[A clinical study of multistage isoproterenol tilt table test for patients with unexplained syncope].

The purpose of the present study is to evaluate the clinical usefulness of multistage isoproterenol tilt table test (MITTT) in patients with syncope of unexplained origin. 35 patients (mean age 40 +/- 8 years) with syncope of unknown origin and 20 patients (mean age 49 +/- 7 years) with sinus bradycardia as controls were subjected to successive MITTT (4 stage). 28 of the 35 patients with syncope of unknown origin who underwent the MITTT developed syncope (80% positive response). Only 2 of the 20 patients with sinus bradycardia developed syncope (10% positive response). There was a highly significant statistical difference in positive response between the two groups (P < 0.001). If MITTT was combined with isoproterenol test (< or = 3 micrograms/min), positive response was obtained in 95% and only 5 minutes were sufficient to induce positive response. The mean heart rate-pressure product accurately indentified both positive and negative test results (positive predictive value < or = 1.2 x 10(3) kPa/min, negative predictive value > 1.3 x 10(3) kPa/min). These results suggest that MITTT is a valuable provocative test for vasovagal syncope.