Magnetic resonance imaging of human orthotopic heart transplantation: correlation with endomyocardial biopsy.

The ability of magnetic resonance imaging (MRI) to detect allograft rejection was studied concomitantly in two centers. In 29 patients MR images performed on a 0.5 T imager were compared with pathologic findings obtained by transvenous right ventricular endomyocardial biopsies. Eight patients had grade 1 or 2 acute rejection, and their myocardium thickness was increased significantly compared with values obtained in normal volunteers, in normal heart allograft patients, and in patients during the resolving phase of an acute rejection episode, whereas no abnormal signal intensity was found in the myocardium of heart allograft patients with acute rejection. This finding is quite in opposition to what was found in experimental models. This could be the result of the immunosuppressive regimen of those patients including cyclosporine, whereas few experimental studies included cyclosporine treatment. For chronic rejection or fibrosis, MRI did not allow the diagnosis because the MRI appearance was close to normal. Finally, MRI appears as a complementary technique to B-mode ultrasound in detecting nonimmunologic complications such as pericardial effusions and endocavitary processes. These data suggest that MRI could be used in the future to monitor rejection, to guide the timing of endomyocardial biopsy, and to assess the response after immunosuppressive treatment.