Background: Upright tilt testing is widely utilized for the evaluation of syncope. Recently, there have been concerns about the specificity and the lack of standard methodology for this test. The purpose of this study was to summarize the methodologies of upright tilt testing in patients with syncope of unknown origin, the responses in control subjects, and the reproducibility and selection of therapy.
Methods: We used MEDLINE to search English language articles from 1966 to June 30, 1992. Studies were included for content review if they met our inclusion criteria. Data were extracted from each article by two trained reviewers using a predesigned data collection instrument.
Results: Thirty-three articles were included for review. There was considerable variability in the methodologies of tilt testing. Overall positive responses were reported in 49% of patients in passive-only studies as compared with 66% of patients in studies using isoproterenol with tilt testing. The percentage of positive responses increased with increasing angle of testing for studies using isoproterenol. There was no relationship between the percentage of positive responses and the maximum dose of isoproterenol. When we compared the results of passive studies that tested patients for 60 minutes at 60 degrees with the results of isoproterenol studies that tested patients at 60 degrees, the positive rate for passive-only studies was 54% as compared with 52% for the isoproterenol studies. The percentage of positive response in control subjects with passive studies was 8.9% (range 0% to 100%), and with isoproterenol 27% (range 0% to 65%). Other groups of patients showed a wide range of positive responses (range 0% to 83%). Reproducibility ranged from 71% to 87%. Upon retesting while the patient was receiving therapy, 90% of 115 positive patients were negative. Eighty-nine percent of 105 positive patients who were receiving therapy and followed for a mean time of 12 months were free of syncope.
Conclusions: This review strongly suggests that isoproterenol may not have an effect on stimulating vasovagal syncope during upright tilt testing. We recommend protocols of passive tilt testing procedures at 60 degrees for 45 to 60 minutes since the overall specificity is higher with this method. The use of isoproterenol during tilt testing adds to the cost and complexity of the test, is associated with a higher rate of false-positive responses, leads to potential complications, and, thus, should be avoided.