Exercise-induced ventricular ectopy in children and young adults with complete heart block.

Twenty-five children and young adults with complete heart block and 50 normal control subjects were maximally exercised on a treadmill and their electrocardiograms were analyzed for the presence and degree of ventricular ectopy activity. Sixty-eight % (17 of 25) of the heart block patients and significant ventricular ectopy (frequent unifocal ectopy or worse) on exercise compared to 2% (one of 50) of the controls (p = less than 0.01). In the patients with block there was a significant trend toward more frequent and more severe ectopy with increasing age (p = less than 0.05) independent of heart rate. More severe ventricular ectopy was also seen in those patients with QRS prolongation (p = less than 0.05). No significant differences were found between the 14 patients with isolated "congenital" heart block, the seven with associated defects, and the four with surgically acquired block. We believe that severe ventricular ectopy is common at exercise in patients with complete heart block and they may have an increased risk for sudden death.