Head-up tilt table testing with low dose sublingual isosorbide dinitrate in the evaluation of unexplained syncope: a comparison with isoproterenol infusion.
OBJECTIVE
To investigate the value of head-up tilt table testing (HUTT) with low-dose isosorbide dinitrate (ISDN) in the evaluation of patients with unexplained syncope and to compare the results of HUTT with ISDN and HUTT with isoproterenol.


METHODS
Forty-three patients with unexplained syncope (21 women, with a mean age of 45.4 18 years) and 18 control subjects without syncope (eight women, with a mean age of 45.8 12 years) were tilted (80 ) for 30 min (passive period). When this period was negative, 2.5 mg sublingual ISDN was administered and patients were observed for an additional 15 min (ISDN period). The first 25 patients studied (10 women, with a mean age of 46.2 18 years) were tested again after a mean period of three weeks using the isoproterenol protocol. After the passive period, intravenous isoproterenol was administered (1 to 3  g/min) to patients lying in the supine position, and they were tilted again (80 ) for 10 min (isoproterenol period).


RESULTS
During the passive period, 10 of 43 patients (23%) had a positive response compared with none in the control group. Syncope was observed in another 14 patients and in two control subjects during the ISDN period. The positivity rate (sensitivity) and specificity of HUTT with low dose ISDN were 56% and 89%, respectively. Among the patients (n=25) tested with the isoproterenol protocol, 14 (56%) patients had syncope. The agreement rate between the protocols was 78.9%.


CONCLUSIONS
The total positivity rate of HUTT significantly increased with the use of the low dose ISDN, while specificity remained high. Due to its simplicity and tolerability, the ISDN protocol can be chosen when the results of the passive period tilt testing are negative.
Aslan
Ozgur
O
Department of Cardiology, Dokuz Eylül University, School of Medicine, Izmir, Turkey. ozgur.aslan@deu.edu.tr
Guneri
Sema
S
Badak
Ozer
O
Kirimli
Onder
O
Goldeli
Ozhan
O
Keskin
Vehip
V
Akdeniz
Bahri
B
Tekin
Umit
U
D000286:Administration, Sublingual; D000328:Adult; D002317:Cardiovascular Agents / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007545:Isoproterenol; D007548:Isosorbide Dinitrate / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013575:Syncope / Q000209:etiology*; D019462:Syncope, Vasovagal / Q000175:diagnosis*; D018667:Tilt-Table Test / Q000379:methods*
D002317:Cardiovascular Agents; D007548:Isosorbide Dinitrate; D007545:Isoproterenol