Characterization of clinically relevant copy-number variants from exomes of patients with inherited heart disease and unexplained sudden cardiac death.

PURPOSE: Copy-number variant (CNV) analysis is increasingly performed in genetic diagnostics. We leveraged recent gene curation efforts and technical standards for interpretation and reporting of CNVs to characterize clinically relevant CNVs in patients with inherited heart disease and sudden cardiac death. METHODS: Exome sequencing data were analyzed for CNVs using eXome-Hidden Markov Model tool in 48 established disease genes. CNV breakpoint junctions were characterized. CNVs were classified using the American College of Medical Genetics and Genomics technical standards. RESULTS: We identified eight CNVs in 690 unrelated probands (1.2%). Characterization of breakpoint junctions revealed nonhomologous end joining was responsible for four deletions, whereas one duplication was caused by nonallelic homologous recombination between duplicated sequences in MYH6 and MYH7. Identifying the precise breakpoint junctions determined the genomic involvement and proved useful for interpreting the clinical relevance of CNVs. Three large deletions involving TTN, MYBPC3, and KCNH2 were classified as pathogenic in three patients. Haplotype analysis of a deletion in ACTN2, found in two families, suggests the deletion was caused by an ancestral event. CONCLUSION: CNVs infrequently cause inherited heart diseases and should be investigated when standard genetic testing does not reveal a genetic diagnosis.

A systematic review and meta-analysis of the prevalence of left ventricular non-compaction in adults.

AIMS: To assess the reported prevalence of left ventricular non-compaction (LVNC) in different adult cohorts, taking in to consideration the role of diagnostic criteria and imaging modalities used. METHODS AND RESULTS: A systematic review and meta-analysis of studies reporting LVNC prevalence in adults. Studies were sourced from Pre-Medline, Medline, and Embase and assessed for eligibility according to inclusion criteria. Eligible studies provided a prevalence of LVNC in adult populations (≥12 years). Studies were assessed, and data extracted by two independent reviewers. Fifty-nine eligible studies documenting LVNC in 67 unique cohorts were included. The majority of studies were assessed as moderate or high risk of bias. The pooled prevalence estimates for LVNC were consistently higher amongst cohorts diagnosed on cardiac magnetic resonance (CMR) imaging (14.79%, n = 26; I2 = 99.45%) compared with echocardiogram (1.28%, n = 36; I2 = 98.17%). This finding was unchanged when analysis was restricted to studies at low or moderate risk of bias. The prevalence of LVNC varied between disease and population representative cohorts. Athletic cohorts demonstrated high pooled prevalence estimates on echocardiogram (3.16%, n = 5; I2 = 97.37%) and CMR imaging (27.29%, n = 2). CONCLUSION: Left ventricular non-compaction in adult populations is a poorly defined entity which likely encompasses both physiological adaptation and pathological disease. There is a higher prevalence with the introduction of newer imaging technologies, specifically CMR imaging, which identify LVNC changes more readily. The clinical significance of these findings remains unclear; however, there is significant potential for overdiagnosis, overtreatment, and unnecessary follow-up.

Left Ventricular Non-Compaction: Review of the Current Diagnostic Challenges and Consequences in Athletes.

Left ventricular non-compaction (LVNC) is a complex clinical condition with no diagnostic gold standard. At present, there is trepidation about the accuracy of the diagnosis, the correlation to clinical outcomes and the long-term medical management. This article reviews the current imaging criteria, the limitations of echocardiography and cardiac magnetic resonance and the consequences of LV hypertrabeculation in athletes.

Transcriptome Sequencing of Patients With Hypertrophic Cardiomyopathy Reveals Novel Splice-Altering Variants in MYBPC3.

BACKGROUND: Transcriptome sequencing can improve genetic diagnosis of Mendelian diseases but requires access to tissue expressing disease-relevant transcripts. We explored genetic testing of hypertrophic cardiomyopathy using transcriptome sequencing of patient-specific human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs). We also explored whether antisense oligonucleotides (AOs) could inhibit aberrant mRNA splicing in hiPSC-CMs. METHODS: We derived hiPSC-CMs from patients with hypertrophic cardiomyopathy due to MYBPC3 splice-gain variants, or an unresolved genetic cause. We used transcriptome sequencing of hiPSC-CM RNA to identify pathogenic splicing and used AOs to inhibit this splicing. RESULTS: Transcriptome sequencing of hiPSC-CMs confirmed aberrant splicing in 2 people with previously identified MYBPC3 splice-gain variants (c.1090+453C>T and c.1224-52G>A). In a patient with an unresolved genetic cause of hypertrophic cardiomyopathy following genome sequencing, transcriptome sequencing of hiPSC-CMs revealed diverse cryptic exon splicing due to an MYBPC3 c.1928-569G>T variant, and this was confirmed in cardiac tissue from an affected sibling. Antisense oligonucleotide treatment demonstrated almost complete inhibition of cryptic exon splicing in one patient-specific hiPSC-CM line. CONCLUSIONS: Transcriptome sequencing of patient specific hiPSC-CMs solved a previously undiagnosed genetic cause of hypertrophic cardiomyopathy and may be a useful adjunct approach to genetic testing. Antisense oligonucleotide inhibition of cryptic exon splicing is a potential future personalized therapeutic option.

Long term clinical outcomes associated with CMR quantified isolated left ventricular non-compaction in adults.

BACKGROUND: Left ventricular non-compaction (LVNC) is a complex clinical condition with several diagnostic criteria but no diagnostic gold standard. We aimed to evaluate our thresholding technique in a group of patients with LVNC and assess the risk of major adverse cardiovascular and cerebrovascular events (MACCE). METHODS: We retrospectively analyzed cardiac magnetic resonance (CMR) scans of patients with Petersen criteria LVNC and quantified noncompacted myocardial mass. We assessed the association of noncompacted myocardial mass, CMR derived LV volumetric parameters and late gadolinium enhancement (LGE) to MACCE including cardiac death, cardiac transplantation, sustained ventricular tachycardia/ventricular fibrillation (VT/VF) and ischemic stroke. Patients with known genetic mutations and cardiovascular disease were excluded. RESULTS: 98 patients with LVNC were included (55 males,56.7%); 17(17.3%) patients had impaired LV function and five (5.1%) had LGE. Patients with impaired LV function had more end-systolic noncompacted mass (61.9 g±22.4 vs. 38.1 g±15.8, p < 0.001) and larger end-systolic noncompacted to total myocardial mass (44%±9 vs. 36%±12, p = 0.003). At 78 months follow-up [interquartile range(IQR) 66-90], MACCE occurred in 11(11.3%) patients; nine(81.8%) had impaired LV function and two(18.2%) had LGE. Impaired LV function and LV LGE were predictors of MACCE (HR = 35.6, 95% CI = 7.65-165.21, p < 0.001 and HR = 16.2, 95% CI = 4.54-57.84, p < 0.001) whereas noncompacted mass were not. CONCLUSION: Noncompacted mass was not an independent predictor of major adverse events but in patients with impaired LV function and/or LV LGE, the risk of MACCE was high. These results highlight the importance of including LV volumetrics and scar in the assessment of patients with LV noncompaction.