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Chapter 18. Syncope

C. Keith Stone, MD; Margaret Strecker-McGraw, MD, FACEP; Andrew Juergens, MD

Cardiac Arrest

See also Chapter 9.

Clinical Findings

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.

Treatment and Disposition

Initiate cardiopulmonary resuscitation; see Chapter 9 for further details. Immediate hospitalization in an intensive care unit for evaluation and treatment is required.

Cardiac Arrhythmias

See also Chapter 34.

Clinical Findings

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.

Table 18–1. Common Causes of Syncope Due to Cardiopulmonary and Cerebrovascular Disease.
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Table 18–1. Common Causes of Syncope Due to Cardiopulmonary and Cerebrovascular Disease.
  • Cardiac arrest due to any cause
  • Acute myocardial infarction
  • Cardiac dysrhythmias
    • Tachyarrhythmias
      • Supraventricular
        • Paroxysmal atrial tachycardia
        • Atrial flutter
        • Atrial fibrillation
        • Accelerated junctional tachycardia
      • Ventricular
        • Ventricular tachycardia
        • Ventricular fibrillation
    • Bradyarrhythmias
      • Sinus bradycardia
      • Sinus arrest
      • Second-degree or complete (third-degree) heart block
      • Implanted pacemaker failure or malfunction
    • Mitral valve prolapse (click-murmur syndrome)
    • Prolonged QT interval syndromes
    • Brugada syndrome
    • Sick sinus syndromes (tachycardia–bradycardia syndrome)
    • Drug toxicity (especially digitalis, quinidine or procainamide, propranolol, phenothiazines, tricyclic antidepressants, potassium)
  • Cardiac inflow obstruction
    • Left atrial myxoma or thrombus
    • Constrictive pericarditis or cardiac tamponade
    • Tension pneumothorax
  • Cardiac outflow obstruction
    • Aortic stenosis
    • Pulmonary stenosis
    • Hypertrophic obstructive cardiomyopathy (idiopathic hypertrophic subaortic stenosis)
  • Severe pulmonary hypertension due to any cause
    • Pulmonary hypertension
    • Acute pulmonary embolus
  • Cerebrovascular syncope
    • Basilar artery insufficiency
    • Subclavian steal syndrome
    • Migraine
    • Takayasu's disease
    • Carotid sinus syncope
  • Orthostatic hypotension

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.

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.

Treatment and Disposition

Patients with syncopal attacks thought to be due to structural cardiac disease or an ...

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