Syncope is characterized by a transient loss of consciousness due to cerebral hypoperfusion, loss of postural tone, varying degrees of recall of events surrounding the syncopal spell, and absence of neurologic sequelae. Syncope is extremely common, constituting up to 3% of all visits to emergency departments and up to 5% to 6% of all hospital admissions. A carefully performed history review (including family history) and physical examination (Table 1) of the patient with syncope suggests a diagnosis in about 45% of patients. Many of these patients will have structural heart disease suggested or identified in this manner; in others, this initial evaluation will be unrevealing. Although in some cases the 12-lead electrocardiogram can establish or suggest a diagnosis (as in, for example, congenital complete atrioventricular block or long QT syndrome), in many instances the 12-lead electrocardiogram, chest radiograph, and echocardiogram can fail to indicate cardiac abnormalities (Table 2).
Approach to the patient with syncope. The asterisk indicates syncope after recent head trauma, seizures, headache, or new neurologic abnormality—refer to neurologist; dagger, atrioventricular block, ventricular tachycardia, supraventricular tachyarrhythmias including atrial fibrillation and flutter, sinus bradycardia, myocardial infarction, ectopy, QT interval 0.50 seconds or longer (receiving/not receiving QT-prolonging drugs), arrhythmogenic right ventricular dysplasia, hypertrophic cardiomyopathy, Wolff-Parkinson-White syndrome, and Brugada syndrome; ECG, electrocardiogram; BBB, bundle branch block; LVEF, left ventricular ejection fraction; and Rx, treatment as appropriate.
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