COMPARISON OF PATIENTS WITH SYNCOPE OF UNKNOWN CAUSE HAVING NEGATIVE OR POSITIVE TILT-TABLE TESTS

Many patients without an identified cause of syncope have negative til t tests. We hypothesized that many of these might be falsely negative tilt tests. If so, then patients with negative and positive tilt tests should have similar pretest clinical characteristics, post-test proba bilities of remaining free of syncope, and similar risk factors for sy ncope recurrence after the tilt-table test. Demographic characteristic s and historic features were compared between 153 syncope patients wit h a positive tilt test, and 74 syncope patients with a negative tilt t est and no obvious cause of syncope. Patients with negative and positi ve tests had similar numbers of syncopal spells, durations of symptoms , frequency of spells, and peak heart rate during tilt test, but patie nts with negative tests were older (48 +/- 19 vs 39 +/- 20 years). The actuarial probabilities of remaining free of syncope were very simila r, with 2-year risks of syncope of 41% and 37% in patients with negati ve and positive tests, respectively. The regression coefficients of ri sk factors predicting syncope recurrence were similar for both populat ions, and the confidence intervals of all regression coefficients decr eased when the populations were combined. The outcome of tilt testing did not predict the clinical outcome of patients. Patients with syncop e and either negative or positive tilt tests share many pretest and po st-test clinical characteristics, suggesting that they may be part of the same population. (C) 1997 by Excerpta Medica, Inc.