Recurrent vasovagal syncope: comparison between clomipramine and nitroglycerin as drug challenges during head-up tilt testing.

AIMS: To compare the responses between clomipramine, a centrally acting substance, and nitroglycerin, with mainly peripheral action, when each drug is used during tilt test for the induction of vasovagal syncope (VVS). METHODS AND
RESULTS: Hundred patients with recurrent episodes of classical VVS underwent two tilt tests in a randomized sequence. One test included 20 min of tilt at 60 degrees with intravenous administration of 5 mg clomipramine (clomipramine tilt), whereas the other test included an initial 30 min period of passive 60 degrees tilt, followed by sublingual spray administration of 400 microg nitroglycerin (nitroglycerin tilt). Fifty asymptomatic subjects served as controls. Following clomipramine tilt, a positive response occurred in 73 patients (73%), a negative response in 23 (23%), and drug intolerance in 4 (4%). With nitroglycerin tilt, these percentages were 52, 48, and 0%, respectively. Significant differences were observed regarding positive responses (clomipramine vs. nitroglycerin: 73/100 vs. 52/100, P < 0.05), as well as negative responses (23/100 vs. 48/100, respectively, P < 0.05). A high concordance rate was observed in positive responses.
CONCLUSION: In the evaluation of patients with recurrent classical VVS, clomipramine tilt is associated with an increased positive yield relative to nitroglycerin tilt. This suggests that central mechanisms may be more important than peripheral ones in VVS pathogenesis.