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Background: Although atrial fibrillation (AF) and coronary artery disease (CAD) are increasing in prevalence in Japan, real-world data regarding clinical outcomes in Japanese AF patients with CAD are limited.Methods: The SAKURA AF Registry is a prospective multi-center registry created to investigate outcomes of oral anticoagulant (OAC) use in Japanese AF patients. A study was conducted involving 3237 enrollees from 63 Tokyo-area institutions who were followed up for a median of 39.3 months. Clinical adverse events were compared between the patients accompanied with (n = 312) and without CAD (n = 2925).Results: The incidence of cardiovascular events and all-cause mortality rates were significantly higher among patients with CAD than among those without CAD (5.98 vs 2.52 events per 100 patient-years, respectively, p < 0.001; 3.27 vs 1.94 deaths per 100 patient-years, respectively, p = 0.012), but there was no difference in strokes/transient ischemic attacks or systemic embolisms (1.70 vs 1.34). After a multivariate adjustment, CAD remained a risk factor for cardiovascular events (hazard ratio [HR] = 1.57, 95% confidence interval [CI] = 1.08-2.25, p = 0.018). Among CAD patients, the propensity score-adjusted risk for major bleeding was significantly decreased among direct oral anticoagulant (DOAC) users in comparison to that among warfarin users (HR = 0.29, 95% CI = 0.07-0.94, p = 0.04), but other adverse clinical events did not differ significantly between these two groups.Conclusions: CAD did not appear to be a major determinant of strokes/TIAs, major bleeding, or all-cause mortality, but appeared to increase the risk of cardiovascular events in Japanese AF patients. The risk of major bleeding in CAD patients appeared to decrease when a DOAC rather than warfarin was administered. The data suggested that patients with AF and concomitant CAD require careful management and follow-up to reduce cardiovascular risks, and DOACs may be a better choice over warfarin when considering the risk of major bleeding. [ABSTRACT FROM AUTHOR]

Background Although a ventriculoatrial interval (VAI) of ≤70 ms is used to distinguish atrioventricular nodal reentrant tachycardia from orthodromic atrioventricular reciprocating tachycardia (AVRT), a VAI of ≤70 ms is sometimes observed in cases of AVRT. The study aimed to evaluate the short VAI that is seen in AVRT and to understand its underlying mechanism. Methods Electrophysiologic studies of 46 consecutive patients with AVRT involving an accessory pathway (AP) were examined retrospectively. Results AP was right sided in seven patients and left sided in 39. A VAI (interval from QRS onset to the earliest intracardiac atrial electrogram recorded by any mapping catheter during AVRT) ≤70 ms during AVRT (short VAI) was observed in eight patients: six with a left lateral AP and two with a left posteroseptal AP. During AVRT involving a left-sided AP, the QRS-V interval (from the earliest QRS onset to the local ventricular electrogram at a site which showed earliest atrial electrogram recorded from the coronary sinus catheter) was significantly shorter (37 ± 7 ms vs 54 ± 13 ms, P = 0.001) and supernormal conduction (QRS duration or the QRS-V interval shortening by ≥10 ms during AVRT) was more frequently seen (63% vs 6%, P = 0.02) in the short VAI group than in the normal VAI group. Furthermore, these parameters were shown to be determinants for short VAI. Conclusions A short VAI is sometimes observed during AVRT involving a left-sided AP. The short VAI may be caused by rapid propagation or supernormal conduction between the proximal Purkinje-muscle junction and basal left ventricular myocardium. [ABSTRACT FROM AUTHOR]

LA Wall Thickness, LA Electrogram, and Dormant PV Conduction Introduction Atrial remodeling plays a key role in development of the substrate for atrial fibrillation (AF). Whether the wall thicknesses of the left atrium (LA) and pulmonary vein (PV)-LA junction affect remodeling and AF ablation is unknown. We investigated the relationship between wall thicknesses, electrogram characteristics, and adenosine triphosphate (ATP)-provoked dormant PV conduction as they pertain to AF. Methods In 50 patients with AF and 25 patients without AF, wall thicknesses of the LA and PV-LA junction were measured on 320-slice computed tomography images. For the AF patients, NavX-based voltage maps generated during sinus rhythm were obtained, and ATP-provoked dormant PV conduction after PV isolation was evaluated. Results Walls of the LA and PV-LA junction were significantly thicker in the AF patients than in the control patients (1.83 ± 0.29 mm vs. 1.59 ± 0.28 mm, respectively; P = 0.0010; and 0.88 ± 0.14 mm vs. 0.65 ± 0.11 mm, P<0.0001, respectively). Wall thickness at the PV-LA junction was independently associated with AF (β = 0.40, P = 0.0002). In AF patients, the walls of the PV-LA junction showed stepwise thickening across bipolar voltages indicative of severe (bipolar voltage <33rd percentile) to moderate (33rd-66th percentiles) to mild fibrosis/scarring (≥66th percentile). Walls of the PV-LA junction with dormant PV conduction were significantly thicker than those without it (0.94 ± 0.19 mm vs. 0.86 ± 0.21 mm, respectively; P = 0.0025). Conclusions Together, the association between thickened PV-LA junction walls and AF and the increased bipolar voltage suggests that such wall thickening increases PV electrical activities, leading to initiation and maintenance of AF and perhaps to ATP-provoked dormant PV conduction. [ABSTRACT FROM AUTHOR]

Anatomic Distortion of 3D Mapping. Background: Although catheter tip-tissue contact is known as a reliable basis for mapping and ablation of atrial fibrillation (AF), the effects of different mapping methods on 3-dimensional (3D) map configuration remain unknown. Methods and Results: Twenty AF patients underwent C arto-based 3D ultrasound (US) evaluation. Left atrium (LA)/pulmonary vein (PV) geometry was constructed with the 3D US system. The resulting geometry was compared to geometries created with a fast electroanatomical mapping (FAM) algorithm and 3D US merged with computed tomography (merged 3D US-CT). The 3D US-derived LA volumes were smaller than the FAM- and merged 3D US-CT-derived volumes (75 ± 21 cm3 vs 120 ± 20 cm3 and 125 ± 25 cm3, P < 0.0001 for both). Differences in anatomic PV orifice fiducials between 3D US- and FAM- and merged 3D US-CT-derived geometries were 6.0 (interquartile range 0-9.3) mm and 4.1 (0-7.0) mm, respectively. Extensive encircling PV isolation guided by 3D US images with real-time 2D intracardiac echocardiography-based visualization of catheter tip-tissue contact generated ablation point (n = 983) drop-out at 1.9 ± 3.8 mm beyond the surface of the 3D US-derived LA/PV geometry. However, these same points were located 1.5 ± 5.4 and 0.4 ± 4.1 mm below the FAM- and merged 3D US-CT-derived surfaces. Conclusions: Different mapping methods yield different 3D geometries. When AF ablation is guided by 3D US-derived images, ablation points fall beyond the 3D US surface but below the FAM- or merged 3D US-CT-derived surface. Our data reveal anatomic distortion of 3D images, providing important information for improving the safety and efficacy of 3D mapping-guided AF ablation. (J Cardiovasc Electrophysiol, Vol. 24, pp. 259-266, March 2013) [ABSTRACT FROM AUTHOR]

MMP-2 Predicts the Outcome of AF Ablation. Introduction: Although catheter ablation can effectively eliminate atrial fibrillation (AF), the progression of atrial remodeling increases the risk of recurrence. AF is associated with inflammation and subsequent myocardial fibrosis. We therefore examined the possibility of determining the postablation prognosis of patients with AF using biomarkers of inflammation and collagen turnover. Methods and Results: Subjects were 50 patients who underwent catheter ablation for drug-resistant AF. High-sensitivity CRP (hs-CRP), interleukin (IL)-6, carboxyl-terminal telopeptide of collagen type I (ICTP), metalloproteinase (MMP)-2, tissue inhibitor of MMP-2 (TIMP-2), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) were measured before and 2.2 ± 0.8 months after ablation. During the follow-up period of 14.0 (4.7-20.9) months, AF recurred in 21 of the 50 patients. Recurrence was associated with an MMP-2 elevation (860.3 ± 120.8 ng/mL vs 687.0 ± 122.5 ng/mL [in patients without recurrence]), ICTP elevation (3.2 ± 1.1 ng/mL vs 2.7 ± 0.6 ng/mL), BNP elevation, greater body mass index, nonparoxysmal AF, and hypertension (P < 0.05 for all). Serum MMP-2 and nonparoxysmal AF were shown by multivariate analysis to be independent predictors for postablation AF recurrence. Overall, hs-CRP, IL-6, ANP, and BNP levels decreased, and MMP-2, TIMP-2, and ICTP levels increased 2 months after ablation. Conclusions: Our finding that markers of collagen turnover were elevated in patients who experienced AF recurrence after ablation indicate that these markers might be a useful guide to identify a subgroup of AF patients who require extensive ablation strategies. A 2-month postablation elevation in collagen turnover markers suggests that the wound healing process persists for that long after ablation. (J Cardiovasc Electrophysiol, Vol. 22, pp. 987-993, September 2011) [ABSTRACT FROM AUTHOR]

Background: Werner's syndrome, a rare autosomal recessive disorder, is characterized by features of premature aging. Seventy-five percent of the alleles of Japanese patients with Werner's syndrome have one of three major mutations.Objective: To determine the genotype of a patient with Werner's syndrome.Methods: We diagnosed Werner's syndrome in a 47-year-old Japanese man who had juvenile cataracts, skin sclerosis and hyperpigmentation of the feet, a high-pitched voice, characteristic bird-like appearance of the face with a beak-shaped nose, thinning of the skin over the whole body and hyperkeratoses on the soles of the feet, hyperlipidemia, and diabetes mellitus. None of his immediate family had entered into a consanguineous marriage. He had undergone surgery to treat duodenal perforation. We screened his family for three major mutations (mutations 1, 4, 6) in the WRN gene by polymerase chain reaction-restriction fragment length polymorphism. Automated DNA sequencing fluorescence-labeled dideoxy terminators proceeded for abnormally migrating bands.Results: The patient and his mother had mutation 1 (nonsense mutation) in one chromosome. Although mutations 4 and 6 were undetectable, screening for mutation 4 revealed an abnormally migrating band. Consequently, we discovered a novel 4-bp deletion in exon 25 only in the patient. This mutation was not detected in any other family member.Conclusion: This is the first description of a patient with Werner's syndrome who has a compound heterozygote of mutation 1 and a novel deletion mutation. [ABSTRACT FROM AUTHOR]

Aims: Malnutrition is common and associated with worse clinical outcomes in patients with heart failure (HF). The Controlling Nutritional Status (CONUT) score is an integrated index for evaluating diverse aspects of the complex mechanism of malnutrition. However, the relationship between the severity of malnutrition assessed by the CONUT score and clinical outcomes of HF patients receiving cardiac resynchronisation therapy (CRT) has not been fully clarified., Methods: Clinical records of 263 patients who underwent pacemaker or defibrillator implantation for CRT between March 2003 and October 2020 were retrospectively evaluated. The CONUT score was calculated from laboratory data obtained before CRT device implantation. Patients were divided into three groups: normal nutrition (CONUT scores 0-1, n=58), mild malnutrition (CONUT scores 2-4, n=132) and moderate or severe malnutrition (CONUT scores 5-12, n=73). The primary endpoint was all-cause mortality., Results: The moderate or severe malnutrition group had a lower body mass index, more advanced New York Heart Association functional class, higher Clinical Frailty Scale score, lower levels of haemoglobin and higher levels of N-terminal probrain natriuretic peptide (all p<0.05). In the moderate or severe malnutrition group, the CRT response rate was significantly lower than for the other two groups (p=0.001). During a median follow-up period of 31 (10-67) months, 103 (39.1%) patients died. Kaplan-Meier analysis revealed that the moderate or severe malnutrition group had a significantly higher mortality rate (log-rank p<0.001). A higher CONUT score and CONUT score ≥5 remained significantly associated with all-cause mortality after adjusting for previously reported clinically relevant factors and the conventional risk score (VALID-CRT risk score) (all p<0.05)., Conclusions: A higher CONUT score before CRT device implantation was strongly associated with HF severity, frailty, lower CRT response rate and subsequent long-term all-cause mortality., Competing Interests: Competing interests: TN received lecture fees from Abbott Medical and Medtronic Japan, and YO belongs to the endowed departments of Boston Scientific Japan, Abbott Medical Japan, Japan Lifeline, Medtronic Japan and Nihon Kohden., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: The burden or benefit of anticoagulation treatment affects patient satisfaction, which may in turn affect the adherence to the treatment and subsequent outcomes. Thus, we hypothesized that the patient satisfaction with direct oral anticoagulants (DOACs) may influence the clinical outcome in patients with atrial fibrillation (AF)., Methods and Results: We investigated the clinical outcomes among 719 DOAC users (age 71.9 ± 9.1 years, 184 females, and 449 persistent AF) enrolled in the SAKURA AF Registry who completed a satisfaction questionnaire with anticoagulation therapy by means of the Anti-Clot Treatment Scale (ACTS), which included 12-item burden and 3-item benefit scales. During a 41.8-month-follow-up, a stroke/systemic embolism (SE) occurred in 27 patients (3.8%) and major bleeding events in 25 (3.5%). A univariate Cox regression analysis revealed that an older age, persistent AF, higher CHA 2 DS 2 -VASc score, no history of AF ablation, lower creatinine clearance, and lower ACTS benefit scores were significantly associated with an increased risk of a stroke/SE, but not with major bleeding events. A low benefit score remained an independent predictor of a stroke/SE even after a multivariate adjustment. The ACTS burden scores were not associated with any clinical events., Conclusions: We found a strong association between a low benefit satisfaction and increased stroke risk. We should follow patients carefully to educate them on treatment importance for patients unsatisfied with the benefits of DOACs for stroke prevention., (Copyright © 2020 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)

A prolonged QRS duration (QRSd) is promising for a response to cardiac resynchronization therapy (CRT). The variation in human body sizes may affect the QRSd. We hypothesized that conduction disturbances may exist in Japanese even with a narrow (< 130 ms)-QRS complex; such patients could be CRT candidates. We investigated the relationships between QRSd and sex and body size in Japanese. We retrospectively analyzed the values of 338 patients without heart failure (HF) (controls) and 199 CRT patients: 12-lead electrocardiographically determined QRSd, left ventricular diastolic and systolic diameters (LVDd and LVDs), body surface area (BSA), body mass index (BMI), and LVEF. We investigated the relationships between the QRSd and BSA, BMI, and LVD. The men's and women's BSA values were 1.74 m 2 and 1.48 m 2 in the controls (p < 0.0001), and 1.70 m 2 and 1.41 m 2 in the CRT patients (p < 0.0001). The men's and women's QRSd values were 96.1 ms and 87.4 ms in the controls (p < 0.0001), and 147.8 ms and 143.9 ms in the CRT group (p = 0.4633). In the controls, all body size and LVD variables were positively associated with QRSd. The CRT response rate did not differ significantly among narrow-, mid-, and wide-QRS groups (83.6%, 91.3%, 92.4%). An analysis of the ROC curve provided a QRS cutoff value of 114 ms for CRT responder. The QRSd appears to depend somewhat on body size in patients without HF. The CRT response rate was better than reported values even in patients with a narrow QRSd (< 130 ms). When patients are considered for CRT, a QRSd > 130 ms may not be necessary, and the current JCS guidelines appear to be appropriate.

Atrial fibrillation (AF) and heart failure (HF) often coexist. The aims of this study were to explore the factors associated with the serum levels of N-terminal pro-brain natriuretic peptide (NT-proBNP), and the association between prognosis and a history of HF or the serum NT-proBNP level in Japanese patients with AF.The present sub-study was based on the SAKURA AF Registry, a Japanese multicenter observational registry that included 3267 AF patients (median follow-up period: 39 months). All the patients were receiving warfarin or any of four direct oral anticoagulants. Serum NT-proBNP levels were available for 2417 patients, and the median value was 508 (interquartile range 202-1095) pg/mL at the time of enrollment. Log NT-proBNP was associated with non-paroxysmal AF, creatinine clearance > 60 mL/minute, history of HF and ischemic heart disease, antiarrhythmic drug use, anemia, being elderly female, and history of AF ablation. The relative risk of adverse clinical events, except major bleeding, was significantly higher in the highest NT-proBNP quartile as compared to the lowest quartile (adjusted hazard ratios: 2.87 for death, 2.39 for stroke), but a history of HF was associated only with a higher incidence of all-cause death.Concomitant HF was associated with a higher mortality, but the high NT-proBNP was associated with higher mortality and stroke events. In Japanese AF patients receiving anticoagulant treatment, high serum NT-proBNP levels predict the risk for both stroke events and deaths, and intensive follow-up is needed in such patients.

Background: Relations between characteristics and outcomes of patients in Japan with atrial fibrillation (AF) and the type of medical facility providing their outpatient care are unclear., Methods and Results: We compared patient characteristics and outcomes between 2 university hospitals (n=1178), 20 general hospitals (n=1308), and 41 private clinics (n=751) (follow-up: 39.3 months) in the prospective SAKURA AF Registry. Private clinic patients were significantly older than university hospital and general hospital patients (73.4±9.2 vs. 70.3±9.8 and 72.6±8.9 years; p<0.001), and these patients' CHADS 2 scores were significantly lower than general hospital, but higher than university hospital patients (1.8±1.1 vs. 2.0±1.2 and 1.6±1.1; p<0.001). The Kaplan-Meier incidences of stroke/systemic embolism (SE) (1.72 vs. 1.58 vs. 0.84 events per 100 patient-years; p=0.120), a cardiovascular event (4.09 vs. 2.44 vs. 1.40; p<0.001), and death were higher (2.39 vs. 2.21 vs. 1.24; p=0.015) for university and general hospital patients than for private clinic patients; the incidences of major bleeding were equivalent (1.78 vs. 1.33 vs. 1.16; p=0.273). After multivariate adjustments, this trend persisted., Conclusions: Adverse clinical events at small to large hospitals appear to be higher than those at private clinics, suggesting that careful attention for preventing stroke/SE and cardiovascular events should be paid to patients at a university or general hospital., (Copyright © 2019 Japanese College of Cardiology. All rights reserved.)

Direct-acting oral anticoagulants (DOACs) are widely used in aged Japanese patients with atrial fibrillation (AF), but outcome data for such patients are limited. We compared outcomes between 1895 (58.5%) patients aged < 75 years (non-elderly), 1078 (33.3%) 75-84 years (elderly) and 264 (8.2%) ≥ 85 years (very elderly) enrolled in a prospective multicenter registry. Kaplan-Meier analysis (median follow-up: 39.3 months) revealed a significantly high incidence of stroke/systemic embolism (SE) among the very elderly relative to that among the non-elderly or elderly (3.2 vs. 1.2 and 1.5 events per 100 patient-years, p < 0.001). Major bleeding in the non-elderly group was significantly infrequent relative to that among the elderly or very elderly group (1.1 vs. 1.6 vs. 1.8 events, p = 0.033). After multivariate adjustment, the stroke/SE incidence was comparable between DOAC and warfarin users, regardless of age, but major bleeding decreased significantly among very elderly DOAC users (adjusted HR 0.220, 95% CI 0.042-0.920). The greater increasing incidence of stroke/SE than major bleeding as patients age suggests that stroke prevention should outweigh the bleeding risk when anticoagulants are being considered for aged patients. Our data indicated that DOACs can be a therapeutic option for stroke prevention in very elderly patients.

Pulmonary vein isolation (PVI) of atrial fibrillation (AF) can reduce the AF burden and, potentially, reduce the long-term risk of strokes and death. However, it remains unclear whether anticoagulants can be stopped after PVI because of post-ablation AF recurrence in some patients. This study aimed to investigate the discontinuation rate of anticoagulants and long-term incidence of strokes after PVI.We enrolled 512 consecutive Japanese patients with AF (mean age, 63.4 ± 10.4 years; 123 women; 234 with non-paroxysmal AF; CHADS2 score/CHA2DS2-VASC score, 1.32 ± 1.12/2.21 ± 1.54) who underwent PVI between 2012 and 2015. During a 28.0 ± 17.1 -month follow-up, anticoagulants were terminated in 230 (44.9%) of the 512 patients, AF recurred in 200 (39.1%), and 10 (1.95%) suffered from a stroke. Death occurred in 5 (0.98%) patients. Although the incidence of strokes, by a Kaplan-Meier analysis, was similar, the incidence of death was lower (Hazard ratio 0.37, 95% confidence interval 0.12-0.93, P = 0.041) in the AF ablation group than the control group without ablation after 1:1 propensity score matching (the control data was derived from 2,986 patients in the SAKURA AF Registry, a large-cohort AF registry).Anticoagulants were discontinued in nearly half the patients who underwent AF ablation; of these, 39.1% experienced AF recurrences, 1.95% suffered from strokes, and 0.98% died, but the risk of death after AF ablation appeared to be lower than that in a propensity score-matched control group without ablation during long-term follow-up.

Defibrillation threshold (DFT) testing is performed routinely in patients undergoing implantable cardioverter-defibrillator (ICD) implantation to verify the ability of the ICD to terminate ventricular fibrillation (VF). However, neither the efficacy nor the safety of DFT testing has been proven; thus, the necessity of such testing is controversial. We conducted a retrospective study of the efficacy of DFT testing, particularly with respect to long-term outcomes of ICD implantation.The study included 150 patients (125 men, 25 women, aged 59.0 ± 17.6 years) who underwent ICD or cardiac resynchronization therapy defibrillator implantation, with (n = 73) or without (n = 77) intraoperative DFT testing, between June 1996 and September 2007. VF was induced by delivery of a T-wave shock, and a 20-25-J shock was then delivered. If the 20-25-J shock failed to terminate VF, 30 J was delivered. We assessed whether undersensed VF events occurred during DFT testing and/or during patient follow-up and checked for any association between undersensing and delayed shock delivery. During DFT testing, fine VF was sensed, and shocks were delivered in a timely manner. Nevertheless, 2 patients in the DFT testing group died from VF within 3 years after device implantation.DFT testing, in comparison to non-DFT testing, appeared to have no influence on the long-term outcomes of our patients, suggesting that DFT testing at the time of ICD implantation is limited.

Background: Sick sinus syndrome (SSS) is a common arrhythmia often associated with aging or organic heart diseases but may also occur in a familial form with a variable mode of inheritance. Despite the identification of causative genes, including cardiac Na channel (SCN5A), the pathogenesis and molecular epidemiology of familial SSS remain undetermined primarily because of its rarity., Methods and Results: We genetically screened 48 members of 15 SSS families for mutations in several candidate genes and determined the functional properties of mutant Na channels using whole-cell patch clamping. We identified 6 SCN5A mutations including a compound heterozygous mutation. Heterologously expressed mutant Na channels showed loss-of-function properties of reduced or no Na current density in conjunction with gating modulations. Among 19 family members with SCN5A mutations, QT prolongation and Brugada syndrome were associated in 4 and 2 individuals, respectively. Age of onset in probands carrying SCN5A mutations was significantly less (mean±SE, 12.4±4.6 years; n=5) than in SCN5A-negative probands (47.0±4.6 years; n=10; P<0.001) or nonfamilial SSS (74.3±0.4 years; n=538; P<0.001). Meta-analysis of SSS probands carrying SCN5A mutations (n=29) indicated profound male predominance (79.3%) resembling Brugada syndrome but with a considerably earlier age of onset (20.9±3.4 years)., Conclusions: The notable pathophysiological overlap between familial SSS and Na channelopathy indicates that familial SSS with SCN5A mutations may represent a subset of cardiac Na channelopathy with strong male predominance and early clinical manifestations., (© 2014 American Heart Association, Inc.)

Background: Recently, we and others reported that early repolarization (J wave) is associated with idiopathic ventricular fibrillation. However, its clinical and genetic characteristics are unclear., Methods and Results: This study included 50 patients (44 men; age, 45 ± 17 years) with idiopathic ventricular fibrillation associated with early repolarization, and 250 age- and sex-matched healthy controls. All of the patients had experienced arrhythmia events, and 8 (16%) had a family history of sudden death. Ventricular fibrillation was inducible by programmed electric stimulation in 15 of 29 patients (52%). The heart rate was slower and the PR interval and QRS duration were longer in patients with idiopathic ventricular fibrillation than in controls. We identified nonsynonymous variants in SCN5A (resulting in A226D, L846R, and R367H) in 3 unrelated patients. These variants occur at residues that are highly conserved across mammals. His-ventricular interval was prolonged in all of the patients carrying an SCN5A mutation. Sodium channel blocker challenge resulted in an augmentation of early repolarization or development of ventricular fibrillation in all of 3 patients, but none was diagnosed with Brugada syndrome. In heterologous expression studies, all of the mutant channels failed to generate any currents. Immunostaining revealed a trafficking defect in A226D channels and normal trafficking in R367H and L846R channels., Conclusions: We found reductions in heart rate and cardiac conduction and loss-of-function mutations in SCN5A in patients with idiopathic ventricular fibrillation associated with early repolarization. These findings support the hypothesis that decreased sodium current enhances ventricular fibrillation susceptibility.