MYOSIN LIGHT-CHAIN EFFLUX AFTER HEART-TRANSPLANTATION IN INFANTS AND CHILDREN AND ITS CORRELATION WITH ISCHEMIC PRESERVATION TIME

Serum levels of cardiac myosin light chain 1 after heart transplantati on were studied in 24 infants and children who underwent heart transpl antation between June 1990 and April 1991. The ages of the patients ra nged from 4 days to 6 years 7 months (mean, 9.9 months), and their bod y weights ranged from 2.2 to 20 kg (mean, 5.6 kg). The ages of the don ors ranged from 2 days to 8 years, 7 months (mean, 26.6 months), and t heir body weights ranged from 2.5 to 26 kg (mean, 11.4 kg). The donor heart ischemic time ranged from 90 minutes to 482 minutes (mean, 279 m inutes). Peak myosin levels after heart transplantation showed signifi cant correlation with the duration of graft ischemia (p < 0.01) and wi th diastolic cardiac function in the first posttransplant week (p < 0. 05). Peak myosin levels did not correlate with systolic cardiac functi on, age of the donor, or age of the recipient. Myosin levels of the 15 patients with graft ischemic times exceeding 4 hours averaged 6.30 +/ - 3.50 ng/ml. These levels were significantly higher than those of pat ients with graft ischemia lasting less than 4 hours (2.60 +/- 1.20 ng/ ml; p < 0.01). Both of the values are higher than previously reported values of normal controls but lower than previously reported values of patients with myocardial infarction. Preservation techniques used for this series of transplant operations provided good clinical protectio n of the donor heart for up to 8 hours, although release of the cardia c myosin light chain fragment correlated with duration of graft ischem ia. Cardiac myosin levels appeared to be a good indicator of heart gra ft damage during ischemic preservation. It remains to be determined at what level of myosin release (and, hence, at what duration of graft i schemia) irreversible myocardial damage, which might result in permane nt functional compromise, occurs.