Chapter 430 Sudden Death

Sudden death other than sudden infant death syndrome (SIDS; Chapter 367) is rare in children younger than 18 yr. Sudden death can be divided into either traumatic or nontraumatic origin. Traumatic causes of sudden death are the most common in children; these include motor vehicle crashes, violent deaths, recreational deaths, and occupational deaths. Nontraumatic sudden deaths are often due to specific cardiac causes. The incidence of sudden death varies from 0.8 to 6.2 per 100,000 per year in children and adolescents as opposed to the higher incidence of sudden cardiac death in adults of 1 per 1,000. Approximately 65% of sudden deaths are due to heart-related problems in patients with either normal or congenitally (corrected, palliated, or unoperated) abnormal hearts. Competitive high-school sports (basketball, football) are high-risk environmental factors. The most common cause of death in competitive athletes is hypertrophic cardiomyopathy, with or without obstruction to left ventricular outflow. Other potential causes are listed in Table 430-1. These can be classified as structural abnormalities, including aortic stenosis and coronary artery abnormalities; myocardial disease, such as myocarditis; conduction system disease, including long Q-T syndrome (LQTS); and miscellaneous causes, including pulmonary hypertension and commotio cordis. Symptoms may be absent before the event but, if present, include syncope, chest pain, dyspnea, and palpitations. Patients may have a family history of heart disease (dilated or hypertrophic cardiomyopathy, long Q-T interval, arrhythmogenic right ventricular dysplasia, Marfan syndrome) or sudden death. Death often follows exertion or exercise.

Cardiac Arrhythmia

A primary conduction system abnormality may result in sudden death. Causes include Wolff-Parkinson-White (WPW) syndrome and long Q-T syndrome. Besides causing supraventricular tachycardia (SVT), WPW syndrome can result in atrial fibrillation with rapid conduction across the accessory pathway leading to ventricular fibrillation and sudden death (Fig. 430-1) (Chapter 429). This is unusual in pediatric patients but has an increasing incidence in adolescence. In adults, there is an incidence of sudden death in asymptomatic patients of 1 per 1,000 patient-years, but this rate may well be higher in children, who by definition have not survived to adulthood. As digoxin and verapamil can augment conduction down accessory pathways, these drugs are contraindicated in WPW syndrome.

Figure 430-1 Atrial fibrillation in a patient with Wolff-Parkinson-White (WPW) syndrome and rapid conduction to the ventricle. Note the wide QRS complexes, due to full preexcitation, and the irregularly irregular ventricular response, due to the atrial fibrillation.

Long Q-T syndrome (Chapter 429), a group of channelopathies that affect ventricular repolarization, is also associated with sudden death (Fig. 430-2). The mechanism of sudden death is polymorphic VT (torsades de pointes) (Fig. 430-3). An initial presentation of sudden cardiac death is found in 9% of patients. Thus, treatment of asymptomatic patients with a long Q-T interval on electrocardiogram (ECG) and positive family history is advised.

Figure 430-2 Long Q-T syndrome in a neonate. QTc is markedly prolonged. T waves are also peaked and abnormal in appearance.

Figure 430-3 Episode of torsades de pointes in a patient with long Q-T syndrome.

Acquired long Q-T intervals may be seen in patients with marked electrolyte abnormalities, CNS injury, or starvation (including bulimia and anorexia nervosa). Medications can also result in prolongation of the Q-T interval (Table 429-4). These patients are also at risk of malignant ventricular arrhythmias, and correction of the underlying problem may be necessary to reduce the risk of sudden death.