Highlights
- Genetic testing in dilated cardiomyopathy (DCM) has evolved from a tool for family screening to an essential component of clinical decision-making and precision therapy.
- The diagnostic yield of genetic testing ranges from 8% to 36%, influenced heavily by the patient’s family history and specific phenotypic features.
- Our understanding of DCM is shifting from a strict monogenic model toward a complex polygenic spectrum, requiring more nuanced interpretation of genetic variants.
- Pathogenic variants in specific genes, such as LMNA, SCN5A, and RBM20, now directly inform decisions regarding ICD implantation and arrhythmia management.
Background
Dilated cardiomyopathy (DCM) is a leading cause of heart failure and the most common indication for cardiac transplantation worldwide. Characterized by left ventricular dilation and systolic dysfunction not explained by abnormal loading conditions or coronary artery disease, DCM is a heterogeneous condition with diverse etiologies including inflammatory, toxic, and genetic factors.
For decades, genetic testing in DCM was primarily utilized for “cascade screening”—identifying asymptomatic relatives at risk of developing the disease. However, the rapid advancement of Next-Generation Sequencing (NGS) and a deeper understanding of the genotype-phenotype correlation have catalyzed a paradigm shift. Today, genetic insights are increasingly used to refine prognosis, guide pharmacological and device therapies, and offer specialized reproductive counseling. Despite these advances, implementing genetic services into routine clinical care remains a challenge for many healthcare systems due to the complexity of variant interpretation and the need for specialized multidisciplinary teams.
Key Content
The Evolving Genetic Architecture of DCM
Historically, DCM was viewed through the lens of Mendelian inheritance, where a single pathogenic variant in a sarcomeric or structural gene led to the disease. While this monogenic model remains relevant for many families, contemporary research suggests a broader polygenic spectrum. Many patients may harbor multiple rare variants or a combination of rare variants and common genetic modifiers that collectively reach a threshold for disease expression.
Major genes implicated in DCM include *TTN* (titin), *LMNA* (lamin A/C), *MYH7* (myosin heavy chain 7), *TNNT2* (troponin T2), and *RBM20*. Truncating variants in the *TTN* gene (TTNtv) are the most common genetic cause, found in approximately 15-25% of familial DCM cases and 10-15% of sporadic cases. However, the penetrance of these variants is often incomplete, suggesting that environmental triggers (e.g., alcohol, pregnancy, or chemotherapy) often act as a “second hit.”
Diagnostic Yield and Testing Strategies
According to the landmark synthesis by Verdonschot et al. (2026), the diagnostic yield of genetic testing varies significantly based on patient selection. In cohorts with a strong family history of DCM or sudden cardiac death, the yield can exceed 35%. In contrast, in patients with apparently sporadic DCM or secondary triggers, the yield may be as low as 8%.
Testing strategies typically involve:
- Broad Multigene Panels: Often including 50-100+ genes, these maximize the chance of finding a variant but increase the risk of identifying Variants of Uncertain Significance (VUS).
- Targeted Panels: Focus on genes with definitive evidence of disease causation (e.g., the “core” DCM genes), reducing noise but potentially missing rarer or emerging genetic causes.
Clinical Actionability and Risk Stratification
One of the most significant advances in the field is the use of genotype to guide clinical intervention. For example:
- LMNA-related DCM: Variants in *LMNA* are associated with a high risk of conduction system disease and sudden cardiac death (SCD), even when the left ventricular ejection fraction (LVEF) is relatively preserved. Current guidelines now suggest a lower threshold for Implantable Cardioverter Defibrillator (ICD) implantation in these patients.
- SCN5A and RBM20: These genotypes are frequently associated with a high arrhythmic burden, necessitating aggressive monitoring and early intervention.
- TTNtv: Patients with titin variants often show a favorable response to standard guideline-directed medical therapy (GDMT) but may remain vulnerable to arrhythmias during periods of physiological stress.
The Process of Genetic Counselling
Effective implementation requires a structured approach to genetic counselling, which is divided into pre-test and post-test phases.
Pre-test Counselling: Focuses on managing patient expectations, discussing the possibility of VUS results, and exploring the implications for life insurance and family dynamics. It is essential to obtain informed consent and establish the clinical utility of the test for the individual patient.
Post-test Counselling: Involves the clinical integration of results. Pathogenic (Class 5) and Likely Pathogenic (Class 4) variants trigger cascade screening for first-degree relatives. VUS (Class 3) results require careful handling; they should generally not be used for clinical decision-making or family screening but should be re-evaluated periodically as genomic databases evolve.
Expert Commentary
The integration of genetics into DCM management represents the pinnacle of precision cardiology, yet several controversies persist. A major challenge is the interpretation of VUS. As we sequence more diverse populations, our ability to distinguish between benign rare variants and truly pathogenic ones is strained. There is also the “penetrance problem”—identifying a pathogenic variant in an asymptomatic relative does not guarantee they will ever develop the disease, leading to potential psychological distress and over-medicalization.
Furthermore, the shift toward a polygenic model suggests that future risk scores may incorporate Polygenic Risk Scores (PRS) alongside rare variant analysis. From a health policy perspective, the cost-effectiveness of broad genetic testing is well-established when it prevents SCD or avoids unnecessary clinical surveillance in genotype-negative relatives. However, access to specialized genetic counsellors remains a significant bottleneck in clinical implementation.
Conclusion
Genetic testing and counselling are no longer optional adjuncts but are fundamental to the modern diagnostic workup of DCM. By shifting the focus from purely familial identification to individualized risk stratification and therapeutic guidance, clinicians can significantly improve outcomes. Future research should prioritize the functional validation of VUS and the development of integrated risk models that combine genetic, imaging, and biomarker data. As we move toward 2030, the goal is a comprehensive approach where every DCM patient has access to a genetic diagnosis that informs their specific journey of care.
References
- Verdonschot JAJ, van Spaendonck-Zwarts KY, et al. Genetic counselling implementation in dilated cardiomyopathy. European Heart Journal. 2026; PMID: 41858107.
- Hershberger RE, Givertz MM, Ho CY, et al. Genetic Evaluation of Cardiomyopathy: A Heart Failure Society of America Practice Guideline. J Card Fail. 2018;24(5):281-302. PMID: 29567486.
- McNally EM, Mestroni L. The Genetic Landscape of Cardiomyopathies. Circ Res. 2017;121(7):731-733. PMID: 28912179.
- Walsh R, et al. Quantitative analysis of Mendelian disease-associated genes in clinical exome sequencing for hereditary cardiomyopathy. Genet Med. 2017;19(2):192-203. PMID: 27532257.