Diagnostic yield of adenosine and nitroglycerine stimulated tilt test in patients with unexplained syncope.

Objectives: We aimed to compare diagnostic yield of adenosine tilt test (A-HUT) with nitroglycerine tilt test (NTG-HUT) in patients with unexplained syncope and to assess the use of adenosine tilt test as an alternative to routine tilt testing.

Background: Adenosine could provoke a vasovagal response in susceptible patients. Adenosine stimulated tilt testing is less time consuming than conventional tilt testing.

Methods: Forty-one consecutive patients with unexplained syncope were tested (29 females /12 males; mean age 44 +/- 20 years). As a part of standard diagnostic testing they undewent both adenosine and nitroglycerin stimulated tilt testing in random fashion.

Results: NTG-HUT was positive in 28 patients (68%). Six patients (14.6 %) developed a vasovagal response after adenosine stimulated head-up tilt test (A-HUT). All patiens with positive A-HUT showed also the positivity of NTG-HUT. No patient from with negative NTG-HUT developed a vasovagal response after adenosine induction. The diagnostic yield of NTG-HUT was significantly higher than yield of A-HUT (p < 0.001). The diagnostic yield of A-HUT was significantly affected by age. Subjects with a positive adenosine tilt test were younger than those with a negative tilt (29 +/- 10 vs. 46 +/- 20 years, p = 0.016). Five of six positive patients were <30 years of age. Diagnostic yield in those patients was 31%, whereas in patients >30 years of age was significantly lower (4%, p = 0.007).

Conclusion: Diagnostic yield of the adenosine stimulated tilt testing is significantly lower than diagnostic yield of nitroglycerine stimulated tilt testing. Given the very short time needed for performing adenosine stimulated HUT, it may be useful in patiens <30 years of age. In this group of patiens positive adenosine-stimulated HUT may obviate need for the time consuming nitroglycerine-stimulated HUT (Tab. 1, Fig. 3, Ref. 17).