A new rejection criteria in the heterotopically placed rat heart by non-invasive measurement of Dp/Dtmax.

BACKGROUND: The heterotopic heart of rats has been a useful model in the evaluation of immunomodulatory protocols. Graft palpation usually determines the day of rejection. We present in this paper an original method of graft monitoring in allograft rejection. METHODS: Heterotopic cardiac abdominal transplantation was performed in Lewis isografts (n = 15) and in ACI to Lewis allograft (n = 15). A balloon connected to a measurement device was inserted in the left ventricle, and calculation of Dp/Dtmax was possible by recording the intra-left ventricular pressure. A ten-day follow-up was achieved with a daily comparison of palaption, ECG, and Dp/Dtmax. RESULTS: In transplanted hearts, Dp/Dtmax did not change in isografts but significantly decreased in allograft on posttransplantation Day 5 (PTD 5) vs PTD 0.1 and 3 (p < .01). Dp/Dtmax values on PTD 5 and 6 were also statistically significant in allograft vs isograft group (p < .01). Histological analysis at this time showed the occurrence of acute rejection in the allograft group. Graft palpation, and ECG remained normal until PTD 10 and no difference was observed between iso and allo groups. CONCLUSION: This study shows that daily measurement of Dp/Dtmax in heterotopic heart is made possible by our implantable system without interrupting the graft, and gives a more accurate definition of graft rejection than a combination of palpation and ECG. In addition, this method would seem desirable when differences in survival may be expected to be of lesser magnitude.