2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

HomeCirculationVol. 136, No. 52017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society Free AccessReview ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessReview ArticlePDF/EPUB2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society Win-Kuang Shen, MD, FACC, FAHA, FHRS, Chair, Robert S. Sheldon, MD, PhD, FHRS, Vice Chair, David G. Benditt, MD, FACC, FHRS, Mitchell I. Cohen, MD, FACC, FHRS, Daniel E. Forman, MD, FACC, FAHA, Zachary D. Goldberger, MD, MS, FACC, FAHA, FHRS, Blair P. Grubb, MD, FACC, Mohamed H. Hamdan, MD, MBA, FACC, FHRS, Andrew D. Krahn, MD, FHRS, Mark S. Link, MD, FACC, Brian Olshansky, MD, FACC, FAHA, FHRS, Satish R. Raj, MD, MSc, FACC, FHRS, Roopinder Kaur Sandhu, MD, MPH, Dan Sorajja, MD, Benjamin C. Sun, MD, MPP, FACEP and Clyde W. Yancy, MD, MSc, FACC, FAHA Win-Kuang ShenWin-Kuang Shen *, †, ‡, §, ‖, ¶ Search for more papers by this author , Robert S. SheldonRobert S. Sheldon Search for more papers by this author , David G. BendittDavid G. Benditt *, †, ‡, §, ‖, ¶ Search for more papers by this author , Mitchell I. CohenMitchell I. Cohen *, †, ‡, §, ‖, ¶ Search for more papers by this author , Daniel E. FormanDaniel E. Forman *, †, ‡, §, ‖, ¶ Search for more papers by this author , Zachary D. GoldbergerZachary D. Goldberger *, †, ‡, §, ‖, ¶ Search for more papers by this author , Blair P. GrubbBlair P. Grubb *, †, ‡, §, ‖, ¶ Search for more papers by this author , Mohamed H. HamdanMohamed H. Hamdan *, †, ‡, §, ‖, ¶ Search for more papers by this author , Andrew D. KrahnAndrew D. Krahn *, †, ‡, §, ‖, ¶ Search for more papers by this author , Mark S. LinkMark S. Link *, †, ‡, §, ‖, ¶ Search for more papers by this author , Brian OlshanskyBrian Olshansky *, †, ‡, §, ‖, ¶ Search for more papers by this author , Satish R. RajSatish R. Raj *, †, ‡, §, ‖, ¶ Search for more papers by this author , Roopinder Kaur SandhuRoopinder Kaur Sandhu *, †, ‡, §, ‖, ¶ Search for more papers by this author , Dan SorajjaDan Sorajja *, †, ‡, §, ‖, ¶ Search for more papers by this author , Benjamin C. SunBenjamin C. Sun *, †, ‡, §, ‖, ¶ Search for more papers by this author and Clyde W. YancyClyde W. Yancy *, †, ‡, §, ‖, ¶ Search for more papers by this author Originally published9 Mar 2017https://doi.org/10.1161/CIR.0000000000000499Circulation. 2017;136:e60–e122is corrected byCorrection to: 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm SocietyOther version(s) of this articleYou are viewing the most recent version of this article. Previous versions: January 1, 2017: Previous Version 1 Table of ContentsPreamblee 611. Introduction e641.1. Methodology and Evidence Review e641.2. Organization of the Writing Committee e641.3. Document Review and Approval e641.4. Scope of the Guideline e642. General Principles e672.1. Definitions: Terms and Classification e672.2. Epidemiology and Demographics e672.3. Initial Evaluation of Patients with Syncope: Recommendations e672.3.1. History and Physical Examination: Recommendation e682.3.2. Electrocardiography: Recommendation e682.3.3. Risk Assessment: Recommendations e682.3.4. Disposition After Initial Evaluation: Recommendations e693. Additional Evaluation and Diagnosis e703.1. Blood Testing: Recommendations e703.2. Cardiovascular Testing: Recommendations e713.2.1. Cardiac Imaging: Recommendations e713.2.2. Stress Testing: Recommendation e723.2.3. Cardiac Monitoring: Recommendations e723.2.4. In-Hospital Telemetry: Recommendation e733.2.5. Electrophysiological Study: Recommendations e743.2.6. Tilt-Table Testing: Recommendations e753.3. Neurological Testing: Recommendations e763.3.1. Autonomic Evaluation: Recommendation e763.3.2. Neurological and Imaging Diagnostics: Recommendations e764. Management of Cardiovascular Conditions e784.1. Arrhythmic Conditions: Recommendations e794.1.1. Bradycardia: Recommendation e794.1.2. Supraventricular Tachycardia: Recommendations e794.1.3. Ventricular Arrhythmia: Recommendation e804.2. Structural Conditions: Recommendations e804.2.1. Ischemic and Nonischemic Cardiomyopathy: Recommendation e804.2.2. Valvular Heart Disease: Recommendation e804.2.3. Hypertrophic Cardiomyopathy: Recommendation e804.2.4. Arrhythmogenic Right Ventricular Cardiomyopathy: Recommendations e814.2.5. Cardiac Sarcoidosis: Recommendations e814.3. Inheritable Arrhythmic Conditions: Recommendations e814.3.1. Brugada Syndrome: Recommendations e814.3.2. Short-QT Syndrome: Recommendation e824.3.3. Long-QT Syndrome: Recommendations e824.3.4. Catecholaminergic Polymorphic Ventricular Tachycardia: Recommendations e834.3.5. Early Repolarization Pattern: Recommendations e845. Reflex Conditions: Recommendations e845.1. Vasovagal Syncope: Recommendations e845.2. Pacemakers in Vasovagal Syncope: Recommendation e855.3. Carotid Sinus Syndrome: Recommendations e865.4. Other Reflex Conditions e866. Orthostatic Hypotension: Recommendations e866.1. Neurogenic Orthostatic Hypotension: Recommendations e866.2. Dehydration and Drugs: Recommendations e887. Orthostatic Intolerance e888. Pseudosyncope: Recommendations e889. Uncommon Conditions Associated with Syncope e8910. Age, Lifestyle, and Special Populations: Recommendations e8910.1. Pediatric Syncope: Recommendations e8910.2. Adult Congenital Heart Disease: Recommendations e9110.3. Geriatric Patients: Recommendations e9210.4. Driving and Syncope: Recommendation e9210.5. Athletes: Recommendations e9311. Quality of Life and Healthcare Cost of Syncope e9411.1. Impact of Syncope on Quality of Life e9411.2. Healthcare Costs Associated with Syncope e9412. Emerging Technology, Evidence Gaps, and Future Directions e9612.1. Definition, Classification, and Epidemiology e9612.2. Risk Stratification and Clinical Outcomes e9712.3. Evaluation and Diagnosis e9712.4. Management of Specific Conditions e9812.5. Special Populations e98Referencese 99Appendix 1. Author Relationships with Industry and Other Entities (Relevant) e115Appendix 2. Reviewer Relationships with Industry and Other Entities (Comprehensive) e117Appendix 3. Abbreviationse 122PreambleSince 1980, the American College of Cardiology (ACC) and American Heart Association (AHA) have translated scientific evidence into clinical practice guidelines (guidelines) with recommendations to improve cardiovascular health. These guidelines, which are based on systematic methods to evaluate and classify evidence, provide a cornerstone for quality cardiovascular care. The ACC and AHA sponsor the development and publication of guidelines without commercial support, and members of each organization volunteer their time to the writing and review efforts. Guidelines are official policy of the ACC and AHA.Intended UsePractice guidelines provide recommendations applicable to patients with or at risk of developing cardiovascular disease. The focus is on medical practice in the United States, but guidelines developed in collaboration with other organizations may have a global impact. Although guidelines may be used to inform regulatory or payer decisions, their intent is to improve patients’ quality of care and align with patients’ interests. Guidelines are intended to define practices meeting the needs of patients in most, but not all, circumstances and should not replace clinical judgment.Clinical ImplementationGuideline-recommended management is effective only when followed by healthcare providers and patients. Adherence to recommendations can be enhanced by shared decision making between healthcare providers and patients, with patient engagement in selecting interventions based on individual values, preferences, and associated conditions and comorbidities.Methodology and ModernizationThe ACC/AHA Task Force on Clinical Practice Guidelines (Task Force) continuously reviews, updates, and modifies guideline methodology on the basis of published standards from organizations including the Institute of Medicine1,2 and on the basis of internal re-evaluation. Similarly, the presentation and delivery of guidelines are re-evaluated and modified on the basis of evolving technologies and other factors to facilitate optimal dissemination of information at the point of care to healthcare professionals. Given time constraints of busy healthcare providers and the need to limit text, the current guideline format delineates that each recommendation be supported by limited text (ideally, <250 words) and hyperlinks to supportive evidence summary tables. Ongoing efforts to further limit text are underway. Recognizing the importance of cost–value considerations in certain guidelines, when appropriate and feasible, an analysis of the value of a drug, device, or intervention may be performed in accordance with the ACC/AHA methodology.3To ensure that guideline recommendations remain current, new data are reviewed on an ongoing basis, with full guideline revisions commissioned in approximately 6-year cycles. Publication of new, potentially practice-changing study results that are relevant to an existing or new drug, device, or management strategy will prompt evaluation by the Task Force, in consultation with the relevant guideline writing committee, to determine whether a focused update should be commissioned. For additional information and policies regarding guideline development, we encourage readers to consult the ACC/AHA guideline methodology manual4 and other methodology articles.5–8Selection of Writing Committee MembersThe Task Force strives to avoid bias by selecting experts from a broad array of backgrounds. Writing committee members represent different geographic regions, sexes, ethnicities, races, intellectual perspectives/biases, and scopes of clinical practice. The Task Force may also invite organizations and professional societies with related interests and expertise to participate as partners, collaborators, or endorsers.Relationships with Industry and Other EntitiesThe ACC and AHA have rigorous policies and methods to ensure that guidelines are developed without bias or improper influence. The complete relationships with industry and other entities (RWI) policy can be found online. Appendix 1 of the current document lists writing committee members’ relevant RWI. For the purposes of full transparency, writing committee members’ comprehensive disclosure information is available online, as is comprehensive disclosure information for the Task Force.Evidence Review and Evidence Review CommitteesWhen developing recommendations, the writing committee uses evidence-based methodologies that are based on all available data.4–7 Literature searches focus on randomized controlled trials (RCTs) but also include registries, nonrandomized comparative and descriptive studies, case series, cohort studies, systematic reviews, and expert opinion. Only key references are cited.An independent evidence review committee (ERC) is commissioned when there are 1 or more questions deemed of utmost clinical importance that merit formal systematic review. This systematic review will determine which patients are most likely to benefit from a drug, device, or treatment strategy and to what degree. Criteria for commissioning an ERC and formal systematic review include: a) the absence of a current authoritative systematic review; b) the feasibility of defining the benefit and risk in a time frame consistent with the writing of a guideline; c) the relevance to a substantial number of patients; and d) the likelihood that the findings can be translated into actionable recommendations. ERC members may include methodologists, epidemiologists, healthcare providers, and biostatisticians. The recommendations developed by the writing committee on the basis of the systematic review are marked with “SR”.Guideline-Directed Management and TherapyThe term guideline-directed management and therapy (GDMT) encompasses clinical evaluation, diagnostic testing, and pharmacological and procedural treatments. For these and all recommended drug treatment regimens, the reader should confirm the dosage by reviewing product insert material and evaluate the treatment regimen for contraindications and interactions. The recommendations are limited to drugs, devices, and treatments approved for clinical use in the United States.Class of Recommendation and Level of EvidenceThe Class of Recommendation (COR) indicates the strength of the recommendation, encompassing the estimated magnitude and certainty of benefit in proportion to risk. The Level of Evidence (LOE) rates the quality of scientific evidence that supports the intervention on the basis of the type, quantity, and consistency of data from clinical trials and other sources (Table 1).4–6Table 1. ACC/AHA Recommendation System: Applying Class of Recommendation and Level of Evidence to Clinical Strategies, Interventions, Treatments, or Diagnostic Testing in Patient Care* (Updated August 2015)Table 1. ACC/AHA Recommendation System: Applying Class of Recommendation and Level of Evidence to Clinical Strategies, Interventions, Treatments, or Diagnostic Testing in Patient Care* (Updated August 2015)Glenn N. Levine, MD, FACC, FAHAChair, ACC/AHA Task Force on Clinical Practice Guidelines1. Introduction1.1. Methodology and Evidence ReviewThe recommendations listed in this guideline are, whenever possible, evidence based. An initial extensive evidence review, which included literature derived from research involving human subjects, published in English, and indexed in MEDLINE (through PubMed), EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline, was conducted from July to October 2015. Key search words included but were not limited to the following: athletes, autonomic neuropathy, bradycardia, carotid sinus hypersensitivity, carotid sinus syndrome, children, death, dehydration, diagnosis, driving, electrocardiogram, electrophysiological study, epidemiology, falls, implantable loop recorder, mortality, older populations, orthostatic hypotension, pediatrics, psychogenic pseudosyncope, recurrent syncope, risk stratification, supraventricular tachycardia, syncope unit, syncope, tilt-table test, vasovagal syncope, and ventricular arrhythmia. Additional relevant studies published through October 2016, during the guideline writing process, were also considered by the writing committee and added to the evidence tables when appropriate. The finalized evidence tables, included in the Online Data Supplement, summarize the evidence used by the writing committee to formulate recommendations. Lastly, the writing committee reviewed documents related to syncope previously published by the ACC and AHA and other organizations and societies. References selected and published in this document are representative and not all inclusive.An independent ERC was commissioned to perform a systematic review of clinical questions, the results of which were considered by the writing committee for incorporation into this guideline. The systematic review report “Pacing as a Treatment for Reflex-Mediated (Vasovagal, Situational, or Carotid Sinus Hypersensitivity) Syncope” is published in conjunction with this guideline.91.2. Organization of the Writing CommitteeThe writing committee was composed of clinicians with expertise in caring for patients with syncope, including cardiologists, electrophysiologists, an emergency physician, and a pediatric cardiologist. The writing committee included representatives from the ACC, AHA, Heart Rhythm Society (HRS), American Academy of Neurology, American College of Emergency Physicians, and Society for Academic Emergency Medicine.1.3. Document Review and ApprovalThis document was reviewed by 2 official reviewers each nominated by the ACC, AHA, and HRS; 1 reviewer each from the American Academy of Neurology, American College of Emergency Physicians and Society for Academic Emergency Medicine, and Pediatric and Congenital Electrophysiology Society; a lay/patient representative; and 25 individual content reviewers. Reviewers’ RWI information was distributed to the writing committee and is published in this document (Appendix 2).This document was approved for publication by the governing bodies of the ACC, AHA, and HRS and was endorsed by the American College of Emergency Physicians, the Society for Academic Emergency Medicine, and the Pediatric and Congenital Electrophysiology Society.1.4. Scope of the GuidelineThe purpose of this ACC/AHA/HRS guideline is to provide contemporary, accessible, and succinct guidance on the management of adult and pediatric patients with suspected syncope. This guideline is intended to be a practical document for cardiologists, arrhythmia specialists, neurologists, emergency physicians, general internists, geriatric specialists, sports medicine specialists, and other healthcare professionals involved in the care of this very large and heterogeneous population. It is not a review of physiology, pathophysiology, or mechanisms of underlying conditions associated with syncope. The nature of syncope as a symptom required that the writing committee consider numerous conditions for which it can be a symptom, and as much as possible, we have addressed the involvement of syncope only as a presenting symptom. Because of the plausible association of syncope and sudden cardiac death (SCD) in selected populations, this document discusses risk stratification and prevention of SCD when appropriate. The use of the terms selected populations and selected patients in this document is intended to direct healthcare providers to exercise clinical judgment, which is often required during the evaluation and management of patients with syncope. When a recommendation is made to refer a patient to a specialist with expertise for further evaluation, such as in the case of autonomic neurology, adult congenital heart disease (ACHD), older populations, or athletes, the writing committee agreed to make Class IIa recommendations because of the paucity of outcome data. The definition of older populations has been evolving. Age >75 years is used to define older populations or older adults in this document, unless otherwise specified. If a study has defined older adults by a different age cutoff, the relevant age is noted in those specific cases. Finally, the guideline addresses the management of syncope with the patient as a focus, rather than larger aspects of health services, such as syncope management units. The goals of the present guideline are:To define syncope as a symptom, with different causes, in different populations and circumstances.To provide guidance and recommendations on the evaluation and management of patients with suspected syncope in the context of different clinical settings, specific causes, or selected circumstances.To identify key areas in which knowledge is lacking, to foster future collaborative research opportunities and efforts.In developing this guideline, the writing committee reviewed the evidence to support recommendations in the relevant ACC/AHA guidelines noted in Table 2 and affirms the ongoing validity of the related recommendations in the context of syncope, thus obviating the need to repeat existing guideline recommendations in the present guideline when applicable or when appropriate. Table 2 also contains a list of other statements that may be of interest to the reader.Table 2. Relevant ACC/AHA GuidelinesTitleOrganizationPublication Year (Reference)ACC/AHA guideline policy relevant to the management of syncope Supraventricular tachycardiaACC/AHA/HRS201510 Valvular heart diseaseAHA/ACC201411 Device-based therapies for cardiac rhythm abnormalitiesACCF/AHA/HRS201212 Ventricular arrhythmias and sudden cardiac deathACC/AHA/ESC200613*Other ACC/AHA guidelines of interest Hypertension*ACC/AHA– Stable ischemic heart diseaseACC/AHA/ACP/AATS/PCNA/SCAI/STS2012 and 201414,15 Atrial fibrillationAHA/ACC/HRS201416 Non–ST-elevation acute coronary syndromesAHA/ACC201417 Assessment of cardiovascular riskACC/AHA201318 Heart failureACC/AHA201319* Hypertrophic cardiomyopathyACC/AHA201120 Assessment of cardiovascular risk in asymptomatic adultsACC/AHA201021 Adult congenital heart diseaseACC/AHA200822*Other related references Scientific statement on electrocardiographic early repolarizationAHA201623 Expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncopeHRS201524 Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac deathESC2015 and 201325,26 Expert consensus statement on the recognition and management of arrhythmias in adult congenital heart diseasePACES/HRS201427 Expert consensus statement on the use of implantable cardioverter-defibrillator therapy in patients who are not included or not well represented in clinical trialsHRS/ACC/AHA201428 Expert consensus statement on ventricular arrhythmiasEHRA/HRS/APHRS201429 Expert consensus statement on the diagnosis and management of patients with inherited primary arrhythmia syndromesHRS/EHRA/APHRS201325 Guidelines for the diagnosis and management of syncopeESC200930*Revisions to the current documents are being prepared, with publication expected in 2017.AATS indicates American Association for Thoracic Surgeons; ACC, American College of Cardiology; ACCF, American College of Cardiology Foundation; ACP, American College of Physicians; AHA, American Heart Association; APHRS, Asia Pacific Heart Rhythm Society; EHRA, European Heart Rhythm Association; ESC, European Society of Cardiology; HRS, Heart Rhythm Society; PACES, Pediatric and Congenital Electrophysiology Society; PCNA, Preventive Cardiovascular Nurses Association; SCAI, Society for Cardiovascular Angiography and Interventions; and STS, Society of Thoracic Surgery.2. General Principles2.1. Definitions: Terms and ClassificationFor the purpose of this guideline, definitions of syncope and relevant terms are provided in Table 3.Table 3. Relevant Terms and Definitions*TermDefinition/Comments and ReferencesSyncopeA symptom that presents with an abrupt, transient, complete loss of consciousness, associated with inability to maintain postural tone, with rapid and spontaneous recovery. The presumed mechanism is cerebral hypoperfusion.24,30 There should not be clinical features of other nonsyncope causes of loss of consciousness, such as seizure, antecedent head trauma, or apparent loss of consciousness (ie, pseudosyncope).24,30Loss of consciousnessA cognitive state in which one lacks awareness of oneself and one’s situation, with an inability to respond to stimuli.Transient loss of consciousnessSelf-limited loss of consciousness30 can be divided into syncope and nonsyncope conditions. Nonsyncope conditions include but are not limited to seizures, hypoglycemia, metabolic conditions, drug or alcohol intoxication, and concussion due to head trauma. The underlying mechanism of syncope is presumed to be cerebral hypoperfusion, whereas nonsyncope conditions are attributed to different mechanisms.Presyncope (near-syncope)The symptoms before syncope. These symptoms could include extreme lightheadedness; visual sensations, such as “tunnel vision” or “graying out”; and variable degrees of altered consciousness without complete loss of consciousness. Presyncope could progress to syncope, or it could abort without syncope.Unexplained syncope (syncope of undetermined etiology)Syncope for which a cause is undetermined after an initial evaluation that is deemed appropriate by the experienced healthcare provider. The initial evaluation includes but is not limited to a thorough history, physical examination, and ECG.Orthostatic intoleranceA syndrome consisting of a constellation of symptoms that include frequent, recurrent, or persistent lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, exercise intolerance, and fatigue upon standing. These symptoms can occur with or without orthostatic tachycardia, OH, or syncope.24 Individuals with orthostatic intolerance have ≥1 of these symptoms associated with reduced ability to maintain upright posture.Orthostatic tachycardiaA sustained increase in heart rate of ≥30 bpm within 10 min of moving from a recumbent to a quiet (nonexertional) standing position (or ≥40 bpm in individuals 12–19 y of age).24,30,31Orthostatic hypotension (OH)A drop in systolic BP of ≥20 mm Hg or diastolic BP of ≥10 mm Hg with assumption of an upright posture.31 Initial (immediate) OHA transient BP decrease within 15 s after standing, with presyncope or syncope.31,32 Classic OHA sustained reduction of systolic BP of ≥20 mm Hg or diastolic BP of ≥10 mm Hg within 3 min of assuming upright posture.31 Delayed OHA sustained reduction of systolic BP of ≥20 mm Hg (or 30 mm Hg in patients with supine hypertension) or diastolic BP of ≥10 mm Hg that takes >3 min of upright posture to develop. The fall in BP is usually gradual until reaching the threshold.31 Neurogenic OHA subtype of OH that is due to dysfunction of the autonomic nervous system and not solely due to environmental triggers (eg, dehydration or drugs).33,34 Neurogenic OH is due to lesions involving the central or peripheral autonomic nerves.Cardiac (cardiovascular) syncopeSyncope caused by bradycardia, tachycardia, or hypotension due to low cardiac index, blood flow obstruction, vasodilatation, or acute vascular dissection.35,36Noncardiac syncopeSyncope due to noncardiac causes, which include reflex syncope, OH, volume depletion, dehydration, and blood loss.35Reflex (neurally mediated) syncopeSyncope due to a reflex that causes vasodilation, bradycardia, or both.24,30,31 Vasovagal syncope (VVS)The most common form of reflex syncope mediated by the vasovagal reflex. VVS: 1) may occur with upright posture (standing or seated or with exposure to emotional stress, pain, or medical settings; 2) typically is characterized by diaphoresis, warmth, nausea, and pallor; 3) is associated with vasodepressor hypotension and/or inappropriate bradycardia; and 4) is often followed by fatigue. Typical features may be absent in older patients.24 VVS is often preceded by identifiable triggers and/or by a characteristic prodrome. The diagnosis is made primarily on the basis of a thorough history, physical examination, and eyewitness observation, if available. Carotid sinus syndromeReflex syncope associated with carotid sinus hypersensitivity.30 Carotid sinus hypersensitivity is present when a pause ≥3 s and/or a decrease of systolic pressure ≥50 mm Hg occurs upon stimulation of the carotid sinus. It occurs more frequently in older patients. Carotid sinus hypersensitivity can be associated with varying degrees of symptoms. Carotid sinus syndrome is defined when syncope occurs in the presence of carotid sinus hypersensitivity. Situational syncopeReflex syncope associated with a specific action, such as coughing, laughing, swallowing, micturition, or defecation. These syncope events are closely associated with specific physical functions.Postural (orthostatic) tachycardia syndrome (POTS)A clinical syndrome usually characterized by all of the following: 1) frequent symptoms that occur with standing (eg, lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, exercise intolerance, and fatigue); and 2) an increase in heart rate of ≥30 bpm during a positional change from supine to standing (or ≥40 bpm in those 12–19 y of age); and 3) the absence of OH (>20 mm Hg reduction in systolic BP). Symptoms associated with POTS include those that occur with standing (eg, lightheadedness, palpitations); those not associated with particular postures (eg, bloating, nausea, diarrhea, abdominal pain); and those that are systemic (eg, fatigue, sleep disturbance, migraine headaches).37 The standing heart rate is often >120 bpm.31,38–42Psychogenic pseudosyncopeA syndrome of apparent but not true loss of consciousness that may occur in the absence of identifiable cardiac, reflex, neurological, or metabolic causes.30*These definitions are derived from previously published definitions from scientific investigations, guidelines, expert consensus statements, and Webster dictionary after obtaining consensus from the WC.BP indicates blood pressure; ECG, electrocardiogram; OH, orthostatic hypotension; POTS, postural tachycardia syndrome; and VVS, vasovagal syncope.Table 4. Historical Characteristics Associated with Increased Probability of Cardiac and Noncardiac Causes of Syncope60,67–75More Often Associated With Cardiac Causes of Syncope Older age (>60 y) Male sex Presence of known ischemic heart disease, structural heart disease, previous arrhythmias, or reduced ventricular function Brief prodrome, such as palpitations, or sudden loss of consciousness without prodrome Syncope during exertion Syncope in the supine position Low number of syncope episodes (1 or 2) Abnormal cardiac examination Family history of inheritable conditions or premature SCD (<50 y of age) Presence of known congenital heart diseaseMore Often Associated With Noncardiac Causes of Syncope Younger age No known cardiac disease Syncope only in the standing position Positional change from supine or sitting to standing Presence of prodrome: nausea, vomit