Syncope
- category: Undifferentiated Problems
I. Background
Syncope is defined as a transient loss of consciousness with an inability to maintain a postural tone that is followed by spontaneous recovery. The term syncope excludes seizures, coma, shock, or other states of altered consciousness (1).
II. Pathophysiology
A. Etiology
Cardiac causes include vascular disease, cardiomyopathy, arrhythmias, or valvular dysfunction. Noncardiac causes include vasovagal response to pain, dehydration with orthostasis, situational syncope, dysfunction, although neurovascular causes are rare. Alternatively, the etiology may be unknown.
B. Epidemiology
Syncope is a prevalent disorder, accounting for 1% to 3% of emergency department visits and up to 6% of hospital admissions each year in the United States (1). In the United States, the data from the Framingham study demonstrates a first occurrence rate of 6.2 cases/1,000 patient/year. Three percent have recurrences, and approximately 10% have a cardiac etiology (1).
III. Evaluation
A thorough history and physical examination have been shown to establish the cause in up to 45% of patients. A 12-lead electrocardiogram (ECG) provides another 5% to 10% yield. However, after this initial examination, syncope remains unexplainable in 34% to 47% of patients (2).
A. History
- A detailed account of the episode by the patient and from any person witnessing the episode is very important. Specifically, information about activity prior to the syncopal episode, including position or change in position, precipitating factors such as fatigue, alcohol consumption, strong emotions, hunger, and a warm environment should be elicited. Also, questions concerning prior dizziness, nausea, diaphoresis, chest pain, dyspnea, visual changes, headache, and focal neurologic changes should be asked. Finally, the patient and/or witness should be asked to estimate the total time of the syncopal episode.
- Past medical history should include a complete list of medications, whether they are prescription drugs, over-the-counter medications, street drugs, vitamins, and/or health supplements. In addition, the usual inquiry relating to disease states such as hypertension, coronary artery disease, diabetes mellitus, prior stroke, deep vein thrombosis, and anemia should be made. Also, if the patient is a woman of childbearing age, the possibility of pregnancy should be determined.
- It is important to specifically inquire about a family history of sudden death, heart disease, and diabetes mellitus, especially in first-degree relatives.
B. Physical examination
A complete physical examination is always necessary when a patient presents with syncope. Vital signs including mental status should be obtained. Syncope as a presenting complaint always necessitates a head to toe examination; specifically looking for previous or present trauma, cardiac, pulmonary, abdominal, and/or neurologic abnormalities. Also, a rectal examination should be performed along with a test for occult blood.
C. Testing
If a syncopal patient presents to the emergency department, an immediate finger stick blood sugar and/or ECG should be obtained, even as vital signs are taken. Then a complete blood count, comprehensive metabolic profile, cardiac enzymes, and a chest x-ray should be obtained. Later tests or conditions to consider if indicated by the history and the physical examination are:
- A test for pulmonary embolus or abdominal aortic aneurysm.
- A head-up tilt-table test which is useful for confirming autonomic dysfunction safety and can generally be arranged to be done as an outpatient.
- An electroencephalogram to be obtained if a seizure is suspected.
IV. Diagnosis
The differential diagnosis of syncope is presented in Table 2.12.1.
TABLE 2.12.1 Differential Diagnosis of Syncope | ||||
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References
1. Hongo RH, Goldschlager N. Evaluating patients with unexplained syncope MEDSCAPE, 11/2004.
2. Morag R. emedicine.com -- Syncope excerpt June 2005.