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 elder ly 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 st rategy. To test one aspect of these results prospectively, we designed a sm all study focusing only on vasovagal patients with abnormal response to ATP testing. Methods Twenty patients hospitalized for syncope, which was considered to b e vasovagal, and exhibiting an abnormal ATP test-defined by a longer than 1 0 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 w ere not hospitalized for recurrences were assessed every 6 months in the cl inic or by telephone. Results At baseline, the randomized patient groups were similar in their de mographic 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 th e 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 wit h an abnormal ATP test who receive a dual-chamber pacemaker suffer fewer re currences than those who art: monitored only; and (2) consequently further supports the hypothesis that, among vasovagal patients, a cardiac pause of longer than 10s in patients administered ATP identifies those at high risk of symptomatic vagal cardiac inhibition.