Advances in human genetics are improving the understanding of a variety of inherited cardiovascular diseases, including cardiomyopathies, arrhythmic disorders, vascular disorders, and lipid disorders such as familial hypercholesterolemia. However, not all cardiovascular practitioners are fully aware of the utility and potential pitfalls of incorporating genetic test results into the care of patients and their families. This statement summarizes current best practices with respect to genetic testing and its implications for the management of inherited cardiovascular diseases.

Background: Variants in the cardiomyocyte-specific RNA splicing factor RBM20 have been linked to familial cardiomyopathy, but the causative genetic architecture and clinical consequences of this disease are incompletely defined. Methods and Results: To define the genetic architecture of RBM20 cardiomyopathy, we first established a database of RBM20 variants associated with cardiomyopathy and compared these to variants observed in the general population with respect to their location in the RBM20 coding transcript. We identified 2 regions significantly enriched for cardiomyopathy-associated variants in exons 9 and 11. We then assembled a registry of 74 patients with RBM20 variants from 8 institutions across the world (44 index cases and 30 from cascade testing). This RBM20 patient registry revealed highly prevalent family history of sudden cardiac death (51%) and cardiomyopathy (72%) among index cases and a high prevalence of composite arrhythmias (including atrial fibrillation, nonsustained ventricular tachycardia, implantable cardiac defibrillator discharge, and sudden cardiac arrest, 43%). Patients harboring variants in cardiomyopathy-enriched regions identified by our variant database analysis were enriched for these findings. Further, these characteristics were more prevalent in the RBM20 registry than in large cohorts of patients with dilated cardiomyopathy and TTNtv cardiomyopathy and not significantly different from a cohort of patients with LMNA -associated cardiomyopathy. Conclusions: Our data establish RBM20 cardiomyopathy as a highly penetrant and arrhythmogenic cardiomyopathy. These findings underline the importance of arrhythmia surveillance and family screening in this disease and represent the first step in defining the genetic architecture of RBM20 disease causality on a population level.

Severe forms of dilated cardiomyopathy (DCM) are associated with point mutations in the alternative splicing regulator RBM20 that are frequently located in the arginine/serine-rich domain (RS-domain). Such mutations can cause defective splicing and cytoplasmic mislocalization, which leads to the formation of detrimental cytoplasmic granules. Successful development of personalized therapies requires identifying the direct mechanisms of pathogenic RBM20 variants. Here, we decipher the molecular mechanism of RBM20 mislocalization and its specific role in DCM pathogenesis. We demonstrate that mislocalized RBM20 RS-domain variants retain their splice regulatory activity, which reveals that aberrant cellular localization is the main driver of their pathological phenotype. A genome-wide CRISPR knockout screen combined with image-enabled cell sorting identified Transportin-3 (TNPO3) as the main nuclear importer of RBM20. We show that the direct RBM20-TNPO3 interaction involves the RS-domain, and is disrupted by pathogenic variants. Relocalization of pathogenic RBM20 variants to the nucleus restores alternative splicing and dissolves cytoplasmic granules in cell culture and animal models. These findings provide proof-of-principle for developing therapeutic strategies to restore RBM20’s nuclear localization in RBM20-DCM patients.

BACKGROUND: Septal reduction therapy (SRT) provides substantial symptomatic improvement in patients with obstructive hypertrophic cardiomyopathy (HCM). However, long-term disease course after SRT and predictors of adverse outcomes have not been systematically examined. METHODS: Data from 13 high clinical volume HCM centers from the international SHARE (Sarcomeric Human Cardiomyopathy Registry) were analyzed. Patients were followed from the time of SRT until last follow-up or occurrence of heart failure (HF) composite outcome (cardiac transplantation, implantation of a left ventricular assist device, left ventricular ejection fraction <35%, development of New York Heart Association class III or IV symptoms), ventricular arrhythmias composite outcome (sudden cardiac death, resuscitated cardiac arrest, or appropriate implantable cardioverter defibrillator therapy), or HCM-related death. Cox proportional hazards models were used to identify predictors of outcome. RESULTS: Of the 10 225 patients in SHARE, 1832 (18%; 968 [53%] male) underwent SRT, including 455 (25%) with alcohol septal ablation and 1377 (75%) with septal myectomy. The periprocedural 30-day mortality rate was 0.4% (8 of 1832) and 1499 of 1565 (92%) had a maximal left ventricular outflow tract gradient <50 mm Hg at 1 year. After 6.8 years (range, 3.4–9.8 years; 12 565 person-years) from SRT, 77 (4%) experienced HCM-related death (0.6% per year), 236 (13%) a composite HF outcome (1.9% per year), and 87 (5%) a composite ventricular arrhythmia outcome (0.7% per year). Among adults, older age at SRT was associated with a higher incidence of HCM death (hazard ratio, 1.22 [95 CI, 1.1–1.3]; P <0.01) and the HF composite (hazard ratio, 1.14 [95 CI, 1.1–1.2] per 5-year increase; P <0.01) in a multivariable model. Female patients also had a higher risk of the HF composite after SRT (hazard ratio, 1.4 [95 CI, 1.1–1.8]; P <0.01). De novo atrial fibrillation occurred after SRT in 387 patients (21%). Among pediatric patients followed for a median of 13 years after SRT, 26 of 343 (16%) developed the HF composite outcome, despite 96% being free of recurrent left ventricular outflow tract obstruction. CONCLUSIONS: Successful short- and long-term relief of outflow tract obstruction was observed in experienced multidisciplinary HCM centers. A subset of patients progressed to develop HF, but event-free survival at 10 years was 83% and ventricular arrhythmias were rare. Older age, female sex, and SRT during childhood were associated with a greater risk of developing HF.

BACKGROUND: Inflammatory, myocarditis-like episodes precede and are associated with higher risk of sustained ventricular arrhythmias and heart failure in patients with pathogenic or likely pathogenic desmoplakin (DSP) variants. Whether the recurrence and treatment of myocarditis-like episodes influence the outcomes in this population is unknown. This study aimed to assess the prognostic impact of the recurrence and treatment of myocarditis-like episodes in patients with pathogenic or likely pathogenic DSP variants. METHODS: The study was designed as an observational cohort study using all patients with pathogenic or likely pathogenic DSP variants in the DSP -ERADOS Network ( Desmopakin Specific Effort for a Rare Disease Outcome Study) enrolled at 31 institutions up until April 30, 2024. Survival from ventricular arrhythmia and heart failure end points and recurrent myocarditis-like episodes was evaluated for both first and recurrent documented myocarditis-like episodes and the impact of immunosuppressive treatment on outcomes assessed. RESULTS: A total of 1014 patients with pathogenic or likely pathogenic DSP variants (62.4% female; mean age, 40.4±17.4 years; 47.1% probands) were included. Among them, 177 individuals (17.5%) experienced ≥1 documented myocarditis-like episode, with 63 of them (35.6%) receiving immunosuppressive treatment. Immunosuppressive treatment of the first documented myocarditis-like episode was associated with reduced risk of ventricular arrhythmia and heart failure outcomes (hazard ratio, 0.18 [95% CI, 0.07–0.45]; P <0.001; and hazard ratio, 0.09 [95% CI, 0.02–0.39; P =0.001, respectively) over a median follow-up of 6.4 years (95% CI, 4.0–10.5). This risk was comparable to that of patients with no history of myocarditis-like episode but did not correlate with a reduction in recurrent episodes after completion of initial immunosuppression (hazard ratio, 0.85 [95% CI, 0.47–1.54]; P =0.599). In contrast, nonsteroidal anti-inflammatory drugs or colchicine treatment did not influence outcomes. CONCLUSIONS: Immunosuppressive treatment of myocarditis-like episodes in DSP patients was associated with improved combined ventricular arrhythmia or heart failure outcomes, supporting future prospective evaluation in DSP cohorts.