Hokuriku-plus familial hypercholesterolaemia registry study: rationale and study design.

INTRODUCTION: Familial hypercholesterolaemia (FH) is an autosomal-dominant inherited genetic disease. It carries an extremely high cardiovascular risk associated with significantly elevated low-density lipoprotein (LDL) cholesterol. The diagnostic rate of this disease in some European nations is quite high, due to the presence of multiple prospective registries. On the other hand, few data-and in particular multicentre data-exist regarding this issue among Japanese subjects. Therefore, this study intends to assemble a multicentre registry that aims to comprehensively assess cardiovascular risk among Japanese FH patients while taking into account their genetic backgrounds. METHODS AND ANALYSIS: The Hokuriku-plus FH registry is a prospective, observational, multicentre cohort study, enrolling consecutive FH patients who fulfil the clinical criteria of FH in Japan from 37 participating hospitals mostly in Hokuriku region of Japan from April 2020 to March 2024. A total of 1000 patients will be enrolled into the study, and we plan to follow-up participants over 5 years. We will collect clinical parameters, including lipids, physical findings, genetic backgrounds and clinical events covering atherosclerotic and other important events, such as malignancies. The primary endpoint of this study is new atherosclerotic cardiovascular disease (ASCVD) events. The secondary endpoints are as follows: LDL cholesterol, secondary ASCVD events and the occurrence of other diseases including hypertension, diabetes and malignancies. ETHICS AND DISSEMINATION: This study is being conducted in compliance with the Declaration of Helsinki, the Ethical Guidelines for Medical and Health Research Involving Human Subjects, and all other applicable laws and guidelines in Japan. This study protocol has been approved by the Institutional Review Board at Kanazawa University. We will disseminate the final results at international conferences and in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: UMIN000038210.

Impact of functional studies on exome sequence variant interpretation in early-onset cardiac conduction system diseases.

AIMS: The genetic cause of cardiac conduction system disease (CCSD) has not been fully elucidated. Whole-exome sequencing (WES) can detect various genetic variants; however, the identification of pathogenic variants remains a challenge. We aimed to identify pathogenic or likely pathogenic variants in CCSD patients by using WES and 2015 American College of Medical Genetics and Genomics (ACMG) standards and guidelines as well as evaluating the usefulness of functional studies for determining them. METHODS AND RESULTS: We performed WES of 23 probands diagnosed with early-onset (<65 years) CCSD and analysed 117 genes linked to arrhythmogenic diseases or cardiomyopathies. We focused on rare variants (minor allele frequency < 0.1%) that were absent from population databases. Five probands had protein truncating variants in EMD and LMNA which were classified as 'pathogenic' by 2015 ACMG standards and guidelines. To evaluate the functional changes brought about by these variants, we generated a knock-out zebrafish with CRISPR-mediated insertions or deletions of the EMD or LMNA homologs in zebrafish. The mean heart rate and conduction velocities in the CRISPR/Cas9-injected embryos and F2 generation embryos with homozygous deletions were significantly decreased. Twenty-one variants of uncertain significance were identified in 11 probands. Cellular electrophysiological study and in vivo zebrafish cardiac assay showed that two variants in KCNH2 and SCN5A, four variants in SCN10A, and one variant in MYH6 damaged each gene, which resulted in the change of the clinical significance of them from 'Uncertain significance' to 'Likely pathogenic' in six probands. CONCLUSION: Of 23 CCSD probands, we successfully identified pathogenic or likely pathogenic variants in 11 probands (48%). Functional analyses of a cellular electrophysiological study and in vivo zebrafish cardiac assay might be useful for determining the pathogenicity of rare variants in patients with CCSD. SCN10A may be one of the major genes responsible for CCSD.

Impact of cardiac myosin light chain kinase gene mutation on development of dilated cardiomyopathy.

AIMS: Cardiac myosin light chain kinase (cMLCK) phosphorylates ventricular myosin regulatory light chain 2 (MLC2v) and regulates sarcomere and cardiomyocyte organization. However, few data exist regarding the relationship between cMLCK mutations and MLC2v phosphorylation, particularly in terms of developing familial dilated cardiomyopathy (DCM) in whom cMLCK gene mutations were identified. The purpose of the present study was to investigate functional consequences of cMLCK mutations in DCM patients. METHODS AND RESULTS: The diagnosis of DCM was based on the patients' history and on echocardiography. We screened cMLCK gene mutations in DCM probands with high resolution melting analysis. Known DCM-causing genes mutations were excluded by exome sequencing of family members. MLC2v phosphorylation was analysed by Phos-tag sodium dodecyl sulfate-polyacrylamide gel electrophoresis assays. We also performed ADP-Glo assays for determining the total amount of adenosine triphosphate used in the kinase reaction. Unrelated DCM probands (109 males and 40 females) were enrolled in this study, of which 16 were familial and 133 sporadic. By mutation screening, a truncation variant of c1915-1 g>t (p.Pro639Valfs*15) was identified, which was not detected in 400 chromosomes of 200 healthy volunteers; it is listed in the Human Genetic Variation Database with an allele frequency < 0.001. In the proband, the presence of mutations in known DCM-causing genes was excluded with exome analysis. Familial analysis identified a 19-year-old male carrier who manifested slight left ventricular dilation with preserved systolic function. Phosphorylation assays analysed by Phos-tag SDS-PAGE revealed that the identified p.Pro639Valfs*15 mutation results in a complete lack of kinase activity, although it did not affect wild-type cMLCK activity. ADP-Glo assays confirmed that the mutant cMLCK had no kinase activity, whereas wild-type cMLCK had a Km value of 5.93 ± 1.47 µM and a Vmax of 1.28 ± 0.03 mol/min/mol kinase. CONCLUSIONS: These results demonstrate that a truncation mutation in the cMLCK gene p.Pro639Valfs*15 can be associated with significant impairment of MLC2v phosphorylation and possibly with development of DCM, although a larger study of DCM patients is required to determine the prevalence of this mutation and further strengthen its association with disease development.

Functional analysis of KCNH2 gene mutations of type 2 long QT syndrome in larval zebrafish using microscopy and electrocardiography.

Heterologous expression systems play a vital role in the characterization of potassium voltage-gated channel subfamily H member 2 (KCNH2) gene mutations, such as E637K which is associated with long QT syndrome type 2 (LQT2). In vivo assays using zebrafish provide a means for testing genetic variants of cardiac disease; however, limited information on the role of the E637K mutation is available from in vivo systems and their utility has yet to be fully exploited in the context of LQT2. We sought to evaluate the ability of the E637K mutant channel to restore normal repolarization in larval zebrafish with a human KCNH2 orthologue, kcnh2a-knockdown. A morpholino (MO) targeting kcnh2a was injected alone or with wild type (WT) or E637K KCNH2 cRNA into zebrafish embryos at the 1-2 cell stage. Cardiac repolarization phenotypes were screened using light microscopy and the QT interval was measured by single lead electrocardiograph (ECG) analysis at 72-h post-fertilization. In the MO alone group, 17% of zebrafish had a normal phenotype; this rate increased to 60% in the WT KCNH2 cRNA injected zebrafish and to 35% in the E637K injected zebrafish. The ECG of larval zebrafish revealed that QTc was significantly prolonged in the MO alone group compared to the control group. Co-injection of WT KCNH2 cRNA shortened the QTc interval, however, that of the E637K did not. We suggest that this in vivo cardiac assay using microscopy and ECG in larval zebrafish offers a reliable approach for risk discrimination of KCNH2 mutations.

Huge right ventricular mass lesion associated with genital malignant tumor: a case report.

BACKGROUND: Primary heart tumors are rare, whereas metastatic heart tumors occur more frequently. CASE PRESENTATION: We report a case of a 75-year-old Japanese woman who had metastatic heart tumors of the right ventricle. Although she initially received antibiotic therapy following a diagnosis of pneumonia and pleuritis, her symptoms worsened, and she developed dyspnea and bilateral lower limb edema. Echocardiography showed a huge mass lesion occupying the entire right ventricle. Because the patient's tumor markers were elevated, we used computed tomography to search for the primary lesion, which was located in the vagina or the uterus. Histology demonstrated the presence of basaloid squamous cell carcinoma in the vaginal tissue. Chemotherapy with paclitaxel and carboplatin was initiated. CONCLUSIONS: These data suggest that the tumor in the right ventricle metastasized from the genital organs.

J Waves for Predicting Cardiac Events in Hypertrophic Cardiomyopathy.

OBJECTIVES: This study sought to investigate whether the presence of J waves was associated with cardiac events in patients with hypertrophic cardiomyopathy (HCM). BACKGROUND: It has been uncertain whether the presence of J waves predicts life-threatening cardiac events in patients with HCM. METHODS: This study evaluated consecutive 338 patients with HCM (207 men; age 61 ± 17 years of age). A J-wave was defined as J-point elevation >0.1 mV in at least 2 contiguous inferior and/or lateral leads. Cardiac events were defined as sudden cardiac death, ventricular fibrillation or sustained ventricular tachycardia, or appropriate implantable cardiac defibrillator therapy. The study also investigated whether adding the J-wave in a conventional risk model improved a prediction of cardiac events. RESULTS: J waves were seen in 46 (13.6%) patients at registration. Cardiac events occurred in 31 patients (9.2%) during median follow-up of 4.9 years (interquartile range: 2.6 to 7.1 years). In a Cox proportional hazards model, the presence of J waves was significantly associated with cardiac events (adjusted hazard ratio: 4.01; 95% confidence interval [CI]: 1.78 to 9.05; p = 0.001). Compared with the conventional risk model, the model using J waves in addition to conventional risks better predicted cardiac events (net reclassification improvement, 0.55; 95% CI: 0.20 to 0.90; p = 0.002). CONCLUSIONS: The presence of J waves was significantly associated with cardiac events in HCM. Adding J waves to conventional cardiac risk factors improved prediction of cardiac events. Further confirmatory studies are needed before considering J-point elevation as a marker of risk for use in making management decisions regarding risk in patients with HCM.

Whole exome sequencing combined with integrated variant annotation prediction identifies a causative myosin essential light chain variant in hypertrophic cardiomyopathy.

BACKGROUND: The development of candidate gene approaches to enable molecular diagnosis of hypertrophic cardiomyopathy (HCM) has required extensive and prolonged efforts. Whole exome sequencing (WES) technologies have already accelerated genetic studies of Mendelian disorders, yielding approximately 30% diagnostic success. As a result, there is great interest in extending the use of WES to any of Mendelian diseases. This study investigated the potential of WES for molecular diagnosis of HCM. METHODS: WES was performed on seven relatives from a large HCM family with a clear HCM phenotype (five clinically affected and two unaffected) in the Kanazawa University Hypertrophic Cardiomyopathy Registry. Serial bioinformatics filtering methods as well as using combined annotation dependent depletion (CADD) score and high heart expression (HHE) gene data were applied to detect the causative variant. Moreover, additional carriers of the variant were investigated in the HCM registry, and clinical characteristics harboring the variant were collected and evaluated. RESULTS: WES detected 60020 rare variants in the large HCM family. Of those, 3439 were missense, nonsense, splice-site, or frameshift variants. After genotype-phenotype matching, 13 putative variants remained. Using CADD score and HHE gene data, the number of candidates was reduced to one, a variant in the myosin essential light chain (MYL3, NM_000258.2:c.281G>A, p.Arg94His) that was shared by the five affected subjects. Additional screening of the HCM registry (n=600) identified two more subjects with this variant. Serial assessments of the variant carriers revealed the following phenotypic characteristics: (1) disease-penetrance of 88%; (2) all clinically affected carriers exhibited asymmetric septal hypertrophy with a substantial maximum left ventricular wall thickness of 18±3mm without any obstruction. CONCLUSIONS: WES combined with CADD score and HHE gene data may be useful even in HCM. Furthermore, the MYL3 Arg94His variant was associated with high disease penetrance and substantial interventricular septal hypertrophy.

Functional Characterization of Rare Variants Implicated in Susceptibility to Lone Atrial Fibrillation.

BACKGROUND: Few rare variants in atrial fibrillation (AF)-associated genes have been functionally characterized to identify a causal relationship between these variants and development of AF. We here sought to determine the clinical effect of rare variants in AF-associated genes in patients with lone AF and characterized these variants electrophysiologically and bioinformatically. METHODS AND RESULTS: We screened all coding regions in 12 AF-associated genes in 90 patients with lone AF, with an onset of 47±11 years (66 men; mean age, 56±13 years) by high-resolution melting curve analysis and DNA sequencing. The potassium and sodium currents were analyzed using whole-cell patch clamping. In addition to using 4 individual in silico prediction tools, we extended those predictions to an integrated tool (Combined Annotation Dependent Depletion). We identified 7 rare variants in KCNA5, KCNQ1, KCNH2, SCN5A, and SCN1B genes in 8 patients: 2 of 8 probands had a family history of AF. Electrophysiological studies revealed that 2 variants showed a loss-of-function, and 4 variants showed a gain-of-function. Five of 6 variants with electrophysiological abnormalities were predicted as pathogenic by Combined Annotation Dependent Depletion scores. CONCLUSIONS: In our cohort of patients with lone AF, 7 rare variants in cardiac ion channels were identified in 8 probands. A combination of electrophysiological studies and in silico predictions showed that these variants could contribute to the development of lone AF, although further in vivo study is necessary to confirm these results. More than half of AF-associated rare variants showed gain-of-function behavior, which may be targeted using genotype-specific pharmacological therapy.

Electrocardiographic QRS Fragmentation as a Marker for Myocardial Fibrosis in Hypertrophic Cardiomyopathy.

INTRODUCTION: Myocardial fibrosis in patients with hypertrophic cardiomyopathy (HCM) usually shows a patchy distribution, which may not be detected by pathological Q waves on 12-lead ECGs. Fragmented QRS complexes (fQRS) reflect intraventricular conduction delay and can be a marker of myocardial fibrosis. We assessed whether fQRS show better correlation with myocardial fibrosis than pathological Q waves in HCM. METHODS AND RESULTS: This cross-sectional study included 108 patients with HCM who underwent 12-lead ECG and cardiac magnetic resonance imaging with late gadolinium enhancement (LGE-CMR). The number of leads with pathological Q waves was not correlated with the extent of LGE measured at any different standard deviations (SDs) (2, 4, 6, 8, and 10 SD), whereas the number of leads with fQRS showed the best correlation with LGE at 6 SD (r = 0.32, P = 0.0008). Further, the number of leads with fQRS was an independent predictor for the extent of LGE at 6 SD. fQRS showed higher accuracy for detecting myocardial fibrosis defined by LGE at 6 SD than pathological Q waves; the overall sensitivity, specificity, and accuracy of fQRS were 40%, 80%, and 64%, respectively, whereas those of pathological Q waves were 7%, 97%, and 60%, respectively. fQRS in lateral leads showed the highest accuracy (75%), followed by inferior leads (59%) and anterior leads (57%), for detecting LGE at 6 SD in the corresponding left ventricular segment. CONCLUSIONS: These findings suggest that fQRS may have a substantially higher sensitivity and diagnostic accuracy compared with pathological Q waves for detecting myocardial fibrosis in HCM.

Right ventricular hypertrophy is associated with cardiovascular events in hypertrophic cardiomyopathy: evidence from study with magnetic resonance imaging.

BACKGROUND: Although left ventricular (LV) morphology and function have been well studied in hypertrophic cardiomyopathy (HCM), few data exist regarding the right ventricle. Accordingly, we studied right ventricular (RV) morphology and function and their effect on cardiovascular events in HCM using cardiac magnetic resonance (CMR) imaging. METHODS: This retrospective study included 106 HCM patients (age 61.6 ± 14.5 years) examined using CMR imaging during January 2008 to September 2014. RV hypertrophy (RVH) was defined as RV maximal wall thickness > 5 mm. RESULTS: RVH was observed in 30 of the 106 patients (RVH group), with the remaining 76 patients assigned to the non-RVH group. The RVH group had higher brain natriuretic peptide levels (461.6 ± 699.8 pg/mL vs. 225.3 ± 254.5 pg/mL; P = 0.01) and also showed a reduced RV end-diastolic volume index (43.4 ± 16.0 mL/m2 vs. 56.6±15.2 mL/m2; P = 0.0001), in keeping with a greater LV mass index (109.1 ± 24.9 g/m2 vs. 78.6 ± 23.0 g/m2; P < 0.0001). The RVH group was prominently associated with RV late gadolinium enhancement compared with the non-RVH group (33.3% vs. 0%; P < 0.0001). After CMR imaging, 15 patients developed cardiovascular events that included admission for heart failure, ventricular tachyarrhythmia/fibrillation, stroke, and sudden cardiac death. Cox proportional hazard analysis revealed that RVH was an independent predictor of the occurrence of cardiovascular events after adjustments by sex, age, LV mass index, LV ejection fraction, and LV outflow tract obstruction (hazard ratio, 5.42; 95% confidence interval, 1.16-25.3; P = 0.03). CONCLUSIONS: These results suggest that HCM patients with RVH on CMR images have a greater incidence of cardiovascular events than non-RVH patients. Further work is needed to confirm this observation and assess its clinical importance.

Fragmented QRS predicts heart failure progression in patients with hypertrophic cardiomyopathy.

BACKGROUND: Although fragmented QRS complex (frag-QRS) reflecting intra-ventricular conduction delay has been shown to be a prognostic marker for cardiac events, few data exist regarding the impact of frag-QRS on cardiac events in hypertrophic cardiomyopathy (HCM). METHODS AND RESULTS: Ninety-four HCM patients (56 male; mean age, 58 ± 17 years) were retrospectively investigated. Frag-QRS was defined as the presence of various RsR' patterns in at least 2 contiguous ECG leads. Major arrhythmic events (MAE) were defined as sudden cardiac death, and combined sustained ventricular tachycardia/ventricular fibrillation. New-onset atrial fibrillation (AF) was diagnosed based on ECG during provisional or routine medical examination. Heart failure (HF) with hospitalization was defined as hospital admission due to subjective or objective symptoms. Frag-QRS was detected in 31 patients (33%).TNNI3 was the most frequent disease-causing gene. Median follow-up was 4.6 years. The 4-year cumulative survival rates of cardiac death, MAE, new-onset AF and HF with hospitalization were 97.6%, 94.6%, 87.5% and 89.3%, respectively. On multivariate analysis, frag-QRS was significantly associated with HF with hospitalization (adjusted hazard ratios [95% confidence intervals]: 5.4 [1.2-36], P=0.03). Moreover, HF-free survival was significantly lower in the frag-QRS (+) group compared to the frag-QRS (-) group (79.0% vs. 95.1%, P=0.03). CONCLUSIONS: Frag-QRS is associated with HF with hospitalization in HCM patients who had a unique distribution of gene mutations.

Increased extent of myocardial fibrosis in genotyped hypertrophic cardiomyopathy with ventricular tachyarrhythmias.

BACKGROUND: Occurrence of malignant ventricular tachyarrhythmias such as ventricular tachycardia and fibrillation (VT/VF) in hypertrophic cardiomyopathy (HCM) can be related to the extent of myocardial fibrosis. Although late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) imaging has been used to detect myocardial fibrosis, few data exist regarding relationships between CMR-determined myocardial fibrosis and VT/VF in genotyped HCM populations. OBJECTIVE: We retrospectively investigated whether the extent of LGE can be increased in HCM patients with VT/VF compared to those without VT/VF in the genotyped HCM population. METHODS AND RESULTS: We studied 35 HCM patients harboring sarcomere gene mutations (TNNI3=22, MYBPC3=12, MYH7=1) who underwent both CMR imaging and 24-h ambulatory electrocardiographic monitoring. VT/VF were identified in 6 patients (2 men, mean age 55.0 years). The extent of LGE was significantly increased in patients with VT/VF (n=6) compared with those without VT/VF (n=29) (18.6±14.4% vs. 8.3±11.4%, p=0.04), although the LGE extent was not an independent predictor for the occurrence of VT/VF. Applying a cut-off point ≥3.25%, episodes of VT/VF were identified with a sensitivity of 100%, specificity of 51.7%, positive predictive value of 30%, negative predictive value of 100%, and the area under the curve of 0.767 (95% confidence interval: 0.590-0.944). CONCLUSION: These results demonstrate that myocardial fibrosis determined by CMR imaging may be increased in genotyped HCM patients with episodes of VT/VF. A further prospective study will be needed to clarify the association between the LGE extent and arrhythmic events in HCM patients harboring sarcomere gene mutations.

Compound heterozygosity deteriorates phenotypes of hypertrophic cardiomyopathy with founder MYBPC3 mutation: evidence from patients and zebrafish models.

Although most founder mutation carriers of hypertrophic cardiomyopathy (HCM), such as the cardiac myosin-binding protein C gene (MYBPC3), arose from a common ancestor exhibit favorable clinical phenotypes, there still remain small fractions of these carriers associated with increased cardiovascular events. However, few data exist regarding the defining factors that modify phenotypes of these patients, particularly in terms of multiple gene mutations. Therefore, we assessed genotype-phenotype correlations and investigated factors that contribute to phenotypic diversities of mutation carriers from 488 unrelated HCM probands. A prevalent founder mutation (Val762Asp) in MYBPC3 was identified in 33 subjects from 19 families. Among them, 28 carriers harbored an isolated Val762Asp mutation and exhibited a late onset of overt HCM compared with other MYBPC3 mutation carriers (62.8 ± 3.0 vs 50.1 ± 2.6 yr, P < 0.05). In contrast, the remaining five carriers had additional sarcomere gene mutations (3 carriers in MYBPC3 and 2 carriers in the cardiac troponin T gene). Of these five carriers, two carriers showed early disease onset and one carrier exhibited end-stage HCM. These phenotypes were recapitulated in zebrafish models; injection of MYBPC3 Val762Asp alone did not alter ventricular size or function, but ventricular dimension was significantly increased when MYBPC3 Val762Asp mRNA was coinjected with MYBPC3 Arg820Gln mRNA. These results demonstrate that MYBPC3 Val762Asp may be associated with unfavorable HCM phenotypes in some cases when combined with another MYBPC3 mutation.

High sensitivity of late gadolinium enhancement for predicting microscopic myocardial scarring in biopsied specimens in hypertrophic cardiomyopathy.

BACKGROUND: Myocardial scarring can be assessed by cardiac magnetic resonance imaging with late gadolinium enhancement and by endomyocardial biopsy. However, accuracy of late gadolinium enhancement for predicting microscopic myocardial scarring in biopsied specimens remains unknown in hypertrophic cardiomyopathy. We investigated whether late gadolinium enhancement in the whole heart reflects microscopic myocardial scarring in the small biopsied specimens in hypertrophic cardiomyopathy. METHODS AND RESULTS: Twenty-one consecutive patients with hypertrophic cardiomyopathy who were examined both by cardiac magnetic resonance imaging and by endomyocardial biopsy were retrospectively studied. The right interventricular septum was the target site for endomyocardial biopsy in all patients. Late gadolinium enhancement in the ventricular septum had an excellent sensitivity (100%) with a low specificity (40%) for predicting microscopic myocardial scarring in biopsied specimens. The sensitivity of late gadolinium enhancement in the whole heart remained 100% with a specificity of 27% for predicting microscopic myocardial scarring in biopsied specimens. Quantitative assessments of fibrosis revealed that the extent of late gadolinium enhancement in the whole heart was the only independent variable related to the microscopic collagen fraction in biopsied specimens (ß â€Š=  0.59, 95% confident interval: 0.15 - 1.0, p  =  0.012). CONCLUSIONS: Although there was a compromise in the specificity, the sensitivity of late gadolinium enhancement was excellent for prediction of microscopic myocardial scarring in hypertrophic cardiomyopathy. Moreover, the severity of late gadolinium enhancement was independently associated with the quantitative collagen fraction in biopsied specimens in hypertrophic cardiomyopathy. These findings indicate that late gadolinium enhancement can reflect both the presence and the extent of microscopic myocardial scarring in the small biopsied specimens in hypertrophic cardiomyopathy.

Impact of systolic dysfunction in genotyped hypertrophic cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a disease of the sarcomere, and approximately 5% of cases of HCM show systolic dysfunction with poor prognosis. Few data exist regarding the systolic dysfunction in a large population of genotyped HCM subjects. HYPOTHESIS: The aim of this study was to assess the systolic dysfunction and prognosis in sarcomere gene mutation carriers. METHODS: The study included 157 sarcomere gene mutation carriers from 69 unrelated HCM families (87 males; mean age, 46.5 ± 20.5 years). After exclusions for systolic dysfunction at baseline, 107 subjects underwent serial echocardiograms. RESULTS: At a mean follow-up of 7.0 years, 12 subjects experienced systolic dysfunction. In multivariate Cox analysis, systolic dysfunction was related to age and ejection fraction at initial evaluation (P < 0.001 and P = 0.020, respectively), and was associated with the absence of mutations in the cardiac myosin-binding protein C gene (MYBPC3) (P = 0.042). When the subjects were divided into MYBPC3 and non-MYBPC3 mutation carriers, and time from birth to development of systolic dysfunction was compared, the rate of systolic dysfunction was higher in the non-MYBPC3 group than in MYBPC3 group (Kaplan-Meier, log-rank test, P = 0.010). After the onset of systolic dysfunction, 11 of 12 subjects died during a mean follow-up of 8.3 years. CONCLUSIONS: Non-MYBPC3 mutation carriers developed left ventricular systolic dysfunction more frequently than MYBPC3 mutation carriers, and the majority of sarcomere gene mutation carriers with systolic dysfunction had fatal outcomes during follow-up. This suggests that subjects with mutations in sarcomeric genes require careful management for systolic dysfunction.

Immediate disappearance of large thrombus in left atrium without evidence of systemic embolization after heparin treatment.

We report an unusual case with giant left atrial thrombus which disappeared soon after starting anticoagulation without evidence of further systemic embolism. A 75-year-old female with non-valvular atrial fibrillation suddenly complained of pain of her right arm and left leg. Contrast-enhanced computed tomography showed occlusion of right brachial and left popliteal arteries. Transesophageal echocardiography (TEE) revealed a low echoic thrombus attached to the left atrial appendage. She was administered sufficient heparin to maintain activated partial thromboplastin time for 70-90 s. Forty-eight hours later when she was subject to surgical thrombectomy, the thrombus was found to have completely disappeared by TEE without further systemic embolization. This case provides information regarding variability of time for anticoagulation-related resolution of left atrial thrombus associated with atrial fibrillation.

A KCR1 variant implicated in susceptibility to the long QT syndrome.

The acquired long QT syndrome (aLQTS) is frequently associated with extrinsic and intrinsic risk factors including therapeutic agents that inadvertently inhibit the KCNH2 K(+) channel that underlies the repolarizing I(Kr) current in the heart. Previous reports demonstrated that K(+) channel regulator 1 (KCR1) diminishes KCNH2 drug sensitivity and may protect susceptible patients from developing aLQTS. Here, we describe a novel variant of KCR1 (E33D) isolated from a patient with ventricular fibrillation and significant QT prolongation. We recorded the KCNH2 current (I(KCNH2)) from CHO-K1 cells transfected with KCNH2 plus wild type (WT) or mutant KCR1 cDNA, using whole cell patch-clamp techniques and assessed the development of I(KCNH2) inhibition in response to well-characterized KCNH2 inhibitors. Unlike KCR1 WT, the E33D variant did not protect KCNH2 from the effects of class I antiarrhythmic drugs such as quinidine or class III antiarrhythmic drugs including dofetilide and sotalol. The remaining current of the KCNH2 WT+KCR1 E33D channel after 100 pulses in the presence of each drug was similar to that of KCNH2 alone. Simulated conditions of hypokalemia (1mM [K(+)](o)) produced no significant difference in the fraction of the current that was protected from dofetilide inhibition with KCR1 WT or E33D. The previously described α-glucosyltransferase activity of KCR1 was found to be compromised in KCR1 E33D in a yeast expression system. Our findings suggest that KCR1 genetic variations that diminish the ability of KCR1 to protect KCNH2 from inhibition by commonly used therapeutic agents constitute a risk factor for the aLQTS.