Ventricular arrhythmia or supraventricular arrhythmia with aberrant conduction? An electrocardiographic study in halothane-anaesthetized children undergoing adenoidectomy.

The electrocardiograph (ECG) was recorded continuously in 20 children undergoing adenoidectomy during halothane anaesthesia. Five surface ECG leads and an oesophageal lead were used. In 11 children, there were QRS complexes which had a shape distinctly different from that of the ordinary sinus-evoked beats. Except in one child, these anomalous QRS complexes first made their appearance during surgery, although the arrhythmia continued until 0-1 min after adenoidectomy in some children. The severity ranged from that of occasional anomalous QRS complexes with uniform shape to that of a fast irregular rhythm with a variety of QRS shapes. Although the anomalous QRS complexes were premature, P waves and P-P intervals were unchanged. In some children, there appeared to be ventricular capture beats and fusion beats. Because of this, and in view of evidence gathered from studies in animals, by other authors, we considered it likely that the anomalous beats were ventricular in origin.