Abstract: A method is disclosed for monitoring the body reaction against a heart transplant. When a heart is newly transplanted, electrocardiac signals from the transplanted heart are detected. The analog signals are converted to digital signals. A first differentiation of the digital signals is carried out over a continuous time period to create reference differentiated signals. At a later time during monitoring of the transplanted heart, analog electrocardiac signals are again detected from the transplanted heart. These analog signals are converted to digital signals. A first differentiation is carried out of these digital signals over a continuous time period to create monitored differentiated signals. The reference differentiated signals and the monitored differentiated signals are compared at least with respect to amplitude to create comparison results. All of the above operations occur within the body.