P-31-magnetic resonance spectroscopy studies of cardiac transplant patients at rest

Studies in animal models and patients have suggested that P-31-magnetic res onance spectroscopy (MRS) may be useful in diagnosing transplant rejection, but such studies often are confounded by the late inclusion of patients af ter transplantation. The present study examined the utility of P-31-MRS in the diagnosis of acute allograft rejection during the first posttransplant month. Thirteen recent heart transplant recipients underwent 57 resting P-3 1-MRS studies within 24 hr of a biopsy. Subjects lay supine with a 10-cm su rface coil placed over the heart. A 1-dimensional chemical shift imaging pr otocol was used to collect spectral information. Spectra from the heart wer e weighted for distance from the coil and summed before analysis. ANOVA and Duncan's multiple range test were used to analyze the data comparing phosp hocreatine (PCr)/ATP ratios with biopsy scores. Transplant patients had sig nificantly lower myocardial PCr/ATP ratios when compared with a normal cont rol group (1.27 +/- 0.27 versus 1.61 +/- 0.22, p < 0.001). However, when th e patient group was classified by biopsy score, the expected order of score , 0 > 1 > 2 > 3, was not obtained Rather the order was 2 > 0 > 1 > 3. Altho ugh the difference Between scores 2 and 3 was significant (1.46 versus 1.14 , alpha = 0.05 level), the lower three groups were statistically ir indisti nguishable. In addition, the PCr/ATP ratios were not predictive of future b iopsies. Although significantly lower than normal control subjects, resting ,myocardial PCr/ATP ratios of transplant subjects are not useful in assessi ng the level of rejection. It is suggested that the measurement may be more predictive in mildly exercised myocardium.