Sudden cardiac death in childhood

Abstract

Sudden cardiac death in children and adolescents is uncommon but tragic as many should be preventable. Retrospective post-mortem studies suggest that the majority of sudden cardiac deaths in the young are in patients with hypertrophic cardiomyopathy, the long QT syndrome and ventricular arrhythmias associated with morphological abnormalities of the right ventricle. In hypertrophic cardiomyopathy, patients with syncope and a family history of sudden cardiac death are clearly at increased risk but even those with few symptoms and no apparent risk factors have an annual mortality of 4%. Recognition of those at risk is aimed at identifying patients with haemodynamic and/or electrical instability. Exercise hypotension with inappropriate vascular responses are common (30%), while myocardial disarray, the characteristic histological feature, may provide the substrate for propagation of ventricular arrhythmia. Identification of potential mechanisms of sudden death permits initiation of appropriate therapy. Data on the use of long term amiodarone and of myectomy in the young are insufficient, but these therapies appear to improve prognosis when used appropriately. Recognition of the long QT syndrome remains problematic, even when electrocardiographic investigations are performed. The primary myocardial defect and cellular mechanisms resulting in ventricular arrhythmias are uncertain. Therapy therefore remains unsatisfactory. Many patients respond to beta blockade, while left stellate ganglionectomy and atrial pacing may be useful in those who are refractory to drugs. Sustained ventricular arrhythmias of right ventricular origin may cause syncope and sudden death in adolescents and young adults. In those with right ventricular dysplasia, autopsy examination reveals fibro-fatty replacement of the myocardium. Sudden death may occur, however, even in those with apparently 'normal' right ventricle. Sustained ventricular arrhythmias may also cause sudden death in the absence of clinical, macroscopic or histologic evidence of cardiac disease. Altered autonomic behaviour may be important as such deaths are often related to exercise.