Molecular characterization of Portuguese patients with dilated cardiomyopathy.

INTRODUCTION: Dilated cardiomyopathy (DCM) is a disease of the heart muscle characterized by ventricular dilatation and impaired systolic function. Familial forms account for 30-50% of cases. Autosomal dominant inheritance is the predominant pattern of transmission. Causal genetic variants have been identified in several genes and molecular diagnosis has implications for genetic counseling and risk stratification. OBJECTIVE: We aimed to estimate the frequency of genetic variants and the molecular basis of DCM in Portugal. METHODS: We performed a multicenter study of unrelated patients, recruited between 2013 and 2014. Variants in 15 genes were screened using PCR with direct sequencing (next-generation sequencing with at least 30-fold coverage combined with Sanger sequencing). RESULTS: A total of 107 patients were included, 64 (60%) men, mean age at diagnosis 38±13 years, with 48 (45%) familial cases. In total, 31 rare variants in eight genes (mainly in MYBPC3, TNNT2 and LMNA) were identified, in 28 patients (26%). Only four variants had been previously described in association with DCM, 11 with hypertrophic cardiomyopathy, and nine variants were novel. Four variants were likely pathogenic and the remainder were of uncertain significance. We found no major differences in the main clinical and imaging characteristics between patients with or without rare variants and patients with likely pathogenic variants. CONCLUSIONS: Our results reflect the complexity and diversity of DCM genetics. For better interpretation of the pathogenicity of the variants found and their causative roles in DCM, molecular cascade screening of families is imperative. Further insight into genotype-phenotype correlations and risk stratification is desirable.

Genetic Variants Are Not Rare in ICD Candidates with Dilated Cardiomyopathy: Time for Next-Generation Sequencing?

BACKGROUND: Sudden cardiac death (SCD) risk stratification in dilated cardiomyopathy (DCM) has been based on left ventricular ejection fraction (LVEF), even though SCD may occur with LVEF > 35%. Family history of unexplained SCD, especially in the young, raises concern about potential inheritable risk factors. It remains largely unknown how genetic tests can be integrated into clinical practice, particularly in the selection of implantable cardioverter defibrillator (ICD) candidates. We aimed to assess the diagnostic yield of genetic testing in DCM patients with a class I recommendation for ICD implantation, based on current guidelines. METHODS: We included ambulatory stable adult patients with idiopathic or familial DCM with previously implanted ICD. Molecular analysis included 15 genes (LMNA, MYH7, MYBPC3, TNNT2, ACTC1, TPM1, CSRP3, TCAP, SGCD, PLN, MYL2, MYL3, TNNI3, TAZ, and LDB3) using next-generation sequencing. RESULTS: We evaluated 21 patients, 12 (57%) males and 9 (43%) with familial DCM, including 3 (14%) with a family history of premature unexplained SCD. Mean age at DCM diagnosis was 40 ± 2 years, and mean age at ICD implantation was 50 ± 12 years. LVEF was 27 ± 9%, and LV end-diastolic diameter was 65 ± 7 mm. Genetic variants were found in six (29%) patients, occurring in 5 genes: TPM1, TNNT2, MYH7, PLN, and MYBPC3. The majority were classified as variants of uncertain significance. Family history of SCD was present in both patients with PLN variants. CONCLUSION: In patients with DCM and ICD, genetic variants could be identified in a significant proportion of patients in several genes, highlighting the potential role of genetics in DCM SCD risk stratification.