Background: Surgery with cardiopulmonary bypass (CPB) remains the mainstay of therapy in children with congenital heart defects but little is known about its pathophysiologic consequences. We have recently demonstrated that CPB surgery in children leads to increase in coronary flow for at least 1 week after surgery, while others have shown, yet in adults, profound adverse effects of CPB on myocardial repolarization over the same period of time. The latter may be an important mechanism of ventricular arrhythmia, which is a common complication after CPB surgery.
Objective: to investigate the relationship between coronary flow and myocardial repolarization after CPB surgery.
Methods: Coronary flow in the proximal part of the LAD and indexes of myocardial repolarization (QT interval corrected for heart rate (QTc) and QT dispersion) were assessed by transthoracic Doppler echocardiography and in 12-lead surface electrocardiogram, respectively, in children with atrial (n=12) and atrioventricular septal defects (n=16) 1 day before, and 5 days after cardiac surgery with CPB.
Results: Neither QTc nor QT dispersion postoperatively differed significantly compared with preoperative values (“p for mean”>0.2 for both). However postoperative QTc showed a significant positive correlation with both preoperative (r=0.4, p=0.03) and postoperative (r=0.5, p=0.01) coronary flow. In patients with atrial septal defects, QTc postoperatively correlated significantly with the duration of CPB (r=0.6, p=0.04).
Conclusion: In a small cohort of children undergoing CPB surgery, increased coronary flow and, to less extent, prolonged CPB appeared to be associated with heightened risk for delayed myocardial repolarization after surgery.