2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: Executive summary

It is essential that the medical profession play a central role in critically evaluating the evidence related to drugs, devices, and procedures for the detection, management, or prevention of disease. Properly applied, rigorous, expert analysis of the available data documenting absolute and relative benefits and risks of these therapies and procedures can improve the effectiveness of care, optimize patient outcomes, and favorably affect the cost of care by focusing resources on the most effective strategies. One important use of such data is the production of clinical practice guidelines that, in turn, can provide a foundation for a variety of other applications such as performance measures, appropriateness use criteria, clinical decision support tools, and quality improvement tools. The American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) have jointly engaged in the production of guidelines in the area of cardiovascular disease since 1980. The ACCF/AHA Task Force on Practice Guidelines (Task Force) is charged with developing, updating, and revising practice guidelines for cardiovascular diseases and procedures, and the Task Force directs and oversees this effort. Writing committees are charged with assessing the evidence as an independent group of authors to develop, update, or revise recommendations for clinical practice. Experts in the subject under consideration have been selected from both organizations to examine subject-specific data and write guidelines in partnership with representatives from other medical practitioner and specialty groups. Writing committees are specifically charged to perform a formal literature review, weigh the strength of evidence for or against particular tests, treatments, or procedures, and include estimates of expected health outcomes where data exist. Patient-specific modifiers, comorbidities, and issues of patient preference that may influence the choice of tests or therapies are considered. When available, information from studies on cost is considered, but data on efficacy and clinical outcomes constitute the primary basis for recommendations in these guidelines. In analyzing the data and developing the recommendations and supporting text, the writing committee used evidence-based methodologies developed by the Task Force, which are described elsewhere.1ACCF/AHA Task Force on Practice Guidelines. Methodologies and Policies from the ACCF/AHA Task Force on Practice Guidelines. Available at: http://assets.cardiosource.com/Methodology_Manual_for_ACC_AHA_Writing_Committees.pdf and http://circ.ahajournals.org/site/manual/index.xhtml. Accessed July 11, 2011.Google Scholar The committee reviewed and ranked evidence supporting current recommendations with the weight of evidence ranked as Level A if the data were derived from multiple randomized clinical trials (RCTs) or meta-analyses. The committee ranked available evidence as Level B when data were derived from a single RCT or nonrandomized studies. Evidence was ranked as Level C when the primary source of the recommendation was consensus opinion, case studies, or standard of care. In the narrative portions of these guidelines, evidence is generally presented in chronological order of development. Studies are identified as observational, retrospective, prospective, or randomized when appropriate. For certain conditions for which inadequate data are available, recommendations are based on expert consensus and clinical experience and ranked as Level C. An example is the use of penicillin for pneumococcal pneumonia, for which there are no RCTs and treatment is based on clinical experience. When recommendations at Level C are supported by historical clinical data, appropriate references (including clinical reviews) are cited if available. For issues where sparse data are available, a survey of current practice among the clinicians on the writing committee was the basis for Level C recommendations and no references are cited. The schema for Classification of Recommendations and Level of Evidence is summarized in Table 1, which also illustrates how the grading system provides an estimate of the size and the certainty of the treatment effect. A new addition to the ACCF/AHA methodology is separation of the Class III recommendations to delineate whether the recommendation is determined to be of “no benefit” or associated with “harm” to the patient. In addition, in view of the increasing number of comparative effectiveness studies, comparator verbs and suggested phrases for writing recommendations for the comparative effectiveness of one treatment/strategy with respect to another for Class of Recommendation I and IIa, Level of Evidence A or B only have been added.Table 1Applying classification of recommendation and level of evidenceA recommendation with Level of Evidence B or C does not imply that the recommendation is weak. Many important clinical questions addressed in the guidelines do not lend themselves to clinical trials. Although randomized trials are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective. *Data available from clinical trials or registries about the usefulness/efficacy in different subpopulations, such as sex, age, history of diabetes, history of prior myocardial infarction, history of heart failure, and prior aspirin use. †For comparative effectiveness recommendations (Class I and IIa; Level of Evidence A and B only), studies that support the use of comparator verbs should involve direct comparisons of the treatments or strategies being evaluated. Open table in a new tab A recommendation with Level of Evidence B or C does not imply that the recommendation is weak. Many important clinical questions addressed in the guidelines do not lend themselves to clinical trials. Although randomized trials are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective. *Data available from clinical trials or registries about the usefulness/efficacy in different subpopulations, such as sex, age, history of diabetes, history of prior myocardial infarction, history of heart failure, and prior aspirin use. †For comparative effectiveness recommendations (Class I and IIa; Level of Evidence A and B only), studies that support the use of comparator verbs should involve direct comparisons of the treatments or strategies being evaluated. The Task Force makes every effort to avoid actual, potential, or perceived conflicts of interest that may arise as a result of relationships with industry and other entities (RWI) among the writing committee. Specifically, all members of the writing committee, as well as peer reviewers of the document, are required to disclose all relevant relationships and those 12 months prior to initiation of the writing effort. The policies and procedures for RWI for this guideline were those in effect at the initial meeting of this committee (March 28, 2009), which included 50% of the writing committee with no relevant RWI. All guideline recommendations require a confidential vote by the writing committee and must be approved by a consensus of the members voting. Members who were recused from voting are indicated on the title page of this document with detailed information included in Appendix 1. Members must recuse themselves from voting on any recommendations where their RWI apply. If a writing committee member develops a new RWI during his/her tenure, he/she is required to notify guideline staff in writing. These statements are reviewed by the Task Force and all members during each conference call and/or meeting of the writing committee and are updated as changes occur. For detailed information regarding guideline policies and procedures, please refer to the ACCF/AHA methodology and policies manual.1ACCF/AHA Task Force on Practice Guidelines. Methodologies and Policies from the ACCF/AHA Task Force on Practice Guidelines. Available at: http://assets.cardiosource.com/Methodology_Manual_for_ACC_AHA_Writing_Committees.pdf and http://circ.ahajournals.org/site/manual/index.xhtml. Accessed July 11, 2011.Google Scholar RWI pertinent to this guideline for authors and peer reviewers are disclosed in Appendixes 1 and 2, respectively. Comprehensive disclosure information for the Task Force is also available online at http://www.cardiosource.org/ACC/About-ACC/Leadership/Guidelines-and-Documents-Task-Forces.aspx. The work of the writing committee was supported exclusively by the ACCF and AHA without commercial support. Writing committee members volunteered their time for this effort. The ACCF/AHA practice guidelines address patient populations (and healthcare providers) residing in North America. As such, drugs that are currently unavailable in North America are discussed in the text without a specific class of recommendation. For studies performed in large numbers of subjects outside of North America, each writing group reviews the potential impact of different practice patterns and patient populations on the treatment effect and on the relevance to the ACCF/AHA target population to determine whether the findings should inform a specific recommendation. The ACCF/AHA practice guidelines are intended to assist healthcare providers in clinical decision making by describing a range of generally acceptable approaches for the diagnosis, management, and prevention of specific diseases or conditions. These practice guidelines represent a consensus of expert opinion after a thorough review of the available current scientific evidence and are intended to improve patient care. The guidelines attempt to define practices that meet the needs of most patients in most circumstances. The ultimate judgment regarding care of a particular patient must be made by the healthcare provider and patient in light of all the circumstances presented by that patient. Thus, there are situations in which deviations from these guidelines may be appropriate. Clinical decision making should consider the quality and availability of expertise in the area where care is provided. When these guidelines are used as the basis for regulatory or payer decisions, the goal should be improvement in quality of care. The Task Force recognizes that situations arise for which additional data are needed to better inform patient care; these areas will be identified within each respective guideline when appropriate. Prescribed courses of treatment in accordance with these recommendations are effective only if they are followed. Because lack of patient understanding and adherence may adversely affect outcomes, physicians and other healthcare providers should make every effort to engage the patient's active participation in prescribed medical regimens and lifestyles. The guideline will be reviewed annually by the Task Force and considered current unless it is updated, revised, or withdrawn from distribution. The full-text version1aGersh B.J. Maron B.J. Bonow R.O. et al.2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines.J Thorac Cardiovasc Surg. 2011; 142 (e153-203)Abstract Full Text Full Text PDF Scopus (3) Google Scholar of the guideline is e-published in the Journal of the American College of Cardiology and Circulation and is posted on the ACC (www.cardiosource.org) and AHA (my.americanheart.org) World Wide Web sites. Guidelines are official policy of both the ACCF and AHA. Alice K. Jacobs, MD, FACC, FAHA Chair, ACCF/AHA Task Force on Practice Guidelines The recommendations listed in this document are, whenever possible, evidence based. An extensive evidence review was conducted through January 2011. Searches were limited to studies, reviews, and other evidence conducted in human subjects and published in English. Key search words included, but were not limited to, hypertrophic cardiomyopathy (HCM), surgical myectomy, ablation, exercise, sudden cardiac death (SCD), athletes, dual-chamber pacing, left ventricular outflow tract (LVOT) obstruction, alcohol septal ablation, automobile driving and implantable cardioverterdefibrillators (ICDs), catheter ablation, defibrillators, genetics, genotype, medical management, magnetic resonance imaging, pacing, permanent pacing, phenotype, pregnancy, risk stratification, sudden death in athletes, surgical septal myectomy, and septal reduction. References selected and published in this document are representative and not all-inclusive. The committee was composed of physicians and cardiac surgeons with expertise in HCM, invasive cardiology, noninvasive testing and imaging, pediatric cardiology, electrophysiology, and genetics. The committee included representatives from the American Association for Thoracic Surgery, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons. This document was reviewed by 2 outside reviewers nominated by both the ACCF and AHA, as well as 2 reviewers each from the American Association for Thoracic Surgery, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons. Other content reviewers included members from the ACCF Adult Congenital and Pediatric Cardiology Council, ACCF Surgeons' Scientific Council, and ACCF Interventional Scientific Council. All information on reviewers' RWI 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 ACCF and the AHA and endorsed by the American Association for Thoracic Surgery, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Although there are reports of this disease dating back to the 1800s, the first modern pathologic description was provided over 50 years ago by Teare2Teare D. Asymmetrical hypertrophy of the heart in young adults.Br Heart J. 1958; 20: 1-8Crossref PubMed Google Scholar and the most important early clinical report by Braunwald et al in 1964.3Braunwald E. Lambert C.T. Rockoff S.D. et al.Idiopathic Hypertrophic subaortic stenosis, I: a description of the disease based upon an analysis of 64 patients.Circulation. 1964; 30: 119Google Scholar The impetus for the guidelines is based on an appreciation of the frequency of this clinical entity and a realization that many aspects of clinical management, including the use of diagnostic modalities and genetic testing, lack consensus. Moreover, the emergence of 2 different approaches to septal reduction therapy (septal myectomy and alcohol septal ablation) in addition to the ICD has created considerable controversy. The discussion and recommendations about the various diagnostic modalities apply to patients with established HCM and to a variable extent to patients with a high index of suspicion of the disease. Although the Task Force was aware of the lack of high levels of evidence regarding HCM provided by clinical trials, it was believed that a guideline document based on expert consensus that outlines the most important diagnostic and management strategies would be helpful. To facilitate ease of use, it was decided that recommendations in the pediatric and adolescent age groups would not appear as a separate section but instead would be integrated into the overall content of the guideline where relevant. Class I1.Evaluation of familial inheritance and genetic counseling is recommended as part of the assessment of patients with HCM.4Arad M. Maron B.J. Gorham J.M. et al.Glycogen storage diseases presenting as hypertrophic cardiomyopathy.N Engl J Med. 2005; 352: 362-372Crossref PubMed Scopus (210) Google Scholar, 5Ho C.Y. Sweitzer N.K. McDonough B. et al.Assessment of diastolic function with Doppler tissue imaging to predict genotype in preclinical hypertrophic cardiomyopathy.Circulation. 2002; 105: 2992-2997Crossref PubMed Scopus (160) Google Scholar, 6Morita H. Rehm H.L. Menesses A. et al.Shared genetic causes of cardiac hypertrophy in children and adults.N Engl J Med. 2008; 358: 1899-1908Crossref PubMed Scopus (89) Google Scholar, 7Niimura H. Bachinski L.L. Sangwatanaroj S. et al.Mutations in the gene for cardiac myosin-binding protein C and late-onset familial hypertrophic cardiomyopathy.N Engl J Med. 1998; 338: 1248-1257Crossref PubMed Scopus (414) Google Scholar, 8Van Driest S.L. Ackerman M.J. Ommen S.R. et al.Prevalence and severity of “benign” mutations in the beta-myosin heavy chain, cardiac troponin T, and alpha-tropomyosin genes in hypertrophic cardiomyopathy.Circulation. 2002; 106: 3085-3090Crossref PubMed Scopus (100) Google Scholar, 9Van Driest S.L. Jaeger M.A. Ommen S.R. et al.Comprehensive analysis of the beta-myosin heavy chain gene in 389 unrelated patients with hypertrophic cardiomyopathy.J Am Coll Cardiol. 2004; 44: 602-610Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar (Level of Evidence: B)2.Patients who undergo genetic testing should also undergo counseling by someone knowledgeable in the genetics of cardiovascular disease so that results and their clinical significance can be appropriately reviewed with the patient.10Christiaans I. van Langen I.M. Birnie E. et al.Genetic counseling and cardiac care in predictively tested hypertrophic cardiomyopathy mutation carriers: the patients' perspective.Am J Med Genet A. 2009; 149A: 1444-1451Crossref PubMed Scopus (18) Google Scholar, 11Michie S. French D. Allanson A. et al.Information recall in genetic counselling: a pilot study of its assessment.Patient Educ Couns. 1997; 32: 93-100Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar, 12Michie S. Allanson A. Armstrong D. et al.Objectives of genetic counselling: differing views of purchasers, providers and users.J Public Health Med. 1998; 20: 404-408Crossref PubMed Google Scholar, 13Offit K. Groeger E. Turner S. et al.The “duty to warn” a patient's family members about hereditary disease risks.JAMA. 2004; 292: 1469-1473Crossref PubMed Scopus (108) Google Scholar, 14Christiaans I. van Langen I.M. Birnie E. et al.Quality of life and psychological distress in hypertrophic cardiomyopathy mutation carriers: a cross-sectional cohort study.Am J Med Genet A. 2009; 149A: 602-612Crossref PubMed Scopus (30) Google Scholar (Level of Evidence: B)3.Screening (clinical, with or without genetic testing) is recommended in first-degree relatives of patients with HCM.4Arad M. Maron B.J. Gorham J.M. et al.Glycogen storage diseases presenting as hypertrophic cardiomyopathy.N Engl J Med. 2005; 352: 362-372Crossref PubMed Scopus (210) Google Scholar, 5Ho C.Y. Sweitzer N.K. McDonough B. et al.Assessment of diastolic function with Doppler tissue imaging to predict genotype in preclinical hypertrophic cardiomyopathy.Circulation. 2002; 105: 2992-2997Crossref PubMed Scopus (160) Google Scholar, 6Morita H. Rehm H.L. Menesses A. et al.Shared genetic causes of cardiac hypertrophy in children and adults.N Engl J Med. 2008; 358: 1899-1908Crossref PubMed Scopus (89) Google Scholar, 7Niimura H. Bachinski L.L. Sangwatanaroj S. et al.Mutations in the gene for cardiac myosin-binding protein C and late-onset familial hypertrophic cardiomyopathy.N Engl J Med. 1998; 338: 1248-1257Crossref PubMed Scopus (414) Google Scholar, 9Van Driest S.L. Jaeger M.A. Ommen S.R. et al.Comprehensive analysis of the beta-myosin heavy chain gene in 389 unrelated patients with hypertrophic cardiomyopathy.J Am Coll Cardiol. 2004; 44: 602-610Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 15Fokstuen S. Lyle R. Munoz A. et al.A DNA resequencing array for pathogenic mutation detection in hypertrophic cardiomyopathy.Hum Mutat. 2008; 29: 879-885Crossref PubMed Scopus (47) Google Scholar, 16Olivotto I. Girolami F. Ackerman M.J. et al.Myofilament protein gene mutation screening and outcome of patients with hypertrophic cardiomyopathy.Mayo Clin Proc. 2008; 83: 630-638PubMed Scopus (0) Google Scholar (Level of Evidence: B)4.Genetic testing for HCM and other genetic causes of unexplained cardiac hypertrophy is recommended in patients with an atypical clinical presentation of HCM or when another genetic condition is suspected to be the cause.17Maron B.J. Niimura H. Casey S.A. et al.Development of left ventricular hypertrophy in adults in hypertrophic cardiomyopathy caused by cardiac myosin-binding protein C gene mutations.J Am Coll Cardiol. 2001; 38: 315-321Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 18Rosenzweig A. Watkins H. Hwang D.S. et al.Preclinical diagnosis of familial hypertrophic cardiomyopathy by genetic analysis of blood lymphocytes.N Engl J Med. 1991; 325: 1753-1760Crossref PubMed Google Scholar, 19Spada M. Pagliardini S. Yasuda M. et al.High incidence of later-onset Fabry disease revealed by newborn screening.Am J Hum Genet. 2006; 79: 31-40Abstract Full Text Full Text PDF PubMed Scopus (261) Google Scholar (Level of Evidence: B)Class IIa1.Genetic testing is reasonable in the index patient to facilitate the identification of first-degree family members at risk for developing HCM.5Ho C.Y. Sweitzer N.K. McDonough B. et al.Assessment of diastolic function with Doppler tissue imaging to predict genotype in preclinical hypertrophic cardiomyopathy.Circulation. 2002; 105: 2992-2997Crossref PubMed Scopus (160) Google Scholar, 8Van Driest S.L. Ackerman M.J. Ommen S.R. et al.Prevalence and severity of “benign” mutations in the beta-myosin heavy chain, cardiac troponin T, and alpha-tropomyosin genes in hypertrophic cardiomyopathy.Circulation. 2002; 106: 3085-3090Crossref PubMed Scopus (100) Google Scholar, 15Fokstuen S. Lyle R. Munoz A. et al.A DNA resequencing array for pathogenic mutation detection in hypertrophic cardiomyopathy.Hum Mutat. 2008; 29: 879-885Crossref PubMed Scopus (47) Google Scholar (Level of Evidence: B)Class IIb1.The usefulness of genetic testing in the assessment of risk of SCD in HCM is uncertain.20Moolman J.C. Corfield V.A. Posen B. et al.Sudden death due to troponin T mutations.J Am Coll Cardiol. 1997; 29: 549-555Abstract Full Text Full Text PDF PubMed Scopus (214) Google Scholar, 21Woo A. Rakowski H. Liew J.C. et al.Mutations of the beta myosin heavy chain gene in hypertrophic cardiomyopathy: critical functional sites determine prognosis.Heart. 2003; 89: 1179-1185Crossref PubMed Google Scholar (Level of Evidence: B)Class III: No Benefit1.Genetic testing is not indicated in relatives when the index patient does not have a definitive pathogenic mutation.4Arad M. Maron B.J. Gorham J.M. et al.Glycogen storage diseases presenting as hypertrophic cardiomyopathy.N Engl J Med. 2005; 352: 362-372Crossref PubMed Scopus (210) Google Scholar, 5Ho C.Y. Sweitzer N.K. McDonough B. et al.Assessment of diastolic function with Doppler tissue imaging to predict genotype in preclinical hypertrophic cardiomyopathy.Circulation. 2002; 105: 2992-2997Crossref PubMed Scopus (160) Google Scholar, 6Morita H. Rehm H.L. Menesses A. et al.Shared genetic causes of cardiac hypertrophy in children and adults.N Engl J Med. 2008; 358: 1899-1908Crossref PubMed Scopus (89) Google Scholar, 7Niimura H. Bachinski L.L. Sangwatanaroj S. et al.Mutations in the gene for cardiac myosin-binding protein C and late-onset familial hypertrophic cardiomyopathy.N Engl J Med. 1998; 338: 1248-1257Crossref PubMed Scopus (414) Google Scholar, 8Van Driest S.L. Ackerman M.J. Ommen S.R. et al.Prevalence and severity of “benign” mutations in the beta-myosin heavy chain, cardiac troponin T, and alpha-tropomyosin genes in hypertrophic cardiomyopathy.Circulation. 2002; 106: 3085-3090Crossref PubMed Scopus (100) Google Scholar, 9Van Driest S.L. Jaeger M.A. Ommen S.R. et al.Comprehensive analysis of the beta-myosin heavy chain gene in 389 unrelated patients with hypertrophic cardiomyopathy.J Am Coll Cardiol. 2004; 44: 602-610Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 22Ho C.Y. Lever H.M. DeSanctis R. et al.Homozygous mutation in cardiac troponin T: implications for hypertrophic cardiomyopathy.Circulation. 2000; 102: 1950-1955Crossref PubMed Google Scholar (Level of Evidence: B)2.Ongoing clinical screening is not indicated in genotype-negative relatives in families with HCM.22Ho C.Y. Lever H.M. DeSanctis R. et al.Homozygous mutation in cardiac troponin T: implications for hypertrophic cardiomyopathy.Circulation. 2000; 102: 1950-1955Crossref PubMed Google Scholar, 23Ingles J. Doolan A. Chiu C. et al.Compound and double mutations in patients with hypertrophic cardiomyopathy: implications for genetic testing and counseling.J Med Genet. 2005; 42: e59Crossref PubMed Google Scholar, 24Van Driest S.L. Vasile V.C. Ommen S.R. et al.Myosin binding protein C mutations and compound heterozygosity in hypertrophic cardiomyopathy.J Am Coll Cardiol. 2004; 44: 1903-1910Abstract Full Text Full Text PDF PubMed Scopus (184) Google Scholar, 25Jeschke B. Uhl K. Weist B. et al.A high risk phenotype of hypertrophic cardiomyopathy associated with a compound genotype of two mutated beta-myosin heavy chain genes.Hum Genet. 1998; 102: 299-304Crossref PubMed Scopus (47) Google Scholar (Level of Evidence: B) See Online Data Supplement 1 for additional data regarding genetic testing strategies/family screening. Class I1.In individuals with pathogenic mutations who do not express the HCM phenotype, it is recommended to perform serial electrocardiogram (ECG), transthoracic echocardiogram (TTE), and clinical assessment at periodic intervals (12 to 18 months in children and adolescents and about every 5 years in adults), based on the patient's age and change in clinical status.26Christiaans I. Lekanne dit Deprez R.H. van Langen I.M. et al.Ventricular fibrillation in MYH7-related hypertrophic cardiomyopathy before onset of ventricular hypertrophy.Heart Rhythm. 2009; 6: 1366-1369Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar, 27Andersen P.S. Havndrup O. Hougs L. et al.Diagnostic yield, interpretation, and clinical utility of mutation screening of sarcomere encoding genes in Danish hypertrophic cardiomyopathy patients and relatives.Hum Mutat. 2009; 30: 363-370Crossref PubMed Scopus (37) Google Scholar, 28Christiaans I. Birnie E. van Langen I.M. et al.The yield of risk stratification for sudden cardiac death in hypertrophic cardiomyopathy myosin-binding protein C gene mutation carriers: focus on predictive screening.Eur Heart J. 2010; 31: 842-848Crossref PubMed Scopus (23) Google Scholar, 29Michels M. Soliman O.I. Phefferkorn J. et al.Disease penetrance and risk stratification for sudden cardiac death in asymptomatic hypertrophic cardiomyopathy mutation carriers.Eur Heart J. 2009; 30: 2593-2598Crossref PubMed Scopus (25) Google Scholar (Level of Evidence: B) Class I1.A 12-lead ECG is recommended in the initial evaluation of patients with HCM. (Level of Evidence: C)2.Twenty-four–hour ambulatory (Holter) electrocardiographic monitoring is recommended in the initial evaluation of patients with HCM to detect ventricular tachycardia (VT) and identify patients who may be candidates for ICD therapy.30Elliott P.M. Gimeno J.R. Tome M.T. et al.Left ventricular outflow tract obstruction and sudden death risk in patients with hypertrophic cardiomyopathy.Eur Heart J. 2006; 27: 1933-1941Crossref PubMed Scopus (87) Google Scholar, 31Maron B.J. Savage D.D. Wolfson J.K. et al.Prognostic significance of 24 hour ambulatory electrocardiographic monitoring in patients with hypertrophic cardiomyopathy: a prospective study.Am J Cardiol. 1981; 48: 252-257Abstract Full Text PDF PubMed Google Scholar, 32Maron B.J. McKenna W.J. Danielson G.K. et al.American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy.J Am Coll Cardiol. 2003; 42: 1687-1713Abstract Full Text Full Text PDF PubMed Scopus (743) Google Scholar, 33Monserrat L. Elliott P.M. Gimeno J.R. et al.Non-sustained ventricular tachycardia in hypertrophic cardiomyopathy: an independent marker of sudden death risk in young patients.J Am Coll Cardiol. 2003; 42: 873-879Abstract Full Text Full Text PDF PubMed Scopus (157) Google Scholar (Level of Evidence: B)3.Twenty-four–hour ambulatory (Holter) electrocardiographic monitoring or event recording is recommended in patients with HCM who develop palpitations or lightheadedness.30Elliott P.M. Gimeno J.R. Tome M.T. et al.Left ventricular outflow tract obstruction and sudden death risk in patients with hypertrophic cardiomyopathy.Eur Heart J. 2006; 27: 1933-1941Crossref PubMed Scopus (87) Google Scholar, 31Maron B.J. Savage D.D. Wolfson J.K. et al.Prognostic significance of 24 hour ambulatory electrocardiographic monitoring in patients with hypertrophic cardiomyopathy: a prospective study.Am J Cardiol. 1981; 48: 252-257Abstract Full Text PDF PubMed Google Scholar, 32Maron B.J. McKenna W.J. Danielson G.K. et al.American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy.J Am Coll Cardiol. 2003; 42: 1687-1713Abstract Full Text Full Text PDF PubMed Scopus (743) Google Scholar (Level of Evidence: B)4.A repeat ECG is recommended for patients with HCM when there is worsening of symptoms. (Level of Evidence: C)5.A 12-lead ECG is recommended every 12 to 18 months as a component of the screening algorithm for adolescent first-degree relatives of