Magnetic resonance imaging for assessment of tissue rejection after heterotopic heart transplantation.

Detection of myocardial rejection is difficult in patients with heterotopic heart transplantation because of the complex vascular anatomy present after transplant surgery. To determine whether magnetic resonance imaging might be useful for the assessment of heart rejection, eight patients with heterotopic heart transplantation were serially studied on 27 occasions. One patient had two donor hearts implanted, which allowed the study of 33 donor hearts. Data acquisition was gated to the ECG signal of the donor heart. Heavily T2-weighted (TE = 90 ms) velocity compensated spin-echo images were obtained through the midportion of the donor heart to assess tissue rejection. Donor heart function was qualitatively measured by acquiring multiphasic gradient echo images at the same level. A myocardial/skeletal muscle signal intensity ratio was calculated for the donor heart and compared to results of right ventricular biopsy obtained within 24 hours of imaging. A change in signal intensity ratio of 0.14 or more exceeded normal signal variation. All three episodes of rejection detected by biopsy were detected by magnetic resonance imaging. In three instances a significant change in the signal intensity ratio was associated with clinical evidence of rejection and a negative biopsy. Two instances were treated with a steroid bolus, and the signal returned to baseline. In three other instances a significant change in the magnetic resonance imaging signal occurred without clinical or biopsy evidence of rejection. Cardiac toxoplasmosis was present in one of these cases, and signal intensity returned to baseline after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)