Abstract
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. 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. Patients with syncope associated with abrupt bradycardia displayed a better response to cardiac pacing therapy than those with gradual onset bradycardia.
Highlights
Syncope affects 12–48% of the population at some point in their lives.[1]
Eleven patients had progressive sinus bradycardia associated with sinus arrest (1A), three patients had progressive sinus bradycardia associated with complete heart block (1B), 13 patients had abrupt complete heart block without slowing of the sinus rate (1C), and three patients had sinus bradycardia with heart rate,40 for at least 10 s (2B)
The current study suggests that pacemaker implantation after documentation of spontaneous symptomatic bradycardia with an external loop recorder or implanted loop recorder (ILR) dramatically reduces or eliminates syncope
Summary
Syncope affects 12–48% of the population at some point in their lives.[1]. The diagnosis is established in 50% of cases that present to a physician’s office or an emergency department.[2,3,4] Bradycardia causing syncope is often intermittent and typically requires long-term cardiac monitoring with an external loop recorder or implanted loop recorder (ILR) to detect.[5,6,7,8,9,10] The use of an external loop recorder or ILR has been shown to increase the diagnostic yield in the evaluation of patients with unexplained syncope.[11,12] The most common diagnoses after prolonged monitoring are ‘primary’ bradycardia or vasovagal syncope.[13,14,15]Asystole .3 s or bradycardia ,40 in association with complete heart block or sinus node dysfunction are considered to be Class 1 indications for cardiac pacing.[16].
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