31P NMR spectroscopy

Myocardial high-energy phosphate metabolism in heart transplant patients is temporarily altered irrespective of rejection

A reliable, sensitive, non-invasive alternative for transvenous endomyocardial biopsy in detecting cardiac allograft rejection is desirable for optimal management of heart transplant patients. To establish whether (31)P magnetic resonance spectroscopy can become a non-invasive tool for detecting cardiac allograft rejection, the cardiac high-energy phosphate metabolism of human heart transplants was serially examined in 13 patients by means of (31)P MRS from post-operative day 13 to day 294, and compared with histologic evaluation of endomyocardial biopsies. Biopsy scores of 2 or higher, according to the Working Formulation criteria of Billingham et al., were considered to indicate rejection. Logistic regression, which was corrected for differences between the individual patients and the time after transplantation, showed no significant correlation between the occurrence of histologically detected rejection and the PCr:ATP ratio. However, using an analysis of variance, the PCr:ATP ratios of non-rejecting cases obtained within 50 days after transplantation (mean: 27 +/- 11 days) appeared to be significantly different from those obtained after post-operative day 50 [0.95 +/- 0.17 (n = 25) vs 1.17 +/- 0.17 (n = 32), mean +/- SD; p < 0.01]. No significant difference was observed between the PCr:ATP ratios obtained 100 days after transplantation (mean: 162 +/- 52 days) and the PCr:ATP ratios in the hearts of healthy volunteers [1.18 +/- 0. 18 (n = 19) and 1.23 +/- 0.17 (n = 6), mean +/- SD, respectively; p = 0.55]. The PCr:ATP ratio in transplanted human hearts is not a sensitive indicator for the detection of early acute human cardiac allograft rejection. This may be due to a temporarily altered high-energy phosphate metabolism early after transplantation irrespective of rejection.

Functional recovery after human heart transplantation is related to the metabolic condition of the hypothermic donor heart

BACKGROUND

Although strict selection criteria are being used for the acceptance of human donor hearts for transplantation, problems with respect to functional recovery on reperfusion sometimes still occur. Therefore, evaluation of the viability of a human donor heart before implantation during heart transplantation may be of great value.

METHODS AND RESULTS

In the present study, the energy metabolism of 25 excised human donor hearts arrested with St Thomas' Hospital No. 2 cardioplegic solution was evaluated noninvasively by use of 31P magnetic resonance spectroscopy (MRS) before implantation and was correlated with myocardial function measured with thermodilution in heart transplant patients. No significant correlation was observed between the cardiac index of heart transplant patients during the first hours after transplantation and the phosphocreatine/ATP (r = .13, P = .54), inorganic phosphate/ATP (r = .26, P = .21), phosphomonoesters/ATP (r = .02, P = .92), or phosphocreatine/inorganic phosphate (r = .16, P = .44) ratio or the intracellular pH (r = .06, P = .78) at the time of reperfusion. However, 1 week after transplantation, a significant correlation was observed between the cardiac index and the phosphocreatine/ATP (r = .49, P = .01), phosphomonoesters/ATP (r = .45, P = .02), and phosphocreatine/inorganic phosphate (r = .40, P = .05) ratios at the time of reperfusion. In contrast, the inorganic phosphate/ATP (r = .10, P = .63) ratio and pH (r = .31, P = .13) at the time of reperfusion showed a poor correlation with the cardiac index 1 week after transplantation.

CONCLUSIONS

Functional recovery after human heart transplantation is related to the metabolic condition of the hypothermic donor heart.