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It can be difficult to distinguish children with early-stage arrhythmogenic right ventricular cardiomyopathy (ARVC) from those with benign premature ventricular contraction (PVC). We retrospectively evaluated six school-aged children with ARVC and compared with those of 20 with benign PVC. The median age at initial presentation was 11.4 and 10.2 years in ARVC and benign PVC, respectively. None of the ARVC patients fulfilled the diagnostic criteria of ARVC at initial presentation. At ARVC diagnosis, the treadmill exercise test and Holter monitoring showed provoked PVC during exercise and pleomorphic PVC in all ARVC cases, respectively. During the observation period, terminal activation duration (TAD) was prolonged in all ARVC patients. In addition, ΔTAD (5.5 [3–10] ms) were significantly longer than those with benign PVC (p

Background A stiffened, dilated ascending aorta may represent an important predictor of cardiovascular mortality, and has been reported in patients with congenital heart disease, including single ventricle. However, the serial conformational changes and determinants of reduced distensibility in ascending aorta have not been clarified. Methods This retrospective study investigated 115 postoperative Fontan survivors (median age at Fontan: 3.7 years). All patients underwent cardiac catheterization before and 1, 5, 10, and 15 years after the Fontan operation. We measured Z-scores for diameters and stiffness indexes (β) of the ascending aorta and descending aorta from angiograms. We also reviewed the clinical profiles, hemodynamic parameters, and exercise capacities of patients and compared them with results from 47 control subjects. Results Fontan survivors displayed significantly larger Z-score and β of the ascending aorta from before to 15 years after surgery than controls, whereas values for the descending aorta were comparable. Z-score for the ascending aorta was decreased, but β was elevated significantly according to the trend test. In multivariable analysis, β of the ascending aorta at 15 years after Fontan operation and its increasing trend were associated with older age at Fontan operation and elevated ventricular end-diastolic pressure. Reduced exercise capacity also correlated with stiffening of the ascending aorta. Conclusions Fontan survivors showed progressive stiffening and relatively slow growth of the dilated ascending aorta. Progressive stiffening of the ascending aorta may be coupled to diastolic dysfunction and reduced exercise capacity, suggesting the importance of lifelong management of subclinical Fontan pathophysiology.

Several studies have reported aortic dilation and increased stiffness of the ascending aorta in patients after repair of congenital heart disease (CHD), which may be a predominant cardiovascular risk. However, the clinical significance has not been described in detail. In this retrospective study, 175 repaired patients with complex CHD achieving biventricular circulation and age-matched 39 control subjects were reviewed (median age: 14.9 and 15.7 years, respectively). We measured the diameters of the ascending aorta and descending aorta from catheterization angiograms to yield Z-scores and stiffness indexes (β) using diameter fluctuations corresponding to pulsatile pressures. Clinical profile, peak oxygen uptake during the cardiopulmonary exercise test, and incidence of unscheduled hospitalization during follow-up was also reviewed. Compared with controls, patients with complex CHD, except for those with aortic coarctation, exhibited significant dilation and increased stiffness of the aortic root and ascending aorta, but not of the descending aorta. In this CHD population (n = 147, including 112 conotruncal anomalies), exercise capacities correlated independently with the diameter Z-score and stiffness index of the ascending aorta along with the history of repetitive thoracotomies, reduced forced vital capacity, and right ventricular hypertension. During a follow-up period (median 15.6 years), either dilation (Z-score >3.5) or increased stiffness (β >6.0) of the ascending aorta stratified morbidity, but no synergistic impact was detected. In conclusion, in repaired patients with complex CHD, a stiffened and dilated ascending aorta was frequently found, exerting significant adverse impacts on diminished exercise capacity and morbidity.

Background In Japan, the school screening program for heart disease (SS) has been performed since 1973. However, little has been reported on the electrocardiogram (ECG) changes and long-term prognosis in patients with hypertrophic cardiomyopathy (HCM) detected by the SS. Methods All 44 consecutive pediatric HCM patients (10.1 ± 3.0 years old), who had been originally consulted by the SS before the diagnosis of HCM from April 1981 to April 2017, were reviewed retrospectively. Results At the SS, all patients showed mild or no symptoms. All patients showed ECG abnormalities, and 75 % had a high proposed ECG risk score (≧6). However, 30 % of them had no echocardiogram finding of myocardial hypertrophy. During the follow-up period (14.8 ± 10.0 years), life-threatening events (LTE) occurred in 11 (25 %) patients, and the first LTE occurred during exercise in 8 (18 %). The estimated LTE and heart failure death-free survival rate at 10 years was 64.9 %. The LTE-free survival rate was lower in patients without than in those with myocardial hypertrophy at the SS. Conclusions The SS was useful in detecting patients with HCM with mild or no symptoms at the early stage. However, our study indicated that early detection of HCM is not associated with improvement in the prognosis of the patients. Further studies are needed.

Background:Atrioventricular interval optimisation is important in patients with dual-chamber pacing, especially with heart failure. In patients with CHD, especially in those with Fontan circulation, the systemic atrial contraction is supposed to be more important than in patients without structural heart disease.Methods:We retrospectively evaluated two patients after Fontan procedure with dual-chamber pacemaker with a unique setting of optimal sensed atrioventricular interval.Results:The optimal sensed atrioventricular interval determined by echocardiogram was extremely short sensed atrioventricular interval at 25 and 30 ms in both cases; however, the actual P wave and ventricular pacing interval showed 180 and 140 ms, respectively. In both cases, the atrial epicardial leads were implanted on the opposite site of the origin of their own atrial rhythm. The time differences between sensed atrioventricular interval and actual P wave and ventricular pacing interval occurred because of the site of the epicardial atrial pacing leads and the intra-atrial conduction delay.Conclusion:We need to consider the origin of the atrial rhythm, the site of the epicardial atrial lead, and the atrial conduction delay by using electrocardiogram and X-ray when we set the optimal sensed atrioventricular interval in complicated CHD.

In cardiac resynchronization therapy (CRT) for patients with congenital heart disease (CHD) and a ventricular morphology other than a systemic left ventricle (LV), we previously proposed pacing sites that are different from those used for a systemic LV. The leads should be placed laterally on opposite sides of both ventricles in patients with short-axis dyssynchrony and a single ventricular physiology with two ventricles, whereas they should be placed at the farthest sites along the longitudinal direction in the right ventricle (RV) in patients with long-axis dyssynchrony of the RV. Moreover, in patients with interventricular dyssynchrony and a biventricular physiology with a systemic RV, they should be placed at sites that both ventricles can contract simultaneously. We retrospectively investigated 27 consecutive procedures in 24 patients with CHD who underwent CRT to evaluate the effectiveness of a new ventricular morphology-based CRT strategy. The responder rate was 63% (17/27). The reasons for a non-response to CRT in 10 cases were as follows: non-optimal lead positions during CRT, 4; no systemic ventricular conduction delay or heart failure symptoms before the CRT, 5; short follow-up periods after the CRT, 2; and an extremely dilated systemic RV, 1. The responder rate became 88% (14/16), after excluding the procedures without a ventricular conduction delay or heart failure symptoms and those with non-optimal lead positions. This new strategy for CRT can provide favorable results for CHD patients with a systemic ventricular conduction delay and heart failure.

Background Preexcitation-induced cardiomyopathy (PIC) is defined as a disease presenting ventricular dyssynchrony because of preexcitation through an accessory pathway (AP), being a cousin of pacing-induced cardiomyopathy. The present review aims at providing perspective of this uncharted subgroup. Methods In order to determine mechanisms and clinical characteristics of PIC, 63 patients in 29 literature reports were reviewed. Results A median age at onset was 4 (0.1–59) years; 55 patients (87%) under 18 years old including 16 infants. Twenty patients (32%) experienced supraventricular tachycardia prior and subsequent to the PIC onset. Heart failure and left ventricular (LV) dysfunction did not correlate with other clinical features. All the 65 APs identified (duplicated in 2 patients) were located on the right side of the atrioventricular junction; at the septal area (in 55%) or the anterolateral aspect (in 22%). AP conduction was successfully eliminated by medical or interventional treatments where attempted. LV function returned to normal within 6 months in 67% of patients, while recovery took longer than 3 years in 8%. Frequently seen at the basal segments of the interventricular septum were early contraction within the QRS complex, dyskinesis at mid-systole, and aneurysm/bulging or local thinning. Conclusions Several characteristic factors became clear as described above. Rebound stretch following early shortening of the interventricular septum is seemingly the major mechanism of PIC, and thus a right septal or right anterior/anterolateral AP needs attention as a higher risk for PIC.

1 Current status of non‐pharmacotherapies in Japan Pacemaker treatment for bradyarrhythmia was first approved for national health insurance coverage in Japan in 1974, and its use rapidly became widespread thereafter. Approximately 40 years later, in 2017, the number of patients treated with this technology has increased to 60 137 (41 895 new cases and approximately 18 242 replacements). 5 Capsule‐shaped leadless pacemaker also became available in 2016, and this technology is being established as a new option. Non‐pharmacological treatment of tachy‐arrhythmia began in 1969 from when Will C. Sealy performed surgery in patients with Wolff‐Parkinson‐White (WPW) syndrome (Figure 1). Since then, the application of surgical treatment has expanded to conditions such as ventricular tachycardia (VT) and atrial fibrillation (AF), and surgery has been the pioneer of radical therapy for tachyarrhythmias. At the present time, many surgical methods have been replaced by catheter ablation; however, surgical treatment still remains an indispensable option for patients with a tachycardia resistant to other medical treatments. Open in a separate window FIGURE 1 History of non‐pharmacotherapy of cardiac arrhythmia

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 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.

We encountered a unique pattern of cardiac dyssynchrony in a patient with complex congenital heart disease (heterotaxy syndrome) with a biventricular physiology and systemic left ventricle (LV). On speckle tracking echocardiography, dyssynchrony was not detected within the LV, but was noted in an interventricular fashion between the LV and right ventricle (RV). An electrophysiologic study revealed a conduction delay in the subpulmonary RV. Cardiac resynchronization therapy provided reverse cardiac remodeling and an excellent result in our patient by placing the pacing leads around the dyssynchronous lesion.

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.

Background The demographics of patients with congenital heart disease (CHD) and atrial fibrillation (AF) differ significantly from the general population. The etiology and treatment strategy for AF in CHD patients have been investigated but are to date inconclusive. Methods To determine the etiology of AF in CHD and to seek a better treatment strategy, we retrospectively evaluated the atrial overload in 42 complex CHD cases with normal atrial arrangements and AF (age 25; range, 9–66 years) and the impact of a reduction in the atrial overload on the atrial rhythm. Results Cardiac defect diagnoses varied, with 17% of the patients having a persistent left superior vena cava (PLSVC). In regard to the volume overload, the frequencies of an overload in the right atrium (RA), left atrium (LA), or both, were 50 %, 23%, and 10%, respectively (p = 0.015). Other sustained supraventricular tachycardias were observed in 29 patients (69%) before and after the onset of AF. Among these 29 patients, 26 had intra-atrial reentrant tachycardia. Fifteen patients (36%), 10 of whom had chronic AF, died during the follow-up including 3 with arrhythmias and 10 because of heart failure. Fourteen (33%) patients had no AF at the last follow-up due to medical interventions, 8 of which underwent solely an RA-sided catheter ablation and/or surgical RA overload reduction. Conclusions AF in complex CHD with a normal atrial arrangement correlates with a higher RA-sided overload than an LA-sided and exhibits a high incidence of PLSVCs, high comorbidity of intra-atrial reentrant tachycardias, and high mortality rate. In a substantial number of patients, RA-sided interventions were effective in controlling AF. To effectively manage AF in complex CHD it is essential to understand each individual’s hemodynamics and consider hemodynamic interventions.

Background Takayasu’s arteritis is extremely rare in children aged below 6 years. At the onset of Takayasu’s arteritis in children, symptoms are varied but differ from those in adults. Corticosteroids are the mainstay of treatment for preventing irreversible vascular damage but there is no standard treatment for progressive vascular stenosis. Case presentation A Japanese 11-month-old baby boy presented with Takayasu’s arteritis and heart failure, possibly due to afterload mismatch caused by high blood pressure. Computed tomography was performed and revealed thoracic and abdominal aortic aneurysms. It also revealed severe celiac artery stenosis and bilateral renal artery stenosis. Prednisolone was initiated as first-line therapy. The fever resolved, and C-reactive protein levels returned to normal. Although his general condition improved, deterioration of vascular lesions was evident. Celiac artery occlusion, severe right renal artery stenosis, and new superior mesenteric artery stenosis were observed. We decided to use a continuous infusion of lipo-prostaglandin E1 for prevention of branch stenosis of his abdominal aorta. The progression of vascular stenosis was stopped and our patient’s cardiac function gradually improved. Conclusions A differential diagnosis of heart failure with high blood pressure should be considered in babies. The progression of vascular stenosis may be suppressed by lipo-prostaglandin E1.

Background Heart failure (HF) is an important complication in adults with congenital heart disease (CHD), but because only a few studies have focused on acute HF hospitalization in adults with CHD, we study aimed to define the clinical characteristics of such patients and examine the differences in acute HF between adults with CHD and acquired heart disease.Methods and Results:We retrospectively evaluated 50 adults with CHD admitted for treatment of acute HF and compared their data with those from Japanese HF registries. Patient mean age was 37±15 years and 58% were male. In total, 86% of the patients had complex forms of CHD and 62% had undergone corrective surgery, including the Fontan procedure; 66% of patients showed right heart hemodynamic abnormality. In-hospital mortality was 4%, which was comparable to the Japanese HF registries. Survival rate was 93% at 1 year and 75% at 3 years, which was similarly poor to the rates of HF secondary to acquired heart disease. Conclusions We clarified the clinical characteristics of adults with CHD requiring HF hospitalization. Young adults with complex CHD were hospitalized for management of acute right HF. Short-term and mid-term outcomes were similarly poor compared with acute HF secondary to acquired heart disease.

Elevated central venous pressure (CVP), low cardiac output, and mild hypoxia are common early and late after Fontan operations. However, the association of these characteristics with late mortality is unclear. We aimed to elucidate the hemodynamic determinants of mortality after Fontan operation.We evaluated early (group early; 0.5-5years postoperatively, n=387) and late (group late; ≥15years postoperatively, n=161) Fontan hemodynamics that included CVP (mm Hg), cardiac index (CI; L/min per mMortality was higher in group late than in group early (17 vs 11, P.0001). In both groups, higher CVP (hazard ratio [HR]1.46 and 1.38, respectively; P.001-.0001) and lower arterial blood oxygen saturation (HR 1.12, P.001 for both) were associated with increased mortality. Greater end-diastolic volume index (HR per 20: 1.73) and lower EF (HR per 10%: 3.38) were associated with increased mortality only in group early (P.0001 for both). In contrast, only in group late was higher CI associated with increased mortality (HR 2.50, 95% CI 1.30-4.55, P.01). Seven patients in group late with both high CVP (≥14) and CI (≥3.0) had the highest mortality (HR 18.1, 5.55-52.4, P.0001).Elevated CVP and low arterial blood oxygen saturation correlate with mortality in both early and late Fontan survivors. End-diastolic volume index and EF are associated with mortality only in the earlier cohort, whereas interestingly, elevated cardiac output is associated with increased mortality in the later cohort.

The renal resistive index (RRI) reflects non-renal pathophysiology, such as great artery stiffness, haemodynamics and even end-organ damage in patients with hypertension. This study was conducted to clarify the clinical significance of the RRI in Fontan pathophysiology.We measured the RRI in 280 consecutive Fontan patients and 36 healthy controls.The patients exhibited a higher RRI than the controls (0.71±0.07 vs 0.60±0.04, p0.0001). A high central venous pressure, low arterial pressure, greater pulse pressure and low arterial oxygen saturation (SaOThe RRI reflected heart failure severity, hepatorenal function and glucose intolerance, and predicted all-cause mortality in Fontan patients. Therefore, the RRI may be a useful marker of Fontan-associated multiorgan pathophysiology.

Background Pregnancy is one of the biggest concerns for women with long QT syndrome (LQTS). Objectives This study investigated pregnancy-related arrhythmic risk and the efficacy and safety of β-blocker therapy for lethal ventricular arrhythmias in pregnant women with LQTS (LQT-P) and their babies. Methods 136 pregnancies in 76 LQT-P (29±5 years old; 22 LQT1, 36 LQT2, one LQT3, and 17 genotype-unknown) were enrolled. We retrospectively analysed their clinical and electrophysiological characteristics and pregnancy outcomes in the presence (BB group: n=42) or absence of β-blocker therapy (non-BB group: n=94). Results All of the BB group had been diagnosed with LQTS with previous events, whereas 65% of the non-BB group had not been diagnosed at pregnancy. Pregnancy increased heart rate in the non-BB group; however, no significant difference was observed in QT and Tpeak-Tend intervals between the two groups. In the BB group, only two events occurred at postpartum, whereas 12 events occurred in the non-BB group during pregnancy (n=6) or postpartum period (n=6). The frequency of spontaneous abortion did not differ between the two groups. Fetal growth rate and proportion of infants with congenital malformation were similar between the two groups, but premature delivery and low birthweight infants were more common in those taking BB (OR 4.79, 95% CI 1.51 to 15.21 and OR 3.25, 95% CI 1.17 to 9.09, respectively). Conclusions Early diagnosis and β-blocker therapy for high-risk patients with LQTS are important for prevention of cardiac events during pregnancy and the postpartum period, and β-blocker therapy may be tolerated for babies in LQT-P cases.

Systemic right ventricular (RV) failure in patients with congenitally corrected transposition of the great arteries (ccTGA), a major cause of mortality in the long-term follow-up, is usually induced by concomitant severe morphologically tricuspid regurgitation (TR) with/without Ebstein's anomaly or progressive conduction tissue disturbances. However, whether or not myocardial fibrosis is a common cause of systemic RV failure in patients with ccTGA remains unclear. Here, we describe an 82-year-old man who had been diagnosed previously as having uncomplicated ccTGA and situs inversus and recently developed systemic RV failure, which was neither associated with severe TR nor advanced conduction tissue abnormalities. Cardiovascular magnetic resonance (CMR) with delayed-enhancement imaging clearly detected extensive myocardial scars (presumably fibrosis) in the RV wall as well as prominent dilatation, hypertrophy, and systolic dysfunction of the systemic RV. These findings suggest that myocardial fibrosis can cause systemic RV failure in elderly patients with uncomplicated ccTGA despite the absence of severe TR or advanced conduction tissue abnormalities and that CMR may be a useful examination to accurately detect systemic RV failure associated with myocardial fibrosis and to subsequently clarify the prognosis in these patients.

We report multi-organ histopathological changes in a patient with protein-losing enteropathy (PLE) over 12 years after Fontan operation. A 14-year-old boy with right isomerism heart and single ventricle had undergone Fontan procedure at 19 months of age, and PLE was diagnosed at 28 months. He had several episodes of intestinal bleeding and pre-renal failure with elevated creatine, and eventually died of pneumonia. The intrapulmonary small arteries showed medial and intimal thickening resembling pulmonary hypertension. No major ulcerative lesions were found in the small or large intestines. Dilated lymph ducts, one of the characteristic features of PLE, were not seen in mucosal and submucosal areas. Liver cirrhosis was obvious despite little increase in liver enzymes. Histological changes in bilateral kidneys were subtle despite repeated episodes of renal failure. Thus, there may be significant discrepancies between clinical manifestations and multi-organ histological changes in failed Fontan patients.

We report the case of a 12-year-old female patient with a history of four syncopal episodes related to exercise over 2 years and who showed prominent QTc prolongation on electrocardiogram; therefore, she was clinically diagnosed with long QT syndrome type-1. However, genetic analysis did not identify any LQT-related genes but showed a rare missense variant in the cardiac ryanodine receptor gene. From the results of drug-loading tests, administration of oral propranolol was initiated; thereafter, she experienced no syncopal episodes. This is a case report demonstrating the "overlapping clinical features" of long QT syndrome and catecholaminergic polymorphic ventricular tachycardia.

Right ventricle (RV) may determine heart failure (HF) severity in adults with congenital heart disease (ACHD). However, the association of RV properties with clinical profiles remains unclear.To clarify the associations of RV properties with biomarkers, exercise capacity, and unscheduled hospitalization (USH) in postoperative ACHD patients.We evaluated determinants of RV end-diastolic volume (EDVI, ml/m(2)) and pressure (EDP, mmHg) in 260 patients who were divided into 4 groups, i.e., those with RVEDVI100 and EDP≥10 (A, n=49, 19%), those with RVEDVI≥100 with EDP≥10 (B, n=22), those with RVEDVI100 and EDP10 (C, n=134), and those with RVEDVI≥100 and EDP10 (D, n=55). EDVI, EDP, and ejection fraction (EF, %) of the RV were independently associated with the corresponding value of the left ventricle (LV) (p0.0001 for all). Group A had a RV-EF of 53±8 and was defined HF with preserved RV-EF (RV-HFpEF). Younger age, lower platelet count, and elevated plasma γ-glutamyltransferase independently predicted the RV-HFpEF. When the presence of pulmonary hypertension and LV-HFpEF was included in the analysis, these two factors independently predicted the presence of RV-HFpEF (p0.05-0.001). On multivariate analysis, older age, number of surgeries, cardiac index, and RV systolic pressure independently determined peak oxygen uptake (PVO2, p0.05) and RV outflow reconstruction independently predicted USH. The RV-HFpEF group showed the lowest PVO2 and highest incidence of USH among the 4 groups (p0.05).Impaired RV characteristics, especially RV-HFpEF, with liver dysfunction and lower platelet count predicted lower exercise capacity with a poorer prognosis in postoperative ACHD patients.

Objective Exercise training is recommended for its possible favorable effects on Fontan pathophysiology. This study aimed to elucidate the impact of pediatric exercise capacity trajectory, which may mimic the effect of exercise training, on late adult Fontan pathophysiology. Methods Since 1990, 97 Fontan patients had consecutively undergone two serial cardiopulmonary exercise tests (CPX1 and CPX2) during childhood (ages 8 ± 2 and 14 ± 2 years) and one during adulthood (CPX3; age 23 ± 5 years). The changes in peak oxygen uptake (PVO2: % of normal value) from CPX1 to CPX2 (1-dPVO2) and from CPX2 to CPX3 (2-dPVO2) were calculated, and then the patients were divided into four subgroups according the 1-dPVO2 and 2-dPVO2. Results In their adulthood, when compared with groups with negative 1-dPVO2, the central venous pressure, plasma brain natriuretic peptide level, and renal resistive index were lower, whereas liver synthetic function, body fat-free percentage, and PVO2 were higher in those with positive 1-dPVO2 (p Conclusions A positive exercise capacity trajectory during childhood predicts better adult Fontan pathophysiology, including better prognosis. Thus, prescription of exercise could be a promising strategy in the management of pediatric Fontan patients.

Background Cardiac resynchronization therapy (CRT) can result in functional improvement and reduced mortality in patients with medically refractory heart failure. Although CRT is reportedly effective in patients with congenital heart disease (CHD), it is still controversial in patients who have systemic right ventricle. METHODS AND RESULTS: Twenty CHD patients treated with CRT since 2006 were divided into 3 groups based on systemic ventricular (sysV) morphology (7 with left ventricle [sLV], 7 with right ventricle [sRV], and 6 with unbalanced 2 ventricles as a single-ventricular physiology [sBV]). The acute effects of CRT on hemodynamics and sysV function before device implantation was retrospectively evaluated and the chronic (≥6 months) effects of CRT on late outcomes was assessed. In our CHD populations, sysV volume index was reduced from 139±41 to 118±33 ml/m(2)(P=0.04) after CRT, and there was significant improvement in B-type natriuretic peptide levels (from 341±384 to 160±152 pg/ml, P=0.01) and New York Heart Association (NYHA) functional class (from 2.1±0.6 to 1.8±0.7, P=0.02) on a late outcome. The sRV group did not show a late sysV volume reduction despite significant QRS shortening, and an increase of sysV peak dP/dt in the acute study differed from that of other groups. Conclusions CRT improves late hemodynamic and functional status in sLV and sBV CHD patients with a dyssynchronized sysV. However, an acute CRT effect cannot guarantee long-term benefit in sRV patients.

Protein-losing enteropathy (PLE) is a life-threatening complication in patients following the Fontan operation. However, PLE also develops in some patients with congenital heart disease (CHD) after biventricular repair (BVR). This study compared clinical profiles of PLE patients following the Fontan operation with those after BVR. We retrospectively reviewed clinical charts of postoperative CHD patients with PLE. The study population comprised 42 PLE patients (14BVR, 28Fontan). Postoperative follow-up period until onset was significantly shorter in the Fontan group than in the BVR group (14 ± 2 vs. 8 ± 1 years, p = 0.02), while there was no difference in PLE onset age between groups. Furthermore, there were no differences in prevalence of clinically relevant arrhythmias, cardiac output, or central venous pressure between the two groups at PLE onset. Percentage of structural lesions (valve regurgitation and/or stenotic lesions) responsible for development of PLE and ventricular end-diastolic pressure were higher in the BVR group than in the Fontan group (93 vs. 50%, p

ECGs for long-QT syndrome (LQTS) with borderline long-QT intervals can be troublesome because of the absence of a gold standard diagnostic criterion. The approach to diagnose children with borderline long-QT intervals is undefined, and there is no clarity on whether they should be followed up. There is concern that timely diagnosis and treatment may not be achieved for children with true LQTS who are at risk of sudden death. In the international LQTS registry study, the 5-year cumulative probability of aborted cardiac arrest or sudden cardiac death in children and adolescents with a QTc of

BACKGROUND There are no definitive diagnostic criteria or follow-up strategies for long QT syndrome (LQTS) in children with a borderline long QT interval (b-LQT).Methods and Results:We retrospectively evaluated the clinical course, genetic testing results, corrected QT interval (QTc), and LQTS score of 59 school-aged children (5-18 years old) with a b-LQT (400≤QTc

The pathophysiology of congenital heart disease includes aortic dilation and increased stiffness. However, the clinical determinants and significance remain unclear in patients after the Fontan operation.Size and stiffness index (SI) of the ascending and descending aorta (aAO and dAO, respectively) were assessed using angiography in 130 consecutive Fontan patients and 30 age-matched controls. Compared with controls, Fontan patients showed a dilated aAO and smaller dAO (P < 0.0001) with greater SI (3.2 ± 0.7 versus 2.2 ± 0.3 for aAO and 2.7 ± 0.6 versus 2.2 ± 0.3 for dAO, P < 0.0001 for both). aAO was stiffer than dAO (P < 0.0001) and the greater aAO size was independently determined by the presence of pulmonary atresia, older age at Fontan operation, and low arterial oxygen saturation (P < 0.05-0.01). High plasma levels of brain natriuretic peptide (BNP) and glucose were independently associated with aAO SI (P < 0.05-0.01) and the SI ratio of aAO to dAO SI, whereas body mass index, plasma levels of highsensitivity C-reactive protein, and dAO size were independently associated with dAO SI (P < 0.05-0.01). A greater aAO and aAO/dAO ratio predicted an impaired exercise blood pressure response (P < 0.0001). Furthermore, in addition to age at Fontan operation and BNP level, the aAO SI independently predicted a lower peak oxygen uptake (P < 0.05).Fontan patients have a stiffer dilated aAO with rapidly tapering smaller dAO that predicts exercise pathophysiology. In addition to intrinsic aortic structural abnormalities, heart failure severities as well as traditional cardiovascular risk factors are also involved in the aortic structural and functional abnormalities.

The arrhythmogenicity in adult congenital heart disease (ACHD) is mainly related to two factors: congenital abnormalities in the conduction system and acquired unique hemodynamic abnormalities. Aging is an important factor that affects these arrhythmogenicity, mainly resulting in a deterioration of rhythm disturbance. The key to congenital abnormalities in the conduction system is the atrial morphology of both the atria and atrioventricular connection through which the conduction system passes. The acquired unique hemodynamic abnormalities in ACHD are represented by disorders of the subpulmonary right ventricle, systemic right ventricle, Fontan circulation, and unrepaired cyanotic congenital heart disease. Previously reported risk stratification tools for sudden cardiac death in adults with non-congenital heart disease are also relevant in ACHD, especially electrocardiographic findings, but their sensitivities are far from excellent. Disease-specific treatment strategies based on understanding individual arrhythmogenicities are essential for rhythm disturbance in ACHD.

Background The prognostic value of cardiopulmonary exercise testing (CPX) for mortality risk remains controversial in Fontan patients. Purpose Our goal of the present study was to clarify the prognostic value of major CPX variables and the factors determining exercise capacity in a large cohort of Fontan patients. Methods Since 1990, heart rate (HR), oxygen uptake (VO2), and ventilatory equivalent for carbon dioxide production (VE/VCO2) at peak exercise were determined in 335 Fontan patients (18 ± 5 years old), and the CPX variables were compared with the clinical profile and events. Results When compared with 209 controls, peak HR (148 ± 24 bpm), VO2 (27 ± 7 mL/kg/minute, [61 ± 15%]), and VE/VCO2 (40 ± 8 [117 ± 24%]) were markedly impaired in the Fontan patients (P

We treated four postoperative adults with congenital heart disease with severe restrictive hemodynamics (RH), and performed decortication (DC) with the anticipation of some relief of the RH. The catheterizations before DC showed high central venous, and right and left ventricular end-diastolic pressures with "dip-and-plateau" pressure waveforms in the right and left ventricles. Upon myocardial histopathologic examination, moderate myocardial fibrotic change was demonstrated in two of three cases. DC led to decrease in type B natriuretic peptide levels in all cases, resulting in a decline in the central venous, right and left ventricular end-diastolic pressures in three cases. Successful DC-related relief of RH, dilatation of the ventricles with decline in central and end-diastolic pressures, was observed in only one case. Our limited DC-related hemodynamic improvement indicates a complexity of the severe RH, which may represent a unique intractable heart failure pathophysiology in intractable postoperative adult congenital heart disease.

We present a case of a high-risk 19-year-old female with long-QT syndrome (LQTS) with compound mutations. She had a history of aborted cardiac arrest and syncope and had received treatment with propranolol for 15 years. However, because she developed adult-onset asthma we tried to switch propranolol, a nonselective beta-blocker, to beta-1-cardioselective agents, bisoprolol and metoprolol. These resulted in both a markedly prolonged corrected QT interval and the development of LQTS-associated arrhythmias. Eventually, propranolol was reinitiated at a higher dose with the addition of verapamil, and she has had no further cardiac or asthmatic events for 5 years.

Long QT syndrome (LQTS) is caused by several ion channel genes, yet risk of arrhythmic events is not determined solely by the responsible gene pathogenic variants. Female sex after adolescence is associated with a higher risk of arrhythmic events in individuals with congenital LQTS, but the association between sex and genotype-based risk of LQTS is still unclear.To examine the association between sex and location of the LQTS-related pathogenic variant as it pertains to the risk of life-threatening arrhythmias.This retrospective observational study enrolled 1124 genotype-positive patients from 11 Japanese institutions from March 1, 2006, to February 28, 2013. Patients had LQTS type 1 (LQT1), type 2 (LQT2), and type 3 (LQT3) (616 probands and 508 family members), with KCNQ1 (n = 521), KCNH2 (n = 487) and SCN5A (n = 116) genes. Clinical characteristics such as age at the time of diagnosis, sex, family history, cardiac events, and several electrocardiographic measures were collected. Statistical analysis was conducted from January 18 to October 10, 2018.Sex difference in the genotype-specific risk of congenital LQTS.Among the 1124 patients (663 females and 461 males; mean [SD] age, 20 [15] years) no sex difference was observed in risk for arrhythmic events among those younger than 15 years; in contrast, female sex was associated with a higher risk for LQT1 and LQT2 among those older than 15 years. In patients with LQT1, the pathogenic variant of the membrane-spanning site was associated with higher risk of arrhythmic events than was the pathogenic variant of the C-terminus of KCNQ1 (HR, 1.60; 95% CI, 1.19-2.17; P = .002), although this site-specific difference in the incidence of arrhythmic events was observed in female patients only. In patients with LQT2, those with S5-pore-S6 pathogenic variants in KCNH2 had a higher risk of arrhythmic events than did those with others (HR, 1.88; 95% CI, 1.44-2.44; P .001). This site-specific difference in incidence, however, was observed in both sexes. Regardless of the QTc interval, however, female sex itself was associated with a significantly higher risk of arrhythmic events in patients with LQT2 after puberty (106 of 192 [55.2%] vs 19 of 94 [20.2%]; P .001). In patients with LQT3, pathogenic variants in the S5-pore-S6 segment of the Nav1.5 channel were associated with lethal arrhythmic events compared with others (HR, 4.2; 95% CI, 2.09-8.36; P .001), but no sex difference was seen.In this retrospective analysis, pathogenic variants in the pore areas of the channels were associated with higher risk of arrhythmic events than were other variants in each genotype, while sex-associated differences were observed in patients with LQT1 and LQT2 but not in those with LQT3. The findings of this study suggest that risk for cardiac events in LQTS varies according to genotype, variant site, age, and sex.

A uterine tumor, with histological and immunohistochemical features consistent with those of human choriocarcinoma, was identified in a 10-year-old unmated female pot-bellied pig ( Sus scrofa). The tumor showed biphasic proliferation of cytotrophoblast-like cells and syncytiotrophoblast-like cells. Immunohistochemically, the syncytiotrophoblast-like cells were positive for human chorionic gonadotropin, and both types of cells were positive for cytokeratin and negative for vimentin, octamer-binding transcription factor 4, and α-fetoprotein. Because syncytiotrophoblasts are absent in the normal porcine placenta, the tumor was diagnosed as a choriocarcinoma-like tumor.

Background We investigated the long-term outcomes of anatomic repair for congenitally corrected transposition of great arteries (ccTGA) and its variant associated with left ventricular outflow tract obstruction (LVOTO) and ventricular septal defect (VSD). Methods From 1987 to 2011, 47 patients (27 with pulmonary atresia and 20 with pulmonary stenosis) with ccTGA and its variant associated with LVOTO and VSD underwent anatomic repair. The mean operative age was 5.5 ± 3.7 years old (range, 1.6 to 21.3). The preoperative right ventricular end-diastolic volume was 133% ± 31% (81 to 222) of their normal size. The atrial switch procedure was Mustard in 31 patients and Senning in 16, with the latter used in all from 2002. Results The mean follow-up period was 11.6 ± 7.3 years (maximum, 22.7). The VSD was concomitantly enlarged in 4 patients and Damus-Kaye-Stansel (DKS) anastomosis was added in 9 patients with pulmonary stenosis and restrictive VSD. The overall survival rate at 20 years was 70.2% and no mortality has been observed in 21 consecutive patients since 1997. No patient required reoperation for the postoperative systemic ventricular outflow tract obstruction. A surgical heart block developed in 1 patient (2.1%) who underwent concomitant VSD enlargement. None of the patients developed a moderate or greater aortic or neo-aortic regurgitation. Conclusions Recent outcomes after anatomic repair for congenitally corrected transposition of great arteries associated with LVOTO and VSD were excellent. For patients with pulmonary stenosis and restrictive VSD, additional DKS anastomosis seems to be an effective approach to avoid postoperative systemic ventricular outflow tract obstruction and surgical heart block.

OBJECTIVES: Determinant risk factors for developing protein losing enteropathy (PLE), including haemodynamics, remain unclear in patients after the Fontan operation. METHODS: Our purpose was to characterize the serial PLE haemodynamics before and after the onset and to determine the risk factors based on the cardiac catheterization-based analysis. RESULTS: Of 354 Fontan survivors who had undergone postoperative cardiac catheterizations, we experienced 26 PLE patients during the follow-up. Non-left ventricular morphology systemic ventricle, functional one-lung pulmonary circulation and an early postoperative high central venous pressure (CVP) were associated with the PLE onset and the high CVP (odds ratio (OR) = 1.19 per 1 mmHg, 95% confidence interval (CI) 1.04–1.37, especially ≥12 mmHg, OR = 3.09, 95% CI 1.25–7.64, P< 0.05 for both) and one-lung pulmonary circulation (OR = 10.0–10.5, P< 0.001) independently predicted the onset. At the time of the PLE onset, a Fontan route stenosis/obstruction, arrhythmias, ventricular dysfunction/heart failure and pulmonary arterio-venous fistulae were demonstrated in 10 (38%), 8 (31%), 4 (15%) and 3 (12%) patients, respectively. When compared with 56 excellent Fontan survivors, the high CVP, ventricular end-diastolic pressure, and pulmonary artery resistance, and the low arterial oxygen saturation, systemic artery pressure, and ventricular ejection fraction characterized the pre-PLE Fontan haemodynamics (P< 0.05–0.0001). However, the following intensive treatments reduced the CVP, systemic artery pressure and cardiac output (P< 0.05–0.01), resulting in haemodynamics no different from those of the excellent survivors, except for the low systemic pressure (P< 0.0001). CONCLUSIONS: The pre-PLE haemodynamics was characterized by several impaired haemodynamics, while those after PLE only by a low systemic pressure. A high early postoperative CVP was the only haemodynamic predictor for a new onset of PLE. Strict selective criteria for the operation and strategies to eliminate CVP-raising factors are mandatory to prevent a new onset of PLE.

BACKGROUND Although the survival rate for repaired Tetralogy of Fallot (TOF) is dramatically improving, anatomical and functional residua and sequelae followed by arrhythmias and sudden death are still challenging issues to be resolved. Reoperation can reduce the incidence of arrhythmias and sudden death, but there is no consensus on the indications of reoperation for patients with TOF, especially in Japan. METHODS AND RESULTS A cross-sectional questionnaire survey of reoperation indications in patients with TOF was performed through a Japanese multicenter study. The questionnaire, which focused on the number of repaired TOF patients aged >15 years old, reoperation indications and management, was sent to the institutions belonging to Japanese Society for Adult Congenital Heart Disease. In total, 41.5% (78/188) of the institutions replied. The total number of repaired TOF patients was 4,010, and sudden cardiac death was observed in 45.236/4,010 (5.9%) experienced reoperation. Pulmonary stenosis (32%) and pulmonary regurgitation (29%) were the most common reasons for reoperation. There were only 2 implantable cardioverter defibrillator or resynchronization therapy defibrillator implantations. The physiological/anatomical indications of reoperation differed among the hospitals. CONCLUSIONS Approximately 1.1% of patients suffered sudden death and 6% of repaired TOF patients had reoperation. The indications of reoperation, however, varied among the institutions. Therefore, detailed information for each case of sudden death or reoperation should be collected and analyzed in order to establish guidelines for reoperation.

Persistent tachycardia in pediatric patients after congenital heart surgery further deteriorates their hemodynamic condition, and may become fatal. Therefore, immediate control of the tachycardia is mandatory in these patients. For this purpose, quick-acting, short-acting, titratable intravenous agents are required. However, there are no agents with such characteristics among the drugs approved for control of pediatric arrhythmias in Japan, and thus novel and effective medications for these patients are awaited. Landiolol, an ultrashort-acting β-blocker, was approved in 2013 for tachyarrhythmias in adult patients with heart failure. However, its efficacy and safety in pediatric patients remain unclear. The aim of this prospective, multicenter, open-label phase IIb/III study is to investigate the efficacy and safety of landiolol in pediatric patients with tachyarrhythmias as well as heart failure.Eligible patients are aged ≥ 3 months and15 years, and have tachyarrhythmia (atrial fibrillation, atrial flutter, supraventricular tachycardia) as well as heart failure. The primary endpoint of the study is ≥20% reduction from baseline heart rate or return to normal sinus rhythm within 2h after starting intravenous administration of landiolol. Patients will receive intravenous infusion of landiolol, starting at 1μg/kg/min. The dose will be increased by 1μg/kg/min every 15-20min until the tachycardia rate has decreased by20% or tachycardia has terminated, and the dose will then be maintained or further increased depending on the patient's condition. The study was started in April 2015 and will end within a few years.The study was designed and designated the "HEARTFUL study" in the hope of establishing a basis for control of HEART rate in inFant and child tachyarrhythmia Using Landiolol in children with heart failure.

BACKGROUND The long-term prognosis of cardiac ryanodine receptor (RyR2) positive catecholaminergic polymorphic ventricular tachycardia (CPVT) patients after initiation of medical therapy has not been well investigated. This study aimed to assess the recurrence of fatal cardiac event after initiation of medical therapy inRyR2-positive CPVT patients. METHODS AND RESULTS Thirty-fourRyR2-positive CPVT patients with a history of cardiac events were enrolled. All patients had medical treatment initiated after the first symptom or diagnosis. Exercise stress tests (ESTs) were performed to evaluate the efficacy of the medical therapy. Even after the initiation of medical therapy, high-risk ventricular arrhythmias (VAs), including premature ventricular contraction couplets, bigeminy, and ventricular tachycardia, were still induced in the majority of patients (80.6%). During 7.4 years of follow-up after the diagnosis, 7 of the 34 (20.6%) patients developed fatal cardiac events. Among those 7 patients, 6 (85.7%) were not compliant with either exercise restriction or medication therapy at the time of the events. CONCLUSIONS Even after initiation of medical treatment, high-risk VAs were induced during EST in mostRyR2-positive CPVT patients. Most fatal recurrent cardiac events occurred in patients who were noncompliant with exercise restriction and/or medical therapy. Medical management including strict exercise restriction should be emphasized to prevent recurrent cardiac event in mostRyR2-positive CPVT patients. (Circ J 2016; 80: 1907-1915).

We describe of a unique pattern of cardiac dyssynchrony in a patient with a biventricular physiology and systemic right ventricle (RV): the interventricular dyssynchrony due to a contraction delay between the left ventricle and RV. In the present case, the cineangiography and intracardiac electrocardiography of the RV did not reveal intraventricular dyssynchrony of the RV, but revealed interventricular dyssynchrony. In addition, the pressure curves of the ventricles exhibited time phase differences between the two ventricles. The cardiac resynchronization therapy determining the pacing lead positions based on the idea of interventricular dyssynchrony induced reverse cardiac remodeling in this patient with systemic RV dysfunction.

Background Some patients with congenital complete atrioventricular block (CCAVB) develop dilated cardiomyopathy (DCM) after pacemaker implantation (PMI). We evaluated the relationship between pacing site and DCM incidence. Methods and results We retrospectively evaluated 38 patients with CCAVB; 8 (25%) of 32 patients who had PMI developed DCM/heart failure death (HFD) after PMI, although none of the 6 patients without PMI showed DCM/HFD. All DCM/HFD occurred within 50 months of PMI. Among the 32 patients with PMI, the DCM/HFD incidence was 55% (6/11) for right ventricular inlet (RVI), 18% (2/11) for RV apex (RVA), and 0% for left ventricle (LV) (P=0.013). At the endpoint, the LV ejection fraction and septal-to-posterior wall motion delay of patients with LV pacing were better than those for patients with other pacing sites. Among the 8 DCM/HFD patients, 2 in whom the pacing site was changed from RVI to LV apex or in whom therapy was upgraded to cardiac resynchronization remained alive with no heart failure symptoms, whereas the other 6 died of heart failure. Conclusions A total of 25% of the patients who underwent PMI because of CCAVB, but none in the non-PMI group, developed DCM/HFD. DCM/HFD incidence was higher in patients with RVI pacing. Ventricular dyssynchrony related to pacing site may be one cause of DCM in patients with CCAVB. (Circ J 2016; 80: 1251-1258).

Background Cardiorenal interactions adversely impact the prognosis in heart failure patients an effect which crucially involves increased central venous pressure (CVP). However, it is unclear whether the same pathophysiology operates in adults with congenital heart disease (CHD). Purpose The present study was designed to assess cardiorenal interactions in adults with CHD after biventricular repair. Methods and Results We measured the kidney length (KL, cm/m) and renal resistive index (RI) in 77 consecutive patients and 30 controls. We also measured hemodynamics, plasma B-type natriuretic peptide level, 24-hour creatinine clearance, and peak oxygen uptake in each patient. The CVP correlated with the KL (r = 0.44, P

Background: Supraventricular and ventricular tachyarrhythmias (SVT, VT) are major concerns after repair of tetralogy of Fallot (TOF). This study evaluated the impact of comprehensive treatment, including hemodynamic interventions such as surgery, catheter-based intervention and pacemaker implantation (PMI), on tachyarrhythmia in repaired TOF patients. Methods and Results: Of 66 repaired TOF patients with tachyarrhythmia (age at onset, 23±11 years), 29 patients had sustained SVT, 21 had sustained or non-sustained VT, and 16 had both (SVT+VT). Successful treatment with catheter-directed ablation and/or anti-arrhythmic drugs (AADs) alone was achieved in 31 (69%) and partially achieved in 6 (13%) of 45 patients. Surgery, catheter-based intervention, and/or PMI were performed in 21 (32%) of 66 patients and resulted in complete control of the arrhythmia in 8 (38%) and partial control in 7 (33%) of these 21 patients, 20 (95%) of whom were receiving AADs. Patients with successfully controlled tachyarrhythmia in response to catheter ablation and/or AADs without hemodynamic intervention had a significantly higher probability of absence of sinus node dysfunction (odds ratio [OR], 23.2; 95% confidence interval [CI], 1.8–845.2; P=0.02) and lone intra-atrial reentrant tachycardia (OR, 12.4; 95% CI: 1.3–278.7; P=0.03). Conclusions: Hemodynamic interventions resulted in an improvement in outcomes in repaired TOF patients with tachyarrhythmia. To effectively manage intractable tachyarrhythmia with hemodynamic abnormalities, it is essential to understand hemodynamics and consider hemodynamic intervention. (Circ J 2012; 76: 2855–2862)

Background Abnormal cardiac autonomic nervous activity (CANA) is not uncommon in postoperative patients with congenital heart disease (CHD). Methods and results We attempted to clarify the prognostic value of the CANA variables in postoperative CHD patients and prospectively evaluated the CANA variables in 292 consecutive biventricular and 91 Fontan repair patients. The CANA variables included the heart rate variability, arterial baroreflex sensitivity (BRS), washout ratio of the myocardial metaiodobenzylguanidine scintigraphy, and plasma norepinephrine level. With a follow-up of 10 ± 2 years, 98 total events that required hospitalization, including 13 deaths and 48 unscheduled cardiac events (UCEs), occurred. In all the CHD patients, all the CANA indices predicted the total events and UCEs. Of those, the NE level (p = 0.0004) and BRS (p = 0.0373) predicted the mortality. In a multivariate analysis, the BRS was an independent CANA-predictor for the total events (p = 0.007). In the biventricular patients, the plasma NE level, heart rate variability, and BRS predicted the total events and UCEs and the BRS was the only independent CANA-predictor for the total events (p = 0.0329). In the Fontan patients, the plasma NE level was the only predictor for the UCEs (p = 0.0242) and no other CANA variables were independent predictors of the total events or UCEs. Conclusions All CANA variables, especially the BRS, were useful predictors for future clinical events in biventricular CHD patients, whereas no CANA variables, except for the plasma NE level, predicted future clinical events in the Fontan patients.

gradually increasing the number of medications and doses. Oral amiodarone was administered for atrial arrhythmia. Subsequently, her cardiothoracic ratio improved from 70% to 65%. We performed cardiac catheterization and an electrophysiology study (EPS) to evaluate hemodynamics and arrhythmogenic substrates before surgical treatment. In cardiac catheterization, right ventricular (RV) end-diastolic volume index improved, from 255 to 128 ml/m 2 after optimal medical treatment. EPS 1 An EPS was performed with the patient under general anesthesia. For this intervention, a 4-mm-tip 7-F quadripolar catheter (Navistar, Biosense-Webster, Diamond Bar, California) was used for mapping and ablation. A steerable multipolar circular mapping catheter (Lasso, BiosenseWebster) was placed at the junction between the left superior caval veins and the left side of the atrium to serve as a reference for mapping. First, we mapped the area around the common AV ring to determine the location of the AV node during continuous atrial pacing. Two separate His bundle electrograms were recorded at the dorsal and inferior portions of the common AV ring (Figure 1). We detected an anterior AV node based on recording at the dorsal site of the AV ring, while a posterior AV node was recorded at the inferior site of the AV ring. During atrial pacing, 2 different QRS complexes were observed dependent on the pacing rate (Figure 2A). These QRS complexes did not show preexcitation, but QRS duration was prolonged dependent on the pacing rate. Figure 2A indicates 3 types of QRS complexes: (a) was recorded at rest and with lead I positive; (b) was recorded during atrial pacing, which was relatively rapid as compared with that at rest; and (c) was recorded during transient mechanical conduction block of the anterior AV node via catheter manipulation. Thus, QRS complexes at rest represented a fusion beat between the anterior and posterior AV nodes. No ventriculoatrial conduction was seen during ventricular pacing, even with isoproterenol infusion. Next, we initiated AT using atrial burst stimulation. The QRS complexes during AT (atrial tachycardia) (AT cycle length 450