title: Low dose disopyramide often fails to prevent neurogenic syncope during head-up tilt testing.
abstract: Low dose disopyramide has been used to prevent neurally-mediated syncope during head-up tilt testing but a correlation between blood levels and efficacy has not been described. We measured disopyramide levels in 15 patients with recurrent syncope and positive 70 degrees head-up tilt tests who underwent one or more repeat tests on the drug. There were 9 males and 6 females, age range 15-78 years. Fourteen of the 15 patients had structurally normal hearts. The daily disopyramide dose was 645 +/- 165 mg (mean +/- SD). Patients developed syncope during 9 tests and had no syncope during 12 tests. The mean disopyramide level in patients with positive tests was significantly lower than the level in patients with negative tests (2.4 +/- 0.15 mu/mL vs 3.2 +/- 0.22 mu/mL, P = 0.018). Six patients were tested twice on different disopyramide doses. Five of these six patients had syncope during head-up tilt testing on the lower dose and negative tests on the higher dose (disopyramide levels 2.2 +/- 0.17 mu/mL vs 3.2 +/- 0.17 mu/mL, P = 0.004). Thus, disopyramide is effective in preventing neurogenic syncope during head-up tilt testing, but higher blood levels are often necessary for efficacy. In a given patient, failure to respond to low dose disopyramide does not preclude success on higher doses.
authors.affiliation: University of Colorado Health Sciences Center, Denver 80262.
authors.forename: P A
authors.initials: PA
authors.lastname: Kelly
authors.forename: D E
authors.initials: DE
authors.lastname: Mann
authors.forename: S W
authors.initials: SW
authors.lastname: Adler
authors.forename: C E
authors.initials: CE
authors.lastname: Fuenzalida
authors.forename: M J
authors.initials: MJ
authors.lastname: Reiter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D004206:Disopyramide / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D005260:Female; D006257:Head / Q000033:anatomy & histology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D016683:Supine Position / Q000502:physiology; D013575:Syncope / Q000503:physiopathology / Q000517:prevention & control*
chemical_list: D004206:Disopyramide; D007545:Isoproterenol