Phenotypic Expression, Natural History, and Risk Stratification of Cardiomyopathy Caused by Filamin C Truncating Variants.

BACKGROUND: Filamin C truncating variants (FLNCtv) cause a form of arrhythmogenic cardiomyopathy: the mode of presentation, natural history, and risk stratification of FLNCtv remain incompletely explored. We aimed to develop a risk profile for refractory heart failure and life-threatening arrhythmias in a multicenter cohort of FLNCtv carriers. METHODS: FLNCtv carriers were identified from 10 tertiary care centers for genetic cardiomyopathies. Clinical and outcome data were compiled. Composite outcomes were all-cause mortality/heart transplantation/left ventricle assist device (D/HT/LVAD), nonarrhythmic death/HT/LVAD, and sudden cardiac death/major ventricular arrhythmias. Previously established cohorts of 46 patients with LMNA and 60 with DSP-related arrhythmogenic cardiomyopathies were used for prognostic comparison. RESULTS: Eighty-five patients carrying FLNCtv were included (42±15 years, 53% men, 45% probands). Phenotypes were heterogeneous at presentation: 49% dilated cardiomyopathy, 25% arrhythmogenic left dominant cardiomyopathy, 3% arrhythmogenic right ventricular cardiomyopathy. Left ventricular ejection fraction was <50% in 64% of carriers and 34% had right ventricular fractional area changes (RVFAC=(right ventricular end-diastolic area - right ventricular end-systolic area)/right ventricular end-diastolic area) <35%. During follow-up (median time 61 months), 19 (22%) carriers experienced D/HT/LVAD, 13 (15%) experienced nonarrhythmic death/HT/LVAD, and 23 (27%) experienced sudden cardiac death/major ventricular arrhythmias. The sudden cardiac death/major ventricular arrhythmias incidence of FLNCtv carriers did not significantly differ from LMNA carriers and DSP carriers. In FLNCtv carriers, left ventricular ejection fraction was associated with the risk of D/HT/LVAD and nonarrhythmic death/HT/LVAD. CONCLUSIONS: Among patients referred to tertiary referral centers, FLNCtv arrhythmogenic cardiomyopathy is phenotypically heterogeneous and characterized by a high risk of life-threatening arrhythmias, which does not seem to be associated with the severity of left ventricular dysfunction.

FLNC truncations cause arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease that affects predominantly the right ventricle and is part of the spectrum of arrythmogenic cardiomyopathies (ACMs). ARVC is a genetic condition; however, a pathogenic gene variant is found in only half of patients. OBJECTIVE: Filamin C gene truncations (FLNCtv) have recently been identified in dilated cardiomyopathy with ventricular arrhythmia and sudden cardiac death, a phenotype partially overlapping with ARVC and part of the ACM spectrum. We hypothesised that FLNCtv could be a novel gene associated with ARVC. METHODS: One hundred fifty-six patients meeting 2010 ARVC Task Force Criteria and lacking variants in known ARVC genes were evaluated for FLNC variants. Available family members were tested for cosegregation. RESULTS: We identified two unique FLNCtv variants in two families (c.6565 G>T, p.Glu2189Ter and c.8107delG, p.Asp2703ThrfsTer69), with phenotypes of dominant RV disease fulfilling 'definite' diagnosis of ARVC according to the 2010 Task Force Criteria. Variants in other cardiomyopathy genes were excluded in both kindreds, and segregation analysis revealed that p.Asp2703ThrfsTer69 was a de novo variant. In both families, the disease phenotype was characterised by prominent ventricular arrhythmias and sudden cardiac arrest. CONCLUSION: The identification of FLNCtv as a novel cause of ARVC in two unrelated families expands the spectrum of ARVC non-desmosome disease genes for this disorder. Our findings should prompt inclusion of FLNC genetic testing in ARVC to improve diagnostic yield and testing of at-risk relatives in ARVC.

Cardiac and Neuromuscular Features of Patients With LMNA-Related Cardiomyopathy.

Background: Mutations in the LMNA (lamin A/C) gene have been associated with neuromuscular and cardiac manifestations, but the clinical implications of these signs are not well understood. Objective: To learn more about the natural history of LMNA-related disease. Design: Observational study. Setting: 13 clinical centers in Italy from 2000 through 2018. Patients: 164 carriers of an LMNA mutation. Measurements: Detailed cardiologic and neurologic evaluation at study enrollment and for a median of 10 years of follow-up. Results: The median age at enrollment was 38 years, and 51% of participants were female. Neuromuscular manifestations preceded cardiac signs by a median of 11 years, but by the end of follow-up, 90% of the patients had electrical heart disease followed by structural heart disease. Overall, 10 patients (6%) died, 14 (9%) received a heart transplant, and 32 (20%) had malignant ventricular arrhythmias. Fifteen patients had gait loss, and 6 had respiratory failure. Atrial fibrillation and second- and third-degree atrioventricular block were observed, respectively, in 56% and 51% of patients with combined cardiac and neuromuscular manifestations and 37% and 33% of those with heart disease only. Limitations: Some of the data were collected retrospectively. Neuromuscular manifestations were more frequent in this analysis than in previous studies. Conclusion: Many patients with an LMNA mutation have neurologic symptoms by their 30s and develop progressive cardiac manifestations during the next decade. A substantial proportion of these patients will have life-threatening neurologic or cardiologic conditions. Primary Funding Source: None.

Lifelong arrhythmic risk stratification in arrhythmogenic right ventricular cardiomyopathy: distribution of events and impact of periodical reassessment.

Aims: The arrhythmic risk stratification of arrhythmogenic right ventricular cardiomyopathy (ARVC) remains controversial. We evaluated the long-term distribution of life-threatening arrhythmic events assessing the impact of periodical risk reassessment. Methods and results: Ninety-eight ARVC patients with no previous major ventricular arrhythmias were retrospectively analysed. Patients were assessed at baseline, at 22 [inter-quartile range (IQR) 16-26], 49 (IQR 41-55) and 97 months (IQR 90-108). The primary endpoint was a composite of sudden cardiac death, ventricular fibrillation, sustained ventricular tachycardia or appropriate implanted cardioverter-defibrillator intervention. During a median follow-up of 91 months (IQR 34-222) 28 patients (29%) experienced the composite endpoint. The median time for the primary event was 35 months (IQR 18-86 months), and 39% of events occurred beyond 49 months of follow-up. History of syncope (HR 4.034; 95% CI, 1.488 to 10.932; P-value = 0.006), non-sustained ventricular tachycardia (NSVT; HR 3.534; 95% CI 1.265-9.877; P-value = 0.016), premature ventricular contractions (PVC) >1000/24h (HR 2.761; 95% CI 1.120-6.807; P-value = 0.027), and right ventricular fractional area change (RVFAC; HR 0.945; 95% CI 0.906-0.985; P-value = 0.008) were found as independent predictors at baseline multivariate analysis. Nevertheless, when the prognostic impact of each variable was reassessed overtime only NSVT (HR 3.282; 95% CI, 1.122 to 9.598, P-value = 0.023) and RVFAC (HR 0.351, 95% CI, 0.157 to 0.780; P-value = 0.010) remained independent predictors throughout the whole follow-up. Conclusion: In our cohort of ARVC patients only NSVT and RVFAC maintained their independent prognostic impact in predicting arrhythmic events during the long-term follow-up. Periodical re-assessment of risk in these patients is strongly recommended.

The S-wave angle identifies arrhythmogenic right ventricular cardiomyopathy in patients with electrocardiographically concealed disease phenotype.

BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) carries risk of sudden death. We hypothesize that the S-wave angle differentiates ARVD/C with otherwise normal electrocardiograms from controls. MATERIALS AND METHODS: All patients met Task Force 2010 definite ARVD/C criteria. ARVD/C patients without Task Force depolarization/repolarization criteria (-ECG) were compared to controls. Electrocardiogram measures of QRS duration, corrected QT interval, and measured angle between the upslope and downslope of the S-wave in V2, were assessed. RESULTS: Definite ARVD/C was present in 155 patients (42.7 ±â€¯17.3 years, 68.4%male). -ECG ARVD/C patients (66 patients) were compared to 66 control patients (41.8 ±â€¯17.6 years, 65.2%male). Only the S-wave angle differentiated -ECG ARVD/C patients from controls (<0.001) with AU the ROC curve of 0.77 (95%CI 0.53 to 0.71) and odds ratio of 28.3 (95%CI 6.4 to 125.5). CONCLUSION: ARVD/C may lead to development of subtle ECG abnormalities distinguishable using the S-wave angle prior to development of 2010 Taskforce ECG criteria.

Right precordial-directed electrocardiographical markers identify arrhythmogenic right ventricular cardiomyopathy in the absence of conventional depolarization or repolarization abnormalities.

BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) carries a risk of sudden death. We aimed to assess whether vectorcardiographic (VCG) parameters directed toward the right heart and a measured angle of the S-wave would help differentiate ARVD/C with otherwise normal electrocardiograms from controls. METHODS: Task Force 2010 definite ARVD/C criteria were met for all patients. Those who did not fulfill Task Force depolarization or repolarization criteria (-ECG) were compared with age and gender-matched control subjects. Electrocardiogram measures of a 3-dimentional spatial QRS-T angle, a right-precordial-directed orthogonal QRS-T (RPD) angle, a root mean square of the right sided depolarizing forces (RtRMS-QRS), QRS duration (QRSd) and the corrected QT interval (QTc), and a measured angle including the upslope and downslope of the S-wave (S-wave angle) were assessed. RESULTS: Definite ARVD/C was present in 155 patients by 2010 Task Force criteria (41.7 ± 17.6 years, 65.2% male). -ECG ARVD/C patients (66 patients) were compared to 66 control patients (41.7 ± 17.6 years, 65.2% male). All parameters tested except the QRSd and QTc significantly differentiated -ECG ARVD/C from control patients (p < 0.004 to p < 0.001). The RPD angle and RtRMS-QRS best differentiated the groups. Combined, the 2 novel criteria gave 81.8% sensitivity, 90.9% specificity and odds ratio of 45.0 (95% confidence interval 15.8 to 128.2). CONCLUSION: ARVD/C disease process may lead to development of subtle ECG abnormalities that can be distinguishable using right-sided VCG or measured angle markers better than the spatial QRS-T angle, the QRSd or QTc, in the absence of Taskforce ECG criteria.

Titin and desmosomal genes in the natural history of arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Genotype-phenotype correlations are poorly characterised in arrhythmogenic right ventricular cardiomyopathy (ARVC). We investigated whether carriers of rare variants in desmosomal genes (DC) and titin gene (TTN) display different phenotypes and clinical outcomes compared with non-carriers (NT-ND). METHODS AND RESULTS: Thirty-nine ARVC families (173 subjects, 67 affected) with extensive follow-up (mean 9 years), prospectively enrolled in the International Familial Cardiomyopathy Registry since 1991, were screened for rare variants in TTN and desmosomal genes (DSP, PKP2, DSG2, DSC2). Multiple clinical and outcome variables were compared between three genetic groups (TTN, DC, NT-ND) to define genotype-phenotype associations. Of the 39 ARVC families, 13% (5/39) carried TTN rare variants (11 affected subjects), 13% (5/39) DC (8 affected), while 74% (29/39) were NT-ND (48 affected). When compared with NT-ND, DC had a higher prevalence of inverted T waves in V2-3 (75% vs 31%, p=0.004), while TTN had more supraventricular arrhythmias (46% vs 13%, p=0.013) and conduction disease (64% vs 6% p<0.001). When compared with the NT-ND group, the DC group experienced a worse prognosis (67% vs 11%, p=0.03) and exhibited a lower survival free from death or heart transplant (59% vs 95% at 30 years, and 31% vs 89% at 50 years, HR 9.66, p=0.006), while the TTN group showed an intermediate survival curve (HR 4.26, p=0.037). CONCLUSIONS: TTN carriers display distinct phenotypic characteristics including a greater risk for supraventricular arrhythmias and conduction disease. Conversely, DC are characterised by negative T waves in anterior leads, severe prognosis, high mortality and morbidity.

GENETIC CAUSES OF DILATED CARDIOMYOPATHY.

Dilated cardiomyopathy is a disease of the myocardium characterized by left ventricular dilatation and/or dysfunction, affecting both adult and pediatric populations. Almost half of cases are genetically determined with an autosomal pattern of inheritance. Up to 40 genes have been identified affecting proteins of a wide variety of cellular structures such as the sarcomere, the nuclear envelope, the cytoskeleton, the sarcolemma and the intercellular junction. Novel gene mutations have been recently identified thanks to advances in next-generation sequencing technologies. Genetic screening is an essential tool for early diagnosis, risk assessment, prognostic stratification and, possibly, adoption of primary preventive measures in affected patients and their asymptomatic relatives. The purpose of this article is to review the genetic basis of DCM, the known genotype-phenotype correlations, the role of current genetic sequencing techniques in the discovery of novel pathogenic gene mutations and new therapeutic perspectives.

Impact of DCM-Causing Genetic Background on Long-Term Response to Cardiac Resynchronization Therapy.

BACKGROUND: Patients with nonischemic dilated cardiomyopathy (DCM), severe left ventricular (LV) dysfunction, and complete left bundle branch block benefit from cardiac resynchronization therapy (CRT). However, a large heterogeneity of response to CRT is described. Several predictors of response to CRT have been identified, but the role of the underlying genetic background is still poorly explored. OBJECTIVES: In the present study, the authors sought to define differences in LV remodeling and outcome prediction after CRT when stratifying patients according to the presence or absence of DCM-causing genetic background. METHODS: From our center, 74 patients with DCM subjected to CRT and available genetic testing were retrospectively enrolled. Carriers of causative monogenic variants in validated DCM-causing genes, and/or with documented family history of DCM, were classified as affected by genetically determined disease (GEN+DCM) (n = 25). Alternatively, by idiopathic dilated cardiomyopathy (idDCM) (n = 49). The primary outcome was long-term LV remodeling and prevalence of super response to CRT (evaluated at 24-48 months after CRT); the secondary outcome was heart failure-related death/heart transplant/LV assist device. RESULTS: GEN+DCM and idDCM patients were homogeneous at baseline with the exception of QRS duration, longer in idDCM. The median follow-up was 55 months. Long-term LV reverse remodeling and the prevalence of super response were significantly higher in the idDCM group (27% in idDCM vs 5% in GEN+DCM; P = 0.025). The heart failure-related death/heart transplant/LV assist device outcome occurred more frequently in patients with GEN+DCM (53% vs 24% in idDCM; P = 0.028). CONCLUSIONS: Genotyping contributes to the risk stratification of patients with DCM undergoing CRT implantation in terms of LV remodeling and outcomes.

Magnetic Resonance Imaging Characterization and Clinical Outcomes of Dilated and Arrhythmogenic Left Ventricular Cardiomyopathies.

BACKGROUND: Nondilated left ventricular cardiomyopathy (NDLVC) has been recently differentiated from dilated cardiomyopathy (DCM). A comprehensive characterization of these 2 entities using cardiac magnetic resonance (CMR) and genetic testing has never been performed. OBJECTIVES: This study sought to provide a thorough characterization and assess clinical outcomes in a large multicenter cohort of patients with DCM and NDLVC. METHODS: A total of 462 patients with DCM (227) or NDLVC (235) with CMR data from 4 different referral centers were retrospectively analyzed. The study endpoint was a composite of sudden cardiac death or major ventricular arrhythmias. RESULTS: In comparison to DCM, NDLVC had a higher prevalence of pathogenic or likely pathogenic variants of arrhythmogenic genes (40% vs 23%; P < 0.001), higher left ventricular (LV) systolic function (LV ejection fraction: 51% ± 12% vs 36% ± 15%; P < 0.001) and higher prevalence of free-wall late gadolinium enhancement (LGE) (27% vs 14%; P < 0.001). Conversely, DCM showed higher prevalence of pathogenic or likely pathogenic variants of nonarrhythmogenic genes (23% vs 12%; P = 0.002) and septal LGE (45% vs 32%; P = 0.004). Over a median follow-up of 81 months (Q1-Q3: 40-132 months), the study outcome occurred in 98 (21%) patients. LGE with septal location (HR: 1.929; 95% CI: 1.033-3.601; P = 0.039) was independently associated with the risk of sudden cardiac death or major ventricular arrhythmias together with LV dilatation, older age, advanced NYHA functional class, frequent ventricular ectopic activity, and nonsustained ventricular tachycardia. CONCLUSIONS: In a multicenter cohort of patients with DCM and NDLVC, septal LGE together with LV dilatation, age, advanced disease, and frequent and repetitive ventricular arrhythmias were powerful predictors of major arrhythmic events.

Genetic variation in titin in arrhythmogenic right ventricular cardiomyopathy-overlap syndromes.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited genetic myocardial disease characterized by fibrofatty replacement of the myocardium and a predisposition to cardiac arrhythmias and sudden death. We evaluated the cardiomyopathy gene titin (TTN) as a candidate ARVC gene because of its proximity to an ARVC locus at position 2q32 and the connection of the titin protein to the transitional junction at intercalated disks. METHODS AND RESULTS: All 312 titin exons known to be expressed in human cardiac titin and the complete 3' untranslated region were sequenced in 38 ARVC families. Eight unique TTN variants were detected in 7 families, including a prominent Thr2896Ile mutation that showed complete segregation with the ARVC phenotype in 1 large family. The Thr2896IIe mutation maps within a highly conserved immunoglobulin-like fold (Ig10 domain) located in the spring region of titin. Native gel electrophoresis, nuclear magnetic resonance, intrinsic fluorescence, and proteolysis assays of wild-type and mutant Ig10 domains revealed that the Thr2896IIe exchange reduces the structural stability and increases the propensity for degradation of the Ig10 domain. The phenotype of TTN variant carriers was characterized by a history of sudden death (5 of 7 families), progressive myocardial dysfunction causing death or heart transplantation (8 of 14 cases), frequent conduction disease (11 of 14), and incomplete penetrance (86%). CONCLUSIONS: Our data provide evidence that titin mutations can cause ARVC, a finding that further expands the origin of the disease beyond desmosomal proteins. Structural impairment of the titin spring is a likely cause of ARVC and constitutes a novel mechanism underlying myocardial remodeling and sudden cardiac death.

Prognostic Prediction of Genotype vs Phenotype in Genetic Cardiomyopathies.

BACKGROUND: Diverse genetic backgrounds often lead to phenotypic heterogeneity in cardiomyopathies (CMPs). Previous genotype-phenotype studies have primarily focused on the analysis of a single phenotype, and the diagnostic and prognostic features of the CMP genotype across different phenotypic expressions remain poorly understood. OBJECTIVES: We sought to define differences in outcome prediction when stratifying patients based on phenotype at presentation compared with genotype in a large cohort of patients with CMPs and positive genetic testing. METHODS: Dilated cardiomyopathy (DCM), arrhythmogenic right ventricular cardiomyopathy, left-dominant arrhythmogenic cardiomyopathy, and biventricular arrhythmogenic cardiomyopathy were examined in this study. A total of 281 patients (80% DCM) with pathogenic or likely pathogenic variants were included. The primary and secondary outcomes were: 1) all-cause mortality (D)/heart transplant (HT); 2) sudden cardiac death/major ventricular arrhythmias (SCD/MVA); and 3) heart failure-related death (DHF)/HT/left ventricular assist device implantation (LVAD). RESULTS: Survival analysis revealed that SCD/MVA events occurred more frequently in patients without a DCM phenotype and in carriers of DSP, PKP2, LMNA, and FLNC variants. However, after adjustment for age and sex, genotype-based classification, but not phenotype-based classification, was predictive of SCD/MVA. LMNA showed the worst trends in terms of D/HT and DHF/HT/LVAD. CONCLUSIONS: Genotypes were associated with significant phenotypic heterogeneity in genetic cardiomyopathies. Nevertheless, in our study, genotypic-based classification showed higher precision in predicting the outcome of patients with CMP than phenotype-based classification. These findings add to our current understanding of inherited CMPs and contribute to the risk stratification of patients with positive genetic testing.

Genetic Risk of Arrhythmic Phenotypes in Patients With Dilated Cardiomyopathy.

BACKGROUND: Genotype-phenotype correlations in dilated cardiomyopathy (DCM) and, in particular, the effects of gene variants on clinical outcomes remain poorly understood. OBJECTIVES: The purpose of this study was to investigate the prognostic role of genetic variant carrier status in a large cohort of DCM patients. METHODS: A total of 487 DCM patients were analyzed by next-generation sequencing and categorized the disease genes into functional gene groups. The following composite outcome measures were assessed: 1) all-cause mortality; 2) heart failure-related death, heart transplantation, or destination left ventricular assist device implantation (DHF/HTx/VAD); and 3) sudden cardiac death/sustained ventricular tachycardia/ventricular fibrillation (SCD/VT/VF). RESULTS: A total of 183 pathogenic/likely pathogenic variants were found in 178 patients (37%): 54 (11%) Titin; 19 (4%) Lamin A/C (LMNA); 24 (5%) structural cytoskeleton-Z disk genes; 16 (3.5%) desmosomal genes; 46 (9.5%) sarcomeric genes; 8 (1.6%) ion channel genes; and 11 (2.5%) other genes. All-cause mortality was no different between variant carriers and noncarriers (p = 0.99). A trend toward worse SCD/VT/VF (p = 0.062) and DHF/HTx/VAD (p = 0.061) was found in carriers. Carriers of desmosomal and LMNA variants experienced the highest rate of SCD/VT/VF, which was independent of the left ventricular ejection fraction. CONCLUSIONS: Desmosomal and LMNA gene variants identify the subset of DCM patients who are at greatest risk for SCD and life-threatening ventricular arrhythmias, regardless of the left ventricular ejection fraction.

Filamin C Truncation Mutations Are Associated With Arrhythmogenic Dilated Cardiomyopathy and Changes in the Cell-Cell Adhesion Structures.

OBJECTIVES: The purpose of this study was to assess the phenotype of Filamin C (FLNC) truncating variants in dilated cardiomyopathy (DCM) and understand the mechanism leading to an arrhythmogenic phenotype. BACKGROUND: Mutations in FLNC are known to lead to skeletal myopathies, which may have an associated cardiac component. Recently, the clinical spectrum of FLNC mutations has been recognized to include a cardiac-restricted presentation in the absence of skeletal muscle involvement. METHODS: A population of 319 U.S. and European DCM cardiomyopathy families was evaluated using whole-exome and targeted next-generation sequencing. FLNC truncation probands were identified and evaluated by clinical examination, histology, transmission electron microscopy, and immunohistochemistry. RESULTS: A total of 13 individuals in 7 families (2.2%) were found to harbor 6 different FLNC truncation variants (2 stopgain, 1 frameshift, and 3 splicing). Of the 13 FLNC truncation carriers, 11 (85%) had either ventricular arrhythmias or sudden cardiac death, and 5 (38%) presented with evidence of right ventricular dilation. Pathology analysis of 2 explanted hearts from affected FLNC truncation carriers showed interstitial fibrosis in the right ventricle and epicardial fibrofatty infiltration in the left ventricle. Ultrastructural findings included occasional disarray of Z-discs within the sarcomere. Immunohistochemistry showed normal plakoglobin signal at cell-cell junctions, but decreased signals for desmoplakin and synapse-associated protein 97 in the myocardium and buccal mucosa. CONCLUSIONS: We found FLNC truncating variants, present in 2.2% of DCM families, to be associated with a cardiac-restricted arrhythmogenic DCM phenotype characterized by a high risk of life-threatening ventricular arrhythmias and a pathological cellular phenotype partially overlapping with arrhythmogenic right ventricular cardiomyopathy.

Insights into mildly dilated cardiomyopathy: temporal evolution and long-term prognosis.

AIMS: Mildly dilated cardiomyopathy (MDCM) has been proposed as a subtype of dilated cardiomyopathy (DCM) characterized by systolic dysfunction in the absence of significant LV dilatation. Few data on the characteristics and outcomes of MDCM patients are available. We sought to assess the main features and the long-term natural history of MDCM. METHODS AND RESULTS: From 1988 to 2010 we analysed all DCM patients consecutively evaluated at our Institution. MDCM was defined as LVEF <45% and LV end-diastolic volume index (LVEDVI) ≤70 mL/m2 in women and ≤89 mL/m2 in men. Among a total population of 638 patients, 226 (35%) fulfilled the criteria for MDCM. Compared with the other patients, they presented features of a less advanced disease and an overall long-term lower rate of all-cause mortality/heart transplantation (D/HTx; total events = 209; 144 deaths, 65 HTx): D/HTx at 10 years 15% in MDCM vs. 30% in DCM (P < 0.001). However, throughout the follow-up, 55 MDCM patients (24%) evolved to DCM by increasing LVEDVI, consistently worsening their long-term prognosis. Among persistent MDCM patients, a restrictive filling pattern [hazard ratio (HR) 5.30; 95% confidence interval (CI) 2.34-12.01, P < 0.001] and non-sustained ventricular tachycardia (HR 2.21; 95% CI 1.003-5.11, P = 0.047), but not LVEF, were independently associated with D/HTx at multivariate analysis [time-dependent receiver operating characteristic (ROC) curve: area under the curve (AUC) 0.80, 95% CI 0.65-0.94, P = 0.003]. CONCLUSIONS: MDCM identifies a consistent subgroup of DCMs diagnosed in an earlier stage and presenting an apparent better evolution. However, some MDCMs evolve into DCM despite medical therapy, whereas persistent MDCMs with non-sustained ventricular arrhythmias and restrictive filling pattern are characterized by a very poor outcome.

Association between mutation status and left ventricular reverse remodelling in dilated cardiomyopathy.

OBJECTIVE: To explore the genetic landscape of a well selected dilated cardiomyopathy (DCM) cohort, assessing the possible relation between different genotypes and left ventricular reverse remodelling (LVRR). METHODS: A cohort of 152 patients with DCM from the Heart Muscle Disease Registry of Trieste has been studied by next-generation sequencing (NGS). Patients were grouped into different 'gene-clusters' with functionally homogeneous genetic backgrounds. LVRR was defined by left ventricular ejection fraction normalisation or increase ≥10% associated with normalisation in indexed left ventricular end-diastolic diameter or relative decrease ≥10% at 24 months follow-up. RESULTS: A pathogenic disease-related gene variant was identified in 57% of patients: 28 (18%) TTN; 7 (5%) LMNA; 16 (11%) structural cytoskeleton Z-disk genes; 9 (6%) desmosomal genes; 18 (12%) motor sarcomeric genes and 9 (6%) other genes. Baseline clinical features were similar throughout the different genotypes. A significant relationship was found between gene cluster subgroups and LVRR, with a lower rate of LVRR in structural cytoskeleton Z-disk gene mutation carriers (1/16 patients, 6%, p<0.05 vs the other subgroups). Of note, structural cytoskeleton Z-disk gene rare variants were independently and inversely associated with LVRR when adjusted for clinical predictors of LVRR (OR 0.065; 95% CI 0.008 to 0.535, p=0.011). CONCLUSIONS: NGS confirmed a high genetic diagnostic yield in DCM. A specific 'gene-clusters' classification based on functional similarities in different genes might be helpful in the clinical management of genetically determined DCM. In this study, structural cytoskeleton Z-disk gene rare variants were independently associated with a lower rate of LVRR at follow-up.

Multilevel analyses of SCN5A mutations in arrhythmogenic right ventricular dysplasia/cardiomyopathy suggest non-canonical mechanisms for disease pathogenesis.

AIMS: Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C) is often associated with desmosomal mutations. Recent studies suggest an interaction between the desmosome and sodium channel protein Nav1.5. We aimed to determine the prevalence and biophysical properties of mutations in SCN5A (the gene encoding Nav1.5) in ARVD/C. METHODS AND RESULTS: We performed whole-exome sequencing in six ARVD/C patients (33% male, 38.2 ± 12.1 years) without a desmosomal mutation. We found a rare missense variant (p.Arg1898His; R1898H) in SCN5A in one patient. We generated induced pluripotent stem cell-derived cardiomyocytes (hIPSC-CMs) from the patient's peripheral blood mononuclear cells. The variant was then corrected (R1898R) using Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 technology, allowing us to study the impact of the R1898H substitution in the same cellular background. Whole-cell patch clamping revealed a 36% reduction in peak sodium current (P = 0.002); super-resolution fluorescence microscopy showed reduced abundance of NaV1.5 (P = 0.005) and N-Cadherin (P = 0.026) clusters at the intercalated disc. Subsequently, we sequenced SCN5A in an additional 281 ARVD/C patients (60% male, 34.8 ± 13.7 years, 52% desmosomal mutation-carriers). Five (1.8%) subjects harboured a putatively pathogenic SCN5A variant (p.Tyr416Cys, p.Leu729del, p.Arg1623Ter, p.Ser1787Asn, and p.Val2016Met). SCN5A variants were associated with prolonged QRS duration (119 ± 15 vs. 94 ± 14 ms, P < 0.01) and all SCN5A variant carriers had major structural abnormalities on cardiac imaging. CONCLUSIONS: Almost 2% of ARVD/C patients harbour rare SCN5A variants. For one of these variants, we demonstrated reduced sodium current, Nav1.5 and N-Cadherin clusters at junctional sites. This suggests that Nav1.5 is in a functional complex with adhesion molecules, and reveals potential non-canonical mechanisms by which Nav1.5 dysfunction causes cardiomyopathy.

[Dilated cardiomyopathy: a dynamic disease - clinical course, reverse remodeling and prognostic stratification]. / La cardiomiopatia dilatativa come malattia dinamica: storia naturale, rimodellamento inverso e stratificazione prognostica.

Dilated cardiomyopathy (DCM) is a relatively rare primary heart muscle disease with genetic or post-inflammatory etiology. In the last decade, the incidence and prevalence of the disease have significantly increased as a consequence of an earlier diagnosis supported by extensive familial screening programs and by the improvement in diagnostic techniques. Moreover, current therapeutic strategies have deeply modified the prognosis of DCM with a dramatic reduction in mortality. A significant number of patients with DCM present an impressive response to pharmacological and non-pharmacological therapy in terms of left ventricular reverse remodeling (reduction in ventricular size with improvement of systolic function), which confers a more favorable prognosis in the long term. However, the identification of patients with an increased likelihood of improvement after therapeutic optimization remains a challenging issue; in particular the assessment of arrhythmic risk carries important implications. Finally, the long-term follow-up of patients showing a significant left ventricular functional recovery under optimal treatment is still poorly known. Hence, the aim of the present review is to provide an insight into the clinical evolution/long-term follow-up of DCM, which should be actually considered a dynamic process rather than a static and chronic disease. Left ventricular reverse remodeling should be considered a key therapeutic goal, mostly associated with a long-standing recovery, but cannot be considered the expression of permanent "healing", confirming the need for a systematic and careful follow-up over time in this setting.

Risk Stratification in Arrhythmic Right Ventricular Cardiomyopathy Without Implantable Cardioverter-Defibrillators.

OBJECTIVES: The primary objective of this study is risk stratification of patients with arrhythmic right ventricular cardiomyopathy (ARVC). BACKGROUND: There is a need to identify those who need an automatic implantable defibrillator (ICD) to prevent sudden death. METHODS: This is an analysis of 88 patients with ARVC from three centers who were not treated with an ICD. RESULTS: Risk factors for subsequent arrhythmic deaths were pre-enrollment sustained or nonsustained ventricular tachycardia (VT) and decreased left ventricular function. CONCLUSION: These factors serve as proposed guidelines for implantation of an ICD in patients with ARVC to prevent sudden death.

FLNC Gene Splice Mutations Cause Dilated Cardiomyopathy.

OBJECTIVE: To identify novel dilated cardiomyopathy (DCM) causing genes, and to elucidate the pathological mechanism leading to DCM by utilizing zebrafish as a model organism. BACKGROUND: DCM, a major cause of heart failure, is frequently familial and caused by a genetic defect. However, only 50% of DCM cases can be attributed to a known DCM gene variant, motivating the ongoing search for novel disease genes. METHODS: We performed whole exome sequencing (WES) in two multigenerational Italian families and one US family with arrhythmogenic DCM without skeletal muscle defects, in whom prior genetic testing had been unrevealing. Pathogenic variants were sought by a combination of bioinformatic filtering and cosegregation testing among affected individuals within the families. We performed function assays and generated a zebrafish morpholino knockdown model. RESULTS: A novel filamin C gene splicing variant (FLNC c.7251+1 G>A) was identified by WES in all affected family members in the two Italian families. A separate novel splicing mutation (FLNC c.5669-1delG) was identified in the US family. Western blot analysis of cardiac heart tissue from an affected individual showed decreased FLNC protein, supporting a haploinsufficiency model of pathogenesis. To further analyze this model, a morpholino knockdown of the ortholog filamin Cb in zebrafish was created which resulted in abnormal cardiac function and ultrastructure. CONCLUSIONS: Using WES, we identified two novel FLNC splicing variants as the likely cause of DCM in three families. We provided protein expression and in vivo zebrafish data supporting haploinsufficiency as the pathogenic mechanism leading to DCM.