Europace Advance Access originally published online on March 21, 2007
Europace 2007 9(5):312-318; doi:10.1093/europace/eum020
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SYNCOPE
Implications of mechanism of bradycardia on response to pacing in patients with unexplained syncope
Division of Cardiology, University of Western Ontario, London Health Sciences Centre, University Campus, C6-113 339 Windermere road, London, Ontario N6A 5A5, Canada
Aim: Asystole >3 s or sinus bradycardia with a ventricular rate <40 in association with complete heart block or sinus node dysfunction are considered to be Class 1 indications for permanent cardiac pacing. Nevertheless, these phenomena may be observed in symptomatic patients with neurocardiogenic syncope, who may not respond to pacing therapy. We hypothesized that the pattern of spontaneous bradycardia in symptomatic patients would distinguish patients with sinus node dysfunction or conduction system disease who would benefit from pacing from patients with neurally-mediated syncope who would derive lesser benefit.
Methods and results: Patients with symptomatic spontaneous bradycardia during long-term monitoring for unexplained syncope who underwent pacemaker implantation were classified according to the ISSUE classification system and followed for recurrent syncope. Follow-up included review of medical records, pacemaker clinic visits, and telephone interviews. Loop recorder tracings were reviewed to identify characteristics potentially predicting a favourable response to pacing. Thirty-three patients (21 male; age, 70 ± 14) were followed for 3.56 ± 1.71 years. Six patients had a recurrence of syncope during the follow-up. All patients with recurrent syncope despite pacing demonstrated a Type 1A (n = 5) or 1B (n = 1) pattern with gradual onset of bradycardia at baseline, suggesting a neurocardiogenic mechanism. There was no difference in the severity of bradycardia or duration of asystole in baseline loop recorded events in responding and non-responding patients. Multivariate analysis using stepwise logistic regression revealed that the ISSUE classification and the absence of structural heart disease were the only independent predictors of treatment failure of cardiac pacing in patients with spontaneous symptomatic bradycardia.
Conclusion: Patients with syncope associated with abrupt bradycardia displayed a better response to cardiac pacing therapy than those with gradual onset bradycardia.
Key Words: Syncope, Bradycardia, Pacemaker, Diagnosis, Monitoring
* Corresponding author. Tel: +519 663 3746; fax: +519 663 3782. E-mail address: akrahn{at}uwo.ca
Manuscript submitted 10 August 2006. Accepted after revision 7 January 2007.
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  M. Brignole, F. Giada, A. Raviele, and J. J. Blanc Pacing for syncope: what role? which perspective? Eur. Heart J. Suppl., December 1, 2007; 9(suppl_I): I37 - I43. [Abstract] [Full Text] [PDF]
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