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Cited by 66Cardiovascular Syncope and Autonomic DisordersCardiac pacing and defibrillation studiesCardiac electrophysiology and arrhythmias

Implications of mechanism of bradycardia on response to pacing in patients with unexplained syncope

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Sud, Sachin, Klein, George J., Skanes, Allan C., Gula, Lorne J., Yee, Raymond, Krahn, Andrew D.·2007·EP Europace
DOI 10.1093/europace/eum020
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Abstract

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.

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  • Earlier observational, open-label, and single-blind pacing studies were uniformly positive, but two subsequent double-blind studies in adults were negative.

    “Although earlier observational, open-label, and single-blind studies have been uniformly positive, the results of 2 subsequent double-blind studies in adults were negative.133–138”

    From 2015 Heart Rhythm Society Expert Consensus Statement on the Diagnosis and Treatment of Postural Tachycardia Syndrome, Inappropriate Sinus Tachycardia, and Vasovagal Syncope (2015) · cites this paper as [138]

    The Introduction (page unavailable) says two randomized controlled trials failed to show that pacing was superior to sham pacing in patients with positive tilt tests, supporting the negative-trial portion. It mentions earlier pacing studies but does not say that the observational, open-label, and single-blind studies were uniformly positive. (LLM, conf=0.86)

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  • There is strong consensus based on evidence from several controlled trials that a correlation between symptoms and a documented arrhythmia, or the presence of some asymptomatic significant arrhythmias, is diagnostic of the cause of syncope and specific treatment must be prescribed.

    “Even if the quality of evidence is moderate, there is strong consensus based on evidence from several controlled trials that a correlation between symptoms and a documented arrhythmia, or the presence of some asymptomatic significant arrhythmias (defined above), is diagnostic of the cause of syncope and specific treatment must be prescribed.”

    From 2018 ESC Guidelines for the diagnosis and management of syncope (2018) · cites this paper as [200]

    The Discussion stresses the importance of rhythm–symptom correlation before considering pacing and says clinicians should consider the pattern of documented symptomatic bradycardia. It does not establish a consensus based on several controlled trials, address asymptomatic arrhythmias as diagnostic of syncope, or say that specific treatment must be prescribed. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Most evidence in support of the above diagnostic criteria is indirectly based on the benefit of specific therapies guided by ECG monitoring in preventing syncopal recurrences.

    “Most evidence in support of the above diagnostic criteria is indirectly based on the benefit of specific therapies guided by ECG monitoring in preventing syncopal recurrences. 172,184-186,188,200”

    From 2018 ESC Guidelines for the diagnosis and management of syncope (2018) · cites this paper as [200]

    The Patient selection and Recurrent syncope sections describe pacemakers implanted after loop-recorder documentation of bradycardia and report subsequent syncopal recurrence by recorded rhythm pattern (pages unavailable). This provides an example of indirect evidence from monitoring-guided therapy, but the paper does not establish that most evidence for the citing document’s diagnostic criteria comes from such benefits. The Discussion also says the apparent pacing benefit is not conclusive without an untreated control group. (LLM, conf=0.83)

    Experimental — accuracy not yet measured

  • In two observational studies, cardiac pacing reduced syncope burden in patients with documented asystolic syncope by 92% and 83%, but did not prevent all syncopal events.

    “In two observational studies, cardiac pacing reduced syncope burden in patients with documented asystolic syncope by 92 184 and 83%, 200 but did not prevent all syncopal events.”

    From 2018 ESC Guidelines for the diagnosis and management of syncope (2018) · cites this paper as [200]

    Figure 1 (Conclusion; page unavailable) shows that syncope burden fell after pacing, and the Recurrent syncope section reports recurrence in 6 of 33 patients, supporting the statement that pacing did not prevent every event. This paper does not report an 83% reduction: Figure 1 gives subgroup rates of 2.17 to 0.45 and 4.57 to 0 episodes per year. Its cohort also included patients with documented bradycardia without asystole. (LLM, conf=0.87)

    Experimental — accuracy not yet measured

  • Some observational studies suggest that pacing is highly effective in preventing syncope recurrences when AV block is documented.

    “Although formal RCTs of pacing in thirdor second-degree type 2 AV block have not been performed, some observational studies suggest that pacing is highly effective in preventing syncope recurrences when AV block is documented.”

    From 2018 ESC Guidelines for the diagnosis and management of syncope (2018) · cites this paper as [200]

    The Recurrent syncope and Discussion sections report no recurrence after pacing in patients with abrupt AV block, supporting the claim that pacing can be highly effective. But the Discussion also reports recurrence with progressive sinus slowing associated with AV block, so the evidence does not support the claim for documented AV block without that distinction. Page numbers were not available in our copy. (LLM, conf=0.84)

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Authors
Sud, S., Klein, G. J., Skanes, A. C., Gula, L. J., Yee, R., & Krahn, A. D.
Affiliations
Western University (CA)
Corresponding author
Krahn, Andrew D.
ORCID
Venue
EP Europace
Publisher
Oxford University Press (OUP)
Published
2007-03-21
Volume
9
Issue
5
Pages
312-318
ISSN
  • 1099-5129 (ISSN-L)
  • 1532-2092
DOI
10.1093/europace/eum020
OpenAlex
W2154790144
Semantic Scholar
6bfb4a88bce640bbde557fb7b07348ef83db32ec
Cited by
66
References
32
Citations by year
2026: 1 · 2024: 1 · 2023: 1 · 2022: 1 · 2021: 2 · 2020: 1 · 2019: 2 · 2018: 5 · 2017: 2 · 2016: 4 · 2015: 3 · 2014: 8 · 2013: 8 · 2012: 4
FWCI
4.98
Type
journal article
Language
en
Open access
Locations
  • EP Europace (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Surgery › Cardiovascular Syncope and Autonomic Disorders
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Cardiac pacing and defibrillation studies
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Cardiac electrophysiology and arrhythmias
Keywords
unexplained syncope, vasovagal syncope, cardiac pacing, issue classification, recurrent syncope, sick sinus syndrome, cardiac conduction disorders, predictors of treatment response
MeSH terms
Aged, Aged, 80 and over, Bradycardia, Cardiac Pacing, Artificial, Female, Heart Rate, Humans, Male, Middle Aged, Pacemaker, Artificial, Recurrence, Retrospective Studies, Multivariate Analysis, Logistic Models, Syncope, Vasovagal

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