Heart graft rejection assessed by multi-frequency electrical impedance: Human results

Abstract

We measured the myocardial electrical impedance with a custom system using an intracavitary catheter. We calculated the impedance differences between the measurement in the right ventricle with the tip of the catheter in contact with the myocardial wall, and the measurement in the right atrium with the catheter in a floating position. Our study includes two groups of patients. Group I was composed of 33 patients who underwent cardiac transplantation. Some patients in this group were measured more than once, so a total of 57 measurement sessions were done with different biopsies results: 0, 1A and 3A. Group II included 9 control patients without clinical and echocardiographic evidence of structural heart disease, who underwent an electrophysiologic testing. Results show that estimated myocardial impedance difference between ventricle and atrium is higher in controls than in transplanted patients. Furthermore, moderate cardiac rejection causes a significant decrease in the myocardial impedance, differences are more significant (p<0.001) for the magnitude of impedance at 10 kHz and the phase angle at 300 kHz. The cardiac modulation of the impedance signal, which is related to the contractibility of the tissue, is also different depending on the level of rejection. © Springer-Verlag 2007.