Clinical Experience with Thera DR Rate‐Drop Response Pacing Algorithm in Carotid Sinus Syndrome and Vasovagal Syncope

Abstract

This study examined the effectiveness of cardiac pacing using the Thera DR rate-drop response algorithm for prevention of recurrent symptoms in patients with carotid sinus syndrome (CSS) or vasovagal syncope. The algorithm comprises both diagnostic and treatment elements. The diagnostic element consists of a programmable "window" used to identify heart rate changes compatible with an evolving neurally mediated syncopal episode. The treatment arm consists of pacing at a selectable rate and for a programmable duration. Forty-three patients (mean age 53 +/- 20.4 years) with CSS alone (n = 8), CSS in conjunction with vasovagal syncope (n = 4), or vasovagal syncope alone (n = 31) were included. Thirty-nine had recurrent syncope, while the remaining four reported multiple presyncopal events. Prior to pacing, 40 +/- 152 syncopal episodes (range from 1 to approximately 1,000 syncopal events) over the preceding 56 +/- 84.5 months. Postpacing follow-up duration was 204 +/- 172 days. Three patients have been lost to follow-up and in one patient the algorithm was disabled. Among the remaining 39 individuals, 31 (80%) indicated absence or diminished frequency of symptoms, or less severe symptoms. Twenty-three patients (23/29, or 59%) were asymptomatic with respect to syncope or presyncope. Sixteen patients had symptom recurrences. Of these, seven experienced syncope (7/39, or 18%) and 9 (29%) had presyncope: the majority of patients with recurrences (6/7 syncope and 7/9 presyncope) were individuals with a history of vasovagal syncope. Consequently, although symptoms were observed during postpacing follow-up, they appeared to be of reduced frequency and severity. Thus, our findings suggest that a transient period of high rate pacing triggered by the Thera DR rate-drop response algorithm was beneficial in a large proportion of highly symptomatic patients with CSS or vasovagal syncope.

Dual-Chamber Pacing in the Treatment of Neurally Mediated Tilt-Positive Cardioinhibitory Syncope

“…Pacemaker therapy was more effective than in other studies [2][3][4][5] in which syncope recurred in 18% to 50% of patients. We think that a possible explanation for these better results was the different selection of patients.…”

“…In a tilting study, 1 syncope was not prevented by atropine or pacing. A few observational, nonrandomized studies [2][3][4] have suggested a possible benefit from pacing, but syncope recurred in 18% to 50% of patients over a follow-up ranging from 6 to 50 months. In a recent randomized, controlled trial, 5 there was an 84% reduction in risk of syncope in pacemaker patients compared with patients without pacemakers, but syncope still recurred in 22% of patients during a 2-month follow-up.…”

The management of patients with carotid sinus syndrome: is pacing the answer?

“…Duration of CSM should be between 5-10 seconds [2,3,10,11,33,38]. No comparative studies have been done to assess the optimum duration of CSM; however, some suggest that 10 seconds is preferable if one requires the reproduction of symptoms as an endpoint [11].…”

Permanent cardiac pacing as primary therapy for neurocardiogenic (reflex) syncope

“…These functions allow pacing to occur at an accelerated rate in the face of impending syncope. The term "hysteresis" refers to a function that allows the pacing rate to exceed the device's lower rate limit for a programmable period of time [16]. For instance, if a pacemaker was programmed with 50/80 hysteresis, pacing would not begin until the intrinsic heart rate dropped to less than 50 beats/minute.…”