Objective: To review the studies on diagnostic evaluation of syncope and to provide an approach to the diagnostic testing and management of this condition.
Data source: Published studies on the evaluation of syncope in the English language.
Study selection: Cohort studies and case series of patients presenting with syncope and focused studies of various diagnostic tests such as prolonged electrocardiographic monitoring, electrophysiologic studies, and upright tilt testing. Specific selection criteria were used in the case of prolonged electrocardiographic monitoring, in which all studies had to have performed at least 12 hours of monitoring.
Data extraction: Studies reviewed by the author.
Data synthesis: Studies in the 1980s have shown that a cause of syncope is not diagnosed in as many as 47% of the patients presenting with this symptom. When a cause of syncope is established, a history and physical examination lead to the identification of 56% to 85% of the causes. In the remaining patients, arrhythmia detection is a central issue. A major problem with the use of ambulatory electrocardiographic (Holter) monitoring in the diagnosis of arrhythmias is that symptomatic correlation with arrhythmias is rarely found (only 4% of patients). Increasing the duration of monitoring from 24 to 72 hours does not lead to increased yield of symptomatic arrhythmias. Patient-activated intermittent loop recorders that can be worn for several weeks may occasionally show a symptomatic correlation, but they are most useful in patients with multiple recurrences of syncope. Electrophysiologic studies are more likely to be abnormal in patients with underlying heart disease or those who have abnormalities on surface electrocardiogram. The most common abnormality found on electrophysiologic studies is inducible ventricular tachycardia. Upright tilt testing has been used to induce vasovagal syncope in patients with syncope of unknown cause. A positive response has been found in 26% to 87% of patients undergoing this type of testing. The specificity of this test needs to be further investigated. In patients with recurrent syncope of unknown cause, psychiatric evaluation should also be pursued for illnesses such as generalized anxiety disorder, panic disorder, somatization, and major depression.
Conclusions: A directed approach to the evaluation is possible using the studies on diagnostic testing of syncope.