Diagnosing acute liver graft rejection: experimental application of an implantable telemetric impedance device in native and transplanted porcine livers

Background and aims: Diagnosis of acute rejection is a complex and persiste nt problem in liver transplantation. Focused on the use of proprietary impe dance technology a porcine liver model was designed to provide immediate in formation for differentiation of normal and acute rejecting tissue by an im plantable telemetric device. Methods: Electrical impedance was analyzed by electrodes implanted in vitro and in vivo in the liver of pigs, where imped ance is derived from measurements of voltage transients produced in respons e to programmed current pulses. Consequent electric recordings in porcine l ivers after transplantation and after mere laparotomy were evaluated in rel ation to biochemical parameters and histological results of liver biopsies. Results: Acute rejection was correctly predicted in all cases and correctl y excluded in the remaining 32 biopsy related impedance recordings (P < 0.0 04). Impedance measurements not only correlated with the diagnosis from liv er biopsy specimen (r = 0.84, P < 0.0001) but also exemplified the severity of histological acute rejection. Conclusion: Impedance analysis reveals ev ident physiologic relation of acute liver graft rejection and electrical or gan properties. Electrodes implanted in transplanted porcine livers allow r unning less invasive monitoring and thus early detection of rejection. The technology may have broad value in providing an immediate diagnosis of acut e rejection, reducing unnecessary patient anxiety and eliminating the signi ficant expenses associated with multiple referrals, expensive sample handli ng and tissue analysis. <(c)> 2001 Elsevier Science B.V. All rights reserve d.