   Ventricular tachycardia
   Ventricular fibrillation
   Sinus node dysfunction
   Atrio-ventricular conduction disease
   Paroxysmal arrhythmias
   Long QT syndrome
   Brugada syndrome
   Arrhythmogenic right ventricular cardiomyopathy
   Wolfe-Parkinson-White with atrial fibrillation
   Paroxysmal supraventricular tachycardia
Structural Heart Disease with Obstruction to Cardiac Output
   Aortic stenosis
   Hypertrophic obstructive cardiomyopathy
   Other valvular stenotic heart disease
   Atrial myxoma
Other Forms of Structural Heart Disease
   Cardiac ischemia
   Pericardial tamponade
   Pulmonary embolus/severe pulmonary hypertension
   Aortic dissection
Neurocardiogenic Syncope/Vasodepressor Syndrome
   Vasovagal
   Situational (cough, micturition, defecation)
   Carotid sinus syndrome
   Cough syncope
Orthostatic Syndromes
   Dehydration
   Secondary autonomic syndromes (diabetic neuropathy, etc.)
   Primary autonomic failure (Parkinsons, etc.)
   Postural intolerance syndrome (e.g. POTS, rarely)
Cerebrovascular
   Vascular steal syndromes
   Basilar artery insufficiency
   Migraines

TAKE HOME POINT #1

A thorough history and physical examination in addition to simple bedside maneuvers can diagnose the etiology of syncope in the majority of patients.

Furthermore, clinicians should initially concentrate on identifying the presence of structural heart disease such as ischemic heart disease, left ventricular outflow obstruction from hypertrophic obstructive cardiomyopathy or aortic stenosis, congestive heart failure, or other valvular diseases as patients with cardiovascular disease have a higher risk of mortality. Tachyarrhythmias and bradyarrhythmias may also present with an episode of syncope. A history of myocardial infarction or the presence of scar from any etiology renders a patient susceptible to ventricular arrhythmias while bradycardia either from sinus node dysfunction or AV block may account for a syncopal event. Due to significant mortality associated with these disorders, hospitalists should obtain immediate cardiac consultation if a cardiovascular cause of syncope is suspected.

The most common cause of syncope is neurocardiogenic disorders such as vasodepressor syndromes, vasovagal fainting, or carotid sinus hypersensitivity. Neurally-mediated syncope is associated with abnormal blood pressure regulation resulting in hyperperfusion. Although they are generally benign, recurrent episodes of neurocardiogenic syncope can severely limit a patient’s quality of life and pose physical threats, particularly if syncope occurs while driving. Orthostatic syncope also accounts for a substantial percentage of syncopal events. Neurological disorders are rarely a cause of syncope.

17.3 CLINICAL PRESENTATION

The clinical presentation of syncope can be challenging because patients invariably present for clinical evaluation after the episode of syncope has occurred. Patients also may not recall the episode well, making the history of symptoms prior to and following the episode critical to making a diagnosis. Any account from a witness of the episode might also be very instructive. A detailed clinical history can often provide clues to the etiology of a syncopal event (Table 17.2). Patients who suffer an episode of neurocardiogenic syncope often describe a prodrome of nausea and lightheadedness. The syncopal episode is frequently followed by a period of fatigue and weakness. Situational episodes of neurocardiogenic syncope during micturition, defecation, prolonged standing, or the sight of blood during venipuncture offer a clearer history.

Arrhythmias will frequently have no prodrome and occur suddenly. Afterwards, patients often report that they are asymptomatic and feel as if they have returned to their baseline. Chest pain, shortness of breath, lower extremity edema, or palpitations should prompt cardiac evaluation to evaluate for acute ischemia or underlying structural heart disease.

Table 17.2 Characteristics of Various Syncopal Etiologies.

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