POT1 and Damage Response Malfunction Trigger Acquisition of Somatic Activating Mutations in the VEGF Pathway in Cardiac Angiosarcomas

Background: Mutations in the POT1 gene explain abnormally long telomeres and multiple tumors including cardiac angiosarcomas (CAS). However, the link between long telomeres and tumorigenesis is poorly understood. Methods and Results: Here, we have studied the somatic landscape of 3 different angiosarcoma patients with mutations in the POT1 gene to further investigate this tumorigenesis process. In addition, the genetic landscape of 7 CAS patients without mutations in the POT1 gene has been studied. Patients with CAS and nonfunctional POT1 did not repress ATR (ataxia telangiectasia RAD3-related)-dependent DNA damage signaling and showed a constitutive increase of cell cycle arrest and somatic activating mutations in the VEGF (vascular endothelial growth factor)/angiogenesis pathway (KDR gene). The same observation was made in POT1 mutation carriers with tumors different from CAS and also in CAS patients without mutations in the POT1 gene but with mutations in other genes involved in DNA damage signaling. Conclusions: Inhibition of POT1 function and damage-response malfunction activated DNA damage signaling and increased cell cycle arrest as well as interfered with apoptosis, which would permit acquisition of somatic mutations in the VEGF/angiogenesis pathway that drives tumor formation. Therapies based on the inhibition of damage signaling in asymptomatic carriers may diminish defects on cell cycle arrest and thus prevent the apoptosis deregulation that leads to the acquisition of driver mutations

Natural History of MYH7-Related Dilated Cardiomyopathy

BACKGROUND Variants in myosin heavy chain 7 (MYH7) are responsible for disease in 1% to 5% of patients with dilated cardiomyopathy (DCM); however, the clinical characteristics and natural history of MYH7-related DCM are poorly described. OBJECTIVES We sought to determine the phenotype and prognosis of MYH7-related DCM. We also evaluated the influence of variant location on phenotypic expression. METHODS We studied clinical data from 147 individuals with DCM-causing MYH7 variants (47.6% female; 35.6 +/- 19.2 years) recruited from 29 international centers. RESULTS At initial evaluation, 106 (72.1%) patients had DCM (left ventricular ejection fraction: 34.5% +/- 11.7%). Median follow-up was 4.5 years (IQR: 1.7-8.0 years), and 23.7% of carriers who were initially phenotype-negative developed DCM. Phenotypic expression by 40 and 60 years was 46% and 88%, respectively, with 18 patients (16%) first diagnosed at <18 years of age. Thirty-six percent of patients with DCM met imaging criteria for LV noncompaction. During follow-up, 28% showed left ventricular reverse remodeling. Incidence of adverse cardiac events among patients with DCM at 5 years was 11.6%, with 5 (4.6%) deaths caused by end-stage heart failure (ESHF) and 5 patients (4.6%) requiring heart transplantation. The major ventricular arrhythmia rate was low (1.0% and 2.1% at 5 years in patients with DCM and in those with LVEF of <= 35%, respectively). ESHF and major ventricular arrhythmia were significantly lower compared with LMNA-related DCM and similar to DCM caused by TTN truncating variants. CONCLUSIONS MYH7-related DCM is characterized by early age of onset, high phenotypic expression, low left ventricular reverse remodeling, and frequent progression to ESHF. Heart failure complications predominate over ventricular arrhythmias, which are rare. (C) 2022 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation

Paradoxical Effect of Increased Diastolic Ca 2+

BACKGROUND: Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is characterized by stress-triggered syncope and sudden death. CPVT patients manifest sino-atrial node (SAN) dysfunction, the mechanisms of which remain unexplored. METHODS AND RESULTS: We investigated SAN [Ca(2+)](i) handling in mice carrying the CPVT-linked mutation of ryanodine receptor (RyR2(R4496C)) and on their wild-type (WT) littermates. In vivo telemetric recordings showed impaired SAN automaticity in RyR2(R4496C) mice following Isoproterenol (ISO) injection, analogous to what was observed in CPVT patients after exercise. Pacemaker activity was explored by measuring spontaneous [Ca(2+)](i) transients in SAN cells within the intact SAN by confocal microscopy. RyR2(R4496C) SAN presented significantly slower pacemaker activity and impaired chronotropic response under β-adrenergic stimulation, accompanied by the appearance of pauses (in spontaneous [Ca(2+)](i) transients and action potentials) in 75% of the cases. Ca(2+) spark frequency was increased by 2-fold in RyR2(R4496C) SAN. Whole-cell patch-clamp experiments performed on isolated RyR2(R4496C) SAN cells showed that L-type Ca(2+) current (I(Ca,L)) density was reduced by ~50%, an effect blunted with internal Ca(2+) buffering. ISO dramatically increased the frequency of Ca(2+) sparks and waves by ~5 and ~10-fold, respectively. Interestingly, the sarcoplasmic reticulum (SR) Ca(2+) content was significantly reduced in RyR2(R4496C) SAN cells in the presence of ISO, which may contribute to stopping the “Ca(2+)-clock” rhythm generation, originating SAN pauses. CONCLUSIONS: The increased activity of RyR2(R4496C) in SAN leads to an unanticipated decrease on SAN automaticity by Ca(2+)-dependent decrease of I(Ca,L) and SR Ca(2+) depletion during diastole, identifying subcellular pathophysiologic alterations contributing to the SAN dysfunction in CPVT patients

Somatic MYH7, MYBPC3, TPM1, TNNT2 and TNNI3 Mutations in Sporadic Hypertrophic Cardiomyopathy

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous genetic heart disease characterized by left ventricular hypertrophy in the absence of another disease that could explain the wall thickening. Elucidation of the genetic basis of HCM lead to the identification of several genes encoding sarcomeric proteins, such as MYH7, MYBPC3, TPM1, TNNT2, and TNNI3. Sarcomeric genes are mutated in approximately 40% of HCM patients and a possible explanation for the incomplete yield of mutation-positive HCM may be somatic mutations. METHODS AND RESULTS: We studied 104 unrelated patients with non-familial HCM. Patients underwent clinical evaluation and mutation screening of 5 genes implicated in HCM (MYH7, MYBPC3, TPM1, TNNT2, and TNNI3) in genomic DNA isolated from resected cardiac tissue; 41 of 104 were found to carry a mutation, but as several patients carried the same mutations, the total amount of different mutations was 37; 20 of these mutations have been previously described, and pathogenicity has been assessed. To determine the effect of the 17 new mutations an in silico assay was performed and it predicted that 4 variants were damaging mutations. All identified variants were also seen in the DNA isolated from the corresponding blood, which demonstrated the absence of somatic mutations. CONCLUSIONS: Somatic mutations in MYH7, MYBPC3, TPM1, TNNT2, and TNNI3 do not represent an important etiologic pathway in HCM

El volumen extracelular no se asocia a arritmias malignas en miocardiopatía hipertrófica de alto riesgo

Introduction and objectives: Myocardial interstitial fibrosis, a hallmark of hypertrophic cardiomyopathy (HCM), has been proposed as an arrhythmic substrate. Fibrosis is associated with increased extracellular volume (ECV), which can be quantified by computed tomography (CT). We aimed to analyze the association between CT-determined ECV and malignant ventricular arrhythmias. Methods: A retrospective case-control observational study was conducted in HCM patients with implantable cardioverter-defibrillator, undergoing a CT-protocol with continuous iodine contrast infusion to determine equilibrium ECV. Left ventricular septal and lateral CT-determined ECV was compared between prespecified cases (malignant arrhythmia any time before CT scan) and controls (no prior malignant arrhythmias) and among ECV tertiles. Results: A total of 78 implantable cardioverter-defibrillator HCM patients were included; 24 were women, with a mean age of 52.1 ± 15.6 years. Mean ECV ± standard deviation in the septal left ventricular wall and was 29.8% ± 6.3% in cases (n = 24) vs 31.9% ± 8.5% in controls (n = 54); P = .282. Mean ECV in the lateral wall was 24.5% ± 6.8% in cases vs 28.2% ± 7.4% in controls; P = .043. On comparison of the entire population according to septal ECV tertiles, no significant differences were found in the number of patients receiving appropriate shocks. Conversely, we found a trend (P = .056) for a higher number of patients receiving appropriate shocks in the lateral ECV lowest tertile. Conclusions: Extracellular volume was not increased in implantable cardioverter-defibrillator HCM patients with malignant ventricular arrhythmias vs those without arrhythmias. Our findings do not support the use of ECV (a surrogate of diffuse fibrosis) as a predictor of arrhythmias in high-risk HCM patients.Introducción y objetivos: La fibrosis intersticial en miocardiopatía hipertrófica (MCH) se ha propuesto como substrato de arritmias malignas. La fibrosis se asocia a expansión del volumen extracelular (VEC) que se puede cuantificar por tomografía computarizada (TC). El objetivo es analizar la asociación entre VEC determinado por TC y la presencia de arritmias malignas. Métodos: Estudio observacional de casos y controles en pacientes con MCH y desfibrilador automático implantable sometidos a TC con infusión continua de contraste yodado para cuantificar el VEC en equilibrio. Se comparó el VEC determinado por TC en las paredes septal y lateral de ventrículo izquierdo entre casos (presencia de arritmia maligna previa) y controles (sin arritmias malignas). Resultados: Se incluyó a 78 pacientes con MCH-desfibrilador automático implantable, 24 eran mujeres con una edad media de 52,1 ± 15,6 años. El VEC medio ± desviación estándar en pared septal fue 29,8 ± 6,3% en casos (n = 24) frente a 31,9 ± 8,5% en controles (n = 54); p = 0,282. El VEC medio en pared lateral fue 24,5 ± 6,8% en casos frente a 28,2 ± 7,4% en controles; p = 0,043. No se encontraron diferencias en el número de pacientes con choques apropiados entre los diferentes terciles de VEC. Por el contrario, se encontró una tendencia (p = 0,056) de un mayor número de pacientes dentro del menor tercil de VEC en pared lateral con descargas apropiadas. Conclusiones: El VEC en pacientes con MCH-desfibrilador automático implantable con arritmias malignas no se mostró incrementado comparado con pacientes con MCH-desfibrilador automático implantable sin arritmias. Estos hallazgos no apoyan en uso de VEC (subrogado de fibrosis difusa) como predictor de arritmias malignas en pacientes con MCH de alto riesgo.Sin financiación5.166 JCR (2017) Q1, 26/128 Cardiac and Cardiovacular SystemsUE

Natural History and Risk Stratification in Andersen-Tawil Syndrome Type 1.

Andersen-Tawil Syndrome type 1 (ATS1) is a rare arrhythmogenic disorder, caused by loss-of-function mutations in the KCNJ2 gene. We present here the largest cohort of patients with ATS1 with outcome data reported. This study sought to define the risk of life-threatening arrhythmic events (LAE), identify predictors of such events, and define the efficacy of antiarrhythmic therapy in patients with ATS1. Clinical and genetic data from consecutive patients with ATS1 from 23 centers were entered in a database implemented at ICS Maugeri in Pavia, Italy, and pooled for analysis. We enrolled 118 patients with ATS1 from 57 families (age 23 ± 17 years at enrollment). Over a median follow-up of 6.2 years (interquartile range: 2.7 to 16.5 years), 17 patients experienced a first LAE, with a cumulative probability of 7.9% at 5 years. An increased risk of LAE was associated with a history of syncope (hazard ratio [HR]: 4.54; p = 0.02), with the documentation of sustained ventricular tachycardia (HR 9.34; p = 0.001) and with the administration of amiodarone (HR: 268; p  Our data demonstrate that the clinical course of patients with ATS1 is characterized by a high rate of LAE. A history of unexplained syncope or of documented sustained ventricular tachycardia is associated with a higher risk of LAE. Amiodarone is proarrhythmic and should be avoided in patients with ATS1