Ultrastructural assessment of the infant myocardium receiving crystalloid cardioplegia.

The effectiveness of cold crystalloid potassium cardioplegia was evaluated in 26 infants (age 27 days to 17 months, 7.5 +/- 5.2 months, mean +/- SD) who underwent intracardiac repair for various cardiac lesions. A myocardial biopsy sample was obtained before aortic cross-clamping (AXC) and 20 min after release of AXC (AXC time 22 to 161 min, mean 68 +/- 37 min), and semiquantitative assessment of the mitochondrial structure was made by scoring. The post-AXC score was significantly higher than the pre-AXC score (1.1 +/- 0.6 vs 0.4 +/- 0.4, p less than .001) for the whole group. Patients receiving preoperative catecholamine support had higher pre- and post-AXC scores than those who did not (pre-AXC score 0.7 +/- 0.4 vs 0.2 +/- 0.3, p less than .01; post-AXC score 1.4 +/- 0.5 vs 1.0 +/- 0.5, p less than .05). Infants less than 3 months old (n = 7) and those 3 to 12 months old (n = 11) had higher pre AXC scores than infants over 12 months old (n = 8). With respect to post-AXC score, only those less than 3 months old had significantly higher values than the other infants. These results indicate that the myocardial injury was not fully prevented by crystalloid potassium cardioplegia in infants, and that infants with preoperative heart failure and less than 3 months old appear to have increased myocardial susceptibility to ischemic injury under cardioplegia.