Usefulness of clinical factors in predicting outcomes of passive tilt tests in patients with syncope

Pretest patient selection affects the outcome of many diagnostic tests; this may be true for tilt-table tests. We assessed the impact of patient age, sex, and symptom burden on the outcome of passive tilt tests. Two hundred one patients with idiopathic syncope (87 men, aged 45 ± 20 years, median 5 fainting spells each) underwent passive, drug-free tilt tests for 45 minutes. Positive tests were defined as those ending in clinically reminiscent presyncope or syncope. Seventy-eight patients (39%) had a positive tilt test. Patients had a wide range of symptom burden, having a median 5 syncopal spells (interquartile range [IQR] 2.5 to 17.5) over a median 52.5 months (IQR 12 to 180) with a median frequency of 0.17 spells/month (IQR 0.042 to 0.67). None of these measures of symptom burden predicted tilt-test outcome (p = 0.33 to 0.46). In contrast, the age of the patient strongly predicted tilt-test outcome. The likelihood of a positive test was 75% in 36 patients <25 years old and 31% in 165 patients ≥25 years of age (p <0.0001, chi-square for 2 × 5 table). Younger patients also fainted more quickly: patients <25 years old fainted within 22 minutes of tilt and reached a clearly asymptotic value, whereas the likelihood of a positive tilt in patients ≥25 years old increased linearly with time, and did not reach an asymptote. Measures of symptom burden do not predict test outcome, and younger patients are more likely to faint during passive tilt testing.