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JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY
© 2018 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION,
THE AMERICAN HEART ASSOCIATION, INC., AND THE HEART RHYTHM SOCIETY
PUBLISHED BY ELSEVIER
VOL. 72, NO. 14, 2018
CLINICAL PRACTICE GUIDELINE
2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death
A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society
Developed in Collaboration With the Heart Failure Society of America
Writing Committee Members
Sana M. Al-Khatib, MD, MHS, FACC, FAHA, FHRS, Chair
William G. Stevenson, MD, FACC, FAHA, FHRS,
Vice Chair*
Michael J. Ackerman, MD, PhD*†
William J. Bryant, JD, LLM†
David J. Callans, MD, FACC, FHRS*‡
Anne B. Curtis, MD, FACC, FAHA, FHRS*†
Barbara J. Deal, MD, FACC, FAHA†
Timm Dickfeld, MD, PhD, FHRS*†
Michael E. Field, MD, FACC, FAHA, FHRS†
Gregg C. Fonarow, MD, FACC, FAHA, FHFSA*§
Anne M. Gillis, MD, FHRS*†
Christopher B. Granger, MD, FACC, FAHA*†
Stephen C. Hammill, MD, FACC, FHRS‡
Mark A. Hlatky, MD, FACC, FAHA†
José A. Joglar, MD, FACC, FAHA, FHRS∥
G. Neal Kay, MD†
Daniel D. Matlock, MD, MPH†
Robert J. Myerburg, MD, FACC†
Richard L. Page, MD, FACC, FAHA, FHRS‡
*Writing committee members are required to recuse themselves from voting on sections to which their specific relationships with industry may apply; see Appendix 1 for detailed information. †ACC/AHA Representative. ‡HRS Representative. §ACC/AHA Task Force on Performance Measures Liaison/HFSA Representative. ||ACC/AHA Task Force on Clinical Practice Guidelines Liaison.
This document was approved by the American College of Cardiology Clinical Policy Approval Committee, the American Heart Association Science Advisory and Coordinating Committee, and the Heart Rhythm Society in September 2017, and the American Heart Association Executive Committee in October 2017.
The American College of Cardiology requests that this document be cited as follows: Al-Khatib SM, Stevenson WG, Ackerman MJ, Bryant WJ, Callans DJ, Curtis AB, Deal BJ, Dickfeld T, Field ME, Fonarow GC, Gillis AM, Granger CB, Hammill SC, Hlatky MA, Joglar JA, Kay GN, Matlock DD, Myerburg RJ, Page RL. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2018;72:e91-220.
This article has been copublished in Circulation and HeartRhythm.
Copies: This document is available on the World Wide Web sites of the American College of Cardiology (www.acc.org), the American Heart Association (professional.heart.org), and the Heart Rhythm Society (www.hrsonline.org). For copies of this document, please contact the Elsevier Inc. Reprint Department via fax (212-633-3820) or e-mail (reprints@elsevier.com).
Permissions: Multiple copies, modification, alteration, enhancement, and/or distribution of this document are not permitted without the express permission of the American College of Cardiology. Requests may be completed online via the Elsevier site (http://www.elsevier.com/about/policies/author-agreement/obtaining-permission).
ISSN 0735-1097/$36.00
https://doi.org/10.1016/j.jacc.2017.10.054
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ACC/AHA Task Glenn N. Levine, MD, FACC, FAHA, Chair
Force Members Patrick T. O'Gara, MD, MACC, FAHA, Chair-Elect
Jonathan L. Halperin, MD, FACC, FAHA,
Immediate Past Chair
Sana M. Al-Khatib, MD, MHS, FACC, FAHA
Joshua A. Beckman, MD, MS, FAHA
Kim K. Birtcher, MS, PHARMD, AACC
Biykem Bozkurt, MD, PhD, FACC, FAHA
Ralph G. Brindis, MD, MPH, MACC
Joaquin E. Cigarroa, MD, FACC
Anita Deswal, MD, MPH, FACC, FAHA
Lesley H. Curtis, PhD, FAHA
Lee A. Fleisher, MD, FACC, FAHA
Federico Gentile, MD, FACC
Samuel Gidding, MD, FAHA
Zachary D. Goldberger, MD, MS, FACC, FAHA
Mark A. Hlatky, MD, FACC, FAHA
John Ikonomidis, MD, PhD, FAHA
José A. Joglar, MD, FACC, FAHA
Laura Mauri, MD, MSc, FAHA
Barbara Riegel, PhD, RN, FAHA
Susan J. Pressler, PhD, RN, FAHA
Duminda N. Wijeysundera, MD, PhD
Former Task Force member; current member during the writing effort.
TABLE OF CONTENTS
<table><tr><td>PREAMBLE</td><td>e93</td></tr><tr><td>1. INTRODUCTION</td><td>e95</td></tr><tr><td>1.1. Methodology and Evidence Review</td><td>e95</td></tr><tr><td>1.2. Organization of the Writing Committee</td><td>e95</td></tr><tr><td>1.3. Document Review and Approval</td><td>e95</td></tr><tr><td>1.4. Scope of the Guideline</td><td>e97</td></tr><tr><td>1.5. Abbreviations</td><td>e99</td></tr><tr><td>2. EPIDEMIOLOGY</td><td>e99</td></tr><tr><td>2.1. General Concepts</td><td>e99</td></tr><tr><td>2.1.1. Premature Ventricular Complexes and Nonsustained VT</td><td>e99</td></tr><tr><td>2.1.2. VT and VF During ACS</td><td>e101</td></tr><tr><td>2.1.3. Sustained VT and VF Not Associated With ACS</td><td>e102</td></tr><tr><td>2.2. Sudden Cardiac Death</td><td>e102</td></tr><tr><td>2.2.1. Incidence of SCD</td><td>e102</td></tr><tr><td>2.2.2. Population Subgroups and Risk Prediction</td><td>e102</td></tr><tr><td>3. MECHANISMS OF VA</td><td>e103</td></tr><tr><td>3.1. Cellular Mechanisms and Substrates</td><td>e103</td></tr><tr><td>3.2. Automaticity</td><td>e104</td></tr><tr><td>3.3. Triggered Activity</td><td>e104</td></tr><tr><td>3.4. Reentry</td><td>e104</td></tr><tr><td>4. GENERAL EVALUATION OF PATIENTS WITH DOCUMENTED OR SUSPECTED VA</td><td>e105</td></tr></table>
<table><tr><td>4.1. History and Physical Examination</td><td>e105</td></tr><tr><td>4.2. Noninvasive Evaluation</td><td>e106</td></tr><tr><td>4.2.1. 12-lead ECG and Exercise Testing</td><td>e106</td></tr><tr><td>4.2.2. Ambulatory Electrocardiography</td><td>e107</td></tr><tr><td>4.2.3. Implanted Cardiac Monitors</td><td>e108</td></tr><tr><td>4.2.4. Noninvasive Cardiac Imaging</td><td>e108</td></tr><tr><td>4.2.5. Biomarkers</td><td>e109</td></tr><tr><td>4.2.6. Genetic Considerations in Arrhythmia Syndromes</td><td>e109</td></tr><tr><td>4.3. Invasive Testing</td><td>e110</td></tr><tr><td>4.3.1. Invasive Cardiac Imaging: Cardiac Catheterization or CT Angiography</td><td>e110</td></tr><tr><td>4.3.2. Electrophysiological Study for VA</td><td>e111</td></tr><tr><td colspan="2">5. THERAPIES FOR TREATMENT OR PREVENTION OF VA</td></tr><tr><td>5.1. Medication Therapy</td><td>e111</td></tr><tr><td>5.1.1. Medications With Prominent Sodium Channel Blockade</td><td>e112</td></tr><tr><td>5.1.2. Beta Blockers</td><td>e112</td></tr><tr><td>5.1.3. Amiodarone and Sotalol</td><td>e112</td></tr><tr><td>5.1.4. Calcium Channel Blockers</td><td>e115</td></tr><tr><td>5.1.5. Nonantiarrhythmic Medications and Therapies</td><td>e115</td></tr><tr><td>5.2. Preventing SCD With HF Medications</td><td>e116</td></tr><tr><td>5.3. Defibrillators for Treatment of VA and SCD</td><td>e116</td></tr><tr><td>5.4. Catheter Ablation</td><td>e117</td></tr><tr><td>5.4.1. General Considerations</td><td>e117</td></tr><tr><td>5.4.2. VA in Patients With No Apparent Structural Heart Disease</td><td>e117</td></tr><tr><td>5.4.3. Scar-Related VT</td><td>e117</td></tr></table>
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5.5. Surgery and Revascularization Procedures in Patients With Ischemic Heart Disease ..... e117
5.5.1. Surgery for Arrhythmia Management ..... e118
5.6. Autonomic Modulation ..... e118
6. ACUTE MANAGEMENT OF SPECIFIC VA ..... e119
7. ONGOING MANAGEMENT OF VA AND SCD RISK RELATED TO SPECIFIC DISEASE STATES ..... e123
7.1. Ischemic Heart Disease e123
7.1.1. Secondary Prevention of SCD in Patients With Ischemic Heart Disease e123
7.1.2. Primary Prevention of SCD in Patients With Ischemic Heart Disease ..... e126
7.1.3. Treatment and Prevention of Recurrent VA in Patients With Ischemic Heart Disease . e128
7.2. Nonischemic Cardiomyopathy ..... e131
7.2.1. Secondary Prevention of SCD in Patients With NICM e132
7.2.2. Primary Prevention of SCD in Patients With NICM e133
7.2.3. Treatment of Recurrent VA in Patients With NICM e134
7.3 Arrhythmogenic Right Ventricular Cardiomyopathy e135
7.4. Hypertrophic Cardiomyopathy e139
7.5. Myocarditis e142
7.6. Cardiac Sarcoidosis e143
7.6.1. Other Infiltrative Cardiomyopathies . . e145
7.7. Heart Failure e146
7.7.1. HF With Reduced Ejection Fraction . . . e146
7.7.2. HF With Preserved Ejection Fraction . . e146
7.7.3. Left Ventricular Assist Device . . e147
7.7.4. ICD Use After Heart Transplantation . . e147
7.8. Neuromuscular Disorders e148
7.9. Cardiac Channelopathies e149
7.9.1. Specific Cardiac Channelopathy Syndromes e150
8. VA IN THE STRUCTURALLY NORMAL HEART . . e160
8.1. Outflow Tract and Atrioventricular Annular VA . e161
8.2. Papillary Muscle VA e162
8.3. Interfascicular Reentrant VT (Belhassen Tachycardia) e162
8.4. Idiopathic Polymorphic VT/VF e163
9. PVC-INDUCED CARDIOMYOPATHY e164
10. VA AND SCD RELATED TO SPECIFIC POPULATIONS e165
10.1. Athletes e165
10.2. Pregnancy e166
10.3. Older Patients With Comorbidities ..... e166
10.4. Chronic Kidney Disease e167
10.5. Valvular Heart Disease e167
10.6. Sex-Related Differences in the Risk of SCD . e168
10.7. Medication-Induced Arrhythmias e168
10.8. Adult Congenital Heart Disease e170
11. DEFIBRILLATORS OTHER THAN
TRANSVENOUS ICDs e175
11.1. Subcutaneous Implantable Cardioverter-Defibrillator e175
11.2. Wearable Cardioverter-Defibrillator e176
11.3. Automated External Defibrillator e177
12. SPECIAL CONSIDERATIONS FOR CATHETER ABLATION e177
13. POSTMORTEM EVALUATION OF SCD e178
14. TERMINAL CARE e179
15. SHARED DECISION-MAKING e180
16. COST AND VALUE CONSIDERATIONS e181
17. QUALITY OF LIFE e182
18. EVIDENCE GAPS AND FUTURE RESEARCH NEEDS e182
APPENDIX 1
Author Relationships With Industry and Other Entities (Relevant) e214
APPENDIX 2
Reviewer Relationships With Industry and Other Entities (Comprehensive) e216
PREAMBLE
Since 1980, the American College of Cardiology (ACC) and American Heart Association (AHA) have translated scientific evidence into clinical practice 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
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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 Use
Practice 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 Implementation
Guideline-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 Modernization
The 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 Medicine (P-1,P-2) and on the basis of internal reevaluation. Similarly, the presentation and delivery of guidelines are reevaluated 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.
Toward this goal, this guideline heralds the introduction of an evolved format of presenting guideline recommendations and associated text called the “modular knowledge chunk format”. Each modular “chunk” includes a table of related recommendations, a brief synopsis, recommendation-specific supportive text and, when appropriate, flow diagrams or additional tables. References are provided within the modular chunk itself to facilitate quick review. This format also will facilitate seamless updating of guidelines with focused updates as new evidence is published, and content tagging for rapid electronic retrieval of related recommendations on a topic of interest. This evolved format was instituted when this guideline was near completion; therefore, the current document represents a transitional formatting that best suits the text as written. Future guidelines will fully implement this format, including provisions for limiting the amount of text in a guideline.
Recognizing the importance of cost-value considerations in certain guidelines, when appropriate and feasible, an analysis of the value of a medication, device, or intervention may be performed in accordance with the ACC/AHA methodology (P-3).
To 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 medication, 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 manual (P-4) and other methodology articles (P-5–P-8).
Selection of Writing Committee Members
The 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 Entities
The 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 the comprehensive disclosure information for the Task Force.
Evidence Review and Evidence Review Committees
When developing recommendations, the writing committee uses evidence-based methodologies that are based on all available data (P-4–P-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 \( \geq \) 1 questions deemed of utmost clinical importance that merit formal systematic review. This systematic review will strive to determine which patients are most likely to benefit from a test, medication, device, or treatment strategy and to what
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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. When a formal systematic review has been commissioned, the recommendations developed by the writing committee on the basis of the systematic review are marked with “SR”.
Guideline-Directed Management and Therapy
The term guideline-directed management and therapy (GDMT) encompasses clinical evaluation, diagnostic testing, and pharmacological and procedural treatments. For these and all recommended medication 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 medications, devices, and treatments approved for clinical use in the United States.
Class of Recommendation and Level of Evidence
The 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) (P-4, P-6, P-8).
Glenn N. Levine, MD, FACC, FAHA
Chair, ACC/AHA Task Force on Clinical Practice Guidelines
1. INTRODUCTION
1.1. Methodology and Evidence Review
The recommendations listed in this clinical practice 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 April 2016 to September 2016. Key search words included, but were not limited, to the following: sudden cardiac death, ventricular tachycardia, ventricular fibrillation, premature ventricular contractions, implantable cardioverter-defibrillator, subcutaneous implantable cardioverter-defibrillator, wearable cardioverter-defibrillator, and catheter ablation. Additional relevant studies published through March 2017, during the
guideline writing process, were also considered by the writing committee, and added to the evidence tables when appropriate. The final evidence tables are included in the Online Data Supplement and summarize the evidence used by the writing committee to formulate recommendations. Additionally, the writing committee reviewed documents related to ventricular arrhythmias (VA) and sudden cardiac death (SCD) previously published by the ACC, AHA, and the Heart Rhythm Society (HRS). References selected and published in this document are representative and not all-inclusive.
As noted in the Preamble, an independent ERC was commissioned to perform a formal systematic review of 2 important clinical questions for which clear literature and prior guideline consensus were felt to be lacking or limited (Table 2). The results of the ERC review were considered by the writing committee for incorporation into this guideline. Concurrent with this process, writing committee members evaluated other published data relevant to the guideline. The findings of the ERC and the writing committee members were formally presented and discussed, then guideline recommendations were developed. The “Systematic Review for the 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death” is published in conjunction with this guideline (S1.4-1).
The ACC and AHA have acknowledged the importance of value in health care and have called for eventual development of a Level of Value for clinical practice recommendations (S1.4-2). Available cost-effectiveness data were determined to be sufficient to support 2 specific recommendations in this guideline (see Sections 7.1.1 and 7.1.2). As a result, a Level of Value was assigned to those 2 recommendations on the basis of the “ACC/AHA Statement on Cost/Value Methodology in Clinical Practice Guidelines and Performance Measures,” as shown in Table 3 (S1.4-2). Available quality of life (QoL) data were deemed to be insufficient to support specific recommendations in this guideline.
1.2. Organization of the Writing Committee
The writing committee consisted of cardiac electrophysiologists (including those specialized in pediatrics), general adult and pediatric cardiologists (including those specialized in critical care and acute coronary syndromes [ACS], genetic cardiology, heart failure, and cost-effectiveness analyses), a geriatrician with expertise in terminal care and shared decision-making, and a lay representative, in addition to representatives from the ACC, AHA, HRS, and the Heart Failure Society of America (HFSA).
1.3. Document Review and Approval
This document was reviewed by 2 official reviewers nominated by the ACC, AHA, and HRS; 1 official lay
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TABLE 1
Applying Class of Recommendation and Level of Evidence to Clinical Strategies, Interventions, Treatments, or Diagnostic Testing in Patient Care* (Updated August 2015)
CLASS (STRENGTH) OF RECOMMENDATION
CLASS I (STRONG)
Benefit >>> Risk
Suggested phrases for writing recommendations:
■ Is recommended
■ Is indicated/useful/effective/beneficial
■ Should be performed/administered/other
■ Comparative-Effectiveness Phrases†:
- Treatment/strategy A is recommended/indicated in preference to treatment B
- Treatment A should be chosen over treatment B
CLASS IIa (MODERATE)
Benefit >> Risk
Suggested phrases for writing recommendations:
■ Is reasonable
■ Can be useful/effective/beneficial
■ Comparative-Effectiveness Phrases†:
- Treatment/strategy A is probably recommended/indicated in preference to treatment B
- It is reasonable to choose treatment A over treatment B
CLASS IIb (WEAK)
Benefit ≥ Risk
Suggested phrases for writing recommendations:
■ May/might be reasonable
■ May/might be considered
■ Usefulness/effectiveness is unknown/unclear/uncertain or not well established
CLASS III: No Benefit (MODERATE)
(Generally, LOE A or B use only)
Benefit = Risk
Suggested phrases for writing recommendations:
■ Is not recommended
■ Is not indicated/useful/effective/beneficial
■ Should not be performed/administered/other
CLASS III: Harm (STRONG)
Risk > Benefit
Suggested phrases for writing recommendations:
■ Potentially harmful
■ Causes harm
■ Associated with excess morbidity/mortality
■ Should not be performed/administered/other
LEVEL (QUALITY) OF EVIDENCE‡
LEVEL A
■ High-quality evidence‡ from more than 1 RCT
■ Meta-analyses of high-quality RCTs
■ One or more RCTs corroborated by high-quality registry studies
LEVEL B-R
(Randomized)
■ Moderate-quality evidence‡ from 1 or more RCTs
■ Meta-analyses of moderate-quality RCTs
LEVEL B-NR
(Nonrandomized)
■ Moderate-quality evidence‡ from 1 or more well-designed, well-executed nonrandomized studies, observational studies, or registry studies
■ Meta-analyses of such studies
LEVEL C-LD
(Limited Data)
■ Randomized or nonrandomized observational or registry studies with limitations of design or execution
■ Meta-analyses of such studies
■ Physiological or mechanistic studies in human subjects
LEVEL C-EO
(Expert Opinion)
Consensus of expert opinion based on clinical experience
COR and LOE are determined independently (any COR may be paired with any LOE).
A recommendation with LOE C does not imply that the recommendation is weak. Many important clinical questions addressed in guidelines do not lend themselves to clinical trials. Although RCTs are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective.
* The outcome or result of the intervention should be specified (an improved clinical outcome or increased diagnostic accuracy or incremental prognostic information).
† For comparative-effectiveness recommendations (COR I and IIa; LOE A and B only), studies that support the use of comparator verbs should involve direct comparisons of the treatments or strategies being evaluated.
‡ The method of assessing quality is evolving, including the application of standardized, widely used, and preferably validated evidence grading tools; and for systematic reviews, the incorporation of an Evidence Review Committee.
COR indicates Class of Recommendation; EQ, expert opinion; LD, limited data; LOE, Level of Evidence; NR, nonrandomized; R, randomized; and RCT, randomized controlled trial.
TABLE 2 Systematic Review Questions on SCD Prevention
<table><tr><td>Question Number</td><td>Question</td><td>Section Number</td></tr><tr><td>1</td><td>For asymptomatic patients with Brugada syndrome, what is the association between an abnormal programmed ventricular stimulation study and SCD and other arrhythmia endpoints?</td><td>7.9.1.3</td></tr><tr><td>2</td><td>What is the impact of ICD implantation for primary prevention in older patients and patients with significant comorbidities?</td><td>10.3</td></tr></table>
ICD indicates implantable cardioverter-defibrillator; and SCD, sudden cardiac death.
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TABLE 3 Proposed Integration of Level of Value Into Clinical Practice Guideline Recommendations*
Level of Value
High value: Better outcomes at lower cost or ICER <$50,000 per QALY gained
Intermediate value: $50,000 to <$150,000 per QALY gained
Low value: ≥$150,000 per QALY gained
Uncertain value: Value examined but data are insufficient to draw a conclusion because of no studies, low-quality studies, conflicting studies, or prior studies that are no longer relevant
Not assessed: Value not assessed by the writing committee
Proposed abbreviations for each value recommendation:
Level of Value: H to indicate high value; I, intermediate value; L, low value; U, uncertain value; and NA, value not assessed
*Dollar amounts used in this table are based on U.S. GDP data from 2012 and were obtained from WHO-CHOICE Cost-Effectiveness Thresholds (S1.4-3).
GDP indicates gross domestic product; ICER, incremental cost-effectiveness ratio; QALY, quality-adjusted life-years; and WHO-CHOICE, World Health Organization Choosing Interventions that are Cost-Effective.
Reproduced from Anderson, et al. (S1.4-2).
reviewer nominated by the AHA; 1 organizational reviewer nominated by the HFSA; and 28 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, the AHA, and the HRS; and endorsed by the HFSA.
1.4. Scope of the Guideline
The purpose of this AHA/ACC/HRS document is to provide a contemporary guideline for the management of adults who have VA or who are at risk for SCD, including diseases and syndromes associated with a risk of SCD from VA. This guideline supersedes the “ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death” (S1.4-4). It also supersedes some sections of the “ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities” (S1.4-5), specifically those sections on indications for the implantable cardioverter-defibrillator (ICD); and, it updates the SCD prevention recommendations in the “2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy” (S1.4-6). Some recommendations from the earlier guidelines have been updated as warranted by new evidence or a better understanding of existing evidence, and irrelevant or overlapping recommendations were deleted or modified.
In the current guideline, sudden cardiac arrest (SCA) is defined as the “sudden cessation of cardiac activity so that the victim becomes unresponsive, with no normal breathing and no signs of circulation” (S1.4-7). If corrective measures are not taken rapidly, this condition progresses to SCD. Cardiac arrest is used to signify an event that can be reversed, usually by cardiopulmonary resuscitation (CPR), administration of medications and/or defibrillation or cardioversion. SCA and SCD can result from causes other than VA, such as bradyarrhythmias, electromechanical dissociation, pulmonary embolism, intracranial hemorrhage, and aortic dissection; however,
the scope of this document includes only SCA and SCD due to VA.
This guideline includes indications for ICDs for the treatment of VA and prevention of SCD, but it does not delve into details on individual device selection and programming, including considerations relevant to cardiac resynchronization therapy (CRT), bradycardia pacing, and hemodynamic monitoring. These important aspects of ICD management have been covered in an HRS expert consensus statement (S1.4-8). An AHA science advisory discusses the use of wearable cardioverter-defibrillators (S1.4-9). The findings of that document were reviewed; however, recommendations on this topic were developed independently of that document. This guideline includes indications for catheter ablation of VA, but does not provide recommendations on specific techniques or ablation technologies, which were beyond the scope of this document.
Recommendations for interventional therapies, including ablation and the implantation of devices, apply only if these therapies can be implemented by qualified clinicians, such that outcomes consistent with published literature are a reasonable expectation. The writing committee agreed that a high degree of expertise was particularly important for performance of catheter ablation of VA, and this point is further emphasized in relevant sections. In addition, all recommendations related to ICDs require that meaningful survival of >1 year is expected; meaningful survival means that a patient has a reasonable quality of life and functional status.
Although this document is aimed at the adult population ( \( \geq \) 18 years of age) and offers no specific recommendations for pediatric patients, some of the literature on pediatric patients was examined. In some cases, the data from pediatric patients beyond infancy helped to inform this guideline.
The writing committee recognized the importance of shared decision-making and patient-centered care and, when possible, it endeavored to formulate recommendations relevant to these important concepts. The
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importance of a shared decision-making process in which the patient, family, and clinicians discuss risks and benefits of diagnostic and treatment options and consider the patients' personal preferences is emphasized (see Section 15).
In developing this guideline, the writing committee reviewed previously published guidelines and related statements. Table 4 contains a list of guidelines and statements deemed pertinent to this writing effort and is intended for use as a resource, obviating repetition of existing guideline recommendations.
During final production review of the guidelines, several recommendations were refined to better reflect
the data and current recommended medical practice. These refinements were reviewed and approved by the writing committee, the Task Force, and ACC, AHA, and HRS organizational leadership. These recommendations were:
• Section 7.1.1., recommendation 1
• Section 7.1.3., recommendation 2
• Section 7.2.1., recommendation 1
• Section 7.9.1.4., recommendation 2
• Section 10.8., recommendation 6
Readers should refer to these sections for the updated text.
TABLE 4 Associated Guidelines and Statements
<table><tr><td>Title</td><td>Organization</td><td>Publication Year (Reference)</td></tr><tr><td colspan="3">Guidelines</td></tr><tr><td>Syncope</td><td>ACC/AHA/HRS</td><td>2017 (S1.4-10)</td></tr><tr><td>Heart failure</td><td>ACCF/AHA</td><td>2017 (S1.4-11) 2016 (S1.4-12), and 2013 (S1.4-13)</td></tr><tr><td>Valvular heart disease</td><td>AHA/ACC</td><td>2017 (S1.4-14) and 2014 (S1.4-15)</td></tr><tr><td>Supraventricular tachycardia</td><td>ACC/AHA/HRS</td><td>2015 (S1.4-16)</td></tr><tr><td>Ventricular arrhythmias and the prevention of sudden cardiac death</td><td>ESC</td><td>2015 (S1.4-17)</td></tr><tr><td>Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care</td><td>AHA</td><td>2015 (S1.4-18)</td></tr><tr><td>Atrial fibrillation</td><td>AHA/ACC/HRS</td><td>2014 (S1.4-19)</td></tr><tr><td>Non-ST-elevation acute coronary syndromes</td><td>AHA/ACC</td><td>2014 (S1.4-20)</td></tr><tr><td>Assessment of cardiovascular risk</td><td>ACC/AHA</td><td>2013 (S1.4-21)</td></tr><tr><td>ST-elevation myocardial infarction</td><td>ACCF/AHA</td><td>2013 (S1.4-22)</td></tr><tr><td>Acute myocardial infarction in patients presenting with ST-segment elevation</td><td>ESC</td><td>2012 (S1.4-23)</td></tr><tr><td>Device-based therapies for cardiac rhythm abnormalities</td><td>ACCF/AHA/HRS</td><td>2012 (S1.4-24)</td></tr><tr><td>Coronary artery bypass graft surgery</td><td>ACCF/AHA</td><td>2011 (S1.4-25)</td></tr><tr><td>Hypertrophic cardiomyopathy</td><td>ACCF/AHA</td><td>2011 (S1.4-6)</td></tr><tr><td>Percutaneous coronary intervention</td><td>ACCF/AHA/SCAI</td><td>2011 (S1.4-26)</td></tr><tr><td>Secondary prevention and risk reduction therapy for patients with coronary and other atherosclerotic vascular disease</td><td>AHA/ACCF</td><td>2011 (S1.4-27)</td></tr><tr><td colspan="3">Scientific Statements</td></tr><tr><td>Wearable cardioverter-defibrillator therapy for the prevention of sudden cardiac death</td><td>AHA</td><td>2016 (S1.4-9)</td></tr><tr><td>Optimal implantable cardioverter defibrillator programming and testing</td><td>HRS/EHRA/APHRS/SOLAECE</td><td>2016 (S1.4-8)</td></tr><tr><td>Treatment of cardiac arrest: current status and future directions: strategies to improve cardiac arrest survival</td><td>IOM</td><td>2015 (S1.4-28)</td></tr><tr><td>Eligibility and disqualification recommendations for competitive athletes with cardiovascular abnormalities</td><td>ACC/AHA</td><td>2015 (S1.4-29)</td></tr><tr><td>Ventricular arrhythmias</td><td>EHRA/HRS/APHRS</td><td>2014 (S1.4-30)</td></tr><tr><td>Arrhythmias in adult congenital heart disease</td><td>PACES/HRS</td><td>2014 (S1.4-31)</td></tr><tr><td>Implantable cardioverter-defibrillator therapy in patients who are not included or not well represented in clinical trials</td><td>HRS/ACC/AHA</td><td>2014 (S1.4-32)</td></tr><tr><td>Cardiac sarcoidosis</td><td>HRS</td><td>2014 (S1.4-33)</td></tr><tr><td>Inherited primary arrhythmia syndromes</td><td>HRS/EHRA/APHRS</td><td>2013 (S1.4-34)</td></tr></table>
ACC indicates American College of Cardiology; ACCF, American College of Cardiology Foundation; 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; SCAI, Society for Cardiovascular Angiography and Interventions; and, SOLAECE, Sociedad Latinoamericana de Estimulación Cardiaca y Electrofisiologia.
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1.5. Abbreviations
<table><tr><td>Abbreviation</td><td>Meaning/Phrase</td></tr><tr><td>ACS</td><td>acute coronary syndromes</td></tr><tr><td>AED</td><td>automated external defibrillator</td></tr><tr><td>AMI</td><td>acute myocardial infarction</td></tr><tr><td>BNP</td><td>B-type natriuretic peptide</td></tr><tr><td>CABG</td><td>coronary artery bypass graft</td></tr><tr><td>CKD</td><td>chronic kidney disease</td></tr><tr><td>CPR</td><td>cardiopulmonary resuscitation</td></tr><tr><td>CRT</td><td>cardiac resynchronization therapy</td></tr><tr><td>CT</td><td>computed tomography</td></tr><tr><td>ECG</td><td>electrocardiogram</td></tr><tr><td>ERC</td><td>evidence review committee</td></tr><tr><td>ESRD</td><td>end-stage renal disease</td></tr><tr><td>GDMT</td><td>guideline-directed management and therapy</td></tr><tr><td>HCM</td><td>hypertrophic cardiomyopathy</td></tr><tr><td>HF</td><td>heart failure</td></tr><tr><td>HFpEF</td><td>heart failure with preserved ejection fraction</td></tr><tr><td>HFrEF</td><td>heart failure with reduced ejection fraction</td></tr><tr><td>ICD</td><td>implantable cardioverter-defibrillator</td></tr><tr><td>LV</td><td>left ventricular</td></tr><tr><td>LVAD</td><td>left ventricular assist device</td></tr><tr><td>LVEF</td><td>left ventricular ejection fraction</td></tr><tr><td>MI</td><td>myocardial infarction</td></tr><tr><td>NICM</td><td>nonischemic cardiomyopathy</td></tr><tr><td>NSVT</td><td>nonsustained ventricular tachycardia</td></tr><tr><td>PET</td><td>positron emission tomography</td></tr><tr><td>PCI</td><td>percutaneous coronary intervention</td></tr><tr><td>PVC</td><td>premature ventricular complex</td></tr><tr><td>QoL</td><td>quality of life</td></tr><tr><td>RCT</td><td>randomized controlled trial</td></tr><tr><td>RV</td><td>right ventricular</td></tr><tr><td>RVOT</td><td>right ventricular outflow tract</td></tr><tr><td>SCA</td><td>sudden cardiac arrest</td></tr><tr><td>SCD</td><td>sudden cardiac death</td></tr><tr><td>SVT</td><td>supraventricular tachycardia</td></tr><tr><td>TOF</td><td>tetralogy of Fallot</td></tr><tr><td>VA</td><td>ventricular arrhythmia</td></tr><tr><td>VT</td><td>ventricular tachycardia</td></tr></table>
2. EPIDEMIOLOGY
2.1. General Concepts
Table 5
VA include a spectrum that ranges from premature ventricular complex (PVC) to ventricular fibrillation (VF), with a clinical presentation that ranges from a total lack of symptoms to cardiac arrest. Most life-threatening VA are associated with ischemic heart disease, particularly in older patients (S2.2.2-1). The risks of VA and SCD vary in
specific populations with different underlying cardiac conditions, and with specific family history and genetic variants, and this variation has important implications for studying and applying therapies.
2.1.1. Premature Ventricular Complexes and Nonsustained VT
PVCs are common and increase in frequency with age. Although PVCs were found in a healthy military population in only 0.6% of those <20 years of age and 2.7% of those >50 years of age (S2.2.2-5) on 12-lead ECGs, longer term monitoring shows PVCs in about 50% of all people with or without heart disease (S2.2.2-6). The presence of PVCs on 2 minutes of monitoring of middle-aged patients in the ARIC (Atherosclerosis Risk In Communities) study was associated with increased risk of both ischemic heart disease events and mortality, with or without prevalent ischemic heart disease (S2.2.2-7,S2.2.2-8). In the general population, frequent PVCs, which are defined as the presence of at least 1 PVC on a 12-lead ECG or >30 PVCs per hour, are associated with increased cardiovascular risk and increased mortality (S2.2.2-9). In a study from Taiwan of patients without sustained VT or structural heart disease who had 24-hour Holter monitoring for clinical evaluation, multifocal PVCs were associated with increased risk of death and nonfatal cardiovascular adverse outcomes (S2.2.2-10). In the same population, nonsustained ventricular tachycardia (NSVT) was independently associated with increased risk of death and other cardiovascular adverse outcomes, including stroke (S2.2.2-11). An association of PVCs with increased risk of stroke was also seen in the ARIC population (S2.2.2-8).
Because some studies have shown an association of PVCs with adverse outcomes, the detection of PVCs, particularly if multifocal and frequent, is generally considered a risk factor for adverse cardiovascular outcomes, and such patients are generally evaluated to ensure they do not have underlying conditions (e.g., ischemic heart disease, left ventricular [LV] dysfunction) that warrant further treatment to reduce risk. PVC and NSVT in patients with cardiovascular disease are common and have been associated with adverse outcomes (S2.2.2-12,S2.2.2-13). In CAST (Cardiac Arrhythmia Suppression Trials), treatment of patients with post-myocardial infarction (MI) who took antiarrhythmic medications (e.g., flecainide, encainide, moricizine) increased the risk of death despite suppression of VA (S2.2.2-14,S2.2.2-15). Treatment of PVCs with antiarrhythmic medications has not been shown to reduce mortality and, in the post-MI population, treatment with class I sodium channel-blocking medications (e.g., quinidine, flecainide) increases the risk of death (S2.2.2-15,S2.2.2-16). Likewise, in patients with a reduced LVEF class I, sodium channel-blocking medications and d-sotalol increase the risk of death (S2.2.2-16,S2.2.2-17). Beta blockers,
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TABLE 5 Table of Definitions of Commonly Used Terms in this Document
<table><tr><td>Term</td><td>Definition or Description</td></tr><tr><td>Ventricular tachycardia(S2.2.2-2)</td><td>Cardiac arrhythmia of ≥3 consecutive complexes originating in the ventricles at a rate >100 bpm (cycle length: <600 ms). Types of VT:■ Sustained: VT >30 s or requiring termination due to hemodynamic compromise in <30 s.■ Nonsustained/unsustained: ≥3 beats, terminating spontaneously.■ Monomorphic: Stable single QRS morphology from beat to beat.■ Polymorphic: Changing or multiform QRS morphology from beat to beat.■ Bidirectional: VT with a beat-to-beat alternation in the QRS frontal plane axis, often seen in the setting of digitalis toxicity or catecholaminergic polymorphic VT</td></tr><tr><td></td><td><img></td></tr><tr><td></td><td>Polymorphic VT</td></tr><tr><td></td><td><img></td></tr><tr><td></td><td>Bidirectional VT</td></tr><tr><td></td><td><img></td></tr><tr><td>Torsades de pointes(S2.2.2-2)</td><td>Torsades de pointes is polymorphic VT that occurs in the setting of a long-QT interval and is characterized by a waxing and waning QRS amplitude. It often has a long-short initiating sequence with a long coupling interval to the first VT beat and may present with salvos of NSVT. The twisting of the points, although characteristic, may not always be seen, especially if the episode is nonsustained or if only a limited number of leads are available. Torsades de pointes can result from bradycardia including high-grade AV block that leads to a long-short sequence initiating torsades de pointes.</td></tr><tr><td></td><td><img></td></tr><tr><td>Ventricular flutter(S2.2.2-2)</td><td>A regular VA ≈300 bpm (cycle length: 200 ms) with a sinusoidal, monomorphic appearance; no isoelectric interval between successive QRS complexes.</td></tr><tr><td></td><td><img></td></tr><tr><td>Ventricular fibrillation(S2.2.2-2)</td><td>Rapid, grossly irregular electrical activity with marked variability in electrocardiographic waveform, ventricular rate usually >300 bpm (cycle length: <200 ms).</td></tr></table>
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TABLE 5 Continued
<table><tr><td>Term</td><td>Definition or Description</td></tr><tr><td>Sudden cardiac arrest (S2.2.2-2)</td><td>SCA is the sudden cessation of cardiac activity such that the victim becomes unresponsive, with either persisting gasping respirations or absence of any respiratory movements, and no signs of circulation as manifest by the absence of a perceptible pulse. An arrest is presumed to be of cardiac etiology unless it is known or likely to have been caused by trauma, drowning, respiratory failure or asphyxia, electrocution, drug overdose, or any other noncardiac cause.</td></tr><tr><td>Sudden cardiac death (S2.2.2-2)</td><td>Sudden and unexpected death occurring within an hour of the onset of symptoms, or occurring in patients found dead within 24 h of being asymptomatic and presumably due to a cardiac arrhythmia or hemodynamic catastrophe.</td></tr><tr><td>VT/VF storm (S2.2.2-3)</td><td>VT/VF storm (electrical storm or arrhythmic storm) refers to a state of cardiac electrical instability that is defined by ≥3 episodes of sustained VT, VF, or appropriate shocks from an ICD within 24 h.</td></tr><tr><td>Primary prevention ICD (S2.2.2-2)</td><td>ICD placement with the intention of preventing SCD in a patient who has not had sustained VT or SCA but who is at an increased risk for these events.</td></tr><tr><td>Secondary prevention ICD (S2.2.2-2)</td><td>ICD placement in a patient with prior SCA, sustained VT, or syncope caused by VA.</td></tr><tr><td>Structural heart disease*</td><td>This term encompasses IHD, all types of cardiomyopathy, valvular heart disease, and adult congenital heart disease.</td></tr><tr><td>Cardiac channelopathy (S2.2.2-4)</td><td>Arrhythmogenic disease due to a genetic abnormality that results in dysfunction of a cardiac ion channel (e.g., long-QT syndrome, catecholaminergic polymorphic VT).</td></tr></table>
*The definition of this term may differ across publications. Refer to the entry for the definition used in this document.
AV indicates atrioventricular; ICD, implantable cardioverter-defibrillator; IHD, ischemic heart disease; NSVT, nonsustained ventricular tachycardia; SCA, sudden cardiac arrest; SCD, sudden cardiac death; VA, ventricular arrhythmia; VF, ventricular fibrillation; and VT, ventricular tachycardia.
nondihydropyridines calcium channel blockers, and some antiarrhythmic medications may relieve symptoms of palpitations (S2.2.2-18).
PVCs that occur during an exercise test are associated with a higher risk of death (S2.2.2-19). In 1 study, PVCs that occur during recovery are a stronger predictor of death than PVCs occurring only during exercise (S2.2.2-20). However, PVCs are common in trained athletes who have palpitations, in whom there does not appear to be increased risk of death based on studies of small numbers of athletes, at least in those without other cardiovascular abnormalities (S2.2.2-21,S2.2.2-22). Complex PVCs may not represent a benign finding in endurance athletes. An electrophysiological study may be needed to assess patients' arrhythmogenic risk (S2.2.2-22). Very frequent PVCs, >10,000 to 20,000 a day, can be associated with depressed LV function in some patients that is reversible with control of the PVCs, and has been referred to as PVC-induced cardiomyopathy (S2.2.2-23,S2.2.2-24). (See also Section 8.5. PVC-Induced Cardiomyopathy.) Very rarely, idiopathic PVCs from the outflow tract may trigger malignant VA in patients without structural heart disease (S2.2.2-25,S2.2.2-26).
2.1.2. VT and VF During ACS
Approximately half of patients with out-of-hospital cardiac arrest with the first rhythm identified as VF and who survive to hospital admission have evidence of acute MI (AMI) (S2.2.2-27). Of all out-of-hospital cardiac arrests, >50% will have significant coronary artery lesions on acute coronary angiography (S2.2.2-27). Of patients hospitalized with AMI, 5% to 10% have VF or sustained VT prior to hospital presentation, and another 5% will have VF or sustained VT after hospital arrival, most within 48
hours of admission. A study of patients with non-ST-elevation ACS who underwent cardiac catheterization within 48 hours found VT/VF in 7.6% of patients, with 60% of those events within 48 hours of admission (S2.2.2-28). Accelerated idioventricular rhythm is a common arrhythmia in patients with acute MI, including patients with ST-segment elevation MI undergoing primary percutaneous coronary intervention (PCI). Accelerated idioventricular rhythm is more closely related to the extent of infarction than to reperfusion itself (S2.2.2-29).
Sustained VA that occurs in the setting of an ACS is more often polymorphic VT or VF than monomorphic VT. Risk factors for VT/VF include prior history of hypertension, prior MI, ST-segment changes at presentation, and chronic obstructive pulmonary disease (S2.2.2-30). A nationwide Danish study found that 11.6% of patients with ST-segment elevation MI who underwent PCI had VF prior to the PCI, and that VF was associated with alcohol consumption, preinfarction angina, anterior infarct location, and complete coronary occlusion at the time of coronary angiography (S2.2.2-31). In a select group of patients undergoing primary PCI in a clinical trial, 5.7% developed sustained VT or VF, with two thirds of these events occurring prior to the end of the catheterization, and 90% within 48 hours from the procedure. VT or VF after primary PCI was associated with lower blood pressure, higher heart rate, poor coronary flow at the end of the procedure, and incomplete resolution of ST elevation (S2.2.2-32). Importantly, and in contrast to some earlier studies, VT or VF at any time was associated with a substantially higher risk of death within 90 days. Late VT or VF (after 48 hours of hospital presentation) was associated with a higher risk of death than early VT or VF (within 48 hours of hospital presentation) (S2.2.2-33).
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2.1.3. Sustained VT and VF Not Associated With ACS
Patients with structural heart disease are at an increased risk for sustained VT and VF. Sustained VT that is not associated with an ACS is often monomorphic as it is usually due to scar-related reentry, but it may degenerate to VF (S2.2.2-34). The risk and predictors of VT in patients with structural heart disease depend on the type, severity, and duration of structural heart disease, increasing with the severity of ventricular dysfunction and the presence of symptomatic HF. Monomorphic VT occurring in the absence of structural heart disease is commonly referred to as idiopathic VT and is often due to an automatic focus in a characteristic location, giving rise to typical electrocardiographic appearances. Polymorphic VT and VF occurring in the absence of structural heart disease are rare and may be due to a cardiac channelopathy (S2.2.2-35,S2.2.2-36), medication-induced long QT syndrome (S2.2.2-36), or they may be idiopathic (S2.2.2-37,S2.2.2-38).
2.2. Sudden Cardiac Death
2.2.1. Incidence of SCD
SCA and its most common consequence, SCD, constitute major public health problems, accounting for approximately 50% of all cardiovascular deaths (S2.2.2-1,S2.2.2-39), with at least 25% being first symptomatic cardiac events (S2.2.2-1,S2.2.2-40,S2.2.2-41). In addition, analyses of the magnitude of SCD are limited, in part because of the broad range of estimates of the risk based on different epidemiological methods (S2.2.2-42). During the past 20 to 30 years, SCD accounted for approximately 230,000 to 350,000 deaths per year in the United States, with a range of <170,000 to >450,000, depending on epidemiological methods, data sources, and inclusion criteria (S2.2.2-41,S2.2.2-43). The lowest of these extremes came from national extrapolation of data from specific local programs, while the highest rates included noncardiac causes of sudden death such as pulmonary embolism or intracranial bleeding. The mid-range numbers were largely based on death certificate studies that required a code inclusive of ischemic heart disease.
The 2017 update of cardiovascular statistics from the AHA estimated the total annual burden of out-of-hospital cardiac arrest at 356,500 (S2.2.2-44). An additional 209,000 in-hospital cardiac arrests occur annually (S2.2.2-45). Among the out-of-hospital cardiac arrest group, approximately 357,000 events trigger emergency rescue response, with \(97\%\) occurring in adults \(>18\) years of age.
The survival statistics for out-of-hospital cardiac arrest remain disappointing, with an estimated 10% overall survival rate (S2.2.2-44). Among the subgroup of 70% of out-of-hospital cardiac arrests that occur in the home, survival is 6%. The best reported outcomes are from locations with highly developed and publicly visible
emergency rescue response, along with the combination of public location of cardiac arrest, bystander witnesses willing to provide CPR, first responders arriving quickly, shockable rhythm at initial contact, availability of automated external defibrillators (AEDs), and possibly a benefit from telecommunication-directed CPR (S2.2.2-46, S2.2.2-47). Survival to hospital discharge after in-hospital cardiac arrests is estimated to be 24% (S2.2.2-48). In all settings, survival statistics appear to be better when rhythms recorded by responders are shockable (VF, pulseless VT), compared with pulseless electrical activity or asystole (S2.2.2-49). Although the apparent increase in the incidence of pulseless electrical activity or asystole could be due to the later arrival of medical care, the decrease in the incidence of shockable rhythm has also been attributed, in part, to improvements in diagnosis and treatment of structural heart disease (S2.2.2-40).
2.2.2. Population Subgroups and Risk Prediction
Risk prediction for SCA and SCD is complex. Risk analysis is divided into 2 general categories: population risk prediction and individual risk prediction (S2.2.2-41,S2.2.2-50). Conventional epidemiological markers provide insight into probabilities for the development of ischemic heart disease within a general class of subjects, but adequately tested and validated profiles for SCA risk stratification of individuals in the general population do not presently exist. The challenge of defining SCA risk in individuals derives from a population model characterized by large numbers of events diluted into a very large denominator (Figure 1). The overall population can be subgrouped into categories based on integration of age, presence and extent of disease, and identification of small, high-risk subgroups within the large denominator general population.
Increasing age is a strong predictor of risk for SCA, but it is not linear. Risk in the general population, over time, beginning at 35 years of age has been estimated at 1 per 1000 population per year, increasing from a risk <1000 at the younger end of that spectrum to a higher risk in the elderly (S2.2.2-41). However, an analysis of lifetime risk of SCD, derived from the Framingham data, suggested that the incidence of SCD decreases in later years, especially in people >75 years of age (S2.2.2-51). The data also suggested that SCD is uniformly more common in men than in women at all age groups. In contrast, the population of children, adolescents, and young adults has an overall annual risk of 1 per 100,000, and there is somewhat a higher risk of SCD at the younger end of that age range (S2.2.2-41). An age-associated transition range, from the mid-20s to 35 to 40 years of age, is characterized by a steep increase in risk from that of the adolescent group to the middle-aged group, corresponding to the emergence of ischemic heart disease.
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FIGURE 1A SCD Incidence and Total Events (S2.2.2-1)
EF indicates ejection fraction; and SCD, sudden cardiac death.
Although ischemic heart disease remains the most common underlying substrate associated with SCD, the incidence of ischemic heart disease-related SCD appears to be decreasing (S2.2.2-52), with various forms of cardiomyopathy associated with myocardial fibrosis and LV hypertrophy increasing (S2.2.2-53). In addition, a trend over time has suggested that out-of-hospital cardiac arrest patients who are admitted alive to a hospital are becoming more likely to have high-risk clinical profiles, as opposed to manifest disease (S2.2.2-54). The younger population—children, adolescents, and young adults—is affected by a series of disorders that manifest earlier in life, including the genetic structural disorders and cardiac channelopathies, myocarditis, congenital heart disease, and other rare disorders (S2.2.2-43). During the transition range, from the mid-20s to the mid-30s, causes of SCA and SCD include a lower proportion of inherited diseases and increasing proportion of ischemic heart disease (>40% of cases) (S2.2.2-43).
Despite the small progress that has been made in risk prediction of SCA and SCD, the greatest challenge is to identify the relatively small, high-risk subgroups concealed within the large general population who have no identified disease but are at risk of SCA as their first cardiac event (Figure 1) (S2.2.2-50).
3. MECHANISMS OF VA
3.1. Cellular Mechanisms and Substrates
Mechanisms of VA include enhanced normal automaticity, abnormal automaticity, triggered activity induced by early or late afterdepolarizations, and reentry (S3.4-1–S3.4-3). Reentry requires a trigger to initiate the arrhythmia and a substrate to sustain it. The trigger may be a PVC, which may be due to automaticity. The substrate may be structural remodeling secondary to an underlying disease process, and often includes a scar secondary to a prior MI or surgical repair, or patchy
FIGURE 1B SCD and Clinical Subsets (S2.2.2-1)
SCD indicates sudden cardiac death.
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fibrosis in the setting of cardiomyopathy or hypertrophy. Changes in ion channel or transporter function and/or expression and cell to cell coupling secondary to the underlying pathology may alter the initiation or propagation of the cardiac action potential. The electrophysiological substrate is dynamically influenced by a variety of factors including cardiac metabolism, electrolytes, signaling pathways and autonomic effects. Enhanced automaticity or abnormal automaticity causing VA may arise from subordinate pacemaker cells in the His-Purkinje system or ventricular myocardium.
3.2. Automaticity
Normal automaticity results from phase 4 spontaneous depolarization of the transmembrane action potential arising from a normal resting potential, reaching threshold and initiating an action potential (S3.4-1,S3.4-3). An initiating current ( \( I_{f} \) ) is responsible for spontaneous phase 4 depolarization in the sinus node. The rate is determined by the integration of the maximum diastolic potential at the end of repolarization, the slope of phase 4 depolarization, and the threshold potential. In contrast, abnormal automaticity arises from a partially depolarized membrane potential that is usually close to the activation potential for calcium channels in the cell membrane (S3.4-1,S3.4-3). In the acute phase of an MI or during transient ischemia, increased extracellular potassium causes partial depolarization of the resting membrane potential creating injury currents between the infarcted/ischemic tissue and healthy myocardium. These injury currents may initiate spontaneous activity. In ischemia, abnormal automaticity may occur in both ventricular myocytes and Purkinje fibers, and may also enhance normal automaticity in Purkinje fibers in the ischemic zone.
3.3. Triggered Activity
Early afterdepolarizations occur during late phase 2 or early phase 3 of the action potential (S3.4-3-S3.4-5), usually in the setting of action potential prolongation due to an increase in inward currents (the late sodium current, the inward calcium current or the sodium calcium exchange current) or a decrease in repolarizing potassium currents. Under these conditions, early after-depolarizations may be initiated when reactivation of the inward L-type calcium channel occurs before the membrane has returned to a more negative potential than that required for calcium channel reactivat
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