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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Sudden, unexpected, and transient loss of consciousness and postural tone

  • Spontaneous and full recovery

GENERAL CONSIDERATIONS

  • The loss of consciousness resolves spontaneously without intervention

  • Common pathophysiologic mechanism is secondary to reduction in cerebral blood flow and cerebral hypoperfusion

  • Common condition experienced by 5–20% of adults by age 75

  • Responsible for 3% of hospital admissions and 6% of emergency room visits

  • In general, syncope carries a benign prognosis

  • Important causes include:

    • – Valvular stenosis

    • – Hypertrophic cardiomyopathy

    • – Pulmonary emboli

    • – Bradyarrhythmias such as complete heart block

    • – Tachyarrhythmias such as ventricular tachycardia

    • – Neurocardiogenic syncope

    • – Situational syncope such as cough or micturition syncope

  • Iatrogenic causes include:

    • – Medications with negative chronotropic activity such as beta blockers

    • – Orthostatic hypotension secondary to vasodilators or aggressive diuresis

    • – Pacemaker malfunction in a pacemaker-dependent patient

  • A thorough history establishes the cause of syncope or suggests the necessary diagnostic test in up to 85% of patients

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • History and symptoms depend on precipitating causes

  • Relevant information includes:

    • – Details of precipitating factors (micturition, cough, exertion)

    • – Associated symptoms (palpitations, chest pain)

    • – Position (standing, sitting, changing position)

    • – Details about the episode (injury, incontinence, rapid recovery versus postictal state)

PHYSICAL EXAM FINDINGS

  • Orthostatic blood pressure must be assessed (orthostatic hypotension within 3 minutes on standing)

  • Carotid sinus massage may be useful to elicit carotid hypersensitivity with a marked fall in heart rate

  • Evaluate for the presence of murmurs on cardiac auscultation

  • Other findings depend on the cause of syncope

DIFFERENTIAL DIAGNOSIS

  • Seizures

  • Glossopharyngeal neuralgia

  • Metabolic states such as hypoglycemia

  • Cerebrovascular disease such as vertebrobasilar insufficiency

  • Psychiatric disorder with hyperventilation

  • Akinetic falling spells of the elderly

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • CBC

  • Basic metabolic panel

ELECTROCARDIOGRAPHY

  • ECG to detect conduction abnormality

  • Ambulatory ECG, event recorder, or implantable ECG loop recorder to diagnose either marked bradycardia or tachycardia

IMAGING STUDIES

  • Echocardiography is done to exclude valvular heart disease, hypertrophic cardiomyopathy, and other hemodynamically significant changes (should be done only if clinical examination is suggestive)

  • Spiral CT or pulmonary angiogram may be done to diagnose pulmonary embolism or dissection of the aorta

DIAGNOSTIC PROCEDURES

  • Head-up tilt testing to evaluate neurocardiogenic syncope

  • Electrophysiologic studies may be considered to evaluate malignant syncope for life-threatening ventricular arrhythmia

TREATMENT

CARDIOLOGY REFERRAL

  • If a cardiac cause is likely or suggested by initial evaluation, then referral is recommended

HOSPITALIZATION CRITERIA

  • Patients with known structural heart disease and syncope

  • Definite diagnosis is ...

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