Effect of beta-blockers and exercise restriction on the prevention of sudden cardiac death in pediatric hypertrophic cardiomyopathy.

BACKGROUND: Risk assessment tools and effective prevention strategies for sudden cardiac death (SCD) in pediatric patients with hypertrophic cardiomyopathy (HCM) have not been established. This study aimed to evaluate the efficacy of beta-blockers and exercise restriction for SCD prevention in this population. METHODS: We retrospectively reviewed the medical records of patients aged <18 years who were diagnosed with HCM at our center between January 1996 and December 2021. SCD and aborted SCD were defined as SCD equivalents. We divided patients based on whether they were prescribed beta-blockers or exercise restriction and compared the outcomes among the groups. The primary outcome was the overall survival (OS), and the secondary outcome was the cumulative SCD equivalent rate. Outcomes were analyzed using Kaplan-Meier curves and Cox proportional hazard analysis. We also compared patients according to the occurrence of SCD equivalents to identify SCD risk predictors. RESULTS: Among the 43 included patients [mean age, 7.7 (1.6-12.1) years; 23 male individuals], SCD equivalents occurred in 13 patients over 11.2 (4.5-15.6) years of follow-up, among whom 12 were resuscitated and 1 died. The OS rate was significantly higher in the beta-blocker and exercise restriction groups than in the non-beta-blocker and non-exercise restriction groups (81.3 % vs. 19.1 %, p < 0.01 and 57.4 % vs. 12.7 %, p < 0.01, respectively). Among the 13 patients with SCD equivalents, 5 had 9 recurrent SCD equivalents. A significant difference was observed between the SCD equivalent and non-SCD equivalent groups in the history of suspected arrhythmogenic syncope (p < 0.01) in the univariable but not in the multivariable analysis. CONCLUSIONS: Beta-blockers and exercise restriction may decrease the risk of SCD in pediatric patients with HCM and should be considered for SCD prevention in this population, particularly because predicting SCD in these patients remains challenging.

Case report: high-dose carvedilol as a potential key drug for arrhythmias in histiocytoid cardiomyopathy.

Background: Histiocytoid cardiomyopathy is a rare infancy cardiac disorder manifesting as severe cardiac arrhythmias or dilated cardiomyopathy. There is no specific treatment for these arrhythmias. This is the first report of infantile histiocytoid cardiomyopathy whose refractory ventricular arrhythmias were successfully controlled by high-dose carvedilol. Case summary: A 4-month-old girl presented with asystole, and recurrent ventricular tachycardias. From the histological findings and clinical symptoms, she was diagnosed as histiocytoid cardiomyopathy. Sedatives were the most effective therapy for her arrhythmia, but the cardiac sympathetic denervation was not effective enough. Finally, her ventricular arrhythmias were controlled with high-dose carvedilol, and she was discharged on hospitalization Day 393. Discussion: Carvedilol is the only beta blocker that directly acts on the ryanodine receptor (RyR2) and inhibits store-overload-induced Ca2+ release (SOICR) in myocardium at high dosage. The arrhythmias did not disappear with bisoprolol, landiolol, or verapamil, but high-dose carvedilol was effective. This clinical course suggested that the arrhythmias in histiocytoid cardiomyopathy might be related with SOICR. High-dose carvedilol might be a key drug for patients with histiocytoid cardiomyopathy.

Thirty-year outcome in children with hypertrophic cardiomyopathy based on the type.

BACKGROUND: We reviewed the long-term outcome of children with hypertrophic cardiomyopathy (HCM) based on the type. METHODS: We reviewed the medical records of 100 patients (male 54 female 46) with HCM at our hospital between 1977 and 2015. The survival and cardiac event-free survival rates were calculated by the Kaplan-Meier method. RESULTS: The age at the time of the diagnosis ranged from 0 to 15 years with a median of 8 years. The number of patients with Noonan syndrome and hypertrophic obstructive cardiomyopathy (HOCM), idiopathic HCM (i-HCM), and secondary HCM (s-HCM) was 13, 13, 65, and 9 respectively. A dilated phase of HCM occurred in 24 patients. Nineteen (79 %) of the 24 patients died of heart failure, and two underwent a heart transplantation. Eight (33 %) of the 24 patients had s-HCM. The median age when a dilated phase occurred was 15 years old, and the median interval from the initial diagnosis to the dilated phase was 8 years. The median time from the diagnosis of a dilated phase to death was 1.6 years. Sudden death and implantable cardioverter defibrillator implantations occurred in 6 and 11 patients at around 15 years old, respectively. The 20-year survival rates were as follows: Noonan syndrome 84 %; HOCM 82 %; i-HCM 71 %; and s-HCM 17 %. Overall, the survival rates at 10, 20, and 30 years were 83 % (95 % confidence interval 73-89), 69 % (58-78), and 63 % (50-74), respectively. The overall cardiac event-free survival rates at 10, 20, and 30 years were 57 % (47-67), 39 % (31-50), and 32 % (21-44), respectively. CONCLUSION: The long-term outcome in children with HCM was poor, and the outcome of s-HCM was very poor. The occurrence of a dilated phase worsened the outcome in HCM patients. Sudden death and d-HCM often occurred at around 15 years old.

Control of Heart Rate in Infant and Child Tachyarrhythmia With Reduced Cardiac Function Using Landiolol (HEARTFUL)　- Results of a Prospective, Multicenter, Uncontrolled Clinical Study.

BACKGROUND: The prospective Control of HEART rate in inFant and child tachyarrhythmia with reduced cardiac function Using Landiolol (HEARTFUL) study investigated the effectiveness and safety of landiolol, a short-acting ß1 selective blocker, in children.Methods and Results: Twenty-five inpatients aged ≥3 months to <15 years who developed supraventricular tachyarrhythmias (atrial fibrillation, atrial flutter, supraventricular tachycardia, and inappropriate sinus tachycardia) were treated with landiolol. The primary endpoint, the percent of patients with a reduction in heart rate ≥20% from the initial rate of tachycardia, or termination of tachycardia at 2 h after starting landiolol, was achieved in 12/25 patients (48.0%; 95% CI 28.4-67.6), which exceeded the predetermined threshold (38.0%). At 2 h after starting landiolol administration, heart rate had decreased by ≥20% in 45.8% (11/24) and recovery to sinus rhythm was achieved in 40.0% (6/15) of the patients. Adverse reactions (ARs) occurred in 24.0% (6/25) of patients, and the study was discontinued in 4.0% (1/25) of the patients; however, none of these ARs were considered serious. The most common AR was hypotension (20.0% [5/25] of patients). CONCLUSIONS: The HEARTFUL study has demonstrated the efficacy of landiolol, by reducing heart rate or terminating tachycardia, in pediatric patients with supraventricular tachyarrhythmias. Although serious ARs and concerns were not identified in this study, physicians should be always cautious of circulatory collapse due to hypotension.

Utility of perinatal natriuretic peptide for predicting neonatal heart failure.

BACKGROUND: We evaluated the significance of perinatal plasma natriuretic peptide (NP) levels in neonates with congenital heart defects (CHDs) or arrhythmias and determined whether measurement of perinatal plasma NP levels and echocardiographic assessment in utero could predict heart failure after birth. METHODS: The study was conducted between 2012 and 2016 to evaluate the correlation of perinatal atrial NP (ANP) and brain NP (BNP) levels at birth with the modified Ross score after birth and the cardiovascular profile (CVP) score before birth. RESULTS: A total of 122 singletons with CHDs or arrhythmias and 27 controls were analyzed. Neonatal blood sampling was performed at a median of 0.7 h (range, 0.1-1.5) after birth. The neonatal plasma ANP and BNP levels shortly after birth were significantly higher than those in the umbilical artery (UA) plasma. The ANP and BNP levels in UA and neonatal blood were correlated with the modified Ross score. The neonatal plasma ANP and BNP levels and the modified Ross scores were inversely correlated with the CVP score in neonates with CHDs or arrhythmias. The area under the receiver operating characteristic curve of UA ANP levels for predicting neonatal heart failure was highest among those for the CVP score, perinatal plasma ANP and BNP levels, and their combinations. CONCLUSIONS: The plasma ANP and BNP levels increased markedly shortly after birth. Assessment of the UA plasma ANP level at birth and the CVP score in utero may be utilized to predict neonatal heart failure.

Pulmonary Arteriovenous Fistulae After Fontan Operation: Incidence, Clinical Characteristics, and Impact on All-Cause Mortality.

Background: The Fontan operation is a surgical procedure used in children with univentricular hearts. Pulmonary arteriovenous fistulae (PAVF) is a major complication after a Fontan operation. However, the incidence and related clinical pathophysiology of PAVF remain unclear. Purpose: This study aimed to clarify the incidence of PAVF, its clinical characteristics, and its influence on all-cause mortality. Methods and Results: We serially assessed the presence of PAVF using pulmonary artery angiography and/or contrast echocardiography during catheterization in 391 consecutive patients who underwent the Fontan procedure and compared the results with the Fontan pathophysiology and all-cause mortality. PAVF developed in 36 patients (9.2%), including 30 diffuse- and six discrete-PAVF types. The PAVF-free rates at 1, 5, 10, 15, 20, and ≥25 years after Fontan operation were 97, 96, 93, 88, 87, and 83%, respectively. The mean arterial blood oxygen saturation (SaO2) in patients with diffuse PAVF at each corresponding postoperative stage were 90, 91, 91, 91, 89, and 88%, respectively, indicating lower SaO2 levels than those in patients without PAVF (all p < 0.01). However, there was no difference in the SaO2 levels between patients with discrete PAVF and those without PAVF. During a median follow-up period of 2.9 years after the last catheterization, 31 patients, including 12 patients with PAVF, died. Patients with PAVF, especially those with diffuse PAVF, had a higher mortality rate (p = 0.01) than those without PAVF (hazard ratio: 3.6, 95% confidence interval: 1.6-7.8, p = 0.0026). Conclusion: Patients who underwent Fontan surgery had an increased incidence of PAVF as they aged. Discrete PAVF did not influence SaO2 or mortality, whereas the presence of diffuse PAVF caused hypoxia and was associated with all-cause mortality.

Short-term outcomes of EXCOR Paediatric implantation.

OBJECTIVES: The aim of this study was to review a single institution's experience with EXCOR Paediatric implantation. METHODS: Patients <15 years old who underwent EXCOR implantation as a bridge to transplantation between 2015 and 2021 were enrolled. Major adverse events included death, cerebrovascular event resulting in sequelae, major infection (sepsis or surgical site infection requiring open sternal irrigation or device removal) and device malfunction requiring surgical treatment. RESULTS: Overall median age and weight for all 20 children at implantation were 10.8 (interquartile range, 7.9-33.2) months and 6.3 (4.6-10.2) kg. Ten patients (50%) weighed <5 kg. Primary diagnoses were dilated cardiomyopathy in 13 patients, fulminant myocarditis in 3, restrictive cardiomyopathy in 2 and congenital heart disease in 2. Two patients required biventricular assist support. The median support time was 365 (241-636) days. Six patients (30%) were supported for >20 months. One patient died. Seven patients underwent heart transplant. Heart transplant has not been performed in the last 1.5 years. Five patients were weaned from EXCOR support after native myocardial recovery, including a patient with dilated cardiomyopathy who recovered after 24 months of EXCOR support. Major complication-free survival at 6, 12 and 18 months were 79.3%, 49.6% and 38.6%, respectively. Body weight <5 kg at implantation was a risk factor for decreased major complication-free survival. CONCLUSIONS: Survival during EXCOR Paediatric support was good, but it prolonged the wait time for a heart transplant. The number of major complications increased over time and was not negligible, especially in small children.

Successful treatment of symptomatic first-degree atrioventricular block after Occlutech Figulla Flex II atrial septal defect occluder placement.

Given the rarity of significant first-degree atrioventricular block (AVB) after Occlutech Figulla Flex II atrial septal defect occluder (OFF II, Occlutech International AB, Helsingborg, Sweden) placement, its management and predictors of recovery have not been established. We report a 9-year-old boy who developed significant first-degree AVB a day after OFF II deployment. Thereafter, oral prednisolone was initiated at 1.5 mg/kg/day. On day 2 of steroid treatment, normal sinus rhythm without conduction delays was occasionally observed, while the prolonged PR interval on the exercise stress test was ameliorated. After 5 days of steroid administration, normal sinus rhythm without conduction delays was completely achieved. An increase in the frequency of normal sinus rhythm and the absence of conduction delays on electrocardiogram monitoring and exercise stress test play an important role in predicting recovery from prolonged PR interval. Thus, steroid treatment can be effective and should be considered for patients who develop first-degree AVB after undergoing OFF II placement for transcatheter device closure of atrial septal defect. .

Impact of cascade screening for catecholaminergic polymorphic ventricular tachycardia type 1.

OBJECTIVE: Human cardiac ryanodine receptor 2 (RYR2) shows autosomal-dominant inheritance in catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1); however, de novo variants have been observed in sporadic cases. Here, we investigated CPVT1-related RYR2 variant inheritance and its clinical significance between familial and de novo cases. METHODS: We enrolled 82 independent CPVT1 probands (median age: 10.0 (7.0-13.0) years; 45 male) carrying the RYR2 variants and whose biological origin could be confirmed by parental genetic analysis: assured familial inheritance (familial group: n=24) and de novo variants (de novo group: n=58). We examined the clinical characteristics of the probands and their family members carrying the RYR2 variants. RESULTS: In the de novo group, the RYR2 variants were more likely located in the C-terminus domain and less likely in the N-terminus domain than those in the familial group. The cumulative incidence of the first cardiac events (syncope and cardiac arrest (CA) or CA only) of the probands at the age of 5 and 10 years was higher in the de novo group than in the familial group. Nearly half of the probands in both groups experienced CA events before diagnosis. Only 37.5% of their genotype-positive parents had symptoms; however, at least 66.7% of the genotype-positive siblings were symptomatic. CONCLUSIONS: CPVT1 probands harbouring de novo RYR2 variants showed an earlier onset of symptoms than those with assured familial inheritance. Cascade screening may enable early diagnosis, risk stratification and prophylactic therapeutic intervention to prevent sudden cardiac death of probands and potential genotype-positive family members.

Coronary artery aneurysms of unknown origin in a 14-year-old girl.

The case of a 14-year-old girl with acute myocardial infarction due to coronary artery aneurysms (CAAs) of unknown origin, which resembled coronary artery lesions caused by Kawasaki disease, is reported. She was transferred to our hospital due to chest pain with ST-T elevation. She had no history of Kawasaki disease. On the first admission, she was misdiagnosed with acute myocarditis. Then, 54 days later, she experienced chest pain with exertional dyspnea. Her electrocardiogram showed negative T waves in the chest leads. A CAA of the left coronary artery was suspected on two-dimensional echocardiography. Coronary angiograms showed 90% stenosis and multiple CAAs of the left anterior descending artery and the bifurcation of the left coronary artery. Both the right coronary artery and left circumflex artery were occluded. A left ventriculogram showed dyskinesis and an aneurysm at the apex. She underwent triple-vessel coronary artery bypass grafting, and her symptoms improved. In addition, an intracranial aneurysm was also found on cerebral angiography. There were no specific laboratory findings other than SS-A antibodies. It was suspected that the weakness of the vessels was related to the disease. It may have been a different disease that was never previously detected, but her CAAs were Kawasaki-like CAAs.

Cardiac Resynchronization Therapy Using Single Site Left Ventricular Pacing in a Tricuspid Atresia Patient With Left Bundle Branch Block.

Cardiac resynchronization therapy (CRT) is typically achieved by pacing both ventricles. However, left ventricular-only pacing has been shown to be noninferior to biventricular pacing in patients with left bundle branch block and normal atrioventricular conduction. However, there is no evidence in favour of CRT with single-site pacing for patients with single-ventricle physiology. In this case, we performed CRT with single-site pacing in a patient with tricuspid atresia and left bundle branch block, enabling successful Fontan completion.

La thérapie de resynchronisation cardiaque (TRC) consiste généralement en une stimulation des deux ventricules. Il a toutefois été montré que la stimulation du ventricule gauche seulement n'est pas inférieure à la stimulation biventriculaire chez les patients présentant un bloc de branche gauche et une conduction auriculoventriculaire normale. Cependant, aucune donnée probante n'appuie la TRC par stimulation d'une seule cavité cardiaque dans le cas d'un cœur univentriculaire. Dans le cas que nous présentons, nous avons eu recours à la TRC par stimulation d'une seule cavité cardiaque chez une patiente présentant une atrésie tricuspidienne et un bloc de branche gauche, ce qui a permis de réaliser l'intervention de Fontan.

Morphological changes and number of candidates for transcatheter pulmonary valve implantation in conduits involving heterograft and artificial material.

Heterograft and artificial materials have been used for extracardiac conduit implantation to create right ventricular (RV) to pulmonary artery (PA) continuity for biventricular repair in Japan because of the limited availability of homograft valves. However, few studies have examined morphological changes and number of candidates for transcatheter pulmonary valve implantation (TPVI) in which the conduit includes more than one type of material. Overall, 88 patients who underwent biventricular repair with an external conduit were included in this evaluation. Based on catheterization data and surgical records, we estimated morphological change in the RV outflow tract for each material and the number of candidates for Melody valve implantation based on premarket approval application criteria established by the U.S. Food and Drug Administration. There were 63 candidates for TPVI (72%, 63/88). Median anteroposterior and lateral diameter of the RV outflow tract was 20.4 mm (range 9.0-41.5) and 17.8 mm (range 9.5-34.9), respectively. Bovine pericardium tended to dilate by 11.2%. Polytetrafluoroethylene (ePTFE), homograft, and Dacron polyethylene terephthalate (PET) tended to become stenotic by 11.1%, 28.0%, and 13.4%, respectively. While ePTFE (27/33, 82%) and Dacron PET (2/2, 100%) were highly suitable for TPVI, bovine pericardium (32/48, 67%) was less suitable. In Japan, many patients with hemodynamic indications for TPVI following extracardiac conduit implantation to create RV to PA continuity may also meet the morphological indications.

Systemic Artery Vasoconstrictor Therapy in Fontan Patients with High Cardiac Output-Heart Failure: A Single-Center Experience.

Failed Fontan Patients with high cardiac output (CO) heart failure (HF) might have vasodilatory syndrome and markedly high mortality rates. The aim of this study was to review the clinical effects of vasoconstrictor therapy (VCT) for failed Fontan hemodynamics. We retrospectively reviewed 10 consecutive patients with Fontan failure (median age, 33 years) and high CO-HF who had received VCT. The hemodynamics were characterized by high central venous pressure (CVP: median, 16 mm Hg), low systolic blood pressure (median, 83 mm Hg), low systemic vascular resistance (median, 8.8 U·m2), high cardiac index (median, 4.6 L/min/m2), and low arterial oxygen saturation (median, 89%). VCT included intravenous noradrenaline infusion for five unstable patients, oral midodrine administration for nine stable patients, and both for four patients. After VCT introduction with a median interval of 1.7 months, the median systolic blood pressure (102 mm Hg, p = 0.004), arterial oxygen saturation (90%, p = 0.03), and systemic vascular resistance (12.1 U·m2, p = 0.13) increased without significant changes in CVP or cardiac index. After a median follow-up of 21 months, the number of readmissions per year decreased from 4 (1-11) to 1 (0-9) (p = 0.25), and there were no VCT-related complications; however, five patients (50%) developed hepatic encephalopathy, and six patients (60%) eventually died. VCT was safely introduced and could prevent the rapidly deteriorating Fontan hemodynamics. VCT could be an effective therapeutic strategy for failed Fontan patients with high CO-HF.

A burden of sarcomere gene variants in fetal-onset patients with left ventricular noncompaction.

BACKGROUND: Left ventricular noncompaction (LVNC) is a hereditary cardiomyopathy, associated with high morbidity and mortality, but the role of genetics in cases of fetal-onset has not been fully evaluated. The goal of this study was to identify the genetic background in LVNC fetal-onset patients using next-generation sequencing (NGS). METHODS: Thirty-three fetal-onset Japanese probands with LVNC (20 males and 13 females) were enrolled. In the enrolled patients, 81 genes associated with cardiomyopathy were screened using next-generation sequencing (NGS) retrospectively. RESULTS: Twenty-three patients had congestive heart failure (CHF), and six patients had arrhythmias. Prominent trabeculations were mostly observed in lateral LV, posterior LV, and apex of LV in patients with LVNC. Twelve died; three patients experienced intrauterine death or termination of pregnancy. Overall, 15 variants were found among eight genes in 16 patients. Seven variants were detected in MYH7 and two in TPM1. Sarcomere gene variants accounted for 75.0%. A multivariable proportional hazards model revealed that CHF at diagnosis and a higher ratio of the noncompacted layer/compacted layer in the LV posterior wall were independent risk factors for death in LVNC fetal-onset patients (odds ratio = 4.26 × 106 and 1.36 × 108, p = 0.0075 and 0.0005, respectively). CONCLUSIONS: The present study is the first report focusing on genetic background combined with clinical features in LVNC fetal-onset patients using NGS. Sarcomere variants were most commonly identified in fetal-onset patients, and greater attention should be paid to fetal-onset patients with LVNC having prominent trabeculations in the LV because they are more likely to develop CHF.

Interventricular septal haematoma after EXCOR paediatric implantation.

A 3.5-kg boy with dilated cardiomyopathy underwent EXCOR left ventricular assist device implantation, which resulted in right ventricular outflow tract obstruction due to the development of an interventricular septal haematoma (IVSH), which required the implantation of an additional right ventricular assist device. Curettage and haemostasis of the IVSH were successfully performed on postoperative day 17. An 11-kg girl with left ventricular non-compaction also underwent EXCOR left ventricular assist device implantation. An IVSH was initially detected on postoperative day 13 without haemodynamic instability. By decreasing the target-activated partial thromboplastin time, the IVSH completely regressed 2 months later.

Discrepancy Between Pre- and Postnatal Diagnoses of Congenital Heart Disease and Impact on Neonatal Clinical Course　- A Retrospective Study at a Japanese Tertiary Institution.

BACKGROUND: Congenital heart disease (CHD) is often diagnosed prenatally using fetal echocardiography, but few studies have evaluated the accuracy of these fetal cardiac diagnoses in detail. We investigated the discrepancy between pre- and postnatal diagnoses of CHD and the impact of discrepant diagnoses.Methods and Results:This retrospective study at a tertiary institution included data from the medical records of 207 neonates with prenatally diagnosed CHD admitted to the cardiac neonatal intensive care unit between January 2011 and December 2016. Pre- and postnatal diagnoses of CHD differed in 12% of neonates. Coarctation of the aorta and ventricular septal defects were the most frequent causes of discrepant diagnosis. Unexpected treatments were added to 38% of discrepant diagnostic cases. However, discrepant diagnoses did not adversely affect the clinical course. The 9% of the 207 neonates who required invasive intervention within 24 h of delivery were accurately diagnosed prenatally. CONCLUSIONS: Pre- and postnatal diagnoses differed in only a few neonates, with differences not adversely affecting the clinical course. Neonates who required invasive intervention immediately after delivery were accurately diagnosed prenatally. Prenatal diagnosis thus seems to contribute to improved prognosis in neonates with CHD.

Systematic Evaluation of KCNQ1 Variant Using ACMG/AMP Guidelines and Risk Stratification in Long QT Syndrome Type 1.

Background - Mutation/variant-site specific risk stratification in long-QT syndrome type 1 (LQT1) has been well investigated, but it is still challenging to adapt current enormous genomic information to clinical aspects caused by each mutation/variant. We assessed a novel variant-specific risk stratification in LQT1 patients. Methods - We classified a pathogenicity of 141 KCNQ1 variants among 927 LQT1 patients (536 probands) based on the American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines and evaluated whether the ACMG/AMP-based classification was associated with arrhythmic risk in LQT1 patients. Results - Among 141 KCNQ1 variants, 61 (43.3%), 55 (39.0%), and 25 (17.7%) variants were classified into pathogenic (P), likely pathogenic (LP), and variant of unknown significance (VUS), respectively. Multivariable analysis showed that proband (HR = 2.53; 95%CI = 1.94-3.32; p <0.0001), longer QTc (≥500ms) (HR = 1.44; 95%CI = 1.13-1.83; p = 0.004), variants at membrane spanning (MS) (vs. those at N/C terminus) (HR = 1.42; 95%CI = 1.08-1.88; p = 0.01), C-loop (vs. N/C terminus) (HR = 1.52; 95%CI = 1.06-2.16; p = 0.02), and P variants [(vs. LP) (HR = 1.72; 95%CI = 1.32-2.26; p <0.0001), (vs. VUS) (HR = 1.81; 95%CI = 1.15-2.99; p = 0.009)] were significantly associated with syncopal events. The ACMG/AMP-based KCNQ1 evaluation was useful for risk stratification not only in family members but also in probands. A clinical score (0~4) based on proband, QTc (≥500ms), variant location (MS or C-loop) and P variant by ACMG/AMP guidelines allowed identification of patients more likely to have arrhythmic events. Conclusions - Comprehensive evaluation of clinical findings and pathogenicity of KCNQ1 variants based on the ACMG/AMP-based evaluation may stratify arrhythmic risk of congenital long-QT syndrome type 1.

Impact of delayed ventricular wall area ratio on pathophysiology of mechanical dyssynchrony: implication from single-ventricle physiology and 0D modeling.

Electrical disparity can induce inefficient cardiac performance, representing an uncoordinated wall motion at an earlier activated ventricular wall: an early shortening followed by a systolic rebound stretch. Although regional contractility and distensibility modulate this pathological motion, the effect of a morphological factor has not been emphasized. Our strain analysis in 62 patients with single ventricle revealed that those with an activation delay in 60-70% of ventricular wall area suffered from cardiac dysfunction and mechanical discoordination along with prolonged QRS duration. A computational simulation with a two-compartment ventricular model also suggested that the ventricle with an activation delay in 70% of the total volume was most vulnerable to a large activation delay, accompanied by an uncoordinated motion at an earlier activated wall. Taken together, the ratio of the delayed ventricular wall has a significant impact on the pathophysiology due to an activation delay, potentially highlighting an indicator of cardiac dysfunction.