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Carotid Sinus Syncope

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General Information

Description

  • carotid sinus syncope is a form of neurally mediated syncope (also called reflex syncope) caused by abnormal autonomic response to carotid stimulation1,2,3
  • syncope is syndrome of transient loss of consciousness secondary to cerebral hypoperfusion characterized by rapid onset, short duration, and complete spontaneous recovery1,3
  • complete loss of consciousness in syncope lasts 10-30 seconds1

Also called

  • carotid sinus hypersensitivity syncope
  • hypersensitivity carotid sinus syndrome
  • cardioinhibitory carotid sinus sensitivity

Definitions

  • syncope - transient loss of consciousness due to global cerebral hypoperfusion and characterized by1
    • rapid onset
    • short duration
    • spontaneous recovery
  • presyncope may be used as noun or adjective1
    • noun refers to state that resembles prodrome of syncope but that is not followed by loss of consciousness
    • adjective refers to symptoms or signs that occur before loss of consciousness
  • transient loss of consciousness defined as state of real or apparent loss of consciousness with loss of awareness characterized by amnesia for unconscious period, abnormal motor control, loss of responsiveness, and short duration1
  • neurally mediated syncope (also called reflex syncope)
    • includes vasovagal syncope (most common), carotid sinus syncope, and situational syncope1,2,3
    • refers to a group of heterogeneous conditions characterized by intermittent, inappropriate cardiovascular reflexes (usually in response to trigger) that cause drop in arterial blood pressure, heart rate, and global cerebral perfusion2
    • may be classified based on efferent pathway most involved1
      • cardioinhibitory - bradycardia or asystole predominate
      • vasodepressor - hypotension predominates due to loss of upright vasoconstrictor tone
      • mixed type - both cardioinhibitory and vasopressor mechanisms are present
  • neurocardiogenic syncope is frequently used to describe reflex syncope, but the term is discouraged since origin of reflex is rarely in the heart2
  • carotid sinus hypersensitivity (CSH) - ventricular pause > 3 seconds and/or fall in systolic blood pressure > 50 mm Hg in response to carotid sinus massage in asymptomatic patients (also called induced carotid sinus syncope)1,3,4
  • carotid sinus syndrome (CSS) (also called spontaneous carotid sinus syncope) - term used when CSH, diagnosed by carotid sinus massage, is associated with spontaneous syncope that is triggered by typical maneuvers in daily life (rare)1,3,4

References

General references used

  1. Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J. 2018 Jun 1;39(21):1883-1948OpenInNew
  2. Freeman R, Wieling W, Axelrod FB, et al. Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Clin Auton Res. 2011 Apr;21(2):69-72OpenInNew
  3. Shen WK, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society. J Am Coll Cardiol 2017 Aug 1;70(5):620OpenInNew
  4. Amin V, Pavri BB. Carotid sinus syndrome. Cardiol Rev. 2015 May-Jun;23(3):130-4OpenInNew

Recommendation grading systems used

  • American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) grading system for recommendations
    • classifications of recommendations
      • Class I - procedure or treatment should be performed or administered
      • Class IIa - reasonable to perform procedure or administer treatment, but additional studies with focused objectives needed
      • Class IIb - procedure or treatment may be considered; additional studies with broad objectives needed, additional registry data would be useful
      • Class III - procedure or treatment should not be performed or administered because it is not helpful or may be harmful
        • Class III ratings may be subclassified as Class III No Benefit or Class III Harm
    • levels of evidence
      • Level A - high-quality evidence from > 1 randomized controlled trial or meta-analysis of high-quality randomized controlled trials
      • Level B-R - moderate-quality evidence from ≥ 1 randomized controlled trial or meta-analysis of moderate-quality randomized controlled trials
      • Level B-NR - moderate-quality evidence from ≥ 1 well-designed nonrandomized trial, observational studies, or registry studies, or meta-analysis of such studies
      • Level C-LD - randomized or nonrandomized studies with methodological limitations or meta-analyses of such studies
      • Level C-EO - consensus of expert opinion based on clinical experience
  • American College of Cardiology Foundation/American Heart Association (ACCF/AHA) grading system for recommendations
    • classifications of recommendations
      • Class I - procedure or treatment should be performed or administered
      • Class IIa - reasonable to perform procedure or administer treatment, but additional studies with focused objectives needed
      • Class IIb - procedure or treatment may be considered; additional studies with broad objectives needed, additional registry data would be useful
      • Class III - procedure or treatment should not be performed or administered because it is not helpful or may be harmful
        • Class III ratings may be subclassified as Class III No Benefit or Class III Harm
    • levels of evidence
      • Level A - data derived from multiple randomized clinical trials or meta-analyses
      • Level B - data derived from single randomized trial or nonrandomized studies
      • Level C - only expert opinion, case studies, or standard of care
  • European Society of Cardiology (ESC) grading system for recommendations
    • classes of recommendations
      • Class I - evidence and/or general agreement that treatment or procedure is beneficial, useful, effective
      • Class II - conflicting evidence and/or divergence of opinion about usefulness/efficacy of treatment or procedure
        • Class IIa - weight of evidence/opinion in favor of usefulness/efficacy
        • Class IIb - weight of usefulness/efficacy less well established by evidence/opinion
      • Class III - evidence or general agreement that given treatment or procedure is not useful/effective and may be harmful in some cases
    • levels of evidence
      • Level A - data from multiple randomized trials or meta-analyses
      • Level B - data from single randomized trial or large nonrandomized studies
      • Level C - expert consensus opinion and/or small studies, retrospective studies, or registries
    • Reference - European Society of Cardiology (ESC) guideline on diagnosis and management of syncope (29562304Eur Heart J 2018 Jun 1;39(21):1883OpenInNew)

Synthesized Recommendation Grading System for DynaMed

  • DynaMed systematically monitors clinical evidence to continuously provide a synthesis of the most valid relevant evidence to support clinical decision-making (see 7-Step Evidence-Based MethodologyOpenInNew).
  • Guideline recommendations summarized in the body of a DynaMed topic are provided with the recommendation grading system used in the original guideline(s), and allow DynaMed users to quickly see where guidelines agree and where guidelines differ from each other and from the current evidence.
  • In DynaMed (DM), we synthesize the current evidence, current guidelines from leading authorities, and clinical expertise to provide recommendations to support clinical decision-making in the Overview & Recommendations section.
  • We use the Grading of Recommendations Assessment, Development and Evaluation (GRADE)OpenInNew to classify synthesized recommendations as Strong or Weak.
    • Strong recommendations are used when, based on the available evidence, clinicians (without conflicts of interest) consistently have a high degree of confidence that the desirable consequences (health benefits, decreased costs and burdens) outweigh the undesirable consequences (harms, costs, burdens).
    • Weak recommendations are used when, based on the available evidence, clinicians believe that desirable and undesirable consequences are finely balanced, or appreciable uncertainty exists about the magnitude of expected consequences (benefits and harms). Weak recommendations are used when clinicians disagree in judgments of relative benefit and harm, or have limited confidence in their judgments. Weak recommendations are also used when the range of patient values and preferences suggests that informed patients are likely to make different choices.
  • DynaMed (DM) synthesized recommendations (in the Overview & Recommendations section) are determined with a systematic methodology:
    • Recommendations are initially drafted by clinical editors (including ≥ 1 with methodological expertise and ≥ 1 with content domain expertise) aware of the best current evidence for benefits and harms, and the recommendations from guidelines.
    • Recommendations are phrased to match the strength of recommendation. Strong recommendations use "should do" phrasing, or phrasing implying an expectation to perform the recommended action for most patients. Weak recommendations use "consider" or "suggested" phrasing.
    • Recommendations are explicitly labeled as Strong recommendations or Weak recommendations when a qualified group has explicitly deliberated on making such a recommendation. Group deliberation may occur during guideline development. When group deliberation occurs through DynaMed-initiated groups:
      • Clinical questions will be formulated using the PICO (Population, Intervention, Comparison, Outcome) framework for all outcomes of interest specific to the recommendation to be developed.
      • Systematic searches will be conducted for any clinical questions where systematic searches were not already completed through DynaMed content development.
      • Evidence will be summarized for recommendation panel review including for each outcome, the relative importance of the outcome, the estimated effects comparing intervention and comparison, the sample size, and the overall quality rating for the body of evidence.
      • Recommendation panel members will be selected to include at least 3 members that together have sufficient clinical expertise for the subject(s) pertinent to the recommendation, methodological expertise for the evidence being considered, and experience with guideline development.
      • All recommendation panel members must disclose any potential conflicts of interest (professional, intellectual, and financial), and will not be included for the specific panel if a significant conflict exists for the recommendation in question.
      • Panel members will make Strong recommendations if and only if there is consistent agreement in a high confidence in the likelihood that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. Panel members will make Weak recommendations if there is limited confidence (or inconsistent assessment or dissenting opinions) that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. No recommendation will be made if there is insufficient confidence to make a recommendation.
      • All steps in this process (including evidence summaries which were shared with the panel, and identification of panel members) will be transparent and accessible in support of the recommendation.
    • Recommendations are verified by ≥ 1 editor with methodological expertise, not involved in recommendation drafting or development, with explicit confirmation that Strong recommendations are adequately supported.
    • Recommendations are published only after consensus is established with agreement in phrasing and strength of recommendation by all editors.
    • If consensus cannot be reached then the recommendation can be published with a notation of "dissenting commentary" and the dissenting commentary is included in the topic details.
    • If recommendations are questioned during peer review or post publication by a qualified individual, or reevaluation is warranted based on new information detected through systematic literature surveillance, the recommendation is subject to additional internal review.

DynaMed Editorial Process

Special acknowledgements

  • DynaMed topics are written and edited through the collaborative efforts of the above individuals. Deputy Editors, Section Editors, and Topic Editors are active in clinical or academic medical practice. Recommendations Editors are actively involved in development and/or evaluation of guidelines.
  • Editorial Team role definitions
    Topic Editors define the scope and focus of each topic by formulating a set of clinical questions and suggesting important guidelines, clinical trials, and other data to be addressed within each topic. Topic Editors also serve as consultants for the internal DynaMed Editorial Team during the writing and editing process, and review the final topic drafts prior to publication.
    Section Editors have similar responsibilities to Topic Editors but have a broader role that includes the review of multiple topics, oversight of Topic Editors, and systematic surveillance of the medical literature.
    Recommendations Editors provide explicit review of DynaMed Overview and Recommendations sections to ensure that all recommendations are sound, supported, and evidence-based. This process is described in "Synthesized Recommendation Grading."
    Deputy Editors are employees of DynaMed and oversee DynaMed internal publishing groups. Each is responsible for all content published within that group, including supervising topic development at all stages of the writing and editing process, final review of all topics prior to publication, and direction of an internal team.

How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T113656, Carotid Sinus Syncope; [updated 2018 Nov 30, cited place cited date here]. Available from https://www.dynamed.com/topics/dmp~AN~T113656. Registration and login required.
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    Overview and Recommendations

    • Background

    • Evaluation

    • Management

  • Related Summaries

  • KeyboardArrowRight

    General Information

    • Description

    • Also called

    • Definitions

  • KeyboardArrowRight

    Epidemiology

    • Who is most affected

    • Incidence/Prevalence

    • Risk factors

  • KeyboardArrowRight

    Etiology and Pathogenesis

    • Causes

    • Pathogenesis

  • KeyboardArrowRight

    History and Physical

    • KeyboardArrowRight

      History

      • Chief concern (CC)

      • History of present illness (HPI)

    • KeyboardArrowRight

      Physical

      • General physical

  • KeyboardArrowRight

    Diagnosis

    • Making the diagnosis

    • Differential diagnosis

    • Testing overview

    • Electrocardiogram (ECG)

    • KeyboardArrowRight

      Other diagnostic testing

      • Carotid sinus massage

      • Tilt testing

  • KeyboardArrowRight

    Management

    • Management overview

    • Treatment setting

    • Activity

    • Medications

    • KeyboardArrowRight

      Surgery and procedures

      • Cardiac pacing

      • Carotid denervation

  • KeyboardArrowRight

    Complications and Prognosis

    • Complications

    • Prognosis

  • Prevention and Screening

  • KeyboardArrowRight

    Guidelines and Resources

    • KeyboardArrowRight

      Guidelines

      • United States guidelines

      • United Kingdom guidelines

      • European guidelines

    • Review articles

    • MEDLINE search

  • Patient Information

  • KeyboardArrowRight

    ICD Codes

    • ICD-10 codes

  • KeyboardArrowRight

    References

    • General references used

    • Recommendation grading systems used

    • Synthesized Recommendation Grading System for DynaMed

    • DynaMed Editorial Process

    • Special acknowledgements

    • How to cite

Topic Editor
Saumya Das MD, PhD
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Affiliations

Assistant Professor of Medicine, Harvard Medical School; Massachusetts, United States; Physician in Cardiac Electrophysiology, Massachusetts General Hospital; Massachusetts, United States

Conflicts of Interest

Dr. Das declares no relevant financial conflicts of interest.

Recommendations Editor
Zbys Fedorowicz MSc, DPH, BDS, LDSRCS
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Affiliations

Director of Bahrain Branch of the United Kingdom Cochrane Center, The Cochrane Collaboration; Awali, Bahrain

Conflicts of Interest

Dr. Fedorowicz declares no relevant financial conflicts of interest.

Deputy Editor
Peter Oettgen MD
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Affiliations

Editor in Chief, DynaMed; Cardiologist, Beth Israel Deaconess Medical Center; Massachusetts, United States; Associate Professor of Medicine, Harvard Medical School; Massachusetts, United States

Conflicts of Interest

Dr. Oettgen declares no relevant financial conflicts of interest.

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