drug ingestion or cardiac manifestations of eating disorders or central nervous system trauma, but can also be seen in healthy adolescents Syncope is uncommon in patients with first- or second-degree heart block, but complete heart block can potentially lead to more serious symptoms The combination of history, physical examination, and ECG allows identification of a cardiac cause of syncope in a majority of affected children, with reported sensitivity as high as 96% Patients with clinical features or ECG findings suggestive of heart disease should be referred to a cardiologist TABLE 76.2 ECG FINDINGS IN IMPORTANT CARDIAC CAUSES OF PEDIATRIC SYNCOPE Cause ECG findings Long QT syndrome QTc >450 msec; morphology of QT segment and T wave may vary in different genetic subtypes Brugada syndrome Elevated ST segments in precordial leads V1 and V2 Coving seen in Type syndrome; right bundle branch block Wolff–Parkinson– Classic triad of delta wave, shortened PR interval, and White syndrome widened QRS complex There is a slurring in upstroke of R wave Secondary ST-segment–T-wave changes are directed opposite to the major delta wave and QRS complex changes Hypertrophic The most frequent abnormalities found are large amplitude obstructive QRS complexes and associated ST-segment and T-wave cardiomyopathy changes consistent with left ventricular hypertrophy (HOCM) Deep, narrow Q waves in leads II, III, aVF, V5, and V6 are most characteristic and specific findings of HOCM Left atrial enlargement is also seen Bradycardia Second- and third-degree heart block To summarize, risk factors for a cardiac etiology for syncope include the absence of prodromal symptoms, palpitations that occur seconds before loss of consciousness, lack of a prolonged upright posture, exertion-related syncope or syncope that occurs with auditory or emotional stimuli, a family history of sudden cardiac death, abnormal physical examination, and abnormal ECG Patients with