Clinical profiles of four large pedigrees with familial dilated cardiomyopathy: preliminary recommendations for clinical practice

Dilated Cardiomyopathy: A Genetic Journey from Past to Future

Dilated cardiomyopathy (DCM) is characterized by reduced systolic function and cardiac dilation. Cases without an identified secondary cause are classified as idiopathic dilated cardiomyopathy (IDC). Over the last 35 years, many cases of IDC have increasingly been recognized to be genetic in etiology with a core set of definitively causal genes in up to 40% of cases. While over 200 genes have been associated with DCM, the evidence supporting pathogenicity for most remains limited. Further, rapid advances in sequencing and bioinformatics have recently revealed a complex genetic spectrum ranging from monogenic to polygenic in DCM. These advances have also led to the discovery of causal and modifier genetic variants in secondary forms of DCM (e.g., alcohol-induced cardiomyopathy). Current guidelines recommend genetic counseling and screening, as well as endorsing a handful of genotype-specific therapies (e.g., device placement in LMNA cardiomyopathy). The future of genetics in DCM will likely involve polygenic risk scores, direct-to-consumer testing, and pharmacogenetics, requiring providers to have a thorough understanding of this rapidly developing field. Herein we outline three decades of genetics in DCM, summarize recent advances, and project possible future avenues for the field.

Sex Differences, Genetic and Environmental Influences on Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is characterized by dilatation of the left ventricle and impaired systolic function and is the second most common cause of heart failure after coronary heart disease. The etiology of DCM is diverse including genetic pathogenic variants, infection, inflammation, autoimmune diseases, exposure to chemicals/toxins as well as endocrine and neuromuscular causes. DCM is inherited in 20–50% of cases where more than 30 genes have been implicated in the development of DCM with pathogenic variants in TTN (Titin) most frequently associated with disease. Even though male sex is a risk factor for heart failure, few studies have examined sex differences in the pathogenesis of DCM. We searched the literature for studies examining idiopathic or familial/genetic DCM that reported data by sex in order to determine the sex ratio of disease. We found 31 studies that reported data by sex for non-genetic DCM with an average overall sex ratio of 2.5:1 male to female and 7 studies for familial/genetic DCM with an overall average sex ratio of 1.7:1 male to female. No manuscripts that we found had more females than males in their studies. We describe basic and clinical research findings that may explain the increase in DCM in males over females based on sex differences in basic physiology and the immune and fibrotic response to damage caused by mutations, infections, chemotherapy agents and autoimmune responses.

Troponin T Mutation as a Cause of Left Ventricular Systolic Dysfunction in a Young Patient with Previous Surgical Correction of Aortic Coarctation

Coarctation of the aorta is a leading cause of morbidity and mortality among adults with congenital heart disease (ACHD). Lifelong surveillance is mandatory to screen for possible long-term cardiovascular events. Left ventricular systolic dysfunction has been reported in association with recoarctation, and association with dilated cardiomyopathy (DCMP) is very rare. Herein, we report the case of a 19-year-old boy with coarctation of the aorta who complained of mild exertional dyspnea. Cardiac magnetic resonance revealed a moderately dilated, hypokinetic left ventricle (LV), with mildly reduced EF (45%), and residual isthmic coarctation was excluded. Genetic tests revealed a heterozygous missense variant in TNNT2 (NM_001001430.2): c.518G>A (p. Arg173Gln). This case highlights the role of careful history taking: a family history of cardiomyopathy should not be overlooked even when the clinical setting seems to suggest a predisposition to hemodynamic factors for LVSD.

Identification of MYLK3 mutations in familial dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a primary cause of heart failure, life-threatening arrhythmias, and cardiac death. Pathogenic mutations have been identified at the loci of more than 50 genes in approximately 50% of DCM cases, while the etiologies of the remainder have yet to be determined. In this study, we applied whole exome sequencing in combination with segregation analysis to one pedigree with familial DCM, and identified a read-through mutation (c.2459 A > C; p.*820Sext*19) in the myosin light chain kinase 3 gene (MYLK3). We then conducted MYLK3 gene screening of 15 DCM patients (7 familial and 8 sporadic) who were negative for mutation screening of the previously-reported cardiomyopathy-causing genes, and identified another case with a MYLK3 frameshift mutation (c.1879_1885del; p.L627fs*41). In vitro experiments and immunohistochemistry suggested that the MYLK3 mutations identified in this study result in markedly reduced levels of protein expression and myosin light chain 2 phosphorylation. This is the first report that MYLK3 mutations can cause DCM in humans. The clinical phenotypes of DCM patients were consistent with MYLK3 loss-of-function mouse and zebrafish models in which cardiac enlargement and heart failure are observed. Our findings highlight an essential role for cardiac myosin light chain kinase in the human heart.

Familial dilated cardiomyopathy diagnosis is commonly overlooked at the time of transplant listing

BACKGROUND

The prevalence and clinical characteristics of familial dilated cardiomyopathy (FDCM) among patients with end stage heart failure (ESHF) has yet to be elucidated. We sought to determine the prevalence of FDCM in ESHF in the United Network for Organ Sharing (UNOS) registry and compare this with center specific data from a large tertiary teaching hospital. Patients with a banked UNOS diagnosis of dilated cardiomyopathy (DCM) whose care originated at our center then underwent detailed pedigree analysis in order to determine the true prevalence of FDCM.

METHODS AND RESULTS

A total of 16,091 patients with DCM from all centers were identified in the UNOS registry of whom 492 carried the diagnosis of FDCM (3.1%). Patients with the diagnosis of FDCM tended to be younger (42 versus 49 years old in idiopathic dilated cardiomyopathy (IDCM), p=0.001), were less likely to have diabetes (7.8% versus 16.5% in IDCM, p<0.0001), had slightly lower creatinine (1.2 versus 1.4 in IDCM, p=0.0001) and were more likely to have a panel reactive antibody level ≥ 20% (62.1% versus 44.7% in IDCM, p<0.0001). Consecutive living adult patients with ESHF were identified from the UNOS registry that had been treated at the Yale Center for Advanced Heart Failure (YCAHF). After excluding all diagnoses that did not include any form of non-ischemic DCM, 73 patients met the inclusion criteria. Center-specific UNOS data showed pre-pedigree analysis diagnosis of FDCM in 4.12% of patients (3 out of 73), consistent with that found in the UNOS database for all centers. However, after detailed family history and pedigree analysis, 19 (26%) of 73 patients were found to have FDCM, while the remaining 54 were found to have IDCM. Echocardiographic findings including mitral regurgitation, mitral valve annulus and left ventricular end diastolic dimension were not significantly different between groups when adjusting for multiple testing.

CONCLUSIONS

The diagnosis of FDCM was missed in the majority of patients with end stage heart failure enrolled in the UNOS database, as sampled from a large, tertiary care teaching hospital in the United States. Echocardiographic findings are unlikely to aid in the differentiation between DCM and FDCM. Detailed pedigree analysis can successfully identify undiagnosed FDCM and should be encouraged prior to transplant listing as it has important implications for early detection and treatment of disease in family members.

Genetic Counseling and Screening Issues in Familial Dilated Cardiomyopathy

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.

Temporal relationship of conduction system disease and ventricular dysfunction in LMNA cardiomyopathy

BACKGROUND

LMNA cardiomyopathy presents with electrocardiogram (ECG) abnormalities, conduction system disease (CSD), and/or arrhythmias before the onset of dilated cardiomyopathy (DCM). Knowing the time interval between the onset of CSD and its progression to DCM would help to guide clinical care.

METHODS AND RESULTS

We evaluated family members from 16 pedigrees previously identified to carry LMNA mutations for the ages of onset of ECG abnormalities, CSD, or arrhythmia and of left ventricular enlargement (LVE) and/or systolic dysfunction. Of 103 subjects, 64 carried their family LMNA mutation, and 51 (79%) had ECG abnormalities with a mean age of onset of 41.2 years (range 18-76). Ventricular dysfunction was observed in 26 with a mean age of onset of 47.6 years (range 28-82); at diagnosis 9 had systolic dysfunction but no LVE, 5 had LVE but no systolic dysfunction, and 11 had DCM. Of 16 subjects identified with ECG abnormalities who later developed ventricular dysfunction, the median ages of onset by log-rank analyses were 41 and 48 years, respectively.

CONCLUSIONS

ECG abnormalities preceded DCM with a median difference of 7 years. Clinical surveillance should occur at least annually in those at risk for LMNA cardiomyopathy with any ECG findings.

Return of genetic results in the familial dilated cardiomyopathy research project

The goal of the Familial Dilated Cardiomyopathy (FDC) Research Project, initiated in 1993, has been to identify and characterize FDC genetic cause. All participating individuals have been consented for the return of genetic results, an important but challenging undertaking. Since the inception of the Project we have enrolled 606 probands, and 269 of these had 1670 family members also enrolled. Each subject was evaluated for idiopathic dilated cardiomyopathy (IDC) and pedigrees were categorized as familial or sporadic. The coding regions of 14 genes were resequenced in 311 to 324 probands in five studies. Ninety-two probands were found to carry nonsynonymous rare variants absent in controls, and with Clinical Laboratory Improvement Amendment of 1988 (CLIA) compliant protocols, relevant genetic results were returned to these probands and their consented relatives by study genetic counselors and physicians in 353 letters. In 10 of the 51 families that received results >1 year ago, at least 23 individuals underwent CLIA confirmation testing for their family's rare variant. Return of genetic results has been successfully undertaken in the FDC Research Project. This report describes the methods utilized in the process of returning research results. We use this information as a springboard for providing guidance to other genetic research groups and proposing future directions in this arena.

A randomised, placebo-controlled trial of carvedilol in early familial dilated cardiomyopathy

BACKGROUND

Screening of asymptomatic relatives of patients with dilated cardiomyopathy (DCM) has identified a population of individuals with left ventricular dilatation and/or minimally impaired contraction who are believed to have early disease. A proportion of these individuals with early disease progress to overt cardiomyopathy, however to our knowledge there have been no studies that have examined the impact of early intervention on disease progression.

METHODS

We evaluated 424 asymptomatic relatives in 110 families of probands with DCM and identified 102 individuals (24%) with suspected "early disease" (EDCM). Thirty-two EDCM subjects were randomised into a six-month placebo-controlled trial of the β-blocker, carvedilol. Transthoracic echocardiography and plasma nt-proBNP levels were measured at baseline and repeated at six months. The primary trial endpoint was change in left ventricular end-systolic diameter after six months. Subjects completing six months of blinded trial therapy were offered open-label carvedilol and then observed over an extended period with repeated clinical evaluation and echocardiography.

RESULTS

At baseline, left ventricular dimensions, systolic function and plasma nt-proBNP levels were similar in carvedilol and placebo groups. There were no significant changes observed in these parameters in either treatment group after six months, however reductions in end-diastolic diameter (% predicted) were observed in carvedilol-treated subjects (P=0.002) during an open-label median follow-up of 32 months (range: 13-56 months).

CONCLUSIONS

In an asymptomatic population of individuals with EDCM, treatment with carvedilol for six months had no effect on echocardiographic left ventricular dimensions or systolic function, however longer-term treatment may reverse left ventricular remodelling (Australian Clinical Trials Registry N012605000204640).

Evaluation of left ventricular enlargement as a marker of early disease in familial dilated cardiomyopathy

BACKGROUND

Echocardiographic screening of families with dilated cardiomyopathy has identified a subgroup of asymptomatic relatives with left ventricular enlargement (LVE). The prognostic significance of LVE in this setting is incompletely understood.

METHODS AND RESULTS

We evaluated 457 asymptomatic relatives in 128 dilated cardiomyopathy families and identified 110 individuals (24%) with LVE. Serial echocardiograms in 72 untreated LVE relatives showed that 9 individuals (13%) had development of dilated cardiomyopathy over 10 to 152 months (median, 52). Thirty LVE relatives and 30 age- and sex-matched healthy control subjects were evaluated using 2-dimensional and M-mode echocardiography, tissue Doppler imaging, noninvasive pressure-volume assessment, exercise stress echocardiography, and brain natriuretic peptide levels. LVE relatives showed mild defects of systolic and diastolic LV function, with normal filling pressures and exercise-induced increments in systolic contraction in most cases. LV dimensions and fractional shortening most effectively differentiated LVE relatives from control subjects, with other functional indices lacking additive discriminative value. In a receiver operating characteristics analysis, the area under the curve for LV end-diastolic diameter (% predicted) was 0.96 (P<0.001). LV end-diastolic diameter (% predicted) >116% or LV end-diastolic diameter (% predicted) 112% to 116%+fractional shortening ≤29% had high sensitivity (100%) and specificity (93%) for LVE relatives and identified 8 of 9 progressors.

CONCLUSIONS

LVE is a common finding in asymptomatic relatives in dilated cardiomyopathy families and can be a marker of preclinical cardiomyopathy. Assessment of LV size and contractile function is required for differentiating between pathological and physiological causes of LVE and may help to identify those at risk of disease progression.

Clinical and genetic issues in dilated cardiomyopathy: a review for genetics professionals

Dilated cardiomyopathy (DCM), usually diagnosed as idiopathic dilated cardiomyopathy (IDC), has been shown to have a familial basis in 20-35% of cases. Genetic studies in familial dilated cardiomyopathy (FDC) have shown dramatic locus heterogeneity with mutations identified in >30 mostly autosomal genes showing primarily dominant transmission. Most mutations are private missense, nonsense or short insertion/deletions. Marked allelic heterogeneity is the rule. Although to date most DCM genetics fits into a Mendelian rare variant disease paradigm, this paradigm may be incomplete with only 30-35% of FDC genetic cause identified. Despite this incomplete knowledge, we predict that DCM genetics will become increasingly relevant for genetics and cardiovascular professionals. This is because DCM causes heart failure, a national epidemic, with considerable morbidity and mortality. The fact that early, even pre-symptomatic intervention can prevent or ameliorate DCM, coupled with more cost-effective genetic testing, will drive further progress in the field. Ongoing questions include: whether sporadic (IDC) disease has a genetic basis, and if so, how it differs from familial disease; which gene-specific or genetic pathways are most relevant; and whether other genetic mechanisms (e.g., DNA structural variants, epigenetics, mitochondrial mutations and others) are operative in DCM. We suggest that such new knowledge will lead to novel approaches to the prevention and treatment of DCM.

Collagen XV Is Necessary for Modeling of the Extracellular Matrix and Its Deficiency Predisposes to Cardiomyopathy

Rationale:

The extracellular matrix (ECM) is a major determinant of the structural integrity and functional properties of the myocardium in common pathological conditions, and changes in vasculature contribute to cardiac dysfunction. Collagen (Col) XV is preferentially expressed in the ECM of cardiac muscle and microvessels.

Objective:

We aimed to characterize the ECM, cardiovascular function and responses to elevated cardiovascular load in mice lacking Col XV ( Col15a1 −/− ) to define its functional role in the vasculature and in age- and hypertension-associated myocardial remodeling.

Methods and Results:

Cardiac structure and vasculature were analyzed by light and electron microscopy. Cardiac function, intraarterial blood pressure, microhemodynamics, and gene expression profiles were studied using echocardiography, telemetry, intravital microscopy, and PCR, respectively. Experimental hypertension was induced with angiotensin II or with a nitric oxide synthesis inhibitor. Under basal conditions, lack of Col XV resulted in increased permeability and impaired microvascular hemodynamics, distinct early-onset and age-dependent defects in heart structure and function, a poorly organized fibrillar collagen matrix with marked interstitial deposition of nonfibrillar protein aggregates, increased tissue stiffness, and irregularly organized cardiomyocytes. In response to experimental hypertension, Col15a1 gene expression was increased in the left ventricle of wild-type mice, and mRNA expression of natriuretic peptides (ANP and BNP) and ECM modeling were abnormal in Col15a1 −/− mice.

Conclusions:

Col XV is necessary for ECM organization in the heart, and for the structure and functions of microvessels. Col XV deficiency leads to a complex cardiac phenotype and predisposes the subject to pathological responses under cardiac stress.

Genetics of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a myocardial disorder defined by ventricular chamber enlargement and systolic dysfunction. DCM can result in progressive heart failure, arrhythmias, thromboembolism, and premature death, and contributes significantly to health care costs. In many cases, DCM results from acquired factors that affect cardiomyocyte function or survival. Inherited genetic variants are also now recognized to have an important role in the etiology of DCM. Despite substantial progress over the past decade, our understanding of familial DCM remains incomplete. Current concepts of the molecular pathogenesis, clinical presentation, natural history, and management of familial DCM are outlined in this review.

Identification of novel mutations in RBM20 in patients with dilated cardiomyopathy

The genetic basis of most of dilated cardiomyopathy (DCM) cases remains unknown. A recent study indicated that mutations in a highly localized five amino acid hotspot in exon 9 of RBM20, a gene encoding a ribonucleic acid-binding protein, caused aggressive DCM. We undertook this study to confi rm and extend the nature of RBM20 mutations in another DCM cohort. Clinical cardiovascular data, family histories, and blood samples were collected from patients with idiopathic DCM. DNA from 312 DCM probands was sequenced for nucleotide alterations in exons 6 through 9 of RBM20, and additional family members as possible. We found six unique RBM20 rare variants in six unrelated probands (1.9%). Four mutations, two of which were novel (R634W and R636C) and two previously identified (R634Q and R636H), were identified in a five amino acid hotspot in exon 6. Two other novel variants (V535I in exon 6 and R716Q in exon 9) were outside of this hotspot. Age of onset and severity of heart failure were variable, as were arrhythmias and conduction system defects, but many subjects suffered severe heart failure resulting in early death or cardiac transplantation. This article concludes that DCM in patients with RBM20 mutations is associated with advanced disease.

Lamin A/C deficiency as a cause of familial dilated cardiomyopathy

PURPOSE OF REVIEW

Familial dilated cardiomyopathy is an underrecognized form of dilated cardiomyopathy. Lamin A/C deficiency is probably the most common cause of familial dilated cardiomyopathy. This review will focus on the emerging knowledge of epidemiology, diagnosis, and treatment of patients with lamin A/C deficiency, as well as possible disease mechanisms.

RECENT FINDINGS

Screening of patients with dilated cardiomyopathy continues to indicate that lamin A/C deficiency is a significant cause. Multiple novel mutations have been found, suggesting that many mutations are limited to individuals or families. It is unknown how mutations cause the syndrome, although an animal model has shown that lamin A/C insufficiency causes apoptosis, particularly in the conduction system. Inheritance is predominantly autosomal dominant, but penetrance is variable. For symptomatic patients, the course is malignant, with conduction system disease, atrial fibrillation, heart failure, and sudden cardiac death. The data are contradictory, and currently, there is no clear marker for when a lamin A/C-deficient patient is at risk for sudden death.

SUMMARY

Lamin A/C deficiency is an important cause of dilated cardiomyopathy, and diagnosis requires that clinicians have a high index of suspicion. Our knowledge of the mechanisms, diagnosis, and treatment of lamin A/C deficiency is incomplete. It is clear that patients with this condition have a malignant course and need to be followed aggressively.

Dilated cardiomyopathy caused by a novel TNNT2 mutation-added value of genetic testing in the correct identification of affected subjects

Diagnosing familial dilated cardiomyopathy requires careful family history taking and clinical evaluation in first degree relatives. Based on the results of these findings the diagnosis may be established in the proband. However, due to the age-dependent expression of the disease, doubt may persist regarding the exact status of other family members, especially in young individuals. Here we present a family with DCM in whom we identified an underlying cardiac troponin T (TNNT2) mutation. Genetic testing was essential for the detection of asymptomatic carriers as well as for exclusion of the disease in other family members.

Cardiac magnetic resonance imaging of myocardial contrast uptake and blood flow in patients affected with idiopathic or familial dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC) is characterized by left ventricular (LV) enlargement with systolic dysfunction, other causes excluded. When inherited, it represents familial dilated cardiomyopathy (FDC). We hypothesized that IDC or FDC would show with cardiac magnetic resonance (CMR) increased myocardial accumulation of gadolinium contrast at steady state and decreased baseline myocardial blood flow (MBF) due to structural alterations of the extracellular matrix compared with normal myocardium. CMR was performed in nine persons affected with IDC/FDC. Healthy controls came from the general population (n = 6) or were unaffected family members of FDC patients (n = 3) without signs or symptoms of IDC/FDC or any structural cardiac abnormalities. The myocardial partition coefficient for gadolinium contrast (lambda(Gd)) was determined by T1 measurements. LV shape and function and MBF were assessed by standard CMR methods. lambda(Gd) was elevated in IDC/FDC patients vs. healthy controls (lambda(Gd) = 0.56 +/- 0.15 vs. 0.41 +/- 0.06; P = 0.002), and correlated with LV enlargement (r = 0.61 for lambda(Gd) vs. end-diastolic volume indexed by height; P < 0.01) and with ejection fraction (r = -0.80; P < 0.001). The extracellular volume fraction was higher in IDC patients than in healthy controls (0.31 +/- 0.05 vs. 0.24 +/- 0.03; P = 0.002). Resting MBF was lower in IDC patients (0.64 +/- 0.13 vs. 0.91 +/- 0.22; P = 0.01) than unaffected controls and correlated with both the partition coefficient (r = -0.57; P = 0.012) and the extracellular volume fraction (r = -0.56; P = 0.019). The expansion of the extracellular space correlated with reduced MBF and ventricular dilation. Expansion of the extracellular matrix may be a key contributor to contractile dysfunction in IDC patients.

When the third degree is necessary: do pediatricians obtain enough information to detect patients at risk for HCM?

This study was designed to see if pediatricians are collecting sufficient data in family histories to be able to ascertain whether children are at risk for hypertrophic cardiomyopathy (HCM). Surveys were returned by 326 general pediatricians who were members of the Second Chapter of the American Academy of Pediatrics. The majority of pediatricians (98.2%) reported taking family histories; however, only 51.2% reported that this information was updated on a regular basis. Only 29.8% of the pediatricians reported including all five risk factors for HCM in a medical family history. Although almost all of the pediatricians reported including first-degree relatives in medical family histories, only 40.5% reported including all second-degree relatives. Female physicians were found to take more thorough medical family histories than male physicians, and foreign medical school graduates were found to take more thorough medical family histories than US medical school graduates. Additionally, graduates of foreign medical schools reported updating medical family histories more often than graduates of US medical schools. This study suggests that pediatricians might not be identifying risks pertinent to the identification of HCM.

Coding sequence mutations identified in MYH7, TNNT2, SCN5A, CSRP3, LBD3, and TCAP from 313 patients with familial or idiopathic dilated cardiomyopathy

BACKGROUND

More than 20 genes have been reported to cause idiopathic and familial dilated cardiomyopathy (IDC/FDC), but the frequency of genetic causation remains poorly understood.

METHODS AND RESULTS

Blood samples were collected and DNA prepared from 313 patients, 183 with FDC and 130 with IDC. Genomic DNA underwent bidirectional sequencing of six genes, and mutation carriers were followed up by evaluation of additional family members. We identified in 36 probands, 31 unique protein-altering variants (11.5% overall) that were not identified in 253 control subjects (506 chromosomes). These included 13 probands (4.2%) with 12 beta-myosin heavy chain (MYH7) mutations, nine probands (2.9%) with six different cardiac troponin T (TNNT2) mutations, eight probands (2.6%) carrying seven different cardiac sodium channel (SCN5A) mutations, three probands (1.0%) with three titin-cap or telethonin (TCAP) mutations, three probands (1.0%) with two LIM domain binding 3 (LDB3) mutations, and one proband (0.3%) with a muscle LIM protein (CSRP3) mutation. Four nucleotide changes did not segregate with phentoype and/or did not alter a conserved amino acid and were therefore considered unlikely to be disease-causing. Mutations in 11 probands were assessed as likely disease-causing, and in 21 probands were considered possibly disease-causing. These 32 probands included 14 of the 130 with IDC (10.8%) and 18 of 183 with FDC (9.8%)

CONCLUSIONS

Mutations of these six genes each account for a small fraction of the genetic cause of FDC/IDC. The frequency of possible or likely disease-causing mutations in these genes is similar for IDC and FDC.

Prevention of heart failure: a scientific statement from the American Heart Association Councils on Epidemiology and Prevention, Clinical Cardiology, Cardiovascular Nursing, and High Blood Pressure Research; Quality of Care and Outcomes Research Interdisciplinary Working Group; and Functional Genomics and Translational Biology Interdisciplinary Working Group

The increase in heart failure (HF) rates throughout the developed and developing regions of the world poses enormous challenges for caregivers, researchers, and policymakers. Therefore, prevention of this global scourge deserves high priority. Identifying and preventing the well-recognized illnesses that lead to HF, including hypertension and coronary heart disease, should be paramount among the approaches to prevent HF. Aggressive implementation of evidence-based management of risk factors for coronary heart disease should be at the core of HF prevention strategies. Questions currently in need of attention include how to identify and treat patients with asymptomatic left ventricular systolic dysfunction (Stage B HF) and how to prevent its development. The relationship of chronic kidney disease to HF and control of chronic kidney disease in prevention of HF need further investigation. Currently, we have limited understanding of the pathophysiological basis of HF in patients with preserved left ventricular systolic function and management techniques to prevent it. New developments in the field of biomarker identification have opened possibilities for the early detection of individuals at risk for developing HF (Stage A HF). Patient groups meriting special interest include the elderly, women, and ethnic/racial minorities. Future research ought to focus on obtaining a much better knowledge of genetics and HF, especially both genetic risk factors for development of HF and genetic markers as tools to guide prevention. Lastly, a national awareness campaign should be created and implemented to increase public awareness of HF and the importance of its prevention. Heightened public awareness will provide a platform for advocacy to create national research programs and healthcare policies dedicated to the prevention of HF.

Severe Myocardial Fibrosis Caused by a Deletion of the 5’ End of the Lamin A/C Gene

OBJECTIVES

The goal of this study was to identify the underlying gene defect in a family with inherited myocardial fibrosis.

BACKGROUND

A large family with an autosomal dominantly inherited form of myocardial fibrosis with a highly malignant clinical outcome has been investigated. Because myocardial fibrosis preceded the clinical and echocardiographic signs, we consider the disease to be a hereditary form of cardiac fibrosis.

METHODS

Twenty-five family members were clinically evaluated, and 5 unaffected and 8 affected family members were included in a genome-wide linkage study.

RESULTS

The highest logarithm of the odds (LOD) score (LOD = 2.6) was found in the region of the lamin AC (LMNA) gene. The LMNA mutation analysis, both by denaturing gradient gel electrophoresis and sequencing, failed to show a mutation. Subsequent Southern blotting, complementary deoxyribonucleic acid sequencing, and multiplex ligation-dependent probe amplification analysis, however, revealed a deletion of the start codon-containing exon and an adjacent noncoding exon. In vitro studies demonstrated that the deletion results in the formation of nuclear aggregates of lamin, suggesting that the mutant allele is being transcribed.

CONCLUSIONS

This novel LMNA deletion causes a distinct, highly malignant cardiomyopathy with early-onset primary cardiac fibrosis likely due to an effect of the shortened mutant protein, which secondarily leads to arrhythmias and end-stage cardiac failure.

Mutations of presenilin genes in dilated cardiomyopathy and heart failure

Two common disorders of the elderly are heart failure and Alzheimer disease (AD). Heart failure usually results from dilated cardiomyopathy (DCM). DCM of unknown cause in families has recently been shown to result from genetic disease, highlighting newly discovered disease mechanisms. AD is the most frequent neurodegenerative disease of older Americans. Familial AD is caused most commonly by presenilin 1 (PSEN1) or presenilin 2 (PSEN2) mutations, a discovery that has greatly advanced the field. The presenilins are also expressed in the heart and are critical to cardiac development. We hypothesized that mutations in presenilins may also be associated with DCM and that their discovery could provide new insight into the pathogenesis of DCM and heart failure. A total of 315 index patients with DCM were evaluated for sequence variation in PSEN1 and PSEN2. Families positive for mutations underwent additional clinical, genetic, and functional studies. A novel PSEN1 missense mutation (Asp333Gly) was identified in one family, and a single PSEN2 missense mutation (Ser130Leu) was found in two other families. Both mutations segregated with DCM and heart failure. The PSEN1 mutation was associated with complete penetrance and progressive disease that resulted in the necessity of cardiac transplantation or in death. The PSEN2 mutation showed partial penetrance, milder disease, and a more favorable prognosis. Calcium signaling was altered in cultured skin fibroblasts from PSEN1 and PSEN2 mutation carriers. These data indicate that PSEN1 and PSEN2 mutations are associated with DCM and heart failure and implicate novel mechanisms of myocardial disease.

Clinical characteristics of 304 kindreds evaluated for familial dilated cardiomyopathy

BACKGROUND

Familial dilated cardiomyopathy (FDC) is dilated cardiomyopathy of unknown cause occurring in 2 or more closely related family members.

METHODS AND RESULTS

Members of 304 families suspected to have FDC were evaluated by family history (FH) and medical record review and were categorized as affected with idiopathic dilated cardiomyopathy (IDC), unaffected, unknown, or no data. Pedigrees were categorized with confirmed FDC, probable FDC, possible FDC or IDC based on strength of evidence. Of the 304 pedigrees, 125 were categorized as confirmed FDC, 48 were probable FDC, 72 were possible FDC, and 59 had sporadic, nonfamilial IDC. Numbers of living first- and second-degree family members, and median number of relatives available for FH was greatest with confirmed FDC, and diminished for probable and possible FDC, and IDC categories. LV dimensions increased and LV function worsened in index patients along the spectrum from confirmed FDC, probable FDC, possible FDC and IDC, and a greater proportion of IDC patients underwent heart transplant. However, the age of onset, duration of disease, the time to death or heart transplant, and most other findings were similar among the 4 categories.

CONCLUSION

Clinical characteristics of IDC and FDC are similar, precluding an FDC diagnosis from clinical features only.

Progression of familial and non-familial dilated cardiomyopathy: long term follow up

BACKGROUND

It is unknown whether progression of familial idiopathic dilated cardiomyopathy differs from progression in the non-familial form. It has been suggested that familial disease indicates a worse prognosis, and that this should be considered when planning the timing of heart transplantation.

OBJECTIVE

To compare five year survival or time to heart transplantation in an unselected series of patients with dilated cardiomyopathy who had been evaluated for familial v non-familial disease through the echocardiographic investigation of first degree relatives.

DESIGN

Medical records were reviewed and questionnaires were mailed to all patients who had previously participated in a family based study of dilated cardiomyopathy. Information was gathered about survival, heart transplantation, and left ventricular ejection fraction (LVEF) measurements. Survival data were censored at the time of cardiac transplantation.

RESULTS

Follow up data were obtained for 99 of 101 patients (69 with non-familial and 30 with familial disease). Five year survival was 55% for non-familial and 51% for familial patients (NS). The main predictor of mortality was an LVEF of < 30%. Familial status did not predict mortality. There was no significant difference in follow up LVEF values between the groups.

CONCLUSIONS

Five year survival is not significantly different in the familial and non-familial forms of dilated cardiomyopathy.

Familial cardiomyopathies: significant causes of heart failure

Familial dilated cardiomyopathies (FDCMs) account for about one third of idiopathic dilated cardiomyopathies, yet clinicians under-appreciate their prevalence. Among the inherited cardiomyopathies, FDCMs account for the greatest burden of heart failure and its associated morbidities. This paper summarizes significant molecular-genetic data, and discusses clinical manifestations of the major inherited cardiomyopathies, and the importance of clinical and genetic screening. Suggestions are provided as to how to proceed with screening. The purpose of this paper is to update clinicians about this rapidly growing scientific field, and to encourage application of current evidence to their practices.

A novel lamin A/C mutation in a family with dilated cardiomyopathy, prominent conduction system disease, and need for permanent pacemaker implantation

BACKGROUND

The LMNA gene, which encodes the nuclear envelope protein lamin A/C, is thought to be the most common of 8 autosomal disease genes implicated in familial dilated cardiomyopathy (FDC). Each family reported to date has a unique mutation and variable degrees of cardiac conduction system, dilated cardiomyopathy, or skeletal muscle disease.

METHODS AND RESULTS

Coding regions of the LMNA gene were screened in 12 biological members of a family with dilated cardiomyopathy and conduction system disease. A novel missense mutation (Leu215Pro) in exon 4 was identified in 8 subjects. Disease was manifested as brady- and tachyarrhythmias, often necessitating permanent pacemaker implantation, and later onset of dilated cardiomyopathy and heart failure. No features of skeletal muscle disease were noted. The high percentage of affected individuals who needed pacemaker therapy (88%) was a unique characteristic of this family compared with other FDC families with LMNA mutations.

CONCLUSIONS

Careful examination of clinical data in families with FDC and LMNA mutations may reveal subtle genotype-phenotype correlations. Knowledge of such correlations may help to further define the mechanisms of disease in LMNA-associated FDC and can assist in the monitoring of disease for at-risk family members.

Periodic rescreening is indicated for family members at risk of developing familial dilated cardiomyopathy

OBJECTIVES

This study evaluated the role of clinical rescreening of family members at risk for familial dilated cardiomyopathy (FDC).

BACKGROUND

Familial dilated cardiomyopathy is a genetic cardiomyopathy that usually is transmitted in an autosomal dominant pattern and may underlie from one-quarter to one-half of idiopathic dilated cardiomyopathy (IDC) diagnoses. Thus, FDC may present with advanced heart failure (HF) or sudden cardiac death (SCD). Because FDC may respond to medical intervention, we have previously recommended that screening of first-degree relatives (parents, siblings, children) of patients diagnosed with IDC be undertaken to rule out FDC, and that with a diagnosis of FDC in the kindred, unaffected but at-risk family members be rescreened every three to five years. METHODS; Follow-up screening (history, examination, electrocardiogram, echocardiography) of a large family with FDC was performed six years after initial screening. Of 68 family members who underwent rescreening, two (one with left ventricular enlargement only, one with a left bundle branch block) presented with advanced HF and SCD, respectively. Two additional subjects, asymptomatic at initial screening, were also affected with FDC at follow-up.

CONCLUSIONS

Considerable vigilance for disease presentation and progression is indicated in at-risk members of a kindred with FDC, especially those with incipient FDC.

Cardiac troponin T lysine 210 deletion in a family with dilated cardiomyopathy

BACKGROUND

The gene for cardiac troponin T (TNNT2) is 1 of 7 autosomal disease genes implicated in familial dilated cardiomyopathy (FDC). Identical deletions in exon 13 of TNNT2 have been reported in 2 families with FDC, but little is known about the frequency of this deletion among patients with FDC and idiopathic dilated cardiomyopathy (IDC) and the associated phenotype.

METHODS AND RESULTS

Exon 13 of the cardiac troponin T gene was sequenced in 61 subjects with FDC and 53 subjects with IDC. A 3-base pair deletion (DeltaLys210), identified in 1 family with at least 7 clinically affected family members, is reported. Age of disease onset and disease severity varied widely among affected individuals; phenotypic findings included dilated cardiomyopathy, sudden cardiac death, conduction system disease including atrial fibrillation and atrioventricular block, and heart failure. Sudden-onset, rapidly progressive disease was observed in younger individuals.

CONCLUSIONS

Cardiac troponin T exon 13 lysine deletions can cause FDC of varying severity and are an important but uncommon cause of FDC.

Novel lamin A/C mutations in two families with dilated cardiomyopathy and conduction system disease

BACKGROUND

The LMNA gene, one of 6 autosomal disease genes implicated in familial dilated cardiomyopathy, encodes lamins A and C, alternatively spliced nuclear envelope proteins. Mutations in lamin A/C cause 4 diseases: Emery-Dreifuss muscular dystrophy, limb girdle muscular dystrophy type 1B, Dunnigan-type familial partial lipodystrophy, and dilated cardiomyopathy.

METHODS AND RESULTS

Two 4-generation white families with autosomal dominant familial dilated cardiomyopathy and conduction system disease were found to have novel mutations in the rod segment of lamin A/C. In family A a missense mutation (nucleotide G607A, amino acid E203K) was identified in 14 adult subjects; disease was manifest as progressive conduction disease in the fourth and fifth decades. Death was caused by heart failure. In family B a nonsense mutation (nucleotide C673T, amino acid R225X) was identified in 10 adult subjects; disease was also manifest as progressive conduction disease but with earlier onset (third and fourth decades), ventricular dysrhythmias, left ventricular enlargement, and systolic dysfunction. Death was caused by heart failure and sudden cardiac death. Skeletal muscle disease was not observed in either family.

CONCLUSIONS

Novel rod segment mutations in lamin A/C cause variable conduction system disease and dilated cardiomyopathy without skeletal myopathy.

Difficult cases in heart failure: familial dilated cardiomyopathy

While originally thought to be uncommon, familial dilated cardiomyopathy may occur quite often. Aside from symptoms of heart failure, these forms of dilated cardiomyopathy may be associated with arrhythmias and sudden death. The case detailed describes such a patient and emphasizes the importance of a careful family history. Also discussed is the importance of screening of first- and second-degree relatives of these patients. (c)2001 by CHF, Inc.

Familial dilated cardiomyopathy: echocardiographic diagnostic criteria for classification of family members as affected

BACKGROUND

Echocardiographic criteria for left ventricular enlargement (LVE) used to classify subjects as affected in families with familial dilated cardiomyopathy (FDC) have been inconsistent. A recent report from a large Framingham echocardiographic study provides an opportunity to improve the assignment of LVE and FDC in kindreds, principally with a dilated phenotype. The objective of this study is to evaluate an alternative diagnostic criteria for FDC based only on LVE with no measure of fractional shortening (FS).

METHODS AND RESULTS

We compared our proposed criteria for LVE and FDC with previous approaches by applying them to 166 adults derived from three large FDC pedigrees. Our proposed FDC diagnostic criteria are a sex- and height-specific method based only on LVE, without regard for FS, set as a 97.5% upper limit for left ventricular end-diastolic dimension (LVEDD) from the Framingham study. Other methods used to assign LVE were (1) a 95% upper limit for LVEDD by the Framingham study; (2) the method of Henry et al. (1980) based on age and body surface area (BSA); and (3) the National Heart, Lung, and Blood Institute (NHLBI) method with a cut point of LVEDD greater than 2.7 cm/BSA. Three other commonly used diagnostic criteria for FDC were based on various LVE standards combined with an FS of 27% to 30%. For LVE, the Framingham-97.5% was the most stringent (21 of 134 subjects identified; 15.7%), the NHLBI standard the least stringent (57 of 161 subjects identified; 35.4%), and the Henry-112% method intermediate (44 of 161 subjects identified; 27.3%). More women were identified with the Framingham method (57.1%) versus the Henry-112% (40.9%). The Henry-112% and NHLBI methods identified 11.4% and 7.0% of subjects with body mass indices (BMIs) of 35 or greater, respectively. For FDC, our proposed FDC diagnostic criteria identified similar numbers of subjects (21 subjects) as the three other criteria (range, 22 to 27 subjects), but inconsistency was noted (54.2% to 66.7%), with kappa values from 0.49 to 0.55 resulting from different sensitivities to sex, LVE, FS, and BMI.

CONCLUSION

Our proposed FDC diagnostic criteria are stringent to assign FDC family members as affected compared with other commonly used criteria. The use of LVEDD alone may be preferable for FDC family screening, although further validation of this approach with phenotypic and genotypic data from other large FDC pedigrees is needed.