Purpose: To review the literature on diagnostic testing in syncope tha
t remains unexplained after initial clinical assessment. Data Sources:
MEDLINE search. Study Selection: Published papers were selected if th
ey addressed diagnostic testing in syncope, near syncope, or dizziness
. Data Extraction: Studies were identified as population studies, refe
rral studies, or case series. Data Synthesis: After a thorough history
, physical examination, and electrocardiography, the cause of syncope
remains undiagnosed in 50% of patients. In such patients, information
may be derived from the results of carefully selected diagnostic tests
, especially 1) electrophysiologic studies in patients with organic he
art disease, 2) Holter monitoring or telemetry in patients known to ha
ve or suspected of having heart disease, 3) loop monitoring in patient
s with frequent events and normal hearts, 4) psychiatric evaluation in
patients with frequent events and no injury, and 5) tilt-table testin
g in patients who have infrequent events or in whom vasovagal syncope
is suspected. Hospitalization is indicated for high-risk patients, esp
ecially those with known heart disease and elderly patients. Conclusio
ns: A flexible, focused approach is required to diagnose syncope. Feat
ures of the initial history and physical examination help guide diagno
stic testing.