High Yield of Tilt-Test with Isoproterenol as a Second Provocation in Tilt-Negative and Nitroglycerine Negative Syncope Patients

Background

Syncope is a transient loss of consciousness with spontaneous and rapid recovery within a short period of time. The most common type of syncope is vasovagal (VVS). In order to diagnose VVS in some patients, tilt-table test (TTT) with sublingual nitroglycerine (NTG) or intravenous isoproterenol (ISO) is used. According to ESC guidelines, both protocols have a similar rate of positive responses (61– 69%).

Purpose
We sought to study the effectiveness of ISO provocation as an add on to NTG provocation during TTT .

Methods
From 2013 till 2017, 1712 patients were investigated in our Syncope Center at Sheba Medical Hospital. We used both TTT protocols to diagnose VVS: as first, NTG-TTT was performed (N=880); if this test showed negative results despite high clinical suspicion, ISO-TTT was performed (N=55). A positive response was defined as the occurrence of true syncope accompanied with bradycardia and hypotension.

Results and discussion

The rate of positive response in NTG-TTT protocol was give numbers – 598/880 (67.9%) and in ISO-TTT in those who were previously NTG negative – 45/55 (81.8%). The overall positivity of sequential NTG – ISO provocation was 73%.

There are several potential explanation for this apparent superiority of Isoproterenol over NTG in our series. One may be the fact that ISO provocation was always done on the second test which may be more reliable as patients are initially more relaxed [1]. Another potential mechanism that may increase the tendency to faint may be the insertion of intravenous line that is needed for ISO infusion.

Conclusion

Isoproterenol may increase the yield of TTT in patients who are TTT negative with NTG . Repeated testing with ISO should be considered I the presence of high likelihood of VVV in the presence of negative TTT with NTG

Bibliography

1. The role of Psychological Factors in the Aetiology and Treatment of Vasovagal Syncope. J Gracie, C Baker, M H Freeston, and J L Newton. Indian Pacing Electrophysiol J. 2004 Apr-Jun; 4(2): 79–84.