Familial aggregation of dilated cardiomyopathy--evaluation of clinical characteristics and prognosis

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.

Evolving molecular diagnostics for familial cardiomyopathies: at the heart of it all

Cardiomyopathies are an important and heterogeneous group of common cardiac diseases. An increasing number of cardiomyopathies are now recognized to have familial forms, which result from single-gene mutations that render a Mendelian inheritance pattern, including hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy and left ventricular noncompaction cardiomyopathy. Recently, clinical genetic tests for familial cardiomyopathies have become available for clinicians evaluating and treating patients with these diseases, making it necessary to understand the current progress and challenges in cardiomyopathy genetics and diagnostics. In this review, we summarize the genetic basis of selected cardiomyopathies, describe the clinical utility of genetic testing for cardiomyopathies and outline the current challenges and emerging developments.

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.

Gene mutations in adult Japanese patients with dilated cardiomyopathy

BACKGROUND

Some patients with dilated cardiomyopathy (DCM) have mutations of the genes that encode sarcomeric or cytoskeletal proteins of cardiomyocytes, but the prevalence of these mutations in Japan remains unclear.

METHODS AND RESULTS

A group of 99 unrelated adult patients with DCM (familial n=27, sporadic n=72) were screened for the following genes: cardiac beta-myosin heavy chain, cardiac myosin-binding protein C (MYBPC3), regulatory and essential myosin light chains, alpha cardiac actin, alpha tropomyosin, cardiac troponin T, cardiac troponin I, cardiac troponin C, dystrophin, and lamin A/C. A mutation (R820Q) in MYBPC3 was found in an aged patient. In addition, dystrophin mutations were identified in 3 male patients (2 with exon 45-48 deletion and 1 with exon 48-52 deletion). The prevalence of dystrophin mutations in male patients with DCM was 4.4% (3 of 68). No mutations involving amino acid changes were identified in the other genes.

CONCLUSIONS

Although cases of adult patients with DCM caused by mutations of the genes encoding sarcomeric or cytoskeletal proteins of cardiomyocytes are infrequent in Japan, it may be advisable to screen older DCM patients for MYBPC3 mutations, and male patients with familial DCM for dystrophin mutations.

Prognostic value of serial cardiac assessment and familial screening in patients with dilated cardiomyopathy

OBJECTIVES

This prospective study was performed to analyse whether routine clinical follow-up investigations at 12+/-6 months add to risk stratification and improve survival rates in patients with a first diagnosis of dilated cardiomyopathy (DCM).

METHODS

Four hundred and eighty consecutive patients (mean age 53.4+/-12.3 years, 369 males, mean NYHA class 2.4+/-0.8) with invasively confirmed DCM were included and followed for 3.9+/-3.5 years. Patients were requested to adhere to a follow up investigation within 6-18 months either at the referring physicians or at our out patient department. Two hundred and eighty-one of the 480 patients presented for follow up which consisted of a detailed evaluation of symptoms, standardized physical examination, 12-lead-electrocardiogram recording and echocardiography. Seventeen patients were lost for follow up, 182 did not seek specialized medical follow up. Patients outcome was assessed by structured telephone interviews.

RESULTS

Independent predictors of death or transplantation at initial diagnosis were LV-ejection fraction <30% (P=0.0001, risk ratio 2.25), LV-end diastolic pressure >or=15 mmHg (P=0.002, risk ratio 2.0), age >or=54 years, (P=0.04, risk ratio 1.55), and presence of left bundle branch block (P=0.046, risk ratio 1.53). On follow up investigations only deterioration of clinical status by at least one NYHA-class (P=0.001, risk ratio 2.6) and new onset or worsening of mitral regurgitation (P=0.02, risk ratio 1.8), remained independent prognostic factors for cardiac death. Patients who presented for routine follow up revealed significant better 5-year survival rates (n=281, 70%) than those who did not (n=153, 55%, P=0.005).

CONCLUSIONS

Routine clinical follow up investigations within 6-18 months after first diagnosis of DCM adds to risk stratification and improves survival rates.

Mutational analysis of the cardiac actin gene in familial and sporadic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) results in part from genetic disorders. Recently, missense mutations of the cardiac actin gene have been reported to cause DCM. We studied 136 Japanese DCM cases to elucidate how frequently the gene mutations are involved in its pathogenesis. Genomic DNA samples were obtained from 136 DCM cases (107 males, 29 females), containing 30 familial DCM (5 confirmed and 25 suspected). All six exons of the cardiac actin gene were analyzed by polymerase chain reaction, single-strand conformation polymorphism, and sequencing. We detected no mutations of the disease causation previously reported (G867A or A1014G) but two silent mutations (G979C and C1018T) in exon 6 and one point mutation (T1080A) in the 3'-untranslated region. As a result of screening 128 healthy subjects, these novel silent mutations were found to be mere genetic polymorphisms, not responsible for the disease. Although some genetic polymorphisms exist in the cardiac actin gene, mutations of the gene are rarely responsible for DCM, at least in the Japanese patients.