Myocardial stunning after extracorporal circulation: myth or fact? An experimental analysis in piglets

Objective: Since the invention of the heart-lung-machine in the early 50s, its influence and potential damage to the organs is still controversally discussed. Especially in pediatric cardiac surgery, there is a lack of information and a suitable set up for the new borns is still demanding. The aim of this study was the evaluation of the impact of extracorporeal circulation (ECC) on myocardial tissue of piglets in a standardized pediatric cardiac setup.

Methods: Piglets (8–15kg) were anaesthetized and underwent extracorporeal circulation (ECC) with hypothermic (28°C) cardioplegic arrest (Bretschneider) for 90min followed by 240min of reperfusion. Another group, only receiving a median sternotomy, acted as a control group. Pre- and postoperative cardiac samples were taken and analized for hypoxic damage using histology and ADP/ATP measurements. Additionally we performed pressure/volume curves evaluating the influence of the ECC on myocardial stunning.

Results: Myocardial tissue histologically appeared swollen, oedematous and vacuolized in the HE staining after the ECC. There was a significantly enhanced HIF1µ level in the post ECC group compared to the control group (ECC: 57.9±8.9, Control: 30±7.6; p<0.03). Pressure volume curves showed signs of myocardial stunning expressed by a diminished contractility with statistical significance between both groups (ECC: 0.9±0.4, Control: 1.7±0.9; p<0.05). Dephosphorylation respective an increase of ADP/ATP ratio was observed for the ECC group (ECC: r=0.68, Control: r=0.32; p<0.05).

Conclusion: The ECC has a high impact in cardiac surgery, however the consequences are still worrying. Although we used a standardized ECC setup and a reasonable short perfusion time, the study shows significant functional and cellular impairment of myocardial tissue after the usage of ECC.