“Rate-Drop Response” Cardiac Pacing for Vasovagal Syncope David G Benditt 1 , Richard Sutton 2 , Michael Gammage 3 , Toby Markowitz 4 , JoAnne Gorski 4 , Gary Nygaard 4 , and Joseph Fetter 4 1 Cardiac Arrhythmia Center, Department of Medicine, University of Minnesota Medical School, Minneapolis; 2 the Royal Brompton Hospital, London; 3 Queen Elizabeth Hospital, Birmingham, UK; 4 Medtronic, Inc., Minneapolis, MN, and the Rate-Drop Response Investigators Group. Abstract. Recent reports suggest that cardiac pacing incor- porating a rate-drop response algorithm is associated with a reduction in the frequency of syncopal episodes in pa- tients with apparent cardioinhibitory vasovagal syncope. The detection portion of the algorithm employs a program- mable heart rate change-time duration “window” to both identify abrupt cardiac slowing suggestive of an imminent vasovagal event and trigger “high rate” pacing. The purpose of this study was to develop recommendations for program- ming the rate-drop response algorithm. Pacemaker pro- gramming, symptom status, and drug therapy were assessed retrospectively in 24 patients with recurrent vasovagal syn- cope of suf~cient severity to warrant consideration of pace- maker treatment. In the 5319 months prior to pacing, patients had experienced an approximate syncope burden of 1.2 events / month. During follow-up of 192160 days, syncope recurred in 4 patients (approximate syncope bur- den, 0.3 events / month, p  0.05 vs. pre-pacing), and pre- syncope in 5 patients. In these patients, rate-drop response parameters were initially set based on electrocardiographic and/or tilt-table recordings, and were re-programmed at least once in 14 (58%) individuals. A 20 beat/min window height (top rate minus bottom rate), a window width of 10 beats (61% of patients), and 2 or 3 con~rmation beats (79% of patients) appeared to be appropriate in most patients. Treatment intervention rate was set to 100 beats/min in 89% of patients, with a duration of 1 to 2 min in 79%. In conclusion, a narrow range of rate-drop response parame- ter settings appeared to be effective for most individuals in this group of highly symptomatic patients. Keywords. Vasovagal syncope, cardiac pacemaker, algo- rithm Introduction Vasovagal syncope is usually a benign event for which long-term prophylaxis is not required. On occasion, though, vasovagal symptoms are suf~ciently trouble- some to warrant attempts at prevention. In such cases, patient education and pharmacologic interventions tend to be the preferred approaches currently [1–7]. Cardiac pacemakers are not often recommended de- spite a number of reports which suggest that pacing may be useful for prevention of vasovagal syncope in selected highly symptomatic individuals [8–15]. In this regard, the incorporation of a programmable “rate- drop response” algorithm designed to both recognize heart rate changes often associated with imminent va- sovagal events and trigger a self-limited period of “high rate” dual-chamber pacing, appears to enhance the utility of pacing interventions [9,11,14,15]. How- ever, there are as yet no speci~c recommendations for programming this feature. This report summarizes ~ndings of a multicenter study which undertook to de- velop an understanding of programmable settings for effective use of this algorithm. Methods Study Design A detailed medical history was obtained in each pa- tient. Care was taken to document as accurately as possible the following: 1) timing of initial vasovagal syncopal event, 2) number of symptomatic recur- rences, 3) occurrence of physical injury, 4) occurrence of associated motor vehicle accidents, and 5) nature of previous treatment, with particular focus on prior pharmacologic therapy. Patients were deemed candidates for inclusion in this study if: 1. Vasovagal syncope was established based on care- ful evaluation of medical history, with con~rmation by tilt-table testing in most (20 of 24, 83%) cases [16]. Other causes of syncope were excluded by appropriate testing including electrophysiologic study when deemed necessary (14 cases). Address correspondence to: David G. Benditt MD, Box 508 FUMC, Cardiac Arrhythmia and Syncope Centers, University of Minnesota Medical School, Minneapolis, Minnesota, 55436. Received 16 June 1998; Accepted 15 September 199 27 Journal of Interventional Cardiac Electrophysiology 1999;3:27–33 © Kluwer Academic Publishers. Boston. Printed in U.S.A.