Published on 21/03/2015 by admin
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Last modified 21/03/2015
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Chapter 43 SYNCOPE
Theodore X. O’Connell
Syncope is a sudden, unexpected loss of consciousness associated with a loss of postural tone with spontaneous recovery. A syncopal event is one of the more dramatic and anxiety-provoking symptoms encountered by patients, and it often produces a diagnostic dilemma for the clinician. Syncope is a common manifestation of numerous disorders with a final common pathway of insufficient cerebral blood flow to maintain consciousness. Syncope must be differentiated from other disorders of altered consciousness, including seizures, sleep disorders, metabolic disorders, vertigo, presyncope, and psychiatric disorders.
In the evaluation of syncope, proving a specific diagnosis is often difficult because of a lack of residual abnormalities on examination or on initial diagnostic studies. The clinician must remember that syncope is a symptom, not a disease. By possessing an understanding of the common causes of syncope, the clinician can focus the history, physical examination, and diagnostic evaluation in each case. An understanding of the available diagnostic tests and their indications is imperative.
As many as 15% of children and adolescents will have a syncopal event between the ages of 8 and 18 years. Before age 6 years, syncope is unusual except in the setting of seizure disorders, breath-holding, and primary cardiac dysrhythmias. The cause of most cases of syncope can be placed into one of five categories: (1) autonomic, (2) cardiac, (3) psychiatric, (4) neurologic/cerebrovascular, and (5) metabolic/endocrine. Pediatric and young patients are most likely to have neurocardiogenic syncope (vasovagal syncope), psychiatric causes, and primary arrhythmic causes such as long QT syndrome and Wolff-Parkinson-White syndrome. The most common type of syncope in otherwise healthy children is vasovagal syncope. In infants who have recurrent and severe episodes of syncope that only have their onset in the presence of a particular parent or guardian, factitious or induced illness should be considered.
According to the American Heart Association, the differential diagnosis and evaluation of syncope in pediatric patients are similar to those in adults. The goal of the evaluation is to identify high-risk patients with underlying heart disease, which may include identifiable genetic abnormalities such as the long QT syndrome, Brugada syndrome, or hypertrophic cardiomyopathy.
Syncope associated with high-intensity physical activity is a typical presentation of hypertrophic cardiomyopathy or catecholaminergic polymorphic ventricular tachycardia and generally is evaluated with an electrocardiogram (ECG), echocardiogram, and an exercise stress test. Neurocardiogenic syncope is a common disturbance in the healthy child or adolescent. Breath-holding spells resulting from emotional upset have been reported in 2% to 5% of well patients.
Many algorithms exist for the evaluation of syncope, and most emphasize the importance of the history and physical examination in making an accurate diagnosis. Although algorithms may provide a guide for the evaluation of syncope, the various available algorithms each contain controversial elements. In addition, algorithms do not consider every clinical situation and are not designed to replace individual clinician judgment. The physician should understand the approach to the patient with syncope first and then consult algorithms to focus the diagnostic evaluation.
• α-agonists
• Anticholinergic agents
• Antiparkinsonian agents
• Antipsychotics
• β-adrenergic blockers
• Narcotics
• Vasodilators
Reflex Mediated
• Vasovagal
• Situational (cough, defecation, micturition, swallow)
• Carotid sinus hypersensitivity
Cardiac
• Arrhythmia
• Hypertrophic cardiomyopathy
• Left ventricular outflow tract obstruction
• Myocarditis
• Pulmonary hypertension
• Tamponade
• Tumor or mass
• Valvular disease
Medication Effects
Metabolic Disorders
• Adrenal failure
Hypoglycemia
Neurologic Causes
• Migraine headache (syncopal migraine)
• Transient ischemic attack
Orthostatic Hypotension (Autonomic Dysfunction)
• Amyloidosis
• Diabetes
• Guillain-Barré syndrome
• Human immunodeficiency virus (HIV) infection
• Paraneoplastic neuropathies
• Parkinson’s disease
• Shy-Drager syndrome
Psychiatric Causes
• Hyperventilation
• Major depression
• Panic disorder
• Pseudoseizures
Other Causes
• Breath-holding
• Hypovolemia
• Seizure (not a true case of syncope)
• Subclavian steal syndrome
Unknown
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