DI AGNOSTIC VAL UE OF SUBL INGUAL NITROGLYCERIN TILT TEST: COMPARISON WITH THE STANDARD ISOPROTERENOL TILT TEST

Sublingual nitroglycerin (TNG) has been introduced as a promising provocative agent for tilt table testing, but it has not been compared directly with the standard isoproterenol (ISO) infusion test previously. We tried to assess the diagnostic value and safety of TNG tilt testing as compared with ISO infusion in patients with unexplained syncope. TNG and ISO tilt tests were performed in two successive days on a random basis for both cases and controls. 65 consecutive patients with unexplained syncope after thorough work-up and 20 healthy volunteers were recruited into the study. Positive responses were observed in 20 patients (31 %) during the passive phase, 25 (55% of cases or 38% of total) during the TNG phase and 26 (58% or40% of total) during the ISO phase. In the control group, positive responses during the passive, TNG and ISO phases occurred in 1,1 and 2 cases, respectively. The sensitivity and specificity of the tests can be summarized as 69% and 90% respectively for the TNG test versus 71 % and 85% respectively for the ISO test. Owing to discordant responses in 75% of the cases, the sequential use of the tests (if one is negative) would increase the sensitivity to 89% while decreasing the specificity slightly (to 80%). Side effects were also less frequent with TNG. We conclude that sublingual TNG testing is an effective and safe alternative to the ISO infusion test and can be used as a complementary test.