Key result
Optimized drop rate detection delivers intervention pacing ~6 seconds faster than standard lower rate detection.
Why the study?
Little is known about the variations of heart rate during spontaneous cardioinhibitory neurally-mediated syncope, which has implications for optimizing rate drop response pacing.
Does optimally programmed drop rate detection anticipate pacing intervention compared to lower rate detection in patients with cardioinhibitory neurally-mediated syncope?
Observational (n=48)
Does optimally programmed drop rate detection anticipate pacing intervention compared to lower rate detection in patients with cardioinhibitory neurally-mediated syncope?
Effect estimate: median 5.7 s earlier
Optimal rate drop response programming can anticipate the detection of the cardioinhibitory reflex by a few seconds, potentially increasing the benefit of cardiac pacing therapy for syncope prevention.
May inform RDR parameter selection in neurally-mediated syncope; hypothesis-generating and should not yet change practice.
BACKGROUND: Little is known of the variations of the heart rate during spontaneous cardioinhibitory neurally-mediated syncope. Their knowledge has both academic and practical implications for the optimization of rate drop response (RDR) pacing mode. METHODS AND RESULTS: We describe variations of the rhythm occurring during 48 syncopal episodes documented by implantable loop recorder. The presyncopal phase of 18 s (interquartile range 9-65) was characterized by a fall in heart rate from 83 +/- 20 bpm to maximal bradycardia or (multiple) asystolic pauses which lasted a median of 19 s (10-30). The recovery phase lasted 22 s (7-52). The total duration of the cardioinhibitory reflex was 85 s (47-116). We then calculated the potential increase in benefit that an optimally programmed drop rate detection could provide compared with a reference Lower Rate detection. Compared with Lower Rate detection (defined as two consecutive beats at 40 bpm), drop rate detection (assumed to be drop size = 20 bpm, detection window = 1 min, and drop rate = 50 bpm) would have been able to introduce intervention pacing, a median of 5.7 s (interquartile range -5.1- -10.4) earlier in 28 cases (58%). CONCLUSION: Cardioinhibitory neurally-mediated reflex varies widely from a few seconds to some minutes. In our data the total duration was <2 min. Optimal RDR programming, being potentially able to anticipate the detection of the cardioinhibitory reflex by a few seconds, could provide an increase in benefit for cardiac pacing therapy in prevention of syncope.
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Brignole et al. (2007) conducted an observational in Spontaneous cardioinhibitory neurally-mediated syncope (n=48). Drop rate detection (RDR programming) vs. Lower Rate detection was evaluated on Time to introduction of intervention pacing (median 5.7 s earlier). Optimally programmed drop rate detection would have introduced intervention pacing a median of 5.7 seconds earlier than standard Lower Rate detection in 58% of syncopal episodes.
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