DDD PACING WITH RATE DROP RESPONSE FUNCTION VERSUS DDI WITH RATE HYSTERESIS PACING FOR CARDIOINHIBITORY VASOVAGAL SYNCOPE

Background: The effectiveness of cardiac pacing in preventing vasovaga l syncope remains controversial. However, DDI pacing with rate hystere sis has been reported to prevent the recurrence of cardioinhibitory va sovagal syncope in up to 35% of affected subjects and to reduce the ov erall incidence of syncopal episodes in the others. Recently, DDD paci ng with a new promising rate drop response function (Medtronic Thera-I model 7960) has become available in clinical practice. Aim of the stu dy: The aim of the present open trial was to test the effectiveness of this new pacing modality in patients with cardioinhibitory vasovagal syncope. Study population and methods: The study population included 2 0 patients (12 males and 8 females; mean age 61.1 +/- 14 yrs) with rec urrent syncope (mean number of prior episode = 6.8, range 5-11) and ca rdioinhibitory responses during two head-up tilt tests: the first diag nostic and the second during drug therapy with either beta-blockade or etilephrine. The study patients were randomized to receive either DDI pacing with rate hysteresis (8 patients) or DDD pacing with rate drop response function (11 patients). The head-up tilt test performed 1 mo nth after pacemaker implantation was positive in 3 of 12 patients (25% ) with DDD pacing with rate drop response function and in 5 of 8 patie nts (62.5%) with DDI pacing with rate hysteresis. The mean duration of follow-up was 17.7 +/- 7.4 months. During follow-up no patients with a DDD pacemaker with rate drop response function had syncope, while 3 of 8 patients with a DDI pacemaker with rate hysteresis had recurrence of syncope (P < 0.05). Conclusions: These data suggest that DDD pacin g with rate drop response function is effective in cardioinhibitory va sovagal syncope and may be preferable to DDI pacing with rate hysteres is.