Left ventricular myocardial performance index change for detection of acute cellular rejection in pediatric heart transplantation

EMB, the gold standard for diagnosis of ACR, poses unique risks in children. Limited cross-sectional data have associated LV MPI with ACR. We hypothesize that a relative change in MPI from baseline without ACR to the time of ACR will better detect ACR than an absolute threshold LV MPI value. We identified 40 children with ACR 60days post-transplant matching them by age and time from transplantation to 40 children without ACR. There was a significant increase in LV MPI at time of ACR vs. baseline (0.59 +/- 0.17 vs. 0.41 +/- 0.11; p<0.001). There was no difference in LV MPI between baseline and follow-up (0.41 +/- 0.11 vs. 0.42 +/- 0.11; p=0.65). An absolute increase in LV MPI of 0.47 had 82.5% sensitivity and 85% specificity for ACR, whereas an increase in LV MPI from baseline of 20.4% was 90% sensitive and 100% specific. Serial measurement of LV MPI appears to be a sensitive and specific marker of ACR. LV MPI shows good interobserver agreement and increases at the time of EMB-proven ACR with subsequent resolution to baseline measurements upon EMB-proven resolution of ACR. Future studies in larger, prospective cohorts should be undertaken to validate these findings.