Gene-Based Risk Stratification for Cardiac Disorders in LMNA Mutation Carriers.

BACKGROUND: Mutations in LMNA (lamin A/C), which encodes lamin A and C, typically cause age-dependent cardiac phenotypes, including dilated cardiomyopathy, cardiac conduction disturbance, atrial fibrillation, and malignant ventricular arrhythmias. Although the type of LMNA mutations have been reported to be associated with susceptibility to malignant ventricular arrhythmias, the gene-based risk stratification for cardiac complications remains unexplored. METHODS AND RESULTS: The multicenter cohort included 77 LMNA mutation carriers from 45 families; cardiac disorders were retrospectively analyzed. The mean age of patients when they underwent genetic testing was 45±17, and they were followed for a median 49 months. Of the 77 carriers, 71 (92%) were phenotypically affected and showed cardiac conduction disturbance (81%), low left ventricular ejection fraction (<50%; 45%), atrial arrhythmias (58%), and malignant ventricular arrhythmias (26%). During the follow-up period, 9 (12%) died, either from end-stage heart failure (n=7) or suddenly (n=2). Genetic analysis showed truncation mutations in 58 patients from 31 families and missense mutations in 19 patients from 14 families. The onset of cardiac disorders indicated that subjects with truncation mutations had an earlier occurrence of cardiac conduction disturbance and low left ventricular ejection fraction, than those with missense mutations. In addition, the truncation mutation was found to be a risk factor for the early onset of cardiac conduction disturbance and the occurrence of atrial arrhythmias and low left ventricular ejection fraction, as estimated using multivariable analyses. CONCLUSIONS: The truncation mutations were associated with manifestation of cardiac phenotypes in LMNA-related cardiomyopathy, suggesting that genetic analysis might be useful for diagnosis and risk stratification.

Patient-Specific Human Induced Pluripotent Stem Cell Model Assessed with Electrical Pacing Validates S107 as a Potential Therapeutic Agent for Catecholaminergic Polymorphic Ventricular Tachycardia.

INTRODUCTION: Human induced pluripotent stem cells (hiPSCs) offer a unique opportunity for disease modeling. However, it is not invariably successful to recapitulate the disease phenotype because of the immaturity of hiPSC-derived cardiomyocytes (hiPSC-CMs). The purpose of this study was to establish and analyze iPSC-based model of catecholaminergic polymorphic ventricular tachycardia (CPVT), which is characterized by adrenergically mediated lethal arrhythmias, more precisely using electrical pacing that could promote the development of new pharmacotherapies. METHOD AND RESULTS: We generated hiPSCs from a 37-year-old CPVT patient and differentiated them into cardiomyocytes. Under spontaneous beating conditions, no significant difference was found in the timing irregularity of spontaneous Ca2+ transients between control- and CPVT-hiPSC-CMs. Using Ca2+ imaging at 1 Hz electrical field stimulation, isoproterenol induced an abnormal diastolic Ca2+ increase more frequently in CPVT- than in control-hiPSC-CMs (control 12% vs. CPVT 43%, p<0.05). Action potential recordings of spontaneous beating hiPSC-CMs revealed no significant difference in the frequency of delayed afterdepolarizations (DADs) between control and CPVT cells. After isoproterenol application with pacing at 1 Hz, 87.5% of CPVT-hiPSC-CMs developed DADs, compared to 30% of control-hiPSC-CMs (p<0.05). Pre-incubation with 10 µM S107, which stabilizes the closed state of the ryanodine receptor 2, significantly decreased the percentage of CPVT-hiPSC-CMs presenting DADs to 25% (p<0.05). CONCLUSIONS: We recapitulated the electrophysiological features of CPVT-derived hiPSC-CMs using electrical pacing. The development of DADs in the presence of isoproterenol was significantly suppressed by S107. Our model provides a promising platform to study disease mechanisms and screen drugs.

Electrocardiography as the First Step for the Further Examination of Cardiac Involvement in Myasthenia Gravis.

INTRODUCTION: Cardiac involvement of myasthenia gravis (MG) accompanies a poor prognosis. In the present study, we aimed to investigate the relationship between ECG abnormality and cardiac involvement. METHODS: Of 178 patients diagnosed with MG between 2001 and 2013 at our hospital, we retrospectively analyzed consecutive 58 patients who underwent both ECG and echocardiography and without underlying cardiovascular disease. ECG abnormalities were defined by computer-assigned Minnesota-codes. Cardiac damage was defined as either (1) ejection fraction (EF) <55% on echocardiography or (2) elevated E/e', the ratio of mitral velocity to early diastolic velocity of the mitral annulus >8 on echocardiography. RESULTS: Thirty-three patients (56.8%) had ECG abnormality. An elevated E/e' was observed in patients with ECG abnormality compared to those without ECG abnormality (11.2 ± 3.2, 8.7 ± 2.2, resp., p = 0.03). Among patients with ECG abnormality, 14 of 15 patients showed cardiac damage. Among patients without ECG abnormality, 6 of 33 patients showed cardiac damage (p = 0.003). Reduced EF was observed in five patients (8.6%) with ECG abnormality and none in patients without ECG abnormality. CONCLUSIONS: ECG may aid as the first step for the further examination of cardiac damage in patients with MG.

Impact of renal function deterioration on adverse events during anticoagulation therapy using non-vitamin K antagonist oral anticoagulants in patients with atrial fibrillation.

Renal function is crucial for patients with non-valvular atrial fibrillation (NVAF) using non-vitamin K antagonist oral anticoagulants (NOAC). The incidence of renal function deterioration during anticoagulation therapy and its impact of adverse events are unknown. In 807 consecutive NVAF patients treated with NOAC and with estimated creatinine clearance (eCCr) ≥ 50 ml/min (mean age 68 ± 11 years, mean CHADS2 score = 1.8 ± 1.4, CHA2DS2-VASc score = 2.8 ± 1.8, HAS-BLED score = 1.7 ± 1.1), we analyzed the time course of renal function and clinical outcomes, and compared these with the data of general Japanese inhabitants from the Suita Study (n = 2140). Of the 807 patients, 751 (93 %) maintained eCCr ≥ 50 ml/min (group A) whereas the remaining 56 (7 %) fell into the eCCr < 50 ml/min (group B) during the 382 ± 288 days of follow-up. Multivariate logistic regression analysis revealed that advanced age, lower body weight, and congestive heart failure were independent predictors for renal function deterioration in patients with eCCr ≥ 50 ml/min at baseline. Major and/or minor bleedings were more commonly observed in group B than in group A (21 vs. 8 %; P = 0.0004). The CHADS2, CHA2DS2-VASc, and HAS-BLED scores were also significant predictors of renal function deterioration (P < 0.0001). The incidences of renal function deterioration were 1.4, 3.4, 10.5 and 11.7 % in patients with CHADS2 score of 0, 1, 2 and ≥3, respectively. As to CHA2DS2-VASc score, renal function deterioration occurred in 0, 1.7, 9.8 and 15.0 % with a score of 0, 1-2, 3-4 and ≥5, respectively. In the Suita Study of the general population, on the other hand, 122 of 2140 participants with eCCr ≥ 50 ml/min at baseline (5.7 %) fell into the eCCr < 50 ml/min during about 2 years. The incidence of renal function deterioration increased with the CHADS2 score in the general population as well as in our patients. Renal function deterioration was not uncommon and was associated with more frequent adverse events including major bleeding in NVAF patients with anticoagulation therapy. CHADS2, CHA2DS2-VASc, and HAS-BLED scores may be useful as an index of predicting renal function deterioration.

Evidence for the involvement of double-strand breaks in heat-induced cell killing.

To identify critical events associated with heat-induced cell killing, we examined foci formation of gammaH2AX (histone H2AX phosphorylated at serine 139) in heat-treated cells. This assay is known to be quite sensitive and a specific indicator for the presence of double-strand breaks. We found that the number of gammaH2AX foci increased rapidly and reached a maximum 30 minutes after heat treatment, as well as after X-ray irradiation. When cells were heated at 41.5 degrees C to 45.5 degrees C, we observed a linear increase with time in the number of gammaH2AX foci. An inflection point at 42.5 degrees C and the thermal activation energies above and below the inflection point were almost the same for cell killing and foci formation according to Arrhenius plot analysis. From these results, it is suggested that the number of gammaH2AX foci is correlated with the temperature dependence of cell killing. During periods when cells were exposed to heat, the cell cycle-dependent pattern of cell killing was the same as the cell cycle pattern of gammaH2AX foci formation. We also found that thermotolerance was due to a depression in the number of gammaH2AX foci formed after heating when the cells were pre-treated by heat. These findings suggest that cell killing might be associated with double-strand break formation via protein denaturation.