P1: vendor Journal of Genetic Counseling [jgc]
PH059-343770
July 21, 2001
13:0
Style file version Nov. 19th, 1999
Journal of Genetic Counseling, Vol. 10, No. 5, October 2001 (°C 2001)
Genetic Counseling and Screening Issues in Familial Dilated Cardiomyopathy Emily L. Hanson1,2 and Ray E. Hershberger1
Idiopathic dilated cardiomyopathy (IDC), a treatable condition characterized by left ventricular dilatation and systolic dysfunction of unknown cause, has only recently been recognized to have genetic etiologies. Although familial dilated cardiomyopathy (FDC) was thought to be infrequent, it is now believed that 30–50% of cases of IDC may be familial. Echocardiographic and electrocardiographic (ECG) screening of first-degree relatives of individuals with IDC and FDC is indicated because detection and treatment are possible prior to the onset of advanced, symptomatic disease. However, such screening often creates uncertainty and anxiety surrounding the significance of the results. Furthermore, FDC demonstrates incomplete penetrance, variable expression, and significant locus and allelic heterogeneity, making genetic counseling complex. The provision of genetic counseling for IDC and FDC will require collaboration between cardiologists and genetics professionals, and may also improve the recognition of FDC, the availability of support services, and overall outcomes for patients and families. KEY WORDS: dilated cardiomyopathy; genetic counseling; cardiac genetics.
INTRODUCTION Cardiomyopathy (“heart muscle disease”) is a common cause of heart failure, a constellation of clinical signs and symptoms in which an insufficient quantity of blood is pumped to the body. As the heart muscle weakens, the heart dilates; this condition is termed dilated cardiomyopathy. In the past several years a genetic 1 Division
of Cardiology, Department of Medicine, Oregon Health Sciences University, Portland, Oregon. 2 Correspondence should be directed to Emily L. Hanson, Division of Cardiology, UHN-62, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97201; e-mail: [email protected]. 397 C 2001 National Society of Genetic Counselors, Inc. 1059-7700/01/1000-0397$19.50/1 °
P1: vendor Journal of Genetic Counseling [jgc]
PH059-343770
July 21, 2001
13:0
398
Style file version Nov. 19th, 1999
Hanson and Hershberger
form of dilated cardiomyopathy, termed familial dilated cardiomyopathy (FDC), has been recognized to be more common than previously thought (Baig et al., 1998; Grunig et al., 1998; Michels et al., 1992). The new appreciation that dilated cardiomyopathy often has genetic causes warrants the inclusion of genetic counseling into patient management for three reasons. First, early detection and treatment of dilated cardiomyopathy is beneficial. This disease causes substantial morbidity and mortality and treatment of advanced disease is costly. These facts justify measures to prevent or ameliorate it in its initial stages through the identification and clinical screening of at-risk individuals. Second, cardiologists often do not recognize FDC in their practices; of those who do, it is likely that few provide accurate risk assessment, genetic education, and screening recommendations. Third, with a diagnosis of FDC a host of difficult psychological, social, and ethical issues unique to genetic disease emerge, which often cannot be addressed in a routine cardiology clinic visit. Whether counseled by a genetic counselor, medical geneticist, or other health care professional, the care of patients and families with dilated cardiomyopathy will undoubtedly improve with the inclusion of genetics services.
OVERVIEW Types of Cardiomyopathy Cardiomyopathy is a disease of the myocardium, the heart muscle. The diagnosis of dilated cardiomyopathy is based on left ventricular enlargement (LVE), usually with relative thinning of the ventricular wall, and decreased force of muscle contraction (systolic dysfunction). As the primary function of the heart is to pump blood, an inefficient, weakened, and enlarged left ventricle is unable to provide adequate blood flow to tissues and organs. This is in contrast to hypertrophic cardiomyopathy, in which the ventricular wall becomes thickened because of hypertrophy and the ventricular force of contraction is usually normal or increased. The two most common types of dilated cardiomyopathy are (1) ischemic dilated cardiomyopathy, caused by loss of myocardium from myocardial infarction and (2) idiopathic dilated cardiomyopathy (IDC), or dilated cardiomyopathy of unknown etiology, which has a prevalence of 36.5 per 100,000 (Codd et al., 1989). Diagnosis of IDC The diagnosis of IDC is a diagnosis of exclusion, and is therefore assigned when dilated cardiomyopathy has no obvious or identifiable etiology. Dilated cardiomyopathy is diagnosed with the principal findings of decreased systolic function and LVE. The most common clinical measure of systolic function is a left
P1: vendor Journal of Genetic Counseling [jgc]
PH059-343770
July 21, 2001
13:0
Style file version Nov. 19th, 1999
Genetic Counseling for Familial Dilated Cardiomyopathy
399
Table I. Echocardiographic and Electrocardiographic Features Associated With IDC Echocardiographic features
Electrocardiographic (ECG) features
Left ventricular enlargementa Decreased ejection fraction (usually
PH059-343770
July 21, 2001
13:0
Style file version Nov. 19th, 1999
Journal of Genetic Counseling, Vol. 10, No. 5, October 2001 (°C 2001)
Genetic Counseling and Screening Issues in Familial Dilated Cardiomyopathy Emily L. Hanson1,2 and Ray E. Hershberger1
Idiopathic dilated cardiomyopathy (IDC), a treatable condition characterized by left ventricular dilatation and systolic dysfunction of unknown cause, has only recently been recognized to have genetic etiologies. Although familial dilated cardiomyopathy (FDC) was thought to be infrequent, it is now believed that 30–50% of cases of IDC may be familial. Echocardiographic and electrocardiographic (ECG) screening of first-degree relatives of individuals with IDC and FDC is indicated because detection and treatment are possible prior to the onset of advanced, symptomatic disease. However, such screening often creates uncertainty and anxiety surrounding the significance of the results. Furthermore, FDC demonstrates incomplete penetrance, variable expression, and significant locus and allelic heterogeneity, making genetic counseling complex. The provision of genetic counseling for IDC and FDC will require collaboration between cardiologists and genetics professionals, and may also improve the recognition of FDC, the availability of support services, and overall outcomes for patients and families. KEY WORDS: dilated cardiomyopathy; genetic counseling; cardiac genetics.
INTRODUCTION Cardiomyopathy (“heart muscle disease”) is a common cause of heart failure, a constellation of clinical signs and symptoms in which an insufficient quantity of blood is pumped to the body. As the heart muscle weakens, the heart dilates; this condition is termed dilated cardiomyopathy. In the past several years a genetic 1 Division
of Cardiology, Department of Medicine, Oregon Health Sciences University, Portland, Oregon. 2 Correspondence should be directed to Emily L. Hanson, Division of Cardiology, UHN-62, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97201; e-mail: [email protected]. 397 C 2001 National Society of Genetic Counselors, Inc. 1059-7700/01/1000-0397$19.50/1 °
P1: vendor Journal of Genetic Counseling [jgc]
PH059-343770
July 21, 2001
13:0
398
Style file version Nov. 19th, 1999
Hanson and Hershberger
form of dilated cardiomyopathy, termed familial dilated cardiomyopathy (FDC), has been recognized to be more common than previously thought (Baig et al., 1998; Grunig et al., 1998; Michels et al., 1992). The new appreciation that dilated cardiomyopathy often has genetic causes warrants the inclusion of genetic counseling into patient management for three reasons. First, early detection and treatment of dilated cardiomyopathy is beneficial. This disease causes substantial morbidity and mortality and treatment of advanced disease is costly. These facts justify measures to prevent or ameliorate it in its initial stages through the identification and clinical screening of at-risk individuals. Second, cardiologists often do not recognize FDC in their practices; of those who do, it is likely that few provide accurate risk assessment, genetic education, and screening recommendations. Third, with a diagnosis of FDC a host of difficult psychological, social, and ethical issues unique to genetic disease emerge, which often cannot be addressed in a routine cardiology clinic visit. Whether counseled by a genetic counselor, medical geneticist, or other health care professional, the care of patients and families with dilated cardiomyopathy will undoubtedly improve with the inclusion of genetics services.
OVERVIEW Types of Cardiomyopathy Cardiomyopathy is a disease of the myocardium, the heart muscle. The diagnosis of dilated cardiomyopathy is based on left ventricular enlargement (LVE), usually with relative thinning of the ventricular wall, and decreased force of muscle contraction (systolic dysfunction). As the primary function of the heart is to pump blood, an inefficient, weakened, and enlarged left ventricle is unable to provide adequate blood flow to tissues and organs. This is in contrast to hypertrophic cardiomyopathy, in which the ventricular wall becomes thickened because of hypertrophy and the ventricular force of contraction is usually normal or increased. The two most common types of dilated cardiomyopathy are (1) ischemic dilated cardiomyopathy, caused by loss of myocardium from myocardial infarction and (2) idiopathic dilated cardiomyopathy (IDC), or dilated cardiomyopathy of unknown etiology, which has a prevalence of 36.5 per 100,000 (Codd et al., 1989). Diagnosis of IDC The diagnosis of IDC is a diagnosis of exclusion, and is therefore assigned when dilated cardiomyopathy has no obvious or identifiable etiology. Dilated cardiomyopathy is diagnosed with the principal findings of decreased systolic function and LVE. The most common clinical measure of systolic function is a left
P1: vendor Journal of Genetic Counseling [jgc]
PH059-343770
July 21, 2001
13:0
Style file version Nov. 19th, 1999
Genetic Counseling for Familial Dilated Cardiomyopathy
399
Table I. Echocardiographic and Electrocardiographic Features Associated With IDC Echocardiographic features
Electrocardiographic (ECG) features
Left ventricular enlargementa Decreased ejection fraction (usually
