Is There Any Room for Adenosine Test in Syncope of Unknown Origin?

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Abstract

Background

Some patients with unexplained syncope develop different degrees of paroxysmal AV block with bolus infusion of 18-mg of adenosine. This finding had a low positive predictive value in recent trials, although its use was not standardized.

Objective

To present the experience in our institution in follow up of patients with a first episode of unexplained malignant syncope of uncertain etiology (SUE), to whom were systematically carried out an adenosine test.

Material and Methods

There were included, in a prospective and consecutive way, patients who presented unexplained syncope with severe trauma, none of them had a previous history of syncope, without suspected vasovagal etiology, without organic cardiopathy, with normal neurological and cardiological studies (including sensitized tilt test), to those who underwent an adenosine test. The test was carried out at the end of the electrophysiological study. It was infused in bolus of 18-mg of adenosine through the femoral vein under continuous ECG monitoring; positive test was defined by the development of complete AV block with pauses longer than 6 seconds.

Results

Between 1999 and 2009 adenosine test underwent to 29 patients (mean age 63 ± 12 years, 17 women). The test was positive in 17 patients, with a mean pause of 10,185 ± 3,430 msec. The mean age in this group was 64 ± 13 years, 13 were women. In the remaining 12 patients (59 ± 11 years), the test was negative, with a mean pause of 2,570 ± 1,067 msec. All patients received hygienic-dietetic recommendations for the prevention of neurally mediated syncope and 9 patients with positive adenosine test, a permanent pacemaker was implanted. The follow-up was 51 ± 37 months. Only 2 patients had recurrence of syncope, both with positive adenosine test without pacemaker implantation.

Conclusions

Patients with syncope of uncertain etiology and high initial risk represent in monitoring a low clinical risk population with a very low recurrence rate, regardless of the implemented therapeutic strategy.