Clinical genetic testing in pediatric cardiomyopathy: Is bigger better?

BACKGROUND: For clinical genetic testing of cardiomyopathy (CMP), current guidelines do not address which gene panels to use: targeted panels specific to a CMP phenotype or expanded (panCMP) panels that include genes associated with multiple phenotypic subtypes. AIM: Our objective was to assess the clinical utility of targeted versus panCMP panel testing in pediatric CMPs. METHODS: 151 pediatric patients with primary hypertrophic (n = 66), dilated (n = 64), restrictive (n = 8), or left-ventricular non-compaction (n = 13) CMP who underwent clinical genetic panel testing at a single centre were included. PanCMP (n = 47) and targeted panel testing (n = 104) were compared for yield of pathogenic variants and variants of unknown significance (VUS). RESULTS: Pathogenic variants were identified in 26% of patients, 42% had indeterminate results (only VUS detected), and 32% had negative results. Yield was lower (15%) in panCMP vs. targeted panel testing (32%) (P = .03) in all CMP subtypes. VUS detection was higher with panCMP (87%) than targeted panel testing (30%) (P <.0001). PanCMP panel testing only identified pathogenic variants in genes that overlapped targeted panels. CONCLUSION: PanCMP testing did not increase diagnostic yield compared to targeted panel testing. Until accuracy of variant interpretation with panCMP panels improves, targeted panels may be suitable for clinical testing in pediatric CMP.

Utility of genetics for risk stratification in pediatric hypertrophic cardiomyopathy.

Children with hypertrophic cardiomyopathy (HCM) experience sudden cardiac death (SCD) and other life-threatening events. We assessed if affected gene and variant burden predict outcomes. Patients <18 years old with primary HCM with a pathogenic variant or variant of uncertain significance in cardiomyopathy genes were included. Association of gene and variant number and type with freedom from major adverse cardiac events (MACE), that is, ICD insertion, myectomy, aborted SCD, transplantation or death, was assessed by Cox regression. A total of 98 of 155 gene-tested patients carried a non-benign variant. The primary affected gene was MYH7 in 35% (MYH7+) and MYBPC3 in 49% (MYBPC3+). MYH7+ patients had earlier disease onset and higher risk of MACE (hazard ratio 2.7, 95% CI 1.3-5.7). Risk of MACE was also higher in patients with multiple variants (n = 16) (HR 2.5, CI: 1.1-5.9) compared to a propensity score-matched single variant subset, after adjustment for primary gene, and in patients with de novo (n = 18) vs inherited variants (HR 5.7, CI: 2.6-12.7). Affected gene (eg, MYH7), higher variant burden and de novo variant status are independently associated with earlier onset and higher frequency of adverse outcomes in pediatric HCM, highlighting the importance of genetic risk stratification in HCM.