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Loss of consciousness due to cardiac arrest (ventricular fibrillation or asystole) from any cause occurs in 3–5 seconds if the patient is standing or within 15 seconds if the patient is recumbent. The patient usually rapidly regains consciousness if adequate cardiac output is restored promptly; most patients who regain consciousness within 12 hours will recover without neurologic sequelae.
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Treatment and Disposition
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Initiate cardiopulmonary resuscitation; see Chapter 9 for further details. Immediate hospitalization in an intensive care unit for evaluation and treatment is required.
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See Table 18–1 for common causes of cardiac and neurologic related syncope. Palpitations, fatigue, dyspnea, or chest pain may precede loss of consciousness. Atypical chest pain (mainly nonexertional, left precordial, sharp, and of variable duration) suggests mitral valve prolapse.
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Rapid (≥160 beats/min), slow (≤50 beats/min), or irregular pulse must be carefully investigated. Tachycardia of 180–200 beats/min will produce syncope in half of healthy persons. In patients with underlying heart disease or atherosclerosis, tachycardia as fast as 135 beats/min or bradycardia as slow as 60 beats/min may result in loss of consciousness.
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Chest auscultation with the patient in various positions (eg, sitting, left lateral decubitus, squatting) may disclose abnormal murmurs and clicks in the case of mitral valve prolapse. The electrocardiogram (ECG) may confirm the diagnosis of arrhythmia, heart block, sick sinus, or prolonged QT interval. However, a single ECG, obtained when the patient is asymptomatic, is frequently normal or nondiagnostic. A diagnosis can be firmly established only by demonstrating arrhythmias during symptomatic periods.
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Treatment and Disposition
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Patients with syncopal attacks thought to be due to structural cardiac disease or an arrhythmia should be hospitalized ...