Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy

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1 Technology Evaluation Center Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy Assessment Program Volume 24, No. 11 August 2010 Executive Summary Background Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular condition in the U.S., and the most common cause of sudden cardiac death in adults younger than 35 years of age. For the purpose of this Assessment, HCM will refer to inherited HCM that is not associated with other congenital abnormalities and arises from a mutation in one of the cardiac sarcomere or related genes. This excludes left-ventricular hypertrophy (LVH) that is due to secondary causes, such as hypertension and/or valvular disease, and also excludes increased cardiac mass that is associated with systemic syndromes such as infiltrative disorders (e.g., amyloidosis, sarcoid), glycogen storage diseases (e.g., Fabry disease, Pompe disease), and neuromuscular disorders (e.g., Noonan s syndrome, Friederich s ataxia). The clinical diagnosis of HCM depends on the presence of LVH, in the absence of other known causative factors such as valvular disease, long-standing hypertension, or other myocardial disease. As this definition implies, the diagnosis of HCM is largely one of exclusion. Both cardiac causes and noncardiac causes of increased cardiac mass or LVH need to be excluded prior to a diagnosis of HCM. The genetic basis for HCM is a defect in the cardiac sarcomere, which is the basic contractile unit of cardiac myocytes composed of a number of different protein structures. Mutations in the genes coding for these proteins can result in HCM. The genetics of HCM is complicated by the convergence of several factors, as follows: n Several genes, many mutations. Several hundred distinct mutations in at least 12 different genes have been related to HCM cases. Despite this, known genes and mutations do not yet account for all cases of HCM. n Penetrance. Genetic mutations for HCM may not ever result in clinical disease; the probability that a specific mutation will result in disease is called its penetrance. The penetrance for different HCM mutations is variable, but there are insufficient data to characterize the penetrance of every mutation. n Variable expressivity. Patients with identical mutations may have widely differing clinical phenotypes. This may be the result of other modifying factors that affect disease expression, for example, hypertension or obesity. BlueCross BlueShield Association An Association of Independent Blue Cross and Blue Shield Plans Commercial testing for mutations in the cardiac sarcomere genes is currently available. In the case of predispositional testing (i.e., individual is currently without signs or symptoms), if there is a known mutation in the family, targeted testing of the specific familial mutation can be performed, which examines whether the familial mutation is present or absent in the tested at-risk individual. If there is no known mutation in the family, comprehensive testing can be performed, which examines the relevant known genes in their entirety for sequence variations that may be causative of HCM. Genetic testing for HCM may improve outcomes for the at-risk individual by providing information on the NOTICE OF PURPOSE: TEC Assessments are scientific opinions, provided solely for informational purposes. TEC Assessments should not be construed to suggest that the Blue Cross Blue Shield Association, Kaiser Permanente Medical Care Program or the TEC Program recommends, advocates, requires, encourages, or discourages any particular treatment, procedure, or service; any particular course of treatment, procedure, or service; or the payment or non-payment of the technology or technologies evaluated Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited. 1

2 Technology Evaluation Center likelihood of future disease, which may lead to changes in screening and management and/or may aid individuals in making informed choices regarding decisions on reproduction, employment, or strenuous activities. Objective To determine whether genetic testing for predisposition to inherited HCM improves health outcomes in patients at risk for HCM. Search Strategy MEDLINE was searched (via PubMed) using the terms hypertrophic cardiomyopathy and HCM, cross-referenced with the terms genetics, genomics, and cardiogenomics for the period of 1990 through November 2009; focused searches were completed in March Electronic search was supplemented with the related articles function in PubMed and with manual review of recent relevant review articles. Selection Criteria Studies were selected that included primary evidence on genetic testing in a population of patients with HMC and that assessed the performance characteristics of genetic testing. Studies were selected that: 1) included a cohort of unrelated index patients with HCM; 2) included at least 100 patients with HCM; and 3) performed testing for multiple HCM mutations, including at minimum, the 5 most common genes. Evidence was also sought on whether genetic testing impacted management decisions for at-risk individuals. Studies were selected that: 1) were cohort studies, case-control studies, or controlled clinical trials; 2) used information from genetic testing in determining individual treatment decisions; and 3) applied one of the accepted treatments for HCM, either medical therapy, surgical therapy, implantation of a cardioverter-defibrillator (ICD), or cardiac transplantation. Main Results Seven studies were identified that met the inclusion criteria for review and contained relevant evidence on testing for HCM. No studies met the inclusion criteria for evaluating the impact of genetic testing on treatment decisions. These peer-reviewed articles were supplemented by data on analytic validity available through the manufacturers websites or personal communications. For predispositional genetic testing, the clinical validity (ability to detect a mutation in a patient with HCM and exclude a mutation in a patient without HCM) is more relevant when there is not a known mutation in the family, whereas the analytic validity, rather than the clinical validity, is more relevant for individuals with a known mutation in the family. Evidence on clinical validity consists of several case series of patients with established HCM. An important component of clinical validity in considering predisposition testing for HCM is the clinical sensitivity, also called the mutation detection rate. To date, the published mutation detection rate ranges from 33 63%. The less-than-perfect mutation detection rate is due, in part, to the published studies having investigated some, but not all, of the known genes that underlie HCM, and investigators in these studies using mutation scanning methods such as single-strand conformation polymorphism (SSCP) or denaturing gradient gel electrophoresis (DGGE) that will miss certain deleterious mutations. Presumably more comprehensive mutation analysis methods (e.g., sequence analysis with or without deletion duplication analysis) could identify additional mutations. Another reason for the less-than-perfect mutation detection rate is that other, as yet unidentified, genes may be responsible for HCM. Finally, there may be unknown, nongenetic factors that mimic HCM. The analytic validity of sequence analysis for detecting mutations that cause HCM (ability to identify small nucleotide changes that result in abnormal sarcomere protein products) is likely to be very high based on what is known about the types of mutations that cause HCM and the limited empiric data provided by the manufacturer and detailed description of the testing methodology. There are scant data available on the specificity of HCM testing. The available information on specificity, mainly from series of patients without a personal or family history of HCM, suggests that falsepositive results for known pathologic mutations are uncommon, but that the rate of false-positives is likely to be higher for classification of previously unknown variants. For a patient with a known mutation in the family, the high analytic validity means that targeted genetic testing for a familial mutation has high predictive value for both a positive (mutation detected) and a negative (mutation not detected) test result. The negative predictive value for Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited.

3 Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy targeted familial mutation analysis is substantially higher than for comprehensive testing performed when there is not a known mutation in the family. For patients without a known mutation in the family, genetic testing is not sufficient to rule out HCM. A positive genetic test in a patient without a known family history of disease increases the likelihood that an individual carries a pathologic mutation. In most cases, a positive genetic test is not sufficient to establish clinical disease, since not all patients with a genetic mutation will develop HCM, so the ultimate diagnosis depends on clinical criteria. The other important component to clinical validity in the context of predisposition testing is penetrance, or the probability that an individual with a pathogenic mutation will eventually develop the condition of concern. There is reduced penetrance in HCM (i.e., not everyone with a deleterious mutation will develop manifestations of HCM). In addition, penetrance varies among different mutations and may even vary among different families with an identical pathologic mutation. As a result, it is not possible to estimate accurately the penetrance for any given mutation in a specific family. Author s Conclusions and Comments There are limitations in the strength of the evidence on genetic testing for predisposition to HCM. The published evidence on diagnostic accuracy is primarily limited to a small number of studies on mutation detection rate (clinical sensitivity) in individuals with HCM. There is scant published evidence on the analytic sensitivity of testing, and there is also scant published evidence on the specificity (analytic and clinical) of test results. Despite the limitations in the evidence, some conclusions can be drawn on the utility of genetic testing. There are benefits to predisposition genetic testing for at-risk individuals when there is a known mutation in the family. Inheritance of the predisposition to HCM can be ruled out with certainty when the genetic test is negative (mutation not detected) in this circumstance. A positive test result (mutation detected) is less useful. It confirms the presence of a pathologic mutation and an inherited predisposition to HCM, but recommended surveillance for HCM manifestations will be essentially no different than those based on family history alone. Because of the suboptimal clinical sensitivity relating to less-than-perfect mutation detection, the best genetic testing strategy for predisposition testing for HCM begins with comprehensive testing (e.g., sequence analysis) of a DNA sample from an affected family member. Comprehensive mutation analysis in an index patient with established HCM will improve outcomes for close relatives by informing and directing the subsequent testing of these at-risk relatives. If the same mutation is identified in an at-risk relative, then it confirms the inheritance of the predisposition to HCM and the person is at risk for developing the manifestations of the disease. However, if the familial mutation can be excluded in an at-risk relative, then this confirms that the mutation has not been inherited and there is a very low likelihood (probably similar to or less than the population risk) that the individual will develop signs or symptoms of HCM. Therefore, clinical surveillance for signs of the disorder can be discontinued and they can be reassured that their risk of developing the disease is no greater than the general population. If a familial mutation is not known and an at-risk individual undergoes testing, a positive result (mutation detected) would confirm an inherited predisposition to HCM and an increased risk for clinical manifestations in the future. However, a negative result (no mutation detected) could not exclude the possibility that a mutation was inherited. In this case, risk assessment and surveillance for HCM would depend on the family history and other personal risk factors. Thus, in this situation, testing has limited utility in decision making. Moreover, if a familial mutation is not known, comprehensive mutation analysis would be the method of choice, and in addition to a positive or negative result, there is the possibility of detecting a variant of uncertain significance a variant for which the association with clinical disease is not known. Knowledge of the results of genetic testing may aid in decision-making on such issues as reproduction, employment, and participating in strenuous activities (e.g., sports) by providing information on the susceptibility to develop future disease. Direct evidence on the impact of genetic information on this type of decision making is lacking and the effect of such decisions on health outcomes is uncertain Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited. 3

4 Technology Evaluation Center Based on the available evidence, the Blue Cross and Blue Shield Association Medical Advisory Panel made the following judgments about whether the use of predispositional genetic testing for inherited hypertrophic cardiomyopathy meets the Blue Cross and Blue Shield Association s Technology Evaluation Center (TEC) criteria. 1. The technology must have final approval from the appropriate governmental regulatory bodies. There are no assay kits approved by the U.S. Food and Drug Administration (FDA) for genetic testing for HCM, nor are any kits being actively manufactured and marketed for distribution. Clinical laboratories may develop and validate tests in-house ( home-brew ) and market them as a laboratory service; such tests must meet the general regulatory standards of the Clinical Laboratory Improvement Act (CLIA). The laboratory offering the service must be licensed by CLIA for high-complexity testing. While the FDA has technical authority to regulate home-brew tests, there is currently no active oversight nor any known plans to begin oversight. Home-brew tests may be developed using reagents prepared in-house or, if available, commercially manufactured analyte-specific reagents (ASRs). ASRs are single reagents intended for use in a diagnostic application for identification and quantification of an individual chemical substance or ligand in biological specimens and must meet certain FDA criteria but are not subject to premarket review. 2. The scientific evidence must permit conclusions concerning the effect of the technology on health outcomes. For individuals at risk for HCM and with a known mutation in the family, genetic testing will establish the presence or absence of the same genetic mutation in a close relative with a high degree of certainty. Absence of this mutation will establish that the individual has not inherited the familial predisposition to HCM and thus has a similar risk of developing HCM as the general population. Identifying the familial mutation will confirm the inheritance of the familial predisposition to HCM and will increase the likelihood of developing clinical disease, but the diagnosis of HCM will still depend on the demonstration of clinical signs of the disorder. For at-risk individuals without a known mutation in the family, there is little to no impact of genetic testing on clinical outcomes. In this situation, the negative predictive value of testing is not high enough to rule out the possibility of the presence of a pathologic genetic mutation that has gone undetected given the limitations of current technology. Therefore, a negative test is not likely to be helpful in refining risk estimates for development of HCM and in changing clinical surveillance for signs relating to HCM. A positive test result would confirm the predisposition, and could be helpful in reproductive and personal decision making, but it would not alter clinical decision making that is similar, surveillance/management would be recommended. 3. The technology must improve the net health outcome. For the at-risk individual with a known mutation in the family who does not have the familial predisposition (i.e., tests negative), there is a net improvement in health outcome. These patients no longer need ongoing surveillance for the presence of clinical signs of HCM and can be reassured that they need not consider changes in employment, avoid activities involving physical exertion, or change decisions about reproduction. For the index patient with established HCM, testing improves outcomes for at-risk relatives. By testing a patient with established disease, the predictive value of testing at-risk relatives is improved if a genetic mutation is found in the index patient. The improved predictive value leads to the ability to rule out inherited predisposition to HCM with near certainty in relatives who test negative, which in turn, allows the relative to discontinue screening and not have to consider modifying employment, avoiding activities involving physical exertion, or changing decisions about reproduction. For at-risk individuals without a known mutation in the family, there is not an improvement in health outcomes since the evidence does not permit conclusions of the effect of genetic testing on outcomes. 4. The technology must be as beneficial as any established alternatives. The alternative to genetic testing is periodic clinical follow-up to monitor the development of signs or symptoms of HCM informed by personal and family history risk factors. Therefore, for patients in whom health outcomes are improved, testing is more beneficial than alternatives Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited.

5 Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy 5. The improvement must be attainable outside the investigational settings. Genetic testing for HCM is commercially available in the U.S. For those indications meeting TEC criteria, improvement in health outcomes is based on results of commercial testing, and therefore is attainable outside the investigational setting. For those indications not meeting TEC criteria, improvement in health outcomes was not shown in the investigational setting. For the above reasons, the use of genetic testing for inherited hypertrophic cardiomyopathy meets the TEC criteria for the following indications: n Individuals who are at-risk for development of HCM, defined as having a close relative with established HCM, when there is a known pathogenic gene mutation present in an affected relative. In order to inform and direct genetic testing for at-risk individuals, genetic testing should be initially performed in at least one close relative with definite HCM (index case) if possible. This testing is intended to document whether a known pathologic mutation is present in the family, and optimize the predictive value of predisposition testing for at-risk relatives. Due to the complexity of genetic testing for HCM and the potential for misinterpretation of results, the decision to test and the interpretation of test results should be performed by, or in consultation with an expert in the area of medical genetics and/or hypertrophic cardiomyopathy. Genetic testing for inherited hypertrophic cardiomyopathy does not meet the TEC criteria for predisposition testing in other situations, including the following: n Individuals who are at-risk for development of HCM, defined as having a close relative with established HCM, when there is no known pathogenic gene mutation present in an affected relative. This includes: n Patients with a family history of HCM, with unknown genetic status of affected relatives. n Patients with a family history of HCM, when a pathogenic mutation has not been identified in affected relatives Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited. 5

6 Technology Evaluation Center Contents Assessment Objective 7 Background 7 Methods 12 Formulation of the Assessment 12 Review of Evidence 13 Discussion 20 Summary and Conclusions 20 Summary of Application of the 21 Technology Evaluation Criteria References 23 Published in cooperation with Kaiser Foundation Health Plan and Southern California Permanente Medical Group. TEC Staff Contributors Author Frank Lefevre, M.D.; TEC Executive Director Naomi Aronson, Ph.D.; Director, Clinical Science Services Kathleen M. Ziegler, Pharm.D.; Research/Editorial Staff Claudia J. Bonnell, B.S.N., M.L.S.; Kimberly L. Hines, M.S. Blue Cross and Blue Shield Association Medical Advisory Panel Allan M. Korn, M.D., F.A.C.P. Chairman, Senior Vice President, Clinical Affairs/Medical Director, Blue Cross and Blue Shield Association; Alan M. Garber, M.D., Ph.D. Scientific Advisor, Staff Physician, U.S. Department of Veterans Affairs; Henry J. Kaiser, Jr., Professor, and Professor of Medicine, Economics, and Health Research and Policy, Stanford University; Steven N. Goodman, M.D., M.H.S., Ph.D. Scientific Advisor, Professor, Johns Hopkins School of Medicine, Department of Oncology, Division of Biostatistics (joint appointments in Epidemiology, Biostatistics, and Pediatrics). Panel Members Peter C. Albertsen, M.D., Professor, Chief of Urology, and Residency Program Director, University of Connecticut Health Center; Sarah T. Corley, M.D., F.A.C.P., Chief Medical Officer, NexGen Healthcare Information Systems, Inc. American College of Physicians Appointee; Helen Darling, M.A. President, National Business Group on Health; Josef E. Fischer, M.D., F.A.C.S., William V. McDermott Professor of Surgery, Harvard Medical School American College of Surgeons Appointee; I. Craig Henderson, M.D., Adjunct Professor of Medicine, University of California, San Francisco; Mark A. Hlatky, M.D., Professor of Health Research and Policy and of Medicine (Cardiovascular Medicine), Stanford University School of Medicine; Saira A. Jan, M.S., Pharm.D., Associate Clinical Professor, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Residency Director and Director of Clinical Programs Pharmacy Management, Horizon Blue Cross and Blue Shield of New Jersey; Leslie Levin, M.B., M.D., F.R.C.P.(Lon), F.R.C.P.C., Head, Medical Advisory Secretariat and Senior Medical, Scientific and Health Technology Advisor, Ministry of Health and Long-Term Care, Ontario, Canada; Bernard Lo, M.D., Professor of Medicine and Director, Program in Medical Ethics, University of California, San Francisco; Barbara J. McNeil, M.D., Ph.D., Ridley Watts Professor and Head of Health Care Policy, Harvard Medical School, Professor of Radiology, Brigham and Women s Hospital; William R. Phillips, M.D., M.P.H., Clinical Professor of Family Medicine, University of Washington American Academy of Family Physicians Appointee; Alan B. Rosenberg, M.D., Vice President, Medical Policy, Technology Assessment and Credentialing Programs, WellPoint, Inc.; Maren T. Scheuner, M.D., M.P.H., F.A.C.M.G., Director, Genomics Strategic Program Area, VA HSR&D Center of Excellence for the Study of Healthcare Provider Behavior, VA Greater Los Angeles Healthcare System; Natural Scientist, RAND Corporation; Adjunct Associate Professor, Department of Health Services, UCLA School of Public Health; J. Sanford Schwartz, M.D., F.A.C.P., Leon Hess Professor of Medicine and Health Management & Economics, School of Medicine and The Wharton School, University of Pennsylvania; Earl P. Steinberg, M.D., M.P.P., President and CEO, Resolution Health, Inc.; Robert T. Wanovich, Pharm.D., Vice-President, Pharmacy Affairs, Highmark, Inc.; A. Eugene Washington, M.D., M.Sc., Executive Vice Chancellor and Provost, University of California, San Francisco; Jed Weissberg, M.D., Senior Vice President, Quality and Care Delivery Excellence, The Permanente Federation. CONFIDENTIAL: This document contains proprietary information that is intended solely for Blue Cross and Blue Shield Plans and other subscribers to the TEC Program. The contents of this document are not to be provided in any manner to any other parties without the express written consent of the Blue Cross and Blue Shield Association Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited.

7 Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy Assessment Objective This Assessment reviews the available evidence to determine if genetic testing for predisposition to inherited hypertrophic cardiomyopathy (HCM) improves health outcomes for patients at risk for HCM. Patients who are at risk for HCM are those who have a close relative with documented HCM. As with other TEC Assessments on genetic testing, the framework recommended by EGAPP (Evaluation of Genomic Applications in Practice and Prevention), an initiative of the National Office of Public Health Genomics at the Centers of Disease Control and Prevention, is applied. This framework addresses analytic validity, clinical validity, and clinical utility in evaluating a genetic test. In the absence of direct evidence on the effect of genetic testing for HCM on outcomes, a causal chain is constructed. This causal chain considers the accuracy of genetic testing for HCM; whether the information provided by genetic testing leads to changes in management; and, whether changes in management result in improvements in health outcomes. The outcomes to be considered will be the morbidity and mortality outcomes associated with HCM, including those associated with clinical surveillance for those at risk. In addition, the impact of genetic information on important decisions such as reproductive decision-making, employment choices, and/or avoiding strenuous activities (e.g., sports) will be considered. Background Inherited Hypertrophic Cardiomyopathy Inherited hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular condition in the U.S., with a phenotypic prevalence of approximately 1 in 500 adults (0.2%) (Radhakrishnan 2008). It is the most common cause of sudden cardiac death in adults younger than 35 years of age and is probably also the most the most common cause of death in young athletes (Alcalai et al. 2008). The overall death rate for patients with HCM is estimated to be 1% per year in the adult population (Roberts and Sigwart 2005; Marian 2008). The genetic basis for HCM is a defect in the cardiac sarcomere, which is the basic contractile unit of cardiac myocytes composed of a number of different protein structures (Keren et al. 2008). Several hundred distinct mutations in at least 12 different genes have been identified to date (Cirino and Ho 2008). These genetic defects are inherited in an autosomal dominant pattern (Keren et al. 2008). In the vast majority of cases, the disease is due to a single pathologic mutation, although rare cases have been identified in which there are multiple pathologic mutations (Cirino and Ho 2008). The proportion of patients with multiple mutations is unknown but may be higher than expected by chance due to proximity of pathologic mutations and/or linkage of inherited genes that contain mutations. Many patients with clinically documented disease have a family history, although some exceptions are found presumably due to reduced penetrance, unrecognized disease in relatives, nonpaternity, unknown adoptive status, or de novo mutations (Elliott and McKenna 2004). The rate of mutations that are truly de novo is unknown since an apparently negative family history may often be the result of asymptomatic or unrecognized disease. Table 1 gives a summary of the percentage of individuals from recent case series of HCM who have a positive family history of HCM and the percentage that have sporadic disease (i.e., no family history). The penetrance for HCM is incomplete, meaning that not all patients who inherit the genetic mutation will develop the disease. The penetrance for HCM is also variable, meaning that different mutations will have different rates of penetrance. In addition, the same mutation may have different rates of penetrance in different families (Fananapazir and Epstein 1994). These factors make it difficult to estimate the penetrance for any particular mutation in at-risk relatives of a patient with HCM. Early evidence on the penetrance of HCM was obtained prior to the discovery of genetic mutations and was limited to clinical manifestations of the disease. There is limited evidence that uses knowledge of genetic testing results along with advanced cardiac testing (echocardiography and/or MRI) to determine penetrance. Charron et al. (1997) evaluated penetrance in 90 individuals with different genetic defects from 10 families with documented HCM. The overall penetrance rate in this population, as defined by electrocardiographic and/or echocardiographic evidence of HCM, was 69%. Factors associated with increased penetrance were male sex and increased age. In this study, the authors reported that there was no difference in penetrance for the different genes included Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited. 7

8 Technology Evaluation Center Table 1. Familial Patterns and Frequency of Sporadic Cases in Series of Unrelated Patients with HCM Study/Year N Patients % of Patients with Familial HCM % of Patients with Sporadic HCM 1 Olivotto et al % (57/203) not reported Richard et al not reported 13% (25/197) Erdmann et al % (49/108) not reported Van Driest et al % (120/389) not reported Garcia-Castro et al % (16/30) 17% (5/30) Morner et al % (11/46) 14% (2/14) 1 Defined as no evidence of HCM in family after further testing of relatives by genetic and/or clinical methods However, other studies have suggested that penetrance does vary according to the specific mutation. Michels et al. (2009) evaluated penetrance in a population of 76 patients with a genetic mutation, the majority of which had 1 of 3 Dutch founder mutations. For this cohort of patients, penetrance was higher for patients with an MYH7 mutation compared with an MYBPC3 mutation (60% vs. 36%). Christiaans et al. (2010) also reported a low penetrance for patients with an MYBPC3 mutation. In their cohort of 235 mutation carriers, a diagnosis of clinical HCM was made in 22.6%. Other experts have suggested that penetrance for MYBPC3 may not be this low, but may be age-related with manifestations appearing later in life (Alcalai et al. 2008). Diagnosis. The clinical diagnosis of HCM depends on the presence of left-ventricular hypertrophy (LVH), measured by echocardiography or MRI, in the absence of other known causes such as valvular disease, long-standing hypertension, or other myocardial disease (Cirino and Ho 2008). As this definition implies, the diagnosis of HCM is largely one of exclusion. Patients who are found to have LVH require a thorough evaluation for the presence of other cardiac disorders that can lead to hypertrophy. Exclusion of other predisposing disorders may not always be straightforward. For example, if hypertension or valvular disorders are identified, a determination must be made as to whether these abnormalities are of sufficient severity to have caused LVH, or whether they are coincidental findings that do not have a causal relationship with the degree of LVH. The hypertrophy associated with inherited HCM has several characteristic features that help differentiate HCM from other causes of hypertrophy. On echocardiography, the follow- ing features are associated with inherited HCM (Cirino and Ho 2008): 1) massive hypertrophy of the left ventricle; 2) asymmetric hypertrophy, with exaggerated septal hypertrophy; 3) systolic anterior motion of the mitral valve; 4) left-ventricular outflow tract obstruction; 5) midventricular obstruction resulting from systolic cavity obliteration; and 6) diastolic dysfunction with restrictive physiology. Bos et al. (2009) have recently suggested that the morphologic characteristics of LVH on echocardiography may also predict the presence of a positive genetic test, based on a study of nearly 400 patients with established HCM. For patients with a reverse curve morphology, approximately 80% have an identifiable pathogenic mutation, compared with patients who had a sigmoidal morphology, in which only 10% have a pathogenic mutation. For other morphologies, an intermediate likelihood of 30 40% was reported. These data emphasize the importance of echocardiographic morphology in determining the pretest probability of HCM. In addition to primary cardiac disorders, there are syndromic conditions that increase left ventricular masson echocardiography and thus mimic HCM. These include infiltrative diseases such as amyloidosis, glycogen storage diseases such as Fabry disease and Pompe disease, and neuromuscular disorders such as Noonan s syndrome and Friederich s ataxia (Elliott and McKenna 2004). These disorders also need to be excluded before a diagnosis of inherited HCM is made. These syndromic causes of LVH are systemic diseases that include extracardiac manifestations in the majority of cases. Demonstration of clinical signs and symptoms of the syndrome is Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited.

9 Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy often the first step in differentiating these disorders from inherited HCM. For example, in Noonan s syndrome, malformations on physical exam such as short stature, broad or webbed neck, and characteristic facies are present (Cirino and Ho 2008). In infiltrative disorders, such as Fabry disease, biochemical evidence of reduced or absent enzyme activity is diagnostic of the disorder. Neurologic syndromes such as Friederich s ataxia include progressive ataxia and a wide spectrum of other neurologic abnormalities that can be discerned on physical exam or by neurologic testing. Management of at-risk individuals. At-risk individuals are defined as persons who have a close relative with a diagnosis of HCM. Diagnostic surveillance of at-risk individuals is considered an important component of HCM management. This surveillance is intended to screen for subclinical disease in at-risk patients. Guidelines have been established for clinically unaffected relatives of affected individuals. Screening with physical examination, electrocardiography, and echocardiography is recommended every months for individuals between the ages of and every 3 5 years for adults (Maron et al. 2003). Additional clinical evaluation is recommended for any change in symptoms that might indicate the development of HCM (Maron et al. 2003). In patients who demonstrate signs of disease on diagnostic surveillance, risk stratification is recommended in order to direct further treatment. Further testing for cardiac risk stratification in addition to clinical examination, electrocardiography, and echocardiography may involve Holter monitoring for ventricular arrhythmias and exercise stress testing. Factors that are considered indicators for high risk of sudden cardiac death include a prior history of cardiac arrest, family history of premature sudden death, ventricular tachycardia, unexplained syncope, ventricular wall thickness 30 mm or greater, and an abnormal blood pressure response to exercise (Roberts and Sigwart 2005; Maron et al. 2003). Clinical manifestations. Clinically, HCM is a very heterogenous disorder. Manifestations range from subclinical, asymptomatic disease to severe life-threatening disease. Wide phenotypic variability exists among individuals even when an identical mutation is present, including among affected family members (Alcalai et al. 2008). This variability in clinical expression may be related to environmental factors and modifier genes (Maron et al. 2003). Environmental factors are likely to include other cardiac risk factors such as blood pressure and obesity. The impact of modifier genes is largely theoretical but may include genes that determine sympathetic tone and regulate other neurohumoral activity, such as the renin-angiotensin system. A large percentage of patients with HCM, perhaps the majority of all HCM patients, are asymptomatic or have minimal symptoms (Elliott and McKenna 2004; Maron et al. 2003). These patients do not require treatment and are not generally at high risk for sudden cardiac death. When symptoms occur, they include dyspnea on exertion, palpitations, chest pain, and syncope (Alcalai et al. 2008). These symptoms may encompass a wide range of severity, from infrequent and mild to severe and debilitating. Signs and symptoms of disease can develop any time in life, but most commonly manifest during adolescence or early adulthood (Cirino and Ho 2008). Approximately 25% of patients with HCM have evidence of left-ventricular outflow obstruction due to hypertrophied muscle in the region of the left-ventricular septum. Individuals with outflow obstruction may have more severe symptoms and a higher incidence of sudden death, but the correlation between outflow obstruction and severity of disease is variable and not entirely predictable (Cirino and Ho 2008). A subset of patients has severe disease that causes a major impact on quality of life and life expectancy. Severe disease can lead to disabling symptoms as well as complications of HCM, including congestive heart failure (CHF) and malignant ventricular arrhythmias. Malignant ventricular arrhythmias are the cause of the most dreaded complication of HCM, which is sudden cardiac death. Sudden cardiac death can occur at any age or stage of disease, including in patients with subclinical disease. It is often precipitated by vigorous physical activity, and/or other forms of stress that are associated with increased sympathetic tone in the cardiac muscle. Treatment. Treatment of HCM is aimed at ameliorating symptoms and preventing complications of the disease. For patients who have symptomatic HCM, medical treatment includes the use of beta-blockers or calcium-channel 2010 Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited. 9

10 Technology Evaluation Center antagonists, and/or the use of antiarrhythmic medications such as disopyramide, sotalol, or amiodarone (Roberts and Sigwart 2005; Maron et al. 2003). For patients in whom medical management is not sufficient to control symptoms or prevent progression of CHF, surgical options exist. Septal hypertrophy resulting in left-ventricular outflow obstruction can be treated by myomectomy or septal alcohol ablation (Maron et al. 2003). For patients with endstage CHF, cardiac transplantation is sometimes an option (Maron et al. 2003). Preventing complications of HCM, particularly sudden cardiac death, is another primary goal of treatment. Most cases of sudden death associated with HCM occur with vigorous exercise. Therefore, patients with established HCM are counseled to avoid vigorous exercise such as competitive sports and employment that involves substantial physical labor. This may lead to significant decisions for young athletes, who may have to forego further participation in competitive sports. The diagnosis of HCM may also affect an individual s choice of employment or career. An implantable cardioverter-defibrillator is also a treatment option for HCM patients who are at high risk for sudden cardiac arrest (Maron et al. 2003). High risk is indicated by the presence of any one of the following factors: a prior history of cardiac arrest; family history of premature sudden death; ventricular tachycardia; unexplained syncope; ventricular wall thickness 30 mm or greater; or an abnormal blood pressure response to exercise (Roberts and Sigwart 2005; Maron et al. 2003). It is recommended that surveillance for these risk factors be performed annually, including history, clinical examination, echocardiography, exercise testing, and Holter monitoring (Maron et al. 2003). While precise risk estimation is not possible due to poorly determined predictive value of any single risk factor, the presence of 2 or more risk factors has been associated with an increased risk of sudden cardiac death, estimated at 3% per year or higher (Elliott and McKenna 2004). Genetic Testing for HCM More than 600 distinct mutations in at least 12 genes have been identified to date. The most common genetic mutations identified to date and the proportion of HCM due to mutations in known genes is summarized in Table 2. There are at least 4 commercial companies that currently offer genetic testing for HCM (PGxHealth, Correlagen, Partners Healthcare, Center for Personalized Genetic Medicine, and GeneDx ). Testing has been commercially available since May All companies use genetic sequence analysis as the basis of their testing strategy. According to the PGxHealth website, substantial redundancy is incorporated into the interpretation of results in order to minimize the possibility of faulty interpretation. The sequences are read independently by 2 technologists, with discrepancies resolved by an experienced supervisor. Variants that are detected in this initial analysis are confirmed by repeating the sequencing twice in the forward and twice in the backward direction. Final results are reviewed by a doctorate-level scientist and by the lab director prior to reporting of results to clinicians. A similar approach to minimizing faulty interpretation was reported by Correlagen in a personal communication (Correlagen 2010). The mutation analysis described above is termed comprehensive testing, i.e., any pathogenic mutations are sought using DNA amplification via polymerase chain reaction to generate templates for sequencing. Mutation analysis can also be performed in a specific or targeted fashion, testing for the presence of a known mutation that has previously been identified in the family. For targeted testing of a known familial mutation, sequences from the test are compared with reference standards containing the mutation previously identified in a family member. Results from comprehensive sequence analysis will reveal the location of any variant (i.e., whether it is in a critical functional domain), the type of mutation involved (e.g., missense, nonsense, frameshift, or silent) and the probable effect of that mutation on the transcript (mrna) or protein product. These factors are all taken into account in determining the likelihood that a mutation identified is pathological, or whether it represents a benign polymorphism. In some cases when the laboratory cannot classify a variant as pathogenic or benign, the laboratory will describe it as a variant of uncertain significance (VOUS). In these instances, the association with clinical outcomes is uncertain and the test results cannot be used to refine risk or to guide management, reproductive, or personal decision-making. The manufacturers classify HCM gene variants into classes, based on the above factors indicating Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited.

11 Genetic Testing for Predisposition to Inherited Hypertrophic Cardiomyopathy Table 2. Genetic Mutations Associated with Inherited Hypertrophic Cardiomyopathy Gene Protein Name Percent of HCM Caused by Mutation MYH7 beta-myosin heavy chain 30 40% MYBPC3 Myosin-binding protein C 20 40% TNNT2 Troponin T 3 5% TNNI3 Troponin I 5% TPM1 Tropomyosin 1 alpha chain 2 5% MYL3 Myosin light polypeptide 3 1% ACTC1 Actin protein 1 Rare CSRP3 Cysteine and glycine rich protein 3 Rare TTN Titin Rare MYH6 alpha-myosin heavy chain Rare TCAP Telothonin Rare TNNC1 Troponin C Rare LDB3 LIM binding domain 3 Rare VCL Vinculin/metavinculin Rare ACTN2 alpha-actinin2 Rare PLN Phospholamban Rare MYOZ2 Myozenin2 Rare JPH2 Junctophilin2 Rare Adapted from Cirino and Ho 2008; Keren et al the likelihood that a variant is pathogenic. An example of this classification system by one manufacturer is given below (PGxHealth 2009 and PGxHealth personal communication 2010): n Class I Deleterious and Probable deleterious mutations. Deleterious mutations are mutations which have previously been identified as pathogenic. Probable deleterious mutations are reported when there is a major change in the protein (e.g., nonsense or frame-shift mutations), or when there is an amino acid substitution (missense mutation) in a critical region of the protein(s). n Class II Possible deleterious mutations. These variants encode changes to protein(s) but occur in regions that are not considered critical. Approximately 5% of patients without HCM will exhibit mutations in this category. n Class III Variants not generally expected to be deleterious. These variants encode modified protein(s); however, these are considered more likely to represent benign polymorphisms. Approximately 90% of patients without HCM will have one or more of these variants; therefore patients with only class III variants are considered negative. n Class IV Nonprotein-altering variants (i.e., silent mutations). These are not considered to have clinical significance and are not reported in the results of the Familion test. Other manufacturers use a similar classification system, although classes are named differently. Correlagen employs a variant score that is based on the factors described above, and which places results into 1 of 7 classes (associated; probably associated; possibly associated; unknown significance; unlikely to be associated; very unlikely to be associated; and not associated) (Correlagen, personal communication 2010). Partners Healthcare uses a 3-class system (pathogenic mutations; mutations of unknown significance; and benign variants) (Partners Healthcare, personal communication 2010). GeneDx uses a 4-class system (published 2010 Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited. 11

12 Technology Evaluation Center disease-causing variants; novel, but likely to be disease-causing; variants of uncertain significance; and benign variants) (GeneDx, personal communication 2010). There are no published studies of the reproducibility or validity of the classification as Class I, II, or III of HCM genetic mutations that change the amino acid sequence, or prospective studies validating these classifications against clinical outcomes. Methods Search Methods MEDLINE was searched (via PubMed) using the terms hypertrophic cardiomyopathy and HCM, cross-referenced with the terms genetics, genomics, and cardiogenomics for the period of 1990 through November 2009; focused searches were completed in March Electronic search was supplemented with the related articles function in PubMed and with manual review of recent relevant review articles. Study Selection Studies were selected that included primary evidence from a population of patients with hypertrophic cardiomyopathy, as determined by echocardiography, electrocardiography, clinical exam, or related clinical methods. Separate selection criteria for each specific question were applied as follows: Accuracy of genetic testing: n Included a cohort of unrelated index patients with HCM n Included at least 100 patients with HCM n Genetic testing performed for multiple HCM mutations and included at minimum the 5 most common genes (MYH7, MYBPC3, TNNT2, TNNI3, TPM1) Impact on management: n Study design is a cohort or case-control, or controlled clinical trial n Uses information from genetic testing in determining individual treatment decisions n Applies one of the accepted treatments for HCM n Medical therapy n Surgical therapy n Implantable cardioverter-defibrillator n Cardiac transplantation Medical Advisory Panel Review This Assessment was reviewed by the Blue Cross and Blue Shield Association Medical Advisory Panel (MAP) on December 17, 2009 and tabled for revision with input from an MAP subgroup. The MAP reviewed the revision and voted electronically (by ) in June In order to maintain the timeliness of the scientific information in this Special Report, literature searches were performed subsequent to the Panel s review (see Search Methods ). If the search updates identified any additional studies that met the criteria for detailed review, the results of these studies were included in the tables and text where appropriate. There were no studies that changed the result of the Assessment. Formulation of the Assessment Patient Indications For the purpose of this Assessment, the main indication for genetic testing is predisposition testing for individuals who are at risk for the development of HCM (i.e., do not have signs or symptoms of HCM). An individual is considered to be at risk for developing HCM if there is a known history of HCM in the family. Technologies to be Compared The alternative to genetic testing is periodic clinical monitoring for the development of signs and symptoms of HCM, informed by personal and family history risk. Therefore, the strategy of diagnosis and management with genetic testing will be compared to routine clinical diagnosis and management without genetic testing. Health Outcomes Health outcomes to be considered are morbidity and mortality outcomes associated with HCM. Reproductive, cognitive, psychological, and behavioral outcomes are not included. The health outcomes include: n overall survival n sudden cardiac death n resuscitation from cardiac arrest n cardiac arrhythmias - ventricular tachycardia - atrial fibrillation/flutter n congestive heart failure n improvement in symptoms - chest pain - dyspnea on exertion - exercise tolerance - palpitations - syncope Blue Cross and Blue Shield Association. Reproduction without prior authorization is prohibited.