CHAPTER 30 Syncope
The causes of syncope can be difficult to determine because patients generally are seen after the event has occurred. Syncope can be quite benign, such as a vasovagal response, or it can indicate serious disease. However, even benign syncope can place the patient at risk for falls or injury. Cardiogenic syncope has high associated morbidity and mortality, and the emphasis in diagnosis is to rule out the most serious causes through a careful history and physical examination, with a few laboratory and diagnostic tests to establish a possible diagnosis. The Evidence-Based Practice box describes an evidence-based approach to the diagnosis of syncope.
EVIDENCE-BASED PRACTICEDiagnosing Syncope
1. History, physical examination, and electrocardiography (ECG) are the core of syncope workup (combined diagnostic yield, 50%).
2. Neurological testing is rarely helpful unless additional neurological signs or symptoms are present (diagnostic yield of EEG, CT, and Doppler ultrasound, 2% to 6%).
3. Patients in whom heart disease is known or suspected and those with exertional syncope who are at higher risk for adverse outcomes should have cardiac testing, including echocardiography, stress testing, Holter monitoring, or EPS, alone or in combination (diagnostic yield, 5% to 35%).
4. Syncope in the elderly often results from polypharmacy and abnormal physiological responses to daily events.
5. Long-term loop electrocardiography (diagnostic yield, 25% to 35%) and tilt-table testing (diagnostic yield, ≤60%) are most useful in patients with recurrent syncope in whom heart disease is not suspected.
6. Psychiatric evaluation can detect mental disorders associated with syncope in up to 25% of cases.
7. Hospitalization may be indicated for patients at high risk for cardiac syncope or with acute neurological signs.
Data from Linzer M, Yang EH, Estes NA III, Wang P, Vorperian VR, Kapoor WN: Diagnosing syncope. Part 1: Value of history, physical examination, and electrocardiography. Clinical Efficacy Assessment Project of the American College of Physicians, Ann Intern Med 126:989-996, 1997.
Diagnostic reasoning: focused history
Palpitations
Supraventricular or ventricular tachycardias are associated with syncope and sudden death. Ventricular tachycardia with a heart rate of 200 beats per minute may be asymptomatic or cause syncope. Chaotic ventricular activity of ventricular fibrillation is always fatal unless it is reversed with electrical defibrillation. (See Chapter 23 for more on palpitations.)
Vertigo, dizziness, and visual symptoms
The presence of vertigo, dizziness, diplopia, or other visual changes may accompany migraine headache. Interruption in cerebral perfusion, such as with a transient ischemic attack, also must be considered.
