Myocardial histology and outcome after cardiopulmonary bypass of neonatal piglets.

Background: Early after neonatal cardiac surgery hemodynamic dysfunction may be evident. However, still is not clear if dysfunction and outcome is related to visible myocardial alterations. The aim of the present study was the histological analysis of myocardial tissue of neonatal piglets after cardiopulmonary bypass (CPB) and cardioplegic arrest.

Methods: Neonatal piglets (younger than 7 days) were connected to CPB for 180 min, including 90 min of cardioplegic heart arrest at 32 °C. After termination of CPB the piglets were observed up to 6 h. During this observational period animals did not receive any inotropic support. Some piglets died within this period and formed the non-survivors group (CPB-NS group) and the remaining animals formed the CPB-6 h group. Myocardial biopsies (stained with H&E) were scored from 0 to 3 regarding histological alterations. Then, the histological data were evaluated and compared to the probes of animals handled comparable to previous piglets but without CPB (non-CPB group; n = 3) and to sibling piglets without specific treatment (control; n = 5).

Results: In the first hours after CPB six piglets out of 10 died (median 3.3 h). The animals of CPB-6 h group (n = 4) were sacrificed at the end of experiments (6 h after CPB). Although the myocardial histological score of CPB-6 h group and CPB-NS group were higher than non-CPB group (2.0 ± 0.8, 1.5 ± 0.9, and 0.8 ± 0.3 respectively), these differences were statistically not significant. But compared to control animals (score 0.3 ± 0.5) the scores of CPB-6 h and CPB-NS groups were significantly higher (p < 0.05). Between the left and the right ventricular tissue there were no significant differences.

Conclusions: Myocardial tissue alterations in newborn piglets are related to the surgical trauma and potentiated by cardiopulmonary bypass and ischemia. However, outcome is not related to the degree of tissue alteration.