Usefulness of intravenous metoprolol during positive isoproterenol tilt-table test in the choice of treatment for neurocardiogenic syncope.
BACKGROUND
Isoproterenol tilt-table testing provides a diagnosis of neurocardiogenic syncope in patients with syncope or near-syncope. Although acute beta-blockade may prevent the development of syncope during isoproterenol tilt-table testing, the use of beta-blockers for chronic prophylaxis may not be effective for some patients who show a positive response to isoproterenol tilt-table testing. We evaluated whether the efficacy of intravenous metoprolol in preventing symptoms during repeated tests would be helpful in selecting patients suitable for long-term therapy.


RESULTS
We studied 55 patients (35 females, 20 males; mean age 36+/-11 years) who had been chosen from a group referred to our institute with a history of unexplained syncope (> or = 2 syncopal episodes) and a positive response to isoproterenol tilt-table testing. After a positive response to isoproterenol tilt-table testing, 5 mg metoprolol was infused intravenously as a bolus and the test repeated. Thirty-five patients (group 1) showed a positive response again and 20 (group 2) showed a negative response. We started 50 mg metoprolol once a day for patients in group 1 while group 2 was divided into 2 subgroups: the first subgroup (group 2a, 12 patients) was started on 50 mg sertraline or 20 mg paroxetine once a day and the second subgroup (group 2b, 8 patients) was started on 5 mg midodrine orally once a day. Two months later, isoproterenol tilt-table testing was repeated. In group 1, 13 of 35 patients (37%) were positive on isoproterenol tilt-table testing while in group 2, 8 of 20 patients (40%) were positive on isoproterenol tilt-table testing (p not statistically significant). The therapies of the two groups were then interchanged. Two months later (4 months from the beginning of the study), the isoproterenol tilt-table test was repeated. Eleven patients in group 1 (31%) and 6 in group 2 (30%, p not statistically significant) showed a positive response again.


CONCLUSIONS
We conclude that acute beta-blockade response to positive isoproterenol tilt-table testing is not a useful predictor for the assessment of chronic prophylaxis for neurocardiogenic syncope.
Baran
Ibrahim
I
Department of Cardiology, Uludag University, School of Medicine, Bursa, Turkey.
Gemici
Kani
K
Ozdemir
Bülent
B
Saraç
Murat
M
Güllülü
Sümeyye
S
Aydinlar
Ali
A
Cordan
Jale
J
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D005260:Female; D006801:Humans; D007545:Isoproterenol; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D019462:Syncope, Vasovagal / Q000188:drug therapy*; D018667:Tilt-Table Test
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D008790:Metoprolol; D007545:Isoproterenol