Clinical presentation of calmodulin mutations: the International Calmodulinopathy Registry.

AIMS: Calmodulinopathy due to mutations in any of the three CALM genes (CALM1-3) causes life-threatening arrhythmia syndromes, especially in young individuals. The International Calmodulinopathy Registry (ICalmR) aims to define and link the increasing complexity of the clinical presentation to the underlying molecular mechanisms. METHODS AND RESULTS: The ICalmR is an international, collaborative, observational study, assembling and analysing clinical and genetic data on CALM-positive patients. The ICalmR has enrolled 140 subjects (median age 10.8 years [interquartile range 5-19]), 97 index cases and 43 family members. CALM-LQTS and CALM-CPVT are the prevalent phenotypes. Primary neurological manifestations, unrelated to post-anoxic sequelae, manifested in 20 patients. Calmodulinopathy remains associated with a high arrhythmic event rate (symptomatic patients, n = 103, 74%). However, compared with the original 2019 cohort, there was a reduced frequency and severity of all cardiac events (61% vs. 85%; P = .001) and sudden death (9% vs. 27%; P = .008). Data on therapy do not allow definitive recommendations. Cardiac structural abnormalities, either cardiomyopathy or congenital heart defects, are present in 30% of patients, mainly CALM-LQTS, and lethal cases of heart failure have occurred. The number of familial cases and of families with strikingly different phenotypes is increasing. CONCLUSION: Calmodulinopathy has pleiotropic presentations, from channelopathy to syndromic forms. Clinical severity ranges from the early onset of life-threatening arrhythmias to the absence of symptoms, and the percentage of milder and familial forms is increasing. There are no hard data to guide therapy, and current management includes pharmacological and surgical antiadrenergic interventions with sodium channel blockers often accompanied by an implantable cardioverter-defibrillator.

Non-missense variants of KCNH2 show better outcomes in type 2 long QT syndrome.

AIMS: More than one-third of type 2 long QT syndrome (LQT2) patients carry KCNH2 non-missense variants that can result in haploinsufficiency (HI), leading to mechanistic loss-of-function. However, their clinical phenotypes have not been fully investigated. The remaining two-thirds of patients harbour missense variants, and past studies uncovered that most of these variants cause trafficking deficiency, resulting in different functional changes: either HI or dominant-negative (DN) effects. In this study, we examined the impact of altered molecular mechanisms on clinical outcomes in LQT2 patients. METHODS AND RESULTS: We included 429 LQT2 patients (234 probands) carrying a rare KCNH2 variant from our patient cohort undergoing genetic testing. Non-missense variants showed shorter corrected QT (QTc) and less arrhythmic events (AEs) than missense variants. We found that 40% of missense variants in this study were previously reported as HI or DN. Non-missense and HI-groups had similar phenotypes, while both exhibited shorter QTc and less AEs than the DN-group. Based on previous work, we predicted the functional change of the unreported variants-whether they cause HI or DN via altered functional domains-and stratified them as predicted HI (pHI)- or pDN-group. The pHI-group including non-missense variants exhibited milder phenotypes compared to the pDN-group. Multivariable Cox model showed that the functional change was an independent risk of AEs (P = 0.005). CONCLUSION: Stratification based on molecular biological studies enables us to better predict clinical outcomes in the patients with LQT2.

Holter Electrocardiographic Approach to Predicting Outcomes of Pediatric Patients With Long QT Syndrome.

BACKGROUND: This study was performed to clarify the clinical findings of pediatric patients diagnosed with long QT syndrome (LQTS) through electrocardiographic screening programs and to predict their outcome using Holter electrocardiographic approaches.Methods and Results: This retrospective study included pediatric patients with a Schwartz score of ≥3.5 who visited the National Hospital Organization Kagoshima Medical Center between April 2005 and March 2019. Resting 12-lead and Holter electrocardiograms were recorded at every visit. The maximum resting QTc and maximum Holter QTc values among all recordings were used for statistical analyses. To test the prognostic value of QTc for the appearance of cardiac events after the first hospital visit, receiver operating characteristic curves were used to calculate the area under the curve (AUC). Among 207 patients, 181 (87%) were diagnosed through screening programs. The prevalence of cardiac events after the first hospital visit was 4% (8/207). Among QTc at diagnosis, maximum resting QTc, and maximum Holter QTc, only maximum Holter QTc value was a predictor (P=0.02) of cardiac events after the hospital visit in multivariate regression analysis. The AUC of the maximum Holter QTc was significantly superior to that of maximum resting QTc. CONCLUSIONS: The maximum Holter QTc value can be used to predict the appearance of symptoms in pediatric patients with LQTS.

Clopidogrel Use in CYP2C19 Loss-of-Function Carriers With High Bleeding Risk After Percutaneous Coronary Intervention.

BACKGROUND: It is not known whether clopidogrel use in cytochrome P450 (CYP) 2C19 loss-of-function (LOF) carriers with high bleeding risk (HBR) contributes to adverse outcomes after percutaneous coronary intervention (PCI).Methods and Results: This retrospective observational study included 618 consecutive patients with available CYP2C19 polymorphism information who underwent PCI between September 2014 and August 2021. Patients with HBR (319 [52%] met the Academic Research Consortium definition) were divided into 2 groups according to P2Y12inhibitor action, namely decreased (i.e., clopidogrel in CYP2C19 LOF carriers) and retained (i.e., clopidogrel in CYP2C19 LOF non-carriers or prasugrel regardless of CYP2C19 polymorphisms), and clinical outcomes at 1 year were compared using inverse probability-weighted Cox proportional hazard regression. The primary ischemic outcome (a composite of cardiovascular death, myocardial infarction, or ischemic stroke) was significantly higher in the decreased than retained group (10.2% vs. 3.0%; adjusted hazard ratio [aHR] 2.78; 95% confidence interval [CI] 1.40-5.52; P=0.004). The primary bleeding outcome (Bleeding Academic Research Consortium 3 or 5) did not differ significantly between the decreased and retained groups (3.4% vs. 6.9%, respectively; aHR 0.48; 95% CI 0.22-1.01; P=0.054). There were no interactions between the treatment groups and HBR status in primary ischemic and bleeding outcomes. CONCLUSIONS: Among patients with HBR, clopidogrel use in CYP2C19 LOF carriers was significantly associated with increased ischemic events after PCI.

Calmodulinopathy in Japanese Children　- Their Cardiac Phenotypes Are Severe and Show Early Onset in Fetal Life and Infancy.

BACKGROUND: Cardiac calmodulinopathy, characterized by a life-threatening arrhythmia and sudden death in the young, is extremely rare and caused by genes encoding calmodulin, namely calmodulin 1 (CALM1), CALM2, and CALM3.Methods and Results: We screened 195 symptomatic children (age 0-12 years) who were suspected of inherited arrhythmias for 48 candidate genes, using a next-generation sequencer. Ten probands were identified as carrying variants in any of CALM1-3 (5%; median age 5 years), who were initially diagnosed with long QT syndrome (LQTS; n=5), catecholaminergic polymorphic ventricular tachycardia (CPVT; n=3), and overlap syndrome (n=2). Two probands harbored a CALM1 variant and 8 probands harbored 6 CALM2 variants. There were 4 clinical phenotypes: (1) documented lethal arrhythmic events (LAEs): 4 carriers of N98S in CALM1 or CALM2; (2) suspected LAEs: CALM2 p.D96G and D132G carriers experienced syncope and transient cardiopulmonary arrest under emotional stimulation; (3) critical cardiac complication: CALM2 p.D96V and p.E141K carriers showed severe cardiac dysfunction with QTc prolongation; and (4) neurological and developmental disorders: 2 carriers of CALM2 p.E46K showed cardiac phenotypes of CPVT. Beta-blocker therapy was effective in all cases except cardiac dysfunction, especially in combination with flecainide (CPVT-like phenotype) and mexiletine (LQTS-like). CONCLUSIONS: Calmodulinopathy patients presented severe cardiac features, and their onset of LAEs was earlier in life, requiring diagnosis and treatment at the earliest age possible.

School-based routine screenings of electrocardiograms for the diagnosis of long QT syndrome.

AIMS: School-based routine screenings of electrocardiograms (ECGs) have been performed upon admission to primary school (PS), junior high school (JHS), and high school (HS) in Japan. Though ECGs with prolonged QT intervals are occasionally found, the role of regular ECG screening tests in identifying long QT syndrome (LQTS) remains to be determined. We investigated the usefulness of the ECG screenings by comparing the results of genetic tests between students who showed QT-prolongation in the screenings and patients with LQTS. METHODS AND RESULTS: We genetically screened 341 students (106 PS, 173 JHS, and 62 HS). Of these, 230 subjects showed QT-prolongation during regular screenings (S-S group), and the other 111 patients were clinically consulted with suspected LQTS by paediatricians (C-C group). Genotype-phenotype relationships were compared between the two groups. The positive rates in the genetic tests were comparable among the two groups; however, symptomatic subjects were significantly fewer in the S-S group than the C-C group (3% vs. 70%). Compared to the genotype-negative subjects, the positive subjects showed significantly longer QTc (P < 0.0001) and more frequently presented LQTS risk scores with ≥3.5 points (P < 0.0001). Lethal arrhythmic events (LAE) occurred only in the C-C group; 18 subjects experienced LAE and 83% of them were found to carry variant(s) in the LQTS-related genes. CONCLUSION: The school-based ECG screenings are effective in identifying young patients with LQTS who require genetic analysis. If individuals are screened at a younger age, we can identify patients at risk earlier and provide preventative treatments.

Loss-of-function mutations in cardiac ryanodine receptor channel cause various types of arrhythmias including long QT syndrome.

AIMS: Gain-of-function mutations in RYR2, encoding the cardiac ryanodine receptor channel (RyR2), cause catecholaminergic polymorphic ventricular tachycardia (CPVT). Whereas, genotype-phenotype correlations of loss-of-function mutations remains unknown, due to a small number of analysed mutations. In this study, we aimed to investigate their genotype-phenotype correlations in patients with loss-of-function RYR2 mutations. METHODS AND RESULTS: We performed targeted gene sequencing for 710 probands younger than 16-year-old with inherited primary arrhythmia syndromes (IPAS). RYR2 mutations were identified in 63 probands, and 3 probands displayed clinical features different from CPVT. A proband with p.E4146D developed ventricular fibrillation (VF) and QT prolongation whereas that with p.S4168P showed QT prolongation and bradycardia. Another proband with p.S4938F showed short-coupled variant of torsade de pointes (scTdP). To evaluate the functional alterations in these three mutant RyR2s and p.K4594Q previously reported in a long QT syndrome (LQTS), we measured Ca2+ signals in HEK293 cells and HL-1 cardiomyocytes as well as Ca2+-dependent [3H]ryanodine binding. All mutant RyR2s demonstrated a reduced Ca2+ release, an increased endoplasmic reticulum Ca2+, and a reduced [3H]ryanodine binding, indicating loss-of-functions. In HL-1 cells, the exogenous expression of S4168P and K4594Q reduced amplitude of Ca2+ transients without inducing Ca2+ waves, whereas that of E4146D and S4938F evoked frequent localized Ca2+ waves. CONCLUSION: Loss-of-function RYR2 mutations may be implicated in various types of arrhythmias including LQTS, VF, and scTdP, depending on alteration of the channel activity. Search of RYR2 mutations in IPAS patients clinically different from CPVT will be a useful strategy to effectively discover loss-of-function RYR2 mutations.

Impact of statin therapy on late target lesion revascularization after everolimus-eluting stent implantation according to pre-interventional vessel remodeling and vessel size of treated lesion.

Clinical evidence demonstrating the impact of statins for preventing late target lesion revascularization (TLR) after newer-generation drug-eluting stent implantation and differences in the effect of statins on late TLR according to pre-interventional vessel remodeling and vessel size is limited. We retrospectively evaluated 1193 de novo lesions in 720 patients who underwent everolimus-eluting stent implantation using intravascular ultrasound from January 2010 to December 2012. The primary endpoint was late TLR. Lesions were divided into the statin group (n = 825) and non-statin group (n = 368). The incidence of late TLR was significantly lower in the statin than non-statin group (1.7% vs. 5.2%, respectively; p = 0.001), and within the statin group, it was significantly lower in the follow-up low-density lipoprotein cholesterol (LDL-C) < 100 than ≥ 100 mg/dL level subgroup (1.0% vs. 3.6%, respectively; p = 0.006). Furthermore, in positive remodeling lesions and non-small vessel size lesions, the incidence of late TLR was significantly lower in the statin than non-statin group (1.6% vs. 8.5% and 1.3% vs. 5.3%, respectively; p = 0.001 and p = 0.004). Lowering the LDL-C level using statins was more effective for preventing late TLR after everolimus-eluting stent implantation. Evaluating pre-interventional vessel remodeling patterns and vessel size might be helpful to stratify lesions at high risk of late TLR.

An NGS-based genotyping in LQTS; minor genes are no longer minor.

Mutations in KCNQ1, KCNH2, and SCN5A are the major cause of long QT syndrome (LQTS). More than 90% of the genotyped patients have been reported to carry mutations in any of these three genes. Thanks to increasing popularity of next generation sequencer (NGS), novel CACNA1C mutations have been identified among LQTS patients without extra-cardiac phenotypes. We aimed to clarify the frequency of genotypes in LQTS patients in the era of NGS. The study comprised 160 congenital LQTS patients (71 males) registered from November 2015 to September 2018. Inclusion criteria was QTc > 460 ms and Schwartz score ≥ 3. We performed genetic analysis using target gene method by NGS and confirmed the mutations by Sanger method. The median age for genetic screening was 13 (0-68) years. Sixteen patients suffered cardiac arrest, 47 syncope, and 97 were asymptomatic. We identified genetic mutations in 111 (69.4%) patients including 6 CACNA1C (5.4% of the genotyped patients) with 4 asymptomatic patients. Five (3.1%) patients carried double mutations; three out of them with RYR2 and KCNQ1 or KCNH2. In conclusion, CACNA1C screening would be recommended even if the patient is asymptomatic to elucidate the genetic background of the LQTS patients.

High Prevalence of Late-Appearing T-Wave in Patients With Long QT Syndrome Type 8.

BACKGROUND: Long QT syndrome type 8 (LQT8) is a rare genotype of long QT syndrome. Late-appearing T-waves (LaT) are often documented in patients with LQT8, as in long QT syndrome type 3 (LQT3); however, the frequency of LaT and its relevance to the clinical severity of LQT8 remains unclear. This study investigated T-wave morphology (TWM) in LQT3 and LQT8 patients and compared the phenotypes of different TWMs.Methods and Results:TWMs were classified into 3 types: early onset T-waves (EoT), LaT, and bifid T-waves (biT). Electrocardiogram (ECG) measurements, symptoms, and topology were compared among TWM types. The study cohort comprised 25 patients with LQT8 (14 mutations) and 25 patients with LQT3 (14 mutations). LaT was detected in 17 (68%) and 13 (52%) LQT8 and LQT3 patients, respectively. There were no significant differences in ECG measurements or the severity of symptoms between patients with LaT and those with other TWMs in either the LQT8 or LQT3 group. However, only patients with LaT experienced cardiopulmonary arrest. Compared with the LQT3 group, in the LQT8 group there was a tendency for mutations in patients with LaT to be located in domain-linking regions. CONCLUSIONS: In this study, two-thirds of patients with LQT8 exhibited LaT on ECG, and nearly one-third of those experienced cardiopulmonary arrest. Further investigations are warranted to differentiate between LQT3 and LQT8 in patients exhibiting LaT to optimize therapy.

Comparison Between Clopidogrel and Prasugrel Associated With CYP2C19 Genotypes in Patients Receiving Percutaneous Coronary Intervention in a Japanese Population.

BACKGROUND: The association between cytochrome P450 (CYP) 2C19 genotypes and adverse events in patients treated with clopidogrel or prasugrel after percutaneous coronary intervention (PCI) in the Japanese population is unclear.Methods and Results:This study consisted of 1,580 patients whoseCYP2C19genotypes were assessed at Shiga University of Medical Science Hospital, and 193 clopidogrel-treated and 217 prasugrel-treated patients who were followed more than 1 year after receiving PCI were analyzed. Among 1,580 patients, the prevalence of normal, intermediate, and poor metabolizers was 32%, 49%, and 17%, respectively. Overall incidence of the primary outcome, defined as a composite of cardiovascular death, myocardial infarction, definite stent thrombosis, ischemic stroke, or major bleeding was not significantly different between the clopidogrel and prasugrel groups (adjusted hazard ratio [HR] 1.98, 95% confidence interval [CI] 0.85-4.61, P=0.12). Among patients with theCYP2C19loss-of-function (LOF) allele, however, the incidence of the primary outcome was significantly higher in the clopidogrel group (adjusted HR 3.19, 95% CI 1.10-9.24, P=0.03), whereas no difference was observed among patients without theCYP2C19LOF allele (adjusted HR 0.67, 95% CI 0.14-3.26, P=0.62). CONCLUSIONS: Among patients with theCYP2C19LOF allele, the use of clopidogrel was significantly associated with increased adverse events. Thus, further investigation is needed to establish the practical use ofCYP2C19genotyping.

Novel SCN10A variants associated with Brugada syndrome.

AIMS: The expression of sodium channel Nav1.8 in cardiac nervous systems has been identified, and variants of SCN10A that encodes Nav1.8 contribute to the development of Brugada syndrome (BrS) by modifying the function of Nav1.5 or directly reducing the sodium current. The aim of this study was to identify the frequency of SCN10A mutations in Japanese patients with BrS and to compare the phenotypical differences between patients with BrS and those who have other BrS-causative genes. METHODS AND RESULTS: This study involved 240 Japanese probands who were clinically suspected with BrS and were negative for mutations in major BrS-related genes. We screened for the SCN10A gene using a high-resolution melting method and direct sequencing. In addition, we compared the clinical characteristics among the probands with gene mutations in SCN10A, 6 probands with CACNA1C and 17 probands with SCN5A. We identified six SCN10A variant carriers (2.5%): W189R, R844H (in two unrelated probands), N1328K, R1380Q, and R1863Q. Five were male. Four were symptomatic: one died following sudden cardiopulmonary arrest at age 35, one suffered ventricular fibrillation, and two had recurrent syncope. Compared with BrS patients carrying SCN5A or CACNA1C mutations, although there were no significant differences among them, symptomatic patients in the SCN10A group tended to be older than those in the other gene groups. CONCLUSION: In six BrS probands who carried SCN10A variants, most experienced severe arrhythmic attacks. It is of clinical importance to screen SCN10A mutations in BrS, although the functional significance of these variants remains unclear.

Phenotypic Variability of ANK2 Mutations in Patients With Inherited Primary Arrhythmia Syndromes.

BACKGROUND: Mutations inANK2have been reported to cause various arrhythmia phenotypes. The prevalence ofANK2mutation carriers in inherited primary arrhythmia syndrome (IPAS), however, remains unknown in Japanese. Using a next-generation sequencer, we aimed to identifyANK2mutations in our cohort of IPAS patients, in whom conventional Sanger sequencing failed to identify pathogenic mutations in major causative genes, and to assess the clinical characteristics ofANK2mutation carriers.Methods and Results:We screened 535 probands with IPAS and analyzed 46 genes including wholeANK2exons using a bench-top NGS (MiSeq, Illumina) or performed whole-exome-sequencing using HiSeq2000 (Illumina). As a result, 12 of 535 probands (2.2%, aged 0-61 years, 5 males) were found to carry 7 different heterozygousANK2mutations.ANK2-W1535R was identified in 5 LQTS patients and 1 symptomatic BrS and was predicted as damaging by multiple prediction software. In total, as to phenotype, there were 8 LQTS, 2 BrS, 1 IVF, and 1 SSS/AF. Surprisingly, 4/8 LQTS patients had the acquired type of LQTS (aLQTS) and suffered torsades de pointes. A total of 7 of 12 patients had documented malignant ventricular tachyarrhythmias. CONCLUSIONS: VariousANK2mutations are associated with a wide range of phenotypes, including aLQTS, especially with ventricular fibrillation, representing "ankyrin-B" syndrome. (Circ J 2016; 80: 2435-2442).

A Common Mutation of Long QT Syndrome Type 1 in Japan.

BACKGROUND: Previous studies of long QT syndrome (LQTS) have revealed the presence of country-specific hot spots in KCNQ1 mutations, and the purpose of this study was to evaluate the influence of a common mutation on clinical phenotypes in Japanese LQT1 patients. METHODS AND RESULTS: We retrospectively studied the frequency of each mutation in 190 LQT1 Japanese probands and evaluated the clinical severity of LQT1 among carriers with a common mutation. We also compared it with that of carriers with other mutations. In the Japanese cohort, the most common mutation was p. A344spl (c.1032 G>A), comprising a substitution of a guanine for an adenine at the last base of exon 7, and it was found in 17 probands (8.9%). Regarding the clinical characteristics of A344spl carriers, the mean age-of-onset was 10±4 years, >40% were symptomatic, and the mean corrected QT interval was 461±30 ms. The prognosis for carriers of the A344spl mutation (n=31) was intermediate between that for the A341V mutation reported to be associated with severe phenotypes (n=24) and other mutations (n=290). CONCLUSIONS: The A344spl mutation was a frequent LQTS genotype in Japan, which indicates that the influence of country-specific hot spots should be considered when studying LQT1 clinical phenotypes.

Gain-of-function KCNH2 mutations in patients with Brugada syndrome.

BACKGROUND: Brugada syndrome (BrS) is an inherited disease characterized by right precordial ST segment elevation on electrocardiograms (ECGs) that predisposes patients to sudden cardiac death as a result of polymorphic ventricular tachyarrhythmia or ventricular fibrillation (VF). In BrS patients, except for SCN5A, mutations in other responsible genes are poorly elucidated. METHODS AND RESULTS: We identified 4 KCNH2 mutations, T152I, R164C, W927G, and R1135H, in 236 consecutive probands with BrS or Brugada-like ECG. Three of these mutation carriers showed QTc intervals shorter than 360 milliseconds and 1 experienced VF. We performed patch-clamp analyses on I(Kr) reconstituted with the KCNH2 mutations in Chinese hamster ovary cells and compared the phenotypes of the patients with different genotypes. Three mutations, R164C, W927G, and R1135H, increased I(Kr) densities. Three mutations, T152I, R164C, and W927G, caused a negative shift in voltage-dependent activation curves. Only the R1135H mutant channel prolonged the deactivation time constants. We also identified 20 SCN5A and 5 CACNA1C mutation carriers in our cohort. Comparison of probands' phenotypes with 3 different genotypes revealed that KCNH2 mutation carriers showed shorter QTc intervals and SCN5A mutation carriers had longer QRS durations. CONCLUSIONS: All KCNH2 mutations that we identified in probands with BrS exerted gain-of-function effects on I(Kr) channels, which may partially explain the ECG findings in our patients.

Long QT syndrome type 8: novel CACNA1C mutations causing QT prolongation and variant phenotypes.

AIMS: CACNA1C mutations have been reported to cause LQTS type 8 (LQT8; Timothy syndrome), which exhibits severe phenotypes, although the frequency of patients with LQT8 exhibiting only QT prolongation is unknown. This study aimed to elucidate the frequency of CACNA1C mutations in patients with long QT syndrome (LQTS), except those with Timothy syndrome and investigate phenotypic variants. METHODS AND RESULTS: CACNA1C gene screening was performed in 278 probands negative for LQTS-related gene mutations. Functional analysis of mutant channels using a whole-cell patch-clamp technique was also performed. Using genetic screening, we identified five novel CACNA1C mutations: P381S, M456I, A582D, R858H, and G1783C in seven (2.5%) unrelated probands. Seven mutation carriers showed alternative clinical phenotypes. Biophysical assay of CACNA1C mutations revealed that the peak calcium currents were significantly larger in R858H mutant channels than those of wild-type (WT). In contrast, A582D mutant channels displayed significantly slower inactivation compared with WT. The two mutant channels exerted different gain-of-function effects on calcium currents. CONCLUSION: In patients with LQTS, the frequency of CACNA1C mutations was higher than reported. Even without typical phenotypes of Timothy syndrome, CACNA1C mutations may cause QT prolongation and/or fatal arrhythmia attacks.

Clinical characterization of type 1 long QT syndrome caused by C-terminus Kv7.1 variants.

BACKGROUND: Variants in the KCNQ1 gene, encoding the α-subunit of the slow component of delayed rectifier K+ channel Kv7.1, cause long QT syndrome (LQTS) type 1. The location of variants may be one of the factors in determining prognosis. However, detailed genotype-phenotype relationships associated with C-terminus variants remain unelucidated. OBJECTIVE: We investigated the clinical characteristics and variant-specific arrhythmic risks in patients with LQTS carrying Kv7.1 C-terminus variants. METHODS: The study comprises 202 consecutive patients with LQTS (98 probands and 104 family members) who carry a rare heterozygous variant in the Kv7.1 C-terminus. Their clinical characteristics and arrhythmic events were investigated. RESULTS: We identified 36 unique C-terminus variants (25 missense and 11 non-missense). The p.R366W variant was identified in 8 families, and p.T587M was identified in 21 families in large numbers from northwestern Japan. As for the location of the variant, we found that the variants in highly conserved regions and nonhelical domains were associated with longer QTc intervals compared with the variants in other regions. Both p.R366W and p.T587M variants are located in the highly conserved and functionally pivotal regions close to helices A and D, which are associated with calmodulin binding and channel assembly (tetramerization), respectively. The probands carrying p.T587M and p.R366W variants had worse arrhythmia outcomes compared with those with other C-terminus variants. The haplotype analysis of p.T587M families was suggestive of a founder effect. CONCLUSION: The arrhythmic risk of C-terminus variants in Kv7.1 in LQTS is not homogeneous, and locations of variants can be a determining factor for prognosis.

Age-dependent clinical and genetic characteristics in Japanese patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a heart muscle disease caused by desmosomal gene mutations, and presents as ventricular tachycardia and sudden cardiac death. Although the mean age at onset or diagnosis of ARVC/D are reported to be around the 30-40s, the age-dependent clinical and genetic differences remain unknown. METHODS AND RESULTS: A total of 35 consecutive Japanese probands (23 male) who were clinically diagnosed with ARVC/D were enrolled in the present study, and genetic analysis of PKP2, DSP, DSG2, and DSC2 was done. The mean age at the first symptom and at diagnosis was 38.6±14.8 years and 40.5±17.7 years, respectively. Probands in whom the onset was cardiopulmonary arrest were significantly younger (22.3±15.3 years) than those with arrhythmia (41.1±13.2 years) or congestive heart failure (45.7±8.5 years). On genetic screening, 19 mutation carriers were identified. Although there was no age dependence for each gene mutation carrier, carriers with PKP2 premature stop codon developed the disease at a significantly younger age than other mutation carriers. CONCLUSIONS: The initial clinical manifestations in some young probands were very severe, and PKP2 mutations with a premature stop codon would be associated with disease onset at a younger age.

L-type calcium channel mutations in Japanese patients with inherited arrhythmias.

BACKGROUND: Mutations in genes encoding the L-type cardiac calcium channel (LTCC) are associated with various types of inherited arrhythmias, including Brugada syndrome (BrS). However, the frequency in Asian populations remains unknown. This study aimed to elucidate disease-causing mutations in LTCC-related genes in Japanese patients diagnosed as BrS or idiopathic ventricular fibrillation (IVF), early repolarization syndrome, short QT syndrome, and compare them with those carrying SCN5A mutations. METHODS AND RESULTS: We screened CACNA1C and CACNB2b in 312 probands and compared the clinical characteristics between probands with gene mutations in CACNA1C or SCN5A. In results, we identified 6 CACNA1C mutations in 7 unrelated probands and SCN5A mutations in 20 probands. There were no CACNB2b mutation carriers. In topology, half of the mutations were located in the C-terminus. Among 7 CACNA1C mutation carriers, 2 were female and 3 were symptomatic; 2 patients were resuscitated from ventricular fibrillation, and 1 patient had syncope. Compared with SCN5A mutation carriers, there were no significant differences in the ECG characteristics. 2 of 3 symptomatic CACNA1C patients were female, but all female SCN5A mutation carriers remained asymptomatic. CONCLUSIONS: We identified 6 CACNA1C mutations in BrS and IVF patients and their phenotypes were varied. Although mutation frequency was not high, screening of LTCC channel genes may be clinically important to prevent unexpected sudden death.