technology.