Ventricular arrhythmias: when to worry.

Although isolated premature ventricular contractions may be seen in as many as 15% of normal newborns, one third of normal adolescents, and two thirds of adolescents and adults with repaired heart disease, sustained ventricular arrhythmias are relatively rare in young normal hearts. Sudden cardiac health is rare in young normal hearts, although there is an increased incidence in dilated cardiomyopathies and following repair of particular congenital heart lesions. Noninvasive and invasive techniques imperfectly stratify these patients. Patients with cardiomyopathy often have ventricular arrhythmias, although the risk of mortality is more closely linked to ventricular function. There are many infants and pediatric patients with apparently normal hearts who have combinations of asymptomatic nonsustained ventricular tachycardia and potentially serious symptoms. The clinical concern is to identify diagnoses such as long QT syndrome associated with recurrent cardiac syncope and premature mortality so that appropriate choices can be made regarding drug and device therapy. Although this broad range of disease places a premium on careful evaluation, selective therapy, and continued research, serious symptoms, even in the absence of ectopy, are concerning in any patient.