The c.1617del variant of TMEM260 is identified as the most frequent single gene determinant for Japanese patients with a specific type of congenital heart disease.

Although the molecular mechanisms underlying congenital heart disease (CHD) remain poorly understood, recent advances in genetic analysis have facilitated the exploration of causative genes for CHD. We reported that the pathogenic variant c.1617del of TMEM260, which encodes a transmembrane protein, is highly associated with CHD, specifically persistent truncus arteriosus (PTA), the most severe cardiac outflow tract (OFT) defect. Using whole-exome sequencing, the c.1617del variant was identified in two siblings with PTA in a Japanese family and in three of the 26 DNAs obtained from Japanese individuals with PTA. The c.1617del of TMEM260 has been found only in East Asians, especially Japanese and Korean populations, and the frequency of this variant in PTA is estimated to be next to that of the 22q11.2 deletion, the most well-known genetic cause of PTA. Phenotype of patients with c.1617del appears to be predominantly in the heart, although TMEM260 is responsible for structural heart defects and renal anomalies syndrome (SHDRA). The mouse TMEM260 variant (p.W535Cfs*56), synonymous with the human variant (p.W539Cfs*9), exhibited truncation and downregulation by western blotting, and aggregation by immunocytochemistry. In situ hybridization demonstrated that Tmem260 is expressed ubiquitously during embryogenesis, including in the development of cardiac OFT implicated in PTA. This expression may be regulated by a ~ 0.8 kb genomic region in intron 3 of Tmem260 that includes multiple highly conserved binding sites for essential cardiac transcription factors, thus revealing that the c.1617del variant of TMEM260 is the major single-gene variant responsible for PTA in the Japanese population.

Functional characterization of variants found in Japanese patients with hereditary hemorrhagic telangiectasia.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant form of vascular dysplasia. Genetic diagnosis is made by identifying loss-of-function variants in genes, such as ENG and ACVRL1. However, the causal mechanisms of various variants of unknown significance remains unclear. In this study, we analyzed 12 Japanese patients from 11 families who were clinically diagnosed with HHT. Sequencing analysis identified 11 distinct variants in ACVRL1 and ENG. Three of the 11 were truncating variants, leading to a definitive diagnosis, whereas the remaining eight were splice-site and missense variants that required functional analyses. In silico splicing analyses demonstrated that three variants, c.526-3C > G and c.598C > G in ACVRL1, and c.690-1G > A in ENG, caused aberrant splicing, as confirmed by a minigene assay. The five remaining missense variants were p.Arg67Gln, p.Ile256Asn, p.Leu285Pro, and p.Pro424Leu in ACVRL and p.Pro165His in ENG. Nanoluciferase-based bioluminescence analyses demonstrated that these ACVRL1 variants impaired cell membrane trafficking, resulting in the loss of bone morphogenetic protein 9 (BMP9) signal transduction. In contrast, the ENG mutation impaired BMP9 signaling despite normal cell membrane expression. The updated functional analysis methods performed in this study will facilitate effective genetic testing and appropriate medical care for patients with HHT.

Predictors of long-term mortality among perioperative survivors of Fontan operation.

AIMS: The criteria for 'good' Fontan haemodynamics have been poorly defined in relation to long-term outcomes. The aim of this study was to identify the risk factors for mortality among haemodynamic parameters obtained early after the Fontan operation. METHODS AND RESULTS: Clinical data of all perioperative survivors of the Fontan operation performed before 2011, from nine institutions, were collected through a retrospective chart review. In total, 1260 patients were included. The median age at the time of Fontan operation was 3.6 years. Post-operative cardiac catheterization was conducted in 1117 patients at a median period of 1.0 years after the operation. During the median follow-up period of 10.2 years, 107 patients died. The mortality rates at 10, 20, and 25 years after the operation were 5%, 12%, and 22%, respectively. On multivariable analysis, older age at the time of the operation {≥15 years, hazard ratio (HR) [95% confidence interval (CI)]: 3.2 (1.7-5.9)} and haemodynamic parameters obtained at post-operative catheterization, such as low ejection fraction [<30%, HR (95% CI): 7.5 (3.2-18)], low systemic oxygen saturation [<80%, HR (95% CI): 3.8 (1.6-9.1)], high central venous pressure [≥16 mmHg, HR (95% CI): 2.3 (1.3-3.9)], and low mean systemic arterial pressure [<60 mmHg, HR (95% CI): 3.0 (1.4-6.2)] were identified as independent predictors of mortality. The predictive model based on these parameters had a c-index of 0.75 at 10 years. CONCLUSIONS: Haemodynamic parameters obtained at a median period of 1.0 years, post-operatively, can accurately identify patients with a high mortality risk, who may need intensive management to improve long-term outcomes.

Genetic and functional analyses of TBX4 reveal novel mechanisms underlying pulmonary arterial hypertension.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a fatal disease, with approximately 10% of cases associated with genetic variants. Recent genetic studies have reported pathogenic variants in the TBX4 gene in patients with PAH, especially in patients with childhood-onset of the disease, but the pathogenesis of PAH caused by TBX4 variant has not been fully uncovered. METHODS: We analysed the TBX4 gene in 75 Japanese patients with sporadic or familial PAH using a PCR-based bidirectional sequencing method. Detected variants were evaluated using in silico analyses as well as in vitro analyses including luciferase assay, immunocytochemistry and chromatin immunoprecipitation (ChIP) whether they have altered function. We also analysed the function of TBX4 using mouse embryonic lung explants with inhibition of Tbx4 expression. RESULTS: Putative pathogenic variants were detected in three cases (4.0%). Our in vitro functional analyses revealed that TBX4 directly regulates the transcriptional activity of fibroblast growth factor 10 (FGF10), whereas the identified TBX4 variant proteins failed to activate the FGF10 gene because of disruption of nuclear localisation signal or poor DNA-binding affinity. Furthermore, ex vivo inhibition of Tbx4 resulted in insufficiency of lung morphogenesis along with specific downregulation of Tie2 and Kruppel-like factor 4 expression. CONCLUSION: Our results implicate variants in TBX4 as a genetic cause of PAH in a subset of the Japanese population. Variants in TBX4 may lead to PAH through insufficient lung morphogenesis by disrupting the TBX4-mediated direct regulation of FGF10 signalling and pulmonary vascular endothelial dysfunction involving PAH-related molecules.

Outcomes of Restrictive Cardiomyopathy in Japanese Children　- A Retrospective Cohort Study.

BACKGROUND: There has been no nationwide survey on the prognosis of pediatric restrictive cardiomyopathy (RCM) in Japan; therefore, this retrospective multicentered study was designed to investigate the long-term survival rate of pediatric patients with RCM in Japan.Methods and Results: A multicentered, retrospective observational study was performed between 1990 and 2014 and included patients diagnosed with RCM who were aged <18 years from 18 Japanese institutions. A total of 54 patients were diagnosed with RCM. The median age at diagnosis was 4.4 years, and the median duration of observation was 2.2 years at the time of this study. Of these patients, 54% had symptoms, including heart failure. Twelve patients died without heart transplantation, mostly due to heart failure. The median time to death from diagnosis was 2.5 years. Freedom from death at 1, 5, and 10 years was 91%, 68%, and 62%, respectively. Death occurred within 5 years of diagnosis in most patients. Twenty-two patients underwent heart transplantation. Freedom from heart transplantation at 1, 5, and 10 years was 77%, 58%, and 53%, respectively. Freedom from death or heart transplantation at 1, 5, and 10 years was 72%, 40%, and 34%, respectively. The presence of symptoms was a risk factor for death or transplantation. CONCLUSIONS: The prognosis of pediatric RCM is poor, and the heart transplantation rate is low in Japan.

Outcomes of hypertrophic cardiomyopathy in Japanese children: a retrospective cohort study.

There has been no multicenter study on the prognosis of pediatric hypertrophic cardiomyopathy (HCM) in Japan. Therefore, we conducted a retrospective multicenter observational study on the long-term survival rate in patients diagnosed with HCM under the age of 18 between 1990 and 2014. Twenty institutions participated. A total of 180 patients were identified. The median age at diagnosis was 5.8 years old and median duration of observation was 8.3 years. Although six patients (3%) deteriorated into the dilated phase of HCM, no patient received heart transplantation. Freedom from death at 1, 5, 10, and 20 years were 97%, 92%, 84%, and 80%, respectively. There were 26 deaths. Among them, 11 patients died suddenly, presumably due to arrhythmia, and 15 patients died of heart failure. The presence of heart failure symptoms and a greater cardiothoracic ratio were significant risk factors for heart failure-related death. There were no significant risk factors identified for arrhythmia-related death. In conclusion, the prognosis of pediatric HCM in Japan is good and similar to those reported in population-based studies in the United States and Australia. Significant risk factors for heart failure-related death were identified in pediatric patients with HCM in Japan.

Functional Evaluation of Human Bioengineered Cardiac Tissue Using iPS Cells Derived from a Patient with Lamin Variant Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is caused by various gene variants and characterized by systolic dysfunction. Lamin variants have been reported to have a poor prognosis. Medical and device therapies are not sufficient to improve the prognosis of DCM with the lamin variants. Recently, induced pluripotent stem (iPS) cells have been used for research on genetic disorders. However, few studies have evaluated the contractile function of cardiac tissue with lamin variants. The aim of this study was to elucidate the function of cardiac cell sheet tissue derived from patients with lamin variant DCM. iPS cells were generated from a patient with lamin A/C (LMNA) -mutant DCM (LMNA p.R225X mutation). After cardiac differentiation and purification, cardiac cell sheets that were fabricated through cultivation on a temperature-responsive culture dish were transferred to the surface of the fibrin gel, and the contractile force was measured. The contractile force and maximum contraction velocity, but not the maximum relaxation velocity, were significantly decreased in cardiac cell sheet tissue with the lamin variant. A qRT-PCR analysis revealed that mRNA expression of some contractile proteins, cardiac transcription factors, Ca2+-handling genes, and ion channels were downregulated in cardiac tissue with the lamin variant.Human iPS-derived bioengineered cardiac tissue with the LMNA p.R225X mutation has the functional properties of systolic dysfunction and may be a promising tissue model for understanding the underlying mechanisms of DCM.

Outcomes of Dilated Cardiomyopathy in Japanese Children　- A Retrospective Cohort Study.

BACKGROUND: There has been no nationwide survey on the prognosis of pediatric dilated cardiomyopathy (DCM) in Japan. Therefore, we designed this retrospective multicenter study to investigate the long-term survival rate in pediatric patients with DCM in Japan.Methods and Results:In this multicenter retrospective observational study, data were reviewed for 106 patients aged <18 years who had been diagnosed with DCM at any 1 of 18 Japanese institutions between 1990 and 2014. The median age at diagnosis was 2.0 years and the median duration of observation was 3.3 years. Most DCM patients were diagnosed because of symptoms of heart failure. On echocardiography, the median left ventricular end-diastolic dimension z score was 5.4 and fractional shortening was 0.10. Freedom from death or transplantation rates at 1, 3, 5, 10, and 20 years after diagnosis were 76%, 66%, 64%, 58%, and 43%, respectively. Freedom from death rates at 1, 5, 10, and 20 years after diagnosis were 81%, 75%, 72%, and 53%, respectively. The incidence of heart transplantation at 1, 5, 10, and 20 years after diagnosis was 6%, 15%, 20%, and 20%, respectively, suggesting that only 15% of patients in Japan underwent heart transplantation within 5 years of diagnosis. CONCLUSIONS: In Japan, the prognosis of pediatric DCM is poor and the rate of heart transplantation is low.

Outcomes of idiopathic pulmonary arterial hypertension in Japanese children: a retrospective cohort study.

Recently, targeted therapy has been developed for idiopathic pulmonary arterial hypertension (IPAH). Studies evaluating the prognosis of IPAH have been conducted in adults. However, there is no nationwide survey of pediatric patients with IPAH regarding the long-term prognosis in Japan. Therefore, we investigated the clinical outcomes of Japanese pediatric patients with IPAH and risk factors for a poor prognosis. This multi-center, retrospective cohort study included pediatric patients with IPAH under the age of 15 years, who were gleaned from the nationwide network of Japanese Society of Pediatric Cardiology and Cardiac Surgery (JSPCCS). The questionnaire was sent to members of JSPCCS in 2015. Patients who were diagnosed with IPAH from 1994 to 2014 were included. The primary endpoint was death or lung transplantation. Ninety-five patients were finally enrolled. Both the mean age at diagnosis and the mean follow-up duration were 7 years. Ninety-five percent of patients had received targeted therapy for IPAH during follow-up. The overall 1, 3, 5, and 10-year event free rate, estimated using Kaplan-Meier survival estimate, was 96, 91, 83, and 74%, respectively. The prognosis was significantly poorer in patients with increased right ventricular systolic pressure (RVp), mean pulmonary artery pressure (mPAP) (≥ 52 mmHg), cardiothoracic ratio (≥ 55%), and levels of B-type natriuretic peptide (BNP) during follow-up (≥ 300 pg/mL) than in those without these parameters. In conclusion, in Japanese children with IPAH, the event-free rate for death or lung transplantation was found to be good. Greater RVp, mPAP, BNP levels during follow-up, and cardiothoracic ratio may be predictive indicators for a poor prognosis.

Pregnancy and Delivery in Patients With Repaired Congenital Heart Disease　- A Retrospective Japanese Multicenter Study.

BACKGROUND: Although advances in cardiac surgery have led to an increased number of survivors with congenital heart disease (CHD), epidemiological data regarding the pregnancies and deliveries of patients with repaired CHD are scarce.Methods and Results:In this study, we retrospectively reviewed the clinical outcomes of pregnancies and deliveries of women with repaired CHD. Overall, 131 women with repaired CHD were enrolled and there were 269 gestations. All patients were classified as New York Heart Association (NYHA) Class I or II. The prevalence of cesarean sections was higher in patients with (CyCHD) than without (AcyCHD) a past history of cyanosis (51% vs. 19%, respectively; P<0.01). There were 228 offspring from 269 gestations and the most prevalent neonatal complication was premature birth (10%), which was more frequent in the CyCHD than AcyCHD group (15.7% vs. 5.6%, respectively; P<0.01). Five maternal cardiac complications during delivery were observed only in the CyCHD group (8%); these were classified as NYHA Class II and none was fatal. CONCLUSIONS: Delivery was successful in most women with repaired CHD who were classified as NYHA Class I or II, although some with CyCHD and NYHA Class II required more attention. Cesarean sections were more common in the CyCHD than AcyCHD group, and CyCHD may be a potential risk for preterm deliveries.

Silibinin efficacy in a rat model of pulmonary arterial hypertension using monocrotaline and chronic hypoxia.

BACKGROUND: C-X-C chemokine receptor type 4 (CXCR4) may be involved in the development of pulmonary arterial hypertension (PAH). CXCR4 inhibitor AMD3100 was described to have a positive effect on the prevention of pulmonary arterial muscularization in PAH models. Silibinin is a traditional medicine that has an antagonistic effect on CXCR4. We investigated the effect of silibinin using rat models of PAH. METHODS: PAH was induced by a single subcutaneous injection of monocrotaline. The rats were maintained in a chronic hypoxic condition (10% O2) with or without silibinin. To evaluate the efficacy of silibinin on PAH, right ventricular systolic pressure (RVSP), Fulton index (weight ratio of right ventricle to the left ventricle and septum), percent medial wall thickness (% MT), and vascular occlusion score (VOS) were measured and calculated. Immunohistochemical analysis was performed targeting CXCR4 and c-Kit. Reverse transcription-quantitative polymerase chain reaction was performed for the stem cell markers CXCR4, stromal cell derived factor-1 (SDF-1), c-Kit, and stem cell factor (SCF), and the inflammatory markers monocyte chemoattractant protein 1 (MCP1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNFα). Statistical analyses were performed using t-test and one-way analysis of variance with Bonferroni's post hoc test. RESULTS: Silibinin treatment for 1 week reduced RVSP and Fulton index. Treatment for 2 weeks reduced RVSP, Fulton index, % MT, and VOS, as well as downregulating the expression of CXCR4, SDF-1, and TNFα in pulmonary arteries. In contrast, treatment for 3 weeks failed to ameliorate PAH. The time-course study demonstrated that RVSP, Fulton index, % MT, and VOS gradually increased over time, with a decrease in the expression of CXCR4 and TNFα occurring after 2 weeks of PAH development. After 3 weeks, SDF-1, c-Kit, and SCF began to decrease and, after 5 weeks, MCP1 and IL-6 gradually accumulated. CONCLUSIONS: The CXCR4 inhibitor silibinin can ameliorate PAH, possibly through the suppression of the CXCR4/SDF-1 axis, until the point where PAH becomes a severe and irreversible condition. Silibinin results in reduced pulmonary arterial pressure and delays pulmonary arteriolar occlusion and pulmonary vascular remodeling.

DNAH6 and Its Interactions with PCD Genes in Heterotaxy and Primary Ciliary Dyskinesia.

Heterotaxy, a birth defect involving left-right patterning defects, and primary ciliary dyskinesia (PCD), a sinopulmonary disease with dyskinetic/immotile cilia in the airway are seemingly disparate diseases. However, they have an overlapping genetic etiology involving mutations in cilia genes, a reflection of the common requirement for motile cilia in left-right patterning and airway clearance. While PCD is a monogenic recessive disorder, heterotaxy has a more complex, largely non-monogenic etiology. In this study, we show mutations in the novel dynein gene DNAH6 can cause heterotaxy and ciliary dysfunction similar to PCD. We provide the first evidence that trans-heterozygous interactions between DNAH6 and other PCD genes potentially can cause heterotaxy. DNAH6 was initially identified as a candidate heterotaxy/PCD gene by filtering exome-sequencing data from 25 heterotaxy patients stratified by whether they have airway motile cilia defects. dnah6 morpholino knockdown in zebrafish disrupted motile cilia in Kupffer's vesicle required for left-right patterning and caused heterotaxy with abnormal cardiac/gut looping. Similarly DNAH6 shRNA knockdown disrupted motile cilia in human and mouse respiratory epithelia. Notably a heterotaxy patient harboring heterozygous DNAH6 mutation was identified to also carry a rare heterozygous PCD-causing DNAI1 mutation, suggesting a DNAH6/DNAI1 trans-heterozygous interaction. Furthermore, sequencing of 149 additional heterotaxy patients showed 5 of 6 patients with heterozygous DNAH6 mutations also had heterozygous mutations in DNAH5 or other PCD genes. We functionally assayed for DNAH6/DNAH5 and DNAH6/DNAI1 trans-heterozygous interactions using subthreshold double-morpholino knockdown in zebrafish and showed this caused heterotaxy. Similarly, subthreshold siRNA knockdown of Dnah6 in heterozygous Dnah5 or Dnai1 mutant mouse respiratory epithelia disrupted motile cilia function. Together, these findings support an oligogenic disease model with broad relevance for further interrogating the genetic etiology of human ciliopathies.

Hot water extract of Agaricus blazei Murrill specifically inhibits growth and induces apoptosis in human pancreatic cancer cells.

BACKGROUND: Pancreatic cancer is one of the most aggressive human malignancies. The development of a novel drug to treat pancreatic cancer is imperative, and it is thought that complementary and alternative medicine (CAM) could yield such a candidate. Agaricus blazei Murrill is a CAM that has been tested as an anticancer drug, but its efficacy against pancreatic cancer is poorly understood. To study the potential of A. blazei in the treatment of pancreatic cancer, we examined the effects of its hot water extract on the proliferation and global gene expression profile of human pancreatic cancer cells. METHODS: Three distinct human pancreatic cancer cell lines, MIAPaCa-2, PCI-35, and PK-8, and the immortalized human pancreatic duct-epithelial cell line, HPDE, were employed. The cells were incubated with the appropriate growth medium supplemented with the hot water extract of A. blazei at final concentrations of 0.005, 0.015%, or 0.045%, and cellular proliferation was assessed for five consecutive days using an MTT assay. Apoptosis was examined by using flow cytometry and the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Caspase-dependent apoptosis was assayed using immunoblotting. Global gene expression profiles were examined using a whole human genome 44 K microarray, and the microarray results were validated by using real-time reverse transcription PCR. RESULTS: The hot water extract of A. blazei significantly inhibited the proliferation of cultured pancreatic cancer cells through the induction of G0/G1 cell cycle arrest and caspase-dependent apoptosis; the effect was the smallest in HPDE cells. Furthermore, significant alterations in the global gene expression profiles of pancreatic cancer cells occurred following treatment with the hot water extract of A. blazei. Genes associated with kinetochore function, spindle formation, and centromere maintenance were particularly affected, as well as cyclins and cyclin-dependent kinases that are essential for cell cycle progression. In addition, proapoptotic genes were upregulated. CONCLUSIONS: The hot water extract of A. blazei may be useful for the treatment of pancreatic cancer and is a potential candidate for the isolation of novel, active compounds specific for mitotic spindle dysfunction.

Prognostic predictive value of gene mutations in Japanese patients with hypertrophic cardiomyopathy.

Although some studies have attempted to find useful prognostic factors in hypertrophic cardiomyopathy (HCM), those results are not fully helpful for use in actual clinical practice. Furthermore, several genetic abnormalities associated with HCM have been identified. However, the genotype-phenotype correlation in HCM remains to be elucidated. Here, we attempted to assess patients with different types of gene mutations causing HCM and investigate the prognosis. A total of 140 patients with HCM underwent a screening test for myofilament gene mutations by direct sequencing of eight sarcomeric genes. Patients with a single mutation in cardiac troponin T, cardiac troponin I, α-tropomyosin, and regulatory and essential light chains were excluded from the study because the number of cases was too small. The clinical presentations and outcomes of the remaining 127 patients with HCM, 31 ß-myosin heavy chain (MYH7) mutation carriers, 19 cardiac myosin-binding protein C (MYBPC3) mutation carriers, and 77 mutation non-carriers were analyzed retrospectively. MYBPC3 mutation carriers had a high frequency of ventricular arrhythmia and syncope. Kaplan-Meier curves revealed no significant difference in prognosis among the three groups, but a lack of family history of sudden death (SD) and a past history of syncope were significantly related to poor prognosis. An absence of family history of SD and past history of syncope are useful prognostic factors in patients with HCM. MYH7 and MYBPC3 mutations did not significantly influence prognosis compared to non-carriers. However, patients with the MYBPC3 mutation should be closely followed for the possibility of SD.

Ellis-van Creveld syndrome associated with chronic intestinal pseudo-obstruction.

Ellis-van Creveld (EVC) syndrome is a rare autosomal recessive disorder characterized by hypoplastic nails, polydactyly, and achondroplasia. Patients usually exhibit normal cognitive function and no remarkable developmental delay. We herein present an unusual case of EVC syndrome. A Japanese 2-year-old boy was born at term, but immediately developed severe respiratory failure due to thorax deformity, postaxial polydactyly and nail hypoplasia. We identified a novel pattern of germinal compound heterozygous nonsense EVC2 mutations of c.1814C > A (p. S605X) and c.2653C > T (p. R885X), leading to the diagnosis of EVC syndrome. Interestingly, he also had severe developmental delay, and suddenly developed excessive abdominal distension at the age of 2. On surgery, extensive necrotic bowel with chronic intestinal pseudo-obstruction was noted. This is, to our knowledge, a most severe phenotype of EVC syndrome, illustrating that the specific pattern of EVC2 compound heterozygous mutations may cause severe developmental delay and intestinal malfunction.

Compound Mutations Cause Increased Cardiac Events in Children with Long QT Syndrome: Can the Sequence Homology-Based Tools be Applied for Prediction of Phenotypic Severity?

Long QT syndrome (LQTS) can cause syncope, ventricular fibrillation, and death. Recently, several disease-causing mutations in ion channel genes have been identified, and compound mutations have also been detected. It is unclear whether children who are carriers of compound mutations exhibit a more severe phenotype than those with single mutations. Although predicting phenotypic severity is clinically important, the availability of prediction tools for LQTS is unknown. To determine whether the severity of the LQTS phenotype can be predicted by the presence of compound mutations in children is needed. We detected 97 single mutations (Group S) and 13 compound mutations (Group C) between 1998 and 2012, age at diagnosis ranging 0-19 years old (median age is 9.0) and 18.0 years of follow-up period. The phenotypes and Kaplan-Meier event-free rates of the two groups were compared for cardiac events. This study investigated phenotypic severity in relation to the location of mutations in the protein sequence, which was analyzed using two sequence homology-based tools. In results, compound mutations in children were associated with a high incidence of syncope within the first decade (Group S: 32 % vs. Group C: 61 %), requiring an ICD in the second decade (Group S: 3 % vs. Group C: 56 %). Mortality in these patients was high within 5 years of birth (23 %). Phenotypic prediction tools correctly predicted the phenotypic severity in both Groups S and C, especially by using their coupling method. The coupling prediction method is useful in the initial evaluation of phenotypes both with single and compound mutations of LQTS patients. However, it should be noted that the compound mutation makes more severe phenotype.