Background: Arrhythmias are a significant source of morbidity and mortality in patients with congenital heart defects.
Methods and results: As part of the Second Natural History Study of Congenital Heart Defects (NHS-2), 24-hour ambulatory ECG monitoring was performed for full participants in the study. At least 15.5 hours of monitoring was required for inclusion in the analysis. This was achieved for 755 (90.6%) of the patients. Multiform premature ventricular contractions, ventricular couplets, and ventricular tachycardia were considered "serious arrhythmias." For patients with aortic stenosis, the presence of "serious arrhythmias" was associated with higher left ventricular end-diastolic pressure, presence of aortic regurgitation, male sex, and presence of prior aortic valve replacement. For patients with pulmonary stenosis, only older age on admission to NHS-1 was significantly associated with "serious arrhythmias." For patients with ventricular septal defect, the variables associated with "serious arrhythmias" were different for medically and surgically managed patients. For medically managed patients, higher mean pulmonary artery pressure on admission to NHS-1 and older age on admission to NHS-2 were associated with the presence of serious arrhythmias. For surgically managed patients, higher New York Heart Association functional class and cardiomegaly were associated with serious arrhythmias.
Conclusions: The prevalence of arrhythmias (especially ventricular arrhythmias) was higher for patients with aortic stenosis, pulmonary stenosis, or ventricular septal defect than for an historical control population. "Serious arrhythmias" were most frequently noted in patients with aortic stenosis who also had a higher incidence of sudden death. The prevalence of "serious arrhythmias" was second highest for patients with ventricular septal defect who had the second highest incidence of sudden death.