Recovery of high-frequency QRS potentials following cardioplegic arrest inpediatric cardiac surgery

We examined the hypothesis that recovery of high-frequency QRS potentials a t reperfusion is influenced by the duration of myocardial ischemia during c ardioplegic arrest in pediatric cardiac surgery. Signal-averaged electrocar diograms were recorded after induction of anesthesia (baseline data) and ev ery 1 to 5 minutes after aortic declamping in 14 patients aged 2 months to 6 years. The signals were processed with a band-pass filter between 80 Hz a nd 300 Hz to obtain high-frequency potentials in the QRS complex. The high- frequency QRS potentials (80-300 Hz) were expressed as the root mean square voltage over the filtered QRS complex. The high-frequency QRS potentials a t baseline were 33.9 +/- 4.4 muV. They decreased to 13.7 +/- 9.6 muV 1 minu te after aortic declamping (p = 0.005). Subsequently they gradually increas ed and then returned to the baseline level. The time that the potentials we re over 90% of baseline value ranged from 10 to 35 minutes after aortic dec lamping. The recovery time of this reduction in the high-frequency QRS pote ntials correlated with the duration of aortic cross-clamping (r = 0.80, p = 0.0009) and the value of postoperative MB isozyme of the creatine kinase ( r = 0.81, p = 0.0042). This study demonstrated that the high-frequency QRS potentials decreased at early reperfusion following cardioplegic arrest and then returned to preischemic levels. The recovery time of the high-frequen cy QRS potentials significantly correlated with cardioplegic arrest time an d postoperative MB isozyme of the creatine kinase values. Our re suits rais e the possibility that changes in high-frequency electrocardiographic signa ls in the QRS complex may reflect myocardial ischemia during cardioplegic a rrest.