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

Abstract

Background and aims: Diagnosis of acute rejection is a complex and persistent problem in liver transplantation. Focused on the use of proprietary impedance technology a porcine liver model was designed to provide immediate information for differentiation of normal and acute rejecting tissue by an implantable telemetric device. Methods: Electrical impedance was analyzed by electrodes implanted in vitro and in vivo in the liver of pigs, where impedance is derived from measurements of voltage transients produced in response to programmed current pulses. Consequent electric recordings in porcine livers after transplantation and after mere laparotomy were evaluated in relation to biochemical parameters and histological results of liver biopsies. Results: Acute rejection was correctly predicted in all cases and correctly excluded in the remaining 32 biopsy related impedance recordings ( P<0.004). Impedance measurements not only correlated with the diagnosis from liver biopsy specimen ( r=0.84, P<0.0001) but also exemplified the severity of histological acute rejection. Conclusion: Impedance analysis reveals evident physiologic relation of acute liver graft rejection and electrical organ properties. Electrodes implanted in transplanted porcine livers allow running less invasive monitoring and thus early detection of rejection. The technology may have broad value in providing an immediate diagnosis of acute rejection, reducing unnecessary patient anxiety and eliminating the significant expenses associated with multiple referrals, expensive sample handling and tissue analysis.