Testing In Dilated Cardiomyopathy Research Articles

Diagnostic yield and predictive value on left ventricular remodelling of genetic testing in dilated cardiomyopathy.

We assessed the diagnostic yield of genetic testing and the relationship of left ventricular (LV) reverse remodelling (LVRR) with the presence of DNA pathogenic (P) or likely pathogenic (LP) variants in patients with dilated cardiomyopathy (DCM). From 680 outpatients followed at the Heart Failure Outpatient Clinic of our institution, we selected subjects with a diagnosis of DCM as defined by LV ejection fraction (LVEF) ≤40% and LV dilatation not explained by coronary artery disease or other causes. All patients were offered genetic investigation of 42 disease-associated DCM genes with next-generation sequencing. Seventy patients fulfilled the definition of DCM and 66 underwent genetic investigation. We identified 18 P/LP variants in 16 patients, with a diagnostic yield of 24%. The most common variants were truncating TTN variants (n=7), followed by LMNA (n=3), cytoskeleton Z-disc (n=3), ion channel (n=2), motor sarcomeric (n=2), and desmosomal (n=1) genes. After a median follow-up of 53months (inter-quartile range 20-111), patients without P/LP variants exhibited higher systolic and diastolic blood pressure, lower plasma brain natriuretic peptide levels, and a larger extent of LVRR, as reflected by the increase in LVEF (+14% vs. +1%, P=0.0008) and decrease in indexed LV end-diastolic diameter (-6.5 vs. -2mm/m2 , P=0.03) compared with patients with P/LP variants. Our results confirm the high diagnostic yield of genetic testing in selected DCM patients and suggest that identification of P/LP variants in DCM portends poorer LVRR in response to guideline-directed medical therapy.

Diagnostic and prognostic relevance of using large gene panels in the genetic testing of patients with dilated cardiomyopathy.

It was previously suggested that increasing the number of genes on diagnostic gene panels could increase the genetic yield in patient with dilated cardiomyopathy (DCM). We explored the diagnostic and prognostic relevance of testing DCM patients with an expanded gene panel. The current study included 225 consecutive DCM patients who had no genetic diagnosis after a 48-gene cardiomyopathy-panel. These were then evaluated using an expanded gene panel of 299 cardiac-associated genes. A likely pathogenic/pathogenic (P/LP) variant was detected in 13 patients. Five variants were reclassifications of variants found in genes which were already detected using the 48 gene panel. Only one of the other eight variants could explain the phenotype of the patient (KCNJ2). The panel detected 186 VUSs in 127 patients (of which 6 also had a P/LP variant). The presence of a VUS was significantly associated with the combined end-point of mortality, heart failure hospitalization, heart transplantation or life-threatening arrhythmias(HR, 2.04 [95% CI, 1.15 to 3.65]; p = 0.02). The association of a VUS with prognosis remained when we only included VUSs in robust DCM-associated genes (high suspicious VUSs), but disappeared when we only included VUSs in non-robust DCM-associated genes (low suspicious VUSs), highlighting the importance of weighing of VUSs. Overall, the use of large gene panels for genetic testing in DCM does not increase the diagnostic yield, although a VUS in a robust DCM-associated gene is associated with an adverse prognosis. Altogether, current diagnostic gene panels should be limited to the robust DCM-associated genes.

PO-01-015 YIELD OF GENETIC TESTING AND RESULT UTILITY IN A COHORT OF 2100 DCM PATIENTS

Familial dilated cardiomyopathy (DCM) is typically an autosomal dominant (AD), monogenic disorder. Advances in gene-specific precision medicine approaches increasingly highlight the importance of genetic testing for patients with this diagnosis. The yield of genetic testing in DCM has largely been documented by single center studies and have not evaluated the utility of results for gene-specific management purposes. We report the yield of genetic testing in a large cohort of patients with a clinical suspicion of DCM from multiple centers and describe the potential clinical utility of results. This was a retrospective review of consecutive, deidentified patients who underwent genetic testing with a multigene, cardiomyopathy-focused next generation sequencing (NGS) panel. Patients had a confirmed or suspected diagnosis of DCM based on the test requisition received. Panels included sequence and copy number variant (CNV) analysis by NGS of 23 to 316 genes. An informative result was defined as the identification of pathogenic (P) or likely pathogenic (LP) variant(s) using a modified ACMG/AMP classification scheme. A total of 2,100 index patients underwent testing; 56.4% were tested with large panels (101-316 genes; n=1,184). Sequencing and CNV analysis was performed in 73.0% (n=1,533) of patients and panels that included mtDNA were performed for 38.3% (n=804). In this cohort, 24.2% (n=508) of patients received an informative result. AD inheritance was seen in 94.1% (n=478), followed by autosomal recessive (AR) in 2.6% (n=13), X-linked in 2.0%; (n=10) and mitochondrial in 1.4%; (n=7). Thirteen patients (2.6%) had two P/LP variants in AD genes. The most frequent genes were TTN (46.3%), DSP (6.9%), LMNA (6.9%), RBM20 (5.6%) and MYH7 (5.4%). Among patients with informative results, 12.5% (n=64) had a result associated with neuromuscular or metabolic conditions, 17.9% (n=91) had a result associated with ICD recommendations, and 61.8% (n=314) had a result associated with a clinical trial (clinicaltrials.gov). In this cohort, almost 1 in 4 patients received an informative genetic test result. A total of 5.9% of informative results were in genes associated with an inheritance other than AD. In this cohort, 22.3% received an informative result requiring extra-cardiac management, applicable gene-specific management or potential clinical trial eligibility. This work further supports the utility of genetic testing using large multigene panels for DCM.

An intervention strategy to improve genetic testing for dilated cardiomyopathy in a heart failure clinic

PurposeDespite its clinical implications in screening and therapy, genetic testing in dilated cardiomyopathy (DCM) is underused. This study evaluated implementing a practice intervention in a heart failure clinic to automate and streamline the process of genetic testing. MethodsEligible patients with DCM were compared for frequency of pretest genetic education and testing during pre- and postintervention periods. The intervention comprised automated prescheduling of a cardiovascular genomics e-consult that served as a placeholder for downstream, pretest education, testing, and post-test review of genetic results. ResultsPatients with DCM were more likely to undergo pretest genetic education after intervention than before intervention (33.5% vs 14.8%, P < .0001). Similarly, patients with DCM were more likely to undergo genetic testing after intervention than before intervention (27.3% vs 13.0%, P = .0006). The number of patients who were diagnosed to have likely pathogenic or pathogenic genetic variants were 2 of 21 (9.5%) and 6 of 53 (11.1%) before and after intervention, respectively, and variants were present in the following genes: FLNC, TTN, DES, LMNA, PLN, and TNNT2. ConclusionAn intervention strategy in a heart failure clinic to increase the rates of pretest genetic education and testing in eligible patients with DCM was feasible and efficacious and may have important implications for the management of DCM.

Clinical Implication of Genetic Testing in Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is one of the important causes of heart failure (HF). With the rapidly evolving technologies for gene analysis and tremendous advances in knowledge of HF genetics, the importance of genetic testing in DCM is currently highlighted. Several genetic variants causing DCM have been identified and this information is used for diagnosis, risk stratification and family screening of DCM patients. However, there are still several challenges in applying genetic testing to real clinical practice. In this review, we will summarize recent understandings in DCM genetics and provide an evidence-based practical guide to the use of genetic testing for DCM patients.

Abstract 13271: Combined Assessments of Monogenic and Polygenic Risk for Dilated Cardiomyopathy

Introduction: Genetic testing for non-ischemic dilated cardiomyopathy (DCM) currently comprises assessment of rare (monogenic) mutations in DCM-relevant genes. The role of a common-variant (polygenic) predictor for DCM has yet to be evaluated. Methods: Leveraging genotyping array and exome-sequencing data from UK Biobank, we curated monogenic, predicted loss-of-function (LOF) mutations in 91 genes on clinical genetic testing panels for DCM, and tested their prevalence and penetrance. Next, we constructed and evaluated a polygenic score for DCM from measures of left ventricular structure and function by cardiac magnetic resonance imaging. Finally, we combined monogenic carrier status with the polygenic score to estimate aggregate genetic risk for DCM. Results: Among study participants (N= 166,690), mean age was 57 (SD, 8.1) years, 75,154 (41%) were male, and 336 (0.21%) had DCM. 14.4% of DCM cases harbored a disease-relevant LOF mutation, including 8.8% within cardiac exons of the sarcomeric gene TTN . LOF mutations in TTN (OR, 25.36), DSP (OR, 17.55), and RBM20 (OR, 12.85) were the most strongly associated with dilated cardiomyopathy (all P &lt; 0.001). 0.7% of all LOF carriers - and 4.0% of LOF carriers in TTN - developed DCM. A polygenic score comprising 2.3 million common genetic variants was strongly associated with DCM in all participants (OR per SD=1.62, p=8.61E-39), and in non-carriers (OR per SD=1.60, p=6.28E-15; N=159,811) and carriers (OR per SD=1.79, p=4.76E-05; N=6,879) of LOF mutations. Comparing the top and bottom 20% of the polygenic score, a &gt;3-fold risk difference was observed among non-carriers of TTN LOF, and a &gt;10-fold risk difference among TTN LOF carriers. TTN LOF carriers with high polygenic risk were at 46-fold odds of developing DCM as compared to non-carriers with intermediate polygenic risk (p=4.16E-29). Conclusions: Combining monogenic and polygenic risk expands the scope and improves the precision of clinical genetic testing for DCM.

The influence of age on the diagnostic yield of genetic testing in dilated cardiomyopathy

Abstract Background Dilated cardiomyopathy (DCM) has an estimated population prevalence of 1/250 and is the underlying diagnosis in a third of heart failure patients. A substantial proportion of patients have familial disease caused by dominant mutations in one of more than 50 genes, but clinical practice guidelines recommend genetic testing in young patients with idiopathic DCM. There is an absence of robust data on the influence of age on the diagnostic yield of genetic testing. Methods The study cohort comprised 825 consecutive and unrelated patients (524 male (63.5%)) with DCM who underwent genetic testing from 2015 to 2019. Genetic variants were classified using American College of Medical Genetics (ACMG) criteria. Analyses were stratified by age and sex. Results 173 (20.1%) patients had a positive genetic test (“pathogenic” or “likely pathogenic” variant); 292 (34.4%) had a variant of unknown significance. Mean age at genetic testing was 49.9±14.4 years. Mean age of patients with a positive test was 47.6±13.6 years. 99 (18.9%) men and 67 (22.3%) women had a positive test (p=0.246). Mutations in the TTN gene, encoding for titin, accounted for 46.1% of positive results. 13.8% of mutations were in DSP, 8.4% in RBM20, 6% in FLNC, 4.2% in LMNA, 3.6% in BAG3 and 3.6% in MYH7. There was a trend to declining yield with age (likelihood ratio chi-square p value = 0.047). The yield was 17.2% in the 56–65 year age group and 11.5% above 66 years of age (figure 1). Conclusions Approximately 1 in 5 patients with DCM had a positive genetic test. The yield declined in patients over 66 years but remained above 11%, suggesting that genetic testing should not be confined to younger patients with DCM. Figure 1. Yield of Genetic Testing by Age Funding Acknowledgement Type of funding source: None

Implications of Genetic Testing in Dilated Cardiomyopathy.

Genetic analysis is a first-tier test in dilated cardiomyopathy (DCM). Electrical phenotypes are common in genetic DCM, but their exact contribution to the clinical course and outcome is unknown. We determined the prevalence of pathogenic gene variants in a large unselected DCM population and determined the role of electrical phenotypes in association with outcome. This study included 689 patients with DCM from the Maastricht Cardiomyopathy Registry, undergoing genetic evaluation using a 48 cardiomyopathy-associated gene-panel, echocardiography, endomyocardial biopsies, and Holter monitoring. Upon detection of a pathogenic variant in a patient with DCM, familial segregation was performed. Outcome was defined as cardiovascular death, heart transplantation, heart failure hospitalization, and/or occurrence of life-threatening arrhythmias. A (likely) pathogenic gene variant was found in 19% of patients, varying from 36% in familial to 13% in nonfamilial DCM. Family segregation analysis showed familial disease in 46% of patients with DCM who were initially deemed nonfamilial by history. Overall, 18% of patients with a nongenetic risk factor had a pathogenic gene variant. Almost all pathogenic gene variants occurred in just 12 genes previously shown to have robust disease association with DCM. Genetic DCM was independently associated with electrical phenotypes such as atrial fibrillation, nonsustained ventricular tachycardia, and atrioventricular block and inversely correlated with the presence of a left bundle branch block (P<0.01). After a median follow-up of 4 years, event-free survival was reduced in genetic versus patients with nongenetic DCM (P=0.01). This effect on outcome was mediated by the associated electrical phenotypes of genetic DCM (P<0.001). One in 5 patients with an established nongenetic risk factor or a nonfamilial disease still carries a pathogenic gene variant. Genetic DCM is characterized by a profile of electrical phenotypes (atrial fibrillation, nonsustained ventricular tachycardia, and atrioventricular block), which carries increased risk for adverse outcomes. Based on these findings, we envisage a broader role for genetic testing in DCM.

Reevaluating the Genetic Contribution of Monogenic Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is genetically heterogeneous, with >100 purported disease genes tested in clinical laboratories. However, many genes were originally identified based on candidate-gene studies that did not adequately account for background population variation. Here we define the frequency of rare variation in 2538 patients with DCM across protein-coding regions of 56 commonly tested genes and compare this to both 912 confirmed healthy controls and a reference population of 60 706 individuals to identify clinically interpretable genes robustly associated with dominant monogenic DCM. We used the TruSight Cardio sequencing panel to evaluate the burden of rare variants in 56 putative DCM genes in 1040 patients with DCM and 912 healthy volunteers processed with identical sequencing and bioinformatics pipelines. We further aggregated data from 1498 patients with DCM sequenced in diagnostic laboratories and the Exome Aggregation Consortium database for replication and meta-analysis. Truncating variants in TTN and DSP were associated with DCM in all comparisons. Variants in MYH7, LMNA, BAG3, TNNT2, TNNC1, PLN, ACTC1, NEXN, TPM1, and VCL were significantly enriched in specific patient subsets, with the last 2 genes potentially contributing primarily to early-onset forms of DCM. Overall, rare variants in these 12 genes potentially explained 17% of cases in the outpatient clinic cohort representing a broad range of adult patients with DCM and 26% of cases in the diagnostic referral cohort enriched in familial and early-onset DCM. Although the absence of a significant excess in other genes cannot preclude a limited role in disease, such genes have limited diagnostic value because novel variants will be uninterpretable and their diagnostic yield is minimal. In the largest sequenced DCM cohort yet described, we observe robust disease association with 12 genes, highlighting their importance in DCM and translating into high interpretability in diagnostic testing. The other genes analyzed here will need to be rigorously evaluated in ongoing curation efforts to determine their validity as Mendelian DCM genes but have limited value in diagnostic testing in DCM at present. This data will contribute to community gene curation efforts and will reduce erroneous and inconclusive findings in diagnostic testing.

Genome sequencing as a first-line genetic test in familial dilated cardiomyopathy

Purpose:We evaluated whole-genome sequencing (WGS) as an alternative to multi-gene panel sequencing (PS) for genetic testing in dilated cardiomyopathy (DCM).Methods:Forty-two patients with familial DCM underwent PS and WGS, and detection rates of rare single nucleotide variants and small insertions/deletions in panel genes were compared. Loss-of-function variants in 406 cardiac-enriched genes were evaluated, and an assessment of structural variation was performed.Results:WGS provided broader and more uniform coverage than PS, with high concordance for rare variant detection in panel genes. WGS identified all PS-identified pathogenic or likely-pathogenic variants as well as two additional likely-pathogenic variants: one was missed by PS due to low coverage, the other was a known disease-causing variant in a gene not included on the panel. No loss-of-function variants in the extended gene set met clinical criteria for pathogenicity. One BAG3 structural variant was classified as pathogenic.Conclusions –Our data support the use of WGS for genetic testing in DCM, with high variant detection accuracy and a capacity to identify structural variants. WGS provides an opportunity to go beyond suites of established disease genes, but the incremental yield of clinically-actionable variants is limited by a paucity of genetic and functional evidence for DCM association.

Genetic Testing in Pediatric Cardiomyopathy.

Genetic testing is recommended in patients with dilated cardiomyopathy (DCM); however, limited studies demonstrate high yields of genetic testing in non-hypertrophic (HCM) patients. Furthermore, there is sparse genotype-phenotype data in pediatric DCM patients. We performed a retrospective review of 70 consecutive probands with cardiomyopathy (non-HCM) who underwent genetic evaluation. Mean age at presentation was 5.48years. Echocardiography revealed mean ejection fraction of 32.4%. The LVEDd z score ranged from - 5.7 to + 15.9. Cardiomyopathy was classified as dilated in 56, 10 with non-compaction, 2 with restrictive, and 2 with ARVC. TTN gene mutations were the most common gene involved. Genetic testing was negative in 16/70 (23%) giving a yield of 77% including VUS. 33% (23/70) of probands had a positive family history among whom the diagnostic yield was 57% (13/23) for pathogenic mutations. Yield for positive genetic testing in the DCM with positive family history group was 9/18 (50%). There were 6 deaths (9%) and 26/70 (37%) underwent transplantation. More frequent cardiac transplantations (48 vs. 34%) and deaths (17 vs. 2%) were seen in mutation-positive vs. mutation-negative subgroups. This study demonstrates an increasing yield of genetic testing in DCM although with a high rate of VUS detection. Use of genetic information for better management and prognostication will require big data analysis.

Abstract 391: The Pathophysiological Role of MYBPHL in Dilated Cardiomyopathy

Background: Cardiomyopathy is a leading cause of heart failure and is highly heritable. One common form of cardiomyopathy is dilated cardiomyopathy (DCM), which currently has over 70 identified genes that have been described as causative for the disease. Genetic testing for DCM employs gene panels and has a sensitivity of mutation detection less than 50%, indicating that additional genes contribute to DCM. Here, we employed whole genome sequencing (WGS) in a family with DCM and heart block who had previously undergone unrevealing genetic testing. We identified a premature stop codon in the MYBPHL gene, a gene that has not previously been linked to DCM as a likely cause of DCM in this family. Myosin binding protein H Like (MyBP-HL) is a muscle-expressed protein bearing structural similarity to myosin binding protein C (MyBP-C), which is commonly mutated gene in cardiomyopathies. Objective: Determine the physiological and pathophysiological role of Mybphl . Results: RNA-seq and qPCR from mouse hearts revealed that Mybphl is highly expressed in the right and left atria with lower expression in the ventricle and virtually no expression in skeletal muscle. As MyBP-HL shares a high homology with the myofilament proteins cardiac myosin binding protein-C and H, we investigated if MyBP-HL is also myofilament-associated. We determined that MyBP-HL protein is myofilament-associated in the atria although not clearly so in ventricle. To assess the requirement of MyBP-HL in cardiac function, we used a mouse model with an insertional disruption of the Mybphl gene. These mice have deficits in in vivo cardiac function, with reduced fractional shortening. In addition, ECG recordings from the Mybphl null mice show conduction system abnormalities affecting atrioventricular conduction. Conclusions: WGS identified a premature stop codon in MYBPHL in human DCM. A mouse model with a disrupted Mybphl gene showed similar pathophysiological features as the humans with reduced ventricular function and cardiac conduction system abnormalities. MyBP-HL is an important protein for normal cardiac function.

The Rationale and Timing of Molecular Genetic Testing for Dilated Cardiomyopathy

The genetic evaluation of dilated cardiomyopathy (DCM) has been challenging, owing in large part to marked genetic heterogeneity. However, lower costs from next-generation sequencing have enabled gene discovery and the expansion of genetic testing panels. These advances have improved molecular diagnostics and predictive testing in DCM. We provide a rationale and recommendation for clinical genetic testing in all DCM cases.

Poor Prognosis of Rare Sarcomeric Gene Variants in Patients with Dilated Cardiomyopathy

In dilated cardiomyopathy (DCM), the clinical and prognostic implications of rare variants in sarcomeric genes remain poorly understood. To address this question, we analyzed the outcome of rare sarcomeric gene variants in patients enrolled in our Familial Cardiomyopathy Registry. DCM families harboring rare sarcomeric variants in MYH6, MYH7, MYBPC3, TNNT2, and TTN were identified. Genotype-phenotype association analysis was performed, and long-term survival-free from death or heart transplant was compared between carriers and noncarriers. We found 24 rare variants (3 in MYH6, 3 in MYH7, 3 in MYBPC3, 2 in TNNT2, and 13 in TTN) affecting 52 subjects in 25 families. The phenotypes of variant carriers were severe (3 sudden deaths, 6 heart failure deaths, 8 heart transplants, 2 ventricular fibrillations). There was no difference in the overall long-term survival between carriers and the 33 noncarriers (p = 0.322). However after 50 years of age, the combined endpoint of death or transplant was decreased in carriers as compared to noncarriers (p = 0.026). Patients with DCM carrying rare variants in sarcomeric genes manifest a poorer prognosis as compared to noncarriers after the age of 50 years. These data further support the role of genetic testing in DCM for risk stratification.

Genetic Testing for Dilated Cardiomyopathy in Clinical Practice

BackgroundFamilial involvement is common in dilated cardiomyopathy (DCM) and >40 genes have been implicated in causing disease. However, the role of genetic testing in clinical practice is not well defined. We examined the experience of clinical genetic testing in a diverse DCM population to characterize the prevalence and predictors of gene mutations. Methods and ResultsWe studied 264 unrelated adult and pediatric DCM index patients referred to 1 reference lab for clinical genetic testing. Up to 10 genes were analyzed (MYH7, TNNT2, TNNI3, TPM1, MYBPC3, ACTC, LMNA, PLN, TAZ, and LDB3), and 70% of patients were tested for all genes. The mean age was 26.6 ± 21.3 years, and 52% had a family history of DCM. Rigorous criteria were used to classify DNA variants as clinically relevant (mutations), variants of unknown clinical significance (VUS), or presumed benign. Mutations were found in 17.4% of patients, commonly involving MYH7, LMNA, or TNNT2 (78%). An additional 10.6% of patients had VUS. Genetic testing was rarely positive in older patients without a family history of DCM. Conversely in pediatric patients, family history did not increase the sensitivity of genetic testing. ConclusionsUsing rigorous criteria for classifying DNA variants, mutations were identified in 17% of a diverse group of DCM index patients referred for clinical genetic testing. The low sensitivity of genetic testing in DCM reflects limitations in both current methodology and knowledge of DCM-associated genes. However, if mutations are identified, genetic testing can help guide family management.