Is a pacemaker indicated for vasovagal patients with severe cardioinhibitory reflex as identified by the ATP test? A preliminary randomized trial.

Background: A previous observational study suggested that, in syncopal elderly patients with vasovagal syndrome, a test using adenosine-5'-triphosphate (intravenous ATP 20 mg. 2 ml-1) could identify a subgroup of patients at high risk of severe cardioinhibitory response and guide the therapeutic strategy. To test one aspect of these results prospectively, we designed a small study focusing only on vasovagal patients with abnormal response to ATP testing.

Methods: Twenty patients hospitalized for syncope, which was considered to be vasovagal, and exhibiting an abnormal ATP test--defined by a longer than 10 s cardiac pause--were randomized to two groups: half to implantation with a dual-chamber pacemaker and half to usual medical care. All patients who were not hospitalized for recurrences were assessed every 6 months in the clinic or by telephone.

Results: At baseline, the randomized patient groups were similar in their demographic and health characteristics and in the results of their ATP tests, for example the mean cardiac pause (21.4 +/- 9.3 vs 15.9 +/- 3.7 s) and the mean interval between escape beats during the pause (7.29 +/- 4.2 vs 7.48 +/- 3.3 s). During a mean follow-up of 52 months, recurrences appeared in six of the 10 usual-care patients (range 0.2-29 months) but in none of the implanted patients (P < 0.02).

Conclusions: This limited trial (1) supports the conclusion that patients with an abnormal ATP test who receive a dual-chamber pacemaker suffer fewer recurrences than those who are monitored only; and (2) consequently further supports the hypothesis that, among vasovagal patients, a cardiac pause of longer than 10 s in patients administered ATP identifies those at high risk of symptomatic vagal cardiac inhibition.