The occurrence of syncope while recumbent would be quite unusual in a patient with neurocardiogenic syncope and therefore suggests a cardiac or neurologic cause. Injury because of an episode of syncope indicates sudden occurrence with a lack of adequate prodromal symptoms and suggests an arrhythmia. The occurrence during exercise suggests an arrhythmia or coronary obstruction. Several red flags can be identified that should lead the clinician to suspect that the mechanism is a life-threatening cardiac cause rather than simple fainting ( Table 87.6). The characteristics of cardiac syncope differ significantly from the prodrome seen in neurocardiogenic syncope ( Table 87.5). The most important tool in evaluation is a careful history. Many patients presenting with sudden cardiac arrest caused by conditions such as LQTS will have previously experienced an episode of syncope, so the presentation with syncope is an opportunity to prevent sudden death. The most important goal in the evaluation of the new patient with syncope is to diagnose life-threatening causes of syncope so that these causes can be managed. Kliegman MD, in Nelson Textbook of Pediatrics, 2020 Evaluation Information from a witness can be essential to the evaluation. 2c Each syncopal episode should be reviewed in detail, with special attention to symptoms preceding the episode, events during unconsciousness, and the symptoms and time course of regaining orientation after consciousness is restored. 2bīecause most spells of episodic loss of consciousness occur outside medical observation, the history is the most critical part of the evaluation ( Table 56-2). 2 By comparison, among all patients who present to an emergency department with syncope, only about 1.5% of patients appear to have pulmonary emobli. Among patients who are hospitalized with a first episode of syncope and in whom pulmonary embolism cannot be excluded based on a low Wells score (see Table 74-3) and a negative D-dimer assay, pulmonary embolism may be found in 25% of patients who do not have another obvious cause of their syncope and in about 13% of patients who do have an alternative explanation for their syncope. Patients with syncope from an arrhythmia usually awaken without any neurologic residual, unless the patient experienced a cardiac arrest with prolonged hypoxia and required resuscitation. The most important distinguishing feature is that postictal symptoms, a key feature of seizure disorders, are absent when syncope is the result of an arrhythmia. The possibility of seizures ( Chapter 375) must also be evaluated syncope from an arrhythmia or neurocardiogenic syncope occasionally results in seizure-like activity, and seizures can sometimes be confused with syncope. Vertigo ( Chapter 400), a sense of imbalance or of the “room spinning,” and ataxia ( Chapter 382) can usually be distinguished by the history and physical examination. Important differential diagnoses include conditions other than lightheadedness that may be termed dizziness by the patient. Left ventricular outflow obstruction, due either to aortic stenosis ( Chapter 66) or hypertrophic obstructive cardiomyopathy ( Chapter 54), can present as syncope, often during or just after exertion. Important historical features that suggest an arrhythmic cause are an association with palpitations and the lack of any neurologic deficits preceding or following the event. A careful history and physical examination are necessary to exclude other cardiac causes (e.g., acute ischemia, aortic stenosis) or neurologic causes. Syncope can be a manifestation of tachyarrhythmias, bradyarrhythmias, or neurocardiogenic syncope, or it can be unrelated to any arrhythmia. Syncope, defined as a sudden loss of consciousness, and presyncope, or lightheadedness, are caused by global impairment of blood flow to the brain ( Table 56-1). Lee Goldman MD, in Goldman-Cecil Medicine, 2020 Presyncope and Syncope
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