Europace Advance Access originally published online on March 30, 2007
Europace 2007 9(5):305-311; doi:10.1093/europace/eum017
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SYNCOPE
Analysis of rhythm variation during spontaneous cardioinhibitory neurally-mediated syncope. Implications for RDR pacing optimization: an ISSUE 2 substudy
1 Department of Cardiology, Arrhythmologic Centre, Ospedali del Tigullio, via don Bobbio, 16033 Lavagna, Italy; 2 Department of Cardiology, Royal Brompton Hospital and Chelsea and Westminster Hospital, London, UK; 3 Department of Internal Medicine, Academisch Medisch Centrum, Amsterdam, The, Netherlands; 4 Medtronic Inc., MN, USA and Rome, Italy; 5 Department of Cardiology, Ospedale S. Filippo Neri, Roma, Italy; 6 Cardiac Arrhythmia Center, University of Minnesota Medical School, MN, USA
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.
Key Words: Syncope, Diagnosis, Electrocardiography, Implantable loop recorder, Pacing, Cardioinhibition, Rate drop response
* Corresponding author. Tel: +39 0185 329569; fax: +39 0185 306506. E-mail address: mbrignole{at}asl4.liguria.it
Manuscript submitted 5 August 2006. Accepted after revision 31 December 2006.
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