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

We examined the hypothesis that recovery of high-frequency QRS potentials at reperfusion is influenced by the duration of myocardial ischemia during cardioplegic arrest in pediatric cardiac surgery. Signal-averaged electrocardiograms were recorded after induction of anesthesia (baseline data) and every 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 and 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 at baseline were 33.9 +/- 4.4 microV. They decreased to 13.7 +/- 9.6 microV 1 minute after aortic declamping (p = 0.005). Subsequently they gradually increased and then returned to the baseline level. The time that the potentials were over 90% of baseline value ranged from 10 to 35 minutes after aortic declamping. The recovery time of this reduction in the high-frequency QRS potentials 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-frequency QRS potentials significantly correlated with cardioplegic arrest time and postoperative MB isozyme of the creatine kinase values. Our results raise the possibility that changes in high-frequency electrocardiographic signals in the QRS complex may reflect myocardial ischemia during cardioplegic arrest.