Late life-threatening arrhythmia in patients with Brugada syndrome: Results from long-term follow-up in a large Japanese cohort

INTRODUCTION

Most patients with Brugada syndrome (BrS) are first diagnosed in their 40s, with sudden cardiac death (SCD) often occurring in their 50s. Ventricular fibrillation (VF) may occur in some patients with BrS despite having been asymptomatic for a long period. This study aimed to assess the incidence and risk factors for late life-threatening arrhythmias in patients with BrS.

METHODS

Patients with BrS (n = 523; mean age, 51 ± 13 years; male, n = 497) were enrolled. The risk of late life-threatening arrhythmia was investigated in 225 patients who had experienced no cardiac events (CEs: SCD or ventricular tachyarrhythmia) for at least 10 years after study enrollment. The incidence of CEs during the follow-up period was examined.

RESULTS

During the follow-up of the 523 patients, 59 (11%) experienced CEs. The annual incidences of CEs were 2.87%, 0.77%, and 0.09% from study enrollment to 3, 3-10, and after 10 years, respectively. Among 225 patients who had experienced no CEs for at least 10 years after enrollment, four patients (1.8%) subsequently experienced CEs. Kaplan-Meier analysis revealed significant differences in the incidence of late CEs between patients with and without a history of symptoms (p = .032). The positive and negative predictive values of late CEs for the programmed electrical stimulation (PES) test were 2.9% and 100%, respectively.

CONCLUSION

Our results suggest that patients with BrS who are asymptomatic and have no ventricular tachycardia/VF inducibility by PES are at extremely low risk of experiencing late life-threatening arrhythmias.

J wave dynamicity during coronary angiography and intracoronary acetylcholine administration

BACKGROUND

J-waves may be observed during coronary angiography (CAG) or intracoronary acetylcholine (ACh) administration, but their significance is unknown.

METHODS

Forty-nine patients, 59.1 ± 11.5 years old and 59% male, were studied on suspicion of vasospastic angina, and J wave dynamicity was compared between CAG and Ach administration.

RESULTS

Diagnostic (≥0.1 mV) or nondiagnostic (<0.1 mV) J waves in 9 and 3 patients, respectively, were augmented, and J waves were newly observed in 2 patients during CAG and Ach administration. Similar changes in the J-wave amplitude were observed: from 0.10 ± 0.09 mV to 0.20 ± 0.15 mV (p < .002) and from 0.10 ± 0.10 mV to 0.20 ± 0.16 mV (p < .001) during CAG and Ach administration, respectively. J waves were located in the inferior leads and changed only during the right coronary interventions. In the remaining 35 patients, J waves were absent before and during the coronary interventions. Augmentation of J waves was found when the RR interval was shortened in some patients. Injection of anoxic media into the coronary artery might induce a conduction delay from myocardial ischemia that manifests as augmentation or new occurrence of J waves.

CONCLUSIONS

Both CAG and intracoronary Ach administration affected J waves similarly in the same individuals. A myocardial ischemia-induced conduction delay may be responsible for the changes in J waves, but further studies are needed.

Registry for Evaluating Healthy Life Expectancy and Long-Term Outcomes after Catheter Ablation of Atrial Fibrillation in the Very Elderly (REHEALTH AF) study: rationale and design of a prospective, multicentre, observational, comparative study

INTRODUCTION

Data are lacking on the extent to which patients with non-valvular atrial fibrillation (AF) who are aged ≥80 years benefit from ablation treatment. The question pertains especially to patients' postablation quality of life (QoL) and long-term clinical outcomes.

METHODS AND ANALYSIS

We are initiating a prospective, registry-based, multicentre observational study that will include patients aged ≥80 years with non-valvular AF who choose to undergo treatment by catheter ablation and, for comparison, such patients who do not choose to undergo ablation (either according to their physician's advice or their own preference). Study subjects are to be enrolled from 52 participant hospitals and three clinics located throughout Japan from 1 June 2022 to 31 December 2023, and each will be followed up for 1 year. The planned sample size is 660, comprising 220 ablation group patients and 440 non-ablation group patients. The primary endpoint will be the composite incidence of stroke/transient ischaemic attack (TIA) or systemic embolism (SE), another cardiovascular event, major bleeding and/or death from any cause. Other clinical events such as postablation AF recurrence, a fall or bone fracture will be recorded. We will collect standard clinical background information plus each patient's Clinical Frailty Scale score, AF-related symptoms, QoL (Five-Level Version of EQ-5D) scores, Mini-Mental State Examination (optional) score and laboratory test results, including measures of nutritional status, on entry into the study and 1 year later, and serial changes in symptoms and QoL will also be secondary endpoints. Propensity score matching will be performed to account for covariates that could affect study results.

ETHICS AND DISSEMINATION

The study conforms to the Declaration of Helsinki and the Ethical Guidelines for Clinical Studies issued by the Ministry of Health, Labour and Welfare, Japan. Results of the study will be published in one or more peer-reviewed journals.

TRIAL REGISTRATION NUMBER

UMIN000047023.

Clinical characteristics and electrophysiologic properties of SCN5A variants in fever-induced Brugada syndrome

BACKGROUND

Brugada syndrome (BrS) is a severe inherited arrhythmia syndrome that can be unmasked by fever.

METHODS

A multicentre clinical analysis was performed in 261 patients diagnosed with fever-induced BrS, including 198 (75.9%) and 27 (10.3%) patients who received next-generation genetic sequencing and epicardial arrhythmogenic substrate (AS) mapping, respectively.

FINDINGS

In fever-induced BrS patients, pathogenic or likely pathogenic (P/LP) SCN5A variant carriers developed fever-induced BrS at a younger age, and more often in females and those of Caucasian descent. They exhibited significant electrophysical abnormalities, including a larger epicardial AS area, and more prolonged abnormal epicardial electrograms. During a median follow-up of 50.5 months (quartiles 32.5-81.5 months) after the diagnosis, major cardiac events (MCE) occurred in 27 (14.4%) patients. Patients with P/LP SCN5A variants had a higher ratio of MCE compared with the rest. Additionally, history of syncope, QRS duration, and Tpe interval could also predict an increased risk for future MCE according to univariate analysis. Multivariate analysis indicated that only P/LP SCN5A variants were independent significant predictors of MCE. Computational structural modelling showed that most variants are destabilizing, suggesting that Nav1.5 structure destabilization caused by SCN5A missense variants may contribute to fever-induced BrS.

INTERPRETATION

In our cohort, P/LP SCN5A variant carriers with fever-induced BrS are more prevalent among patients of Caucasian descent, females, and younger patients. These patients exhibit aggressive electrophysiological abnormalities and worse outcome, which warrants closer monitoring and more urgent management of fever.

FUNDING

The current work was supported by the National Natural Science Foundation Project of China (Nos. 82270332 & 81670304), The Fundamental Research Funds for the Central Universities of China - Independent Research Project of Wuhan University (No. 2042022kf1217) from China; the National Institutes of Health of USA [NIH R56 (HL47678), NIH R01 (HL138103), and NIH R01 (HL152201)], the W. W. Smith Charitable Trust and the Wistar and Martha Morris Fund, Sharpe-Strumia Research Foundation, the American Heart Association Postdoctoral Fellowship (20POST35220002) from United States; the Netherlands CardioVascular Research Initiative: the Dutch Heart Foundation, Dutch Federation of University Medical Centers, the Netherlands Organization for Health Research and Development, and the Royal Netherlands Academy of Sciences (PREDICT2) from the Netherlands.

Targeted deep sequencing analyses of long QT syndrome in a Japanese population

Long QT syndrome (LQTS) is one of the most common inherited arrhythmias and multiple genes have been reported as causative. Presently, genetic diagnosis for LQTS patients is becoming widespread and contributing to implementation of therapies. However, causative genetic mutations cannot be detected in about 20% of patients. To elucidate additional genetic mutations in LQTS, we performed deep-sequencing of previously reported 15 causative and 85 candidate genes for this disorder in 556 Japanese LQTS patients. We performed in-silico filtering of the sequencing data and found 48 novel variants in 33 genes of 53 cases. These variants were predicted to be damaging to coding proteins or to alter the binding affinity of several transcription factors. Notably, we found that most of the LQTS-related variants in the RYR2 gene were in the large cytoplasmic domain of the N-terminus side. They might be useful for screening of LQTS patients who had no known genetic factors. In addition, when the mechanisms of these variants in the development of LQTS are revealed, it will be useful for early diagnosis, risk stratification, and selection of treatment.

Incidence and Implications of J waves Observed During Coronary Angiography

J waves may be observed during coronary angiography (CAG), but they have not been fully studied. We investigated the characteristics of J waves in 100 consecutive patients during CAG. The patients and their family members had no history of cardiac arrest. Approximately 60% of patients had ischemic heart disease, previous myocardial infarction, or angina pectoris, but at the time of this study, the right coronary artery was shown to be normal or patent after stenting. Electrocardiogram was serially recorded to monitor J waves and alteration of the QRS complex during CAG. In 12 patients (12%), J waves (0.249 ± 0.074 mV) newly appeared during right CAG, and in another 13 patients (13%), preexisting J waves increased from 0.155 ± 0.060 mV to 0.233 ± 0.133 mV during CAG. Left CAG induced no J waves or augmentation of J waves. Distinct alterations were observed in the QRS complex during CAG of both coronary arteries. Mechanistically, myocardial ischemia induced by contrast medium was considered to result in a local conduction delay, and when it occurred in the inferior wall, the site of the late activation of the ventricle, the conduction delay was manifested as J waves. In conclusion, J waves were confirmed to emerge or increase during angiography of the right but not the left coronary artery. Myocardial ischemia induced by contrast medium caused a local conduction delay that was manifested as J waves in the inferior wall, the site of the late activation of the ventricle.

Distinct Features of Probands With Early Repolarization and Brugada Syndromes Carrying SCN5A Pathogenic Variants

BACKGROUND

Two major forms of inherited J-wave syndrome (JWS) are recognized: early repolarization syndrome (ERS) and Brugada syndrome (BrS).

OBJECTIVES

This study sought to assess the distinct features between patients with ERS and BrS carrying pathogenic variants in SCN5A.

METHODS

Clinical evaluation and next-generation sequencing were performed in 262 probands with BrS and 104 with ERS. Nav1.5 and Kv4.3 channels were studied with the use of patch-clamp techniques. A computational model was used to investigate the protein structure.

RESULTS

The SCN5A+ yield in ERS was significantly lower than in BrS (9.62% vs 22.90%; P = 0.004). Patients diagnosed with ERS displayed shorter QRS and QTc than patients with BrS. More than 2 pathogenic SCN5A variants were found in 5 probands. These patients displayed longer PR intervals and QRS duration and experienced more major arrhythmia events (MAE) compared with those carrying only a single pathogenic variant. SCN5A-L1412F, detected in a fever-induced ERS patient, led to total loss of function, destabilized the Nav1.5 structure, and showed a dominant-negative effect, which was accentuated during a febrile state. ERS-related SCN5A-G452C did not alter the inward sodium current (INa) when SCN5A was expressed alone, but when coexpressed with KCND3 it reduced peak INa by 44.52% and increased the transient outward potassium current (Ito) by 106.81%.

CONCLUSIONS

These findings point to SCN5A as a major susceptibility gene in ERS as much as it is in BrS, whereas the lower SCN5A+ ratio in ERS indicates the difference in underlying electrophysiology. These findings also identify the first case of fever-induced ERS and demonstrate a critical role of Ito in JWS and a higher risk for MAE in JWS probands carrying multiple pathogenic variants in SCN5A.

Thyroid Hormone Plays an Important Role in Cardiac Function: From Bench to Bedside

Thyroid hormones (THs) are synthesized in the thyroid gland, and they circulate in the blood to regulate cells, tissues, and organs in the body. In particular, they exert several effects on the cardiovascular system. It is well known that THs raise the heart rate and cardiac contractility, improve the systolic and diastolic function of the heart, and decrease systemic vascular resistance. In the past 30 years, some researchers have studied the molecular pathways that mediate the role of TH in the cardiovascular system, to better understand its mechanisms of action. Two types of mechanisms, which are genomic and non-genomic pathways, underlie the effects of THs on cardiomyocytes. In this review, we summarize the current knowledge of the action of THs in the cardiac function, the clinical manifestation and parameters of their hemodynamics, and treatment principles for patients with hyperthyroid- or hypothyroid-associated heart disease. We also describe the cardiovascular drugs that induce thyroid dysfunction and explain the mechanism underlying the thyroid toxicity of amiodarone, which is considered the most effective antiarrhythmic agent. Finally, we discuss the recent reports on the involvement of thyroid hormones in the regulation of myocardial regeneration and metabolism in the adult heart.

Novel variant of the glycerol-3-phosphate dehydrogenase-1 Like (GPD1-L) gene in Japanese Brugada syndrome patients

Background

The incidence of Brugada syndrome (BrS) varies among racial groups. Several studies reported Glycerol-3-Phosphate Dehydrogenase 1-Like (GPD1-L) gene is associated with BrS. However, most of these studies were reported from Western countries, so the evidence about GPD1-L mutation is limited especially among Asian BrS patients. This study aimed to search for rare variants in GPD1-L among Japanese BrS patients and to investigate the pathogenicity.

Method

We performed whole-exome sequencing for patients with Brugada type 1 ECG pattern from Japanese multicenter BrS cohort consisting of SCN5A-negative BrS probands (n=288) and controls (n=372). We conducted patch-clamp study in human embryonic kidney (HEK) 293 cells cotransfected with the wild-type sodium channel (SCN5A) and wild-type or mutant GPD1-L expression plasmid.

Results

We identified a rare variant in GPD1-L, p.D262N (c.784g&gt;a) in 2 of 288 BrS probands, which was not identified in 372 controls. The minor allele frequency of the variant is 0.0014% in the Genome Aggregation Database. One proband was a 49-year-old man and the other was 34-year-old man who both developed a ventricular fibrillation. ECGs of both probands showed Brugada Type 1 pattern after administration of the pilsicainide. In functional study, coexpression of D262N GPD1-L with SCN5A in HEK293 cells significantly reduced inward sodium currents compared with wild-type GPD1-L. Additionally, inward sodium currents with D262N were similar to those with A280V GPD1-L, which was associated with BrS in previous reports (Figure). Also, several pathogenicity prediction programs, such as SIFT (score: 0.031) and PolyPhen2 (score: 0.937) predicted deleterious effects of GPD1-L D262N.

Conclusion

We identified a rare variant in GPD1-L at the rate of 0.7% in Japanese BrS patients without SCN5A mutations. GPD1-L, p.D262N reduces inward sodium currents and may be a novel susceptible variant for BrS in the Japanese population.

Funding Acknowledgement

Type of funding sources: None. Figure 1. Current–voltage curve

Successful Leadless Pacemaker Implantation in an Elderly Patient With Dextrocardia and Situs Inversus

Leadless pacemaker is indicated in patients with symptomatic bradycardia as an alternative therapy when transvenous pacemaker implantation is considered difficult or at high risk. The experience of implanting leadless pacemaker in patients with dextrocardia and situs inversus is limited. A 94-year-old male was transferred to our hospital due to advanced atrio-ventricular block with episode of syncope. Chest radiograph and computed tomography revealed dextrocardia with situs inversus. Emergency cardiac catheterization was performed and a temporary pacemaker was inserted, but the patient removed it due to delirium. So, a leadless pacemaker was implanted to him. Shorter time of bed-rest after the implantation and shorter hospital stay would be beneficial of implanting a leadless pacemaker. Precise anatomical evaluation would be important to perform implantation efficiently and safely.

Functionally validated SCN5A variants allow interpretation of pathogenicity and prediction of lethal events in Brugada syndrome

AIMS

The prognostic value of genetic variants for predicting lethal arrhythmic events (LAEs) in Brugada syndrome (BrS) remains controversial. We investigated whether the functional curation of SCN5A variations improves prognostic predictability.

METHODS AND RESULTS

Using a heterologous expression system and whole-cell patch clamping, we functionally characterized 22 variants of unknown significance (VUSs) among 55 SCN5A mutations previously curated using in silico prediction algorithms in the Japanese BrS registry (n = 415). According to the loss-of-function (LOF) properties, SCN5A mutation carriers (n = 60) were divided into two groups: LOF-SCN5A mutations and non-LOF SCN5A variations. Functionally proven LOF-SCN5A mutation carriers (n = 45) showed significantly severer electrocardiographic conduction abnormalities and worse prognosis associated with earlier manifestations of LAEs (7.9%/year) than in silico algorithm-predicted SCN5A carriers (5.1%/year) or all BrS probands (2.5%/year). Notably, non-LOF SCN5A variation carriers (n = 15) exhibited no LAEs during the follow-up period. Multivariate analysis demonstrated that only LOF-SCN5A mutations and a history of aborted cardiac arrest were significant predictors of LAEs. Gene-based association studies using whole-exome sequencing data on another independent SCN5A mutation-negative BrS cohort (n = 288) showed no significant enrichment of rare variants in 16 985 genes including 22 non-SCN5A BrS-associated genes as compared with controls (n = 372). Furthermore, rare variations of non-SCN5A BrS-associated genes did not affect LAE-free survival curves.

CONCLUSION

In vitro functional validation is key to classifying the pathogenicity of SCN5A VUSs and for risk stratification of genetic predictors of LAEs. Functionally proven LOF-SCN5A mutations are genetic burdens of sudden death in BrS, but evidence for other BrS-associated genes is elusive.

Electrocardiographic manifestations in a large right-sided pneumothorax

Background

Pneumothorax is an extrapulmonary air accumulation within the pleural space between the lung and chest wall. Once pneumothorax acquires tension physiology, it turns into a potentially lethal condition requiring prompt surgical intervention. Common symptoms are chest pain and dyspnea; hence an electrocardiogram (ECG) is often performed in emergent settings. However, early diagnosis of pneumothorax remains challenging since chest pain and dyspnea are common symptomatology in various life-threatening emergencies, often leading to overlooked or delayed diagnosis. While the majority of left-sided pneumothorax-related ECG abnormalities have been reported, right-sided pneumothorax-related ECG abnormalities remain elucidated.

Case presentation

A 51-year-old man presented to the emergency department with acute-onset chest pain and dyspnea. Upon initial examination, the patient had a blood pressure of 98/68 mmHg, tachycardia of 100 beats/min, tachypnea of 28 breaths/min, and oxygen saturation of 94% on ambient air. Chest auscultation revealed decreased breath sounds on the right side. ECG revealed sinus tachycardia, phasic voltage variation of QRS complexes in V4–6, P-pulmonale, and vertical P-wave axis. Chest radiographs and computed tomography (CT) scans confirmed a large right-sided pneumothorax. The patient’s symptoms, all the ECG abnormalities, and increased heart rate on the initial presentation resolved following an emergent tube thoracostomy. Moreover, we found that these ECG abnormalities consisted of two independent factors: respiratory components and the diaphragm level. Besides, CT scans demonstrated the large bullae with a maximum diameter of 46 × 49 mm in the right lung apex. Finally, the patient showed complete recovery with a thoracoscopic bullectomy.

Conclusions

Herein, we describe a case of a large right-sided primary spontaneous pneumothorax with characteristic ECG findings that resolved following re-expansion of the lung. Our case may shed new light on the mechanisms underlying ECG abnormalities associated with a large right-sided pneumothorax. Moreover, ECG manifestations may provide useful information to suspect a large pneumothorax or tension pneumothorax in emergent settings where ECGs are performed on patients with acute chest pain and dyspnea.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01470-1.

Discrepancy in recognition of symptom burden among patients with atrial fibrillation

Our aim was to investigate the variability in physician recognition of atrial fibrillation (AF)-related symptoms, which greatly contributes to the management of AF patients. METHODS AND RESULTS: A total of 1493 newly-referredAF patients (67 ± 11 y/o, 1057 men) consecutively registered in an outpatient-based Japanese multicenter database (KiCS-AF) from September 2012 to December 2016 were analyzed. Self-reportedAF symptom burden was assessed via symptom and daily activities domains within the Atrial Fibrillation Effect on QualiTy-of-life (AFEQT) questionnaire. Physician symptom under-recognition (UR) was defined as no subjective complaints recorded in the medical records despite AFEQT score of <80; and physician's apparent over-recognition (OvR) was defined as documentation of subjective complaints despite total AFEQT score of ≥80. There was poor agreement between patient-reported and physicians-estimated symptom burden (kappa 0.28, 95% CI 0.23 to 0.33). In the logistic regression analysis, age> 75 (odds ratio [OR], 1.72; 95% confidence interval [CI], 1.13-2.62), male sex (OR, 1.82; 95% CI, 1.22-2.74), and persistent/permanent AF (OR 2.54/3.36; CI, 1.63-3.99/1.91-5.89, respectively) were predictors of UR. Conversely, heart failure (OR, 2.46; 95% CI, 1.44-4.25) and treatment in an ablation facility (OR, 1.43; 95% CI, 1.02-2.02) were associated with greater odds of OvR in addition to age, sex, and type of AF. CONCLUSIONS: Discordance in recognition of AF symptom burden by physicians was frequent in AF patients seen in outpatient management and involved both patient- and physician-related factors.

Mexiletine shortens the QT interval in a pedigree of KCNH2 related long QT syndrome

A 23-year-old female had been suffering from recurrent syncopal episodes during sleep since her childhood. She had a family history of sudden death and her QTc interval was remarkably prolonged to 537 ms A Holter ECG revealed torsade de pointes, corresponding to syncope. She was started on mexiletine and her QTc interval shortened. Her symptoms were controlled after β-blockers and Ca-blockers were added. A genetic analysis with a next generation sequencer identified a frameshift mutation at the C terminus of the KCNH2 gene. Here we present a type 2 long QT syndrome case in which mexiletine was effective.

Association of Genetic and Clinical Aspects of Congenital Long QT Syndrome With Life-Threatening Arrhythmias in Japanese Patients

Importance

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.

Objective

To examine the association between sex and location of the LQTS-related pathogenic variant as it pertains to the risk of life-threatening arrhythmias.

Design, Setting, and Participants

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.

Main Outcomes and Measures

Sex difference in the genotype-specific risk of congenital LQTS.

Results

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.

Conclusions and Relevance

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.

P5636Lipid core burden index is associated with microcirculatory dysfunction even in stable angina pectoris; Insights from intracoronary electrocardiography

Background

Combined near-infrared spectroscopy (NIRS) and intravascular ultrasonography (NIRS-IVSU) is an imaging modality for precise detection of lipid core burden. Distal embolization has been reported to be a mechanism of microcirculatory dysfunction (MD) caused by percutaneous coronary intervention (PCI). High lipid core burden index at the 4-mm maximal segment (max-LCBI(4)) has been associated with the cardiovascular event. A max-LCBI(4) of >500 was related to perioperative myocardial infarction even in patients with stable angina pectoris. Unlike 12-lead electrocardiography, intracoronary electrocardiography can detect slight ischemia during PCI, maybe indicating distal embolization. However, whether PCI for culprit plaques with a low max-LCBI(4) can cause MD is unclear. Thus, this study aimed to investigate whether plaques with low max-LCBI(4) influence MD, using intracoronary electrocardiography.

Methods

Forty consecutive patients who underwent PCI for stable angina pectoris due to stenosis of the proximal segment of the left anterior descending artery were enrolled. NIRS-IVUS was performed in all the patients before predilatation to evaluate for the culprit lesion. Total LCBI and max-LCBI(4) within the culprit lesion were measured. On gray-scale IVUS, vessel area, lumen area, plaque volume, and percent (%) plaque volume were measured. Intracoronary electrography was performed at stent implantation to measure the time from the initiation of S-T segment elevation from the isoelectric baseline to the return of S-T segment to the isoelectric baseline after the deflation of the stent balloon, which was defined as the severity of the MD. The patients were divided into 2 groups according to median max-LCBI(4) (high [n=20] and low LCBI groups [n=20]).

Results

The mean age was 72±6 years. Of the patients, 80% were male. The mean overall max-LCBI(4) was 140±100. Max-LCBI(4) was significantly higher in the high-LCBI(4) group than in the low-LCBI(4) group. No significant differences in age, body mass index, American College of Cardiology and American Heart Association classification, and low-density lipoprotein level were found between the groups, as well as in the gray-scale IVUS parameters such as %plaque volume. The mean time from the initiation of the initiation of S-T segment elevation from the isoelectric baseline to the return of S-T segment to the isoelectric baseline was significantly longer in the high LCBI group than in the low LCBI group (33 vs 12 sec, P=0.01) despite no change in the S-T segment on 12-lead electrography. The S-T segment elevation occurred only during stent balloon inflation and returned to the isoelectric baseline immediately after stent balloon deflation at a max-LCBI(4) of 0. The no-reflow and slow flow phenomena were not observed.

Conclusion

Even low max-LCBI(4) on NIRS-IVUS was associated with MD during PCI in patients with stable angina pectoris.

A high BNP level predicts an improvement in exercise tolerance after a successful catheter ablation of persistent atrial fibrillation

INTRODUCTION

Restoration of sinus rhythm (SR) by catheter ablation (CA) of atrial fibrillation (AF) improves exercise tolerance. However, it is still unclear what characteristics of patients are contributing to an improvement in exercise tolerance after CA of AF without heart failure.

METHODS AND RESULTS

This study consisted of 51 consecutive patients with persistent or long-standing persistent AF without heart failure who were restored to SR for over 6 months by a successful CA. Exercise tolerance was evaluated by cardiopulmonary exercise testing before and 3 and 6 months after CA. The clinical characteristics contributing to an improvement in exercise tolerance was elucidated. The peak oxygen uptake (VO₂ )% significantly increased from 101.4 ± 20.3% to 110.9 ± 19.9% 3 months after the CA (P < .001). The improvement rate in the peak VO₂ % exhibited a positive correlation to the baseline brain natriuretic peptide (BNP; ρ = 0.39, P < .01), but not to the age, AF duration, left ventricular ejection fraction, or left atrial size. The linear regression analysis revealed that the baseline BNP was an independent predictor of an improvement in the peak VO₂ % (coefficients = 0.32; 95% confidence interval = 0.08, 0.54; P = .01). The peak VO₂ % improved significantly in the patients whose baseline BNP level was greater than 100 pg/mL, compared to the others (P < .01). These favorable findings were also observed 6 months after the CA.

CONCLUSION

Elimination of persistent AF by CA was associated with an improvement in exercise tolerance. This was particularly true in patients with high BNP values at baseline.

Conduction Delay-Induced J-Wave Augmentation in Patients With Coronary Heart Disease

Electrocardiogram records were surveyed for the presence of an atrial premature beat (APB) and J waves in patients with coronary heart disease and patients with noncardiac diseases. The prevalence and response of J waves to sudden shortening of the RR interval on the conducted APB were determined and compared between the 2 patients groups. The change in the QRS complexes on the APB was also determined. Among 17,013 patients, 243 patients who underwent percutaneous coronary intervention for acute myocardial infarction or angina pectoris had an APB, and J waves were observed in 16 patients (6.6%). In an additional 729 patients with noncardiac diseases and APB, 19 patients showed J waves (2.6%; p = 0.010). The clinical features were almost similar between the ischemic and nonischemic groups. J waves were located more often in inferior and high lateral leads in the ischemic group. When the RR interval shortened from 942 ± 228 to 621 ± 175 ms and 869 ± 158 to 570 ± 118 ms at baseline and in the conducted APB (p<0.001 for both), the J-wave amplitude increased from 0.16 ± 0.04 to 0.19 ± 0.06 mV (p<0.001) and 0.21 ± 0.07 to 0.24 ± 0.08 mV (p = 0.010) in the ischemic and nonischemic groups, respectively. J waves in patients with chronic coronary heart disease and in patients with noncardiac diseases were augmented at short RR intervals together with distinct changes in the QRS complexes, and an augmentation of J waves at short RR interval may represent a conduction delay.

"J waves" induced after short coupling intervals: a manifestations of latent depolarization abnormality?

Aims

To confirm the presence of tachycardia-induced slur or notch in the terminal portion of the QRS complexes in a general patient population.

Methods and results

A tachycardia-induced J wave was defined as a slur or notch in the terminal portion of the QRS complexes newly induced at short RR intervals during atrial premature contractions (APCs) or atrial electrical stimulation in the electrophysiological study (EPS). Twenty-three out of 2000 patients with general diseases were involved. All patients with aborted sudden cardiac death, ventricular fibrillation or a family history of sudden cardiac death were excluded. The mean age was 72 ± 9 years, and 11 patients were male (47.8%). When the RR interval was shortened from 821 ± 142 ms to 464 ± 52 ms in the conducted APCs (P < 0.0001), J waves became diagnostic (0.02 ± 0.03 mV to 0.20 ± 0.07 mV, P < 0.0001). J waves were confined to the inferior leads in 22 (95.7%) patients and were notched in 11 (47.8%) and slurred in 12 (52.2%) patients. The induction of J waves was accompanied by visible changes of the QRS morphology. When the post-APC RR interval was prolonged to 992 ± 305 ms (P = 0.0154 vs. baseline), the J waves were similar to baseline levels. During the EPS, J wave induction was confirmed during atrial stimulation. There were no characteristic clinical or ECG features in the patients with tachycardia-induced J waves.

Conclusions

J waves can be newly induced by short RR intervals in a general patient population, and a conduction delay is the likely mechanism causing such J waves.

Importance of the vein of Marshall involvement in mitral isthmus ablation

BACKGROUND

Epicardiac conduction via the vein of Marshall (VOM) can bypass the mitral isthmus (MI) line, making MI ablation difficult. This study aimed to assess the contribution of the VOM in achieving MI conduction block.

METHODS

This study included 143 consecutive patients with nonparoxysmal atrial fibrillation who underwent initial MI ablation. They were retrospectively classified into two groups, a VOM-guided group (n = 28) and a conventional group (n = 115), according to the use of a 2-Fr electrode catheter inserted in the VOM. The acute success rate of achieving MI block and the ablation data were assessed. When the bidirectional block was verified exclusively in the VOM or coronary sinus (CS) electrodes, we defined it as a pseudo MI block. In the VOM-guided group, we ascertained the complete MI block, verified both in the VOM and CS electrodes.

RESULTS

In the VOM-guided group, the pseudoblock was observed in 33.3% of the patients during MI ablation. With significantly less radiofrequency energy (19 322.6 ± 11 352.8 vs 25 389.3 ± 19 951.9, P = 0.04), we achieved a similar level of success rate in MI ablation in the VOM-guided group (96.4% vs 91.3%, P = 0.36). Notably, after achieving complete MI block, atrial burst pacing induced two perimitral flutters in the VOM-guided group, which were successfully terminated by the additional radiofrequency application.

CONCLUSIONS

Assessment of electrical conduction through the VOM could clarify the existence of a pseudo MI conduction block. However, the existence of a slow conduction through the MI could be detected only after induction of perimitral atrial tachycardia with atrial programmed stimulation.

Assessment of Sex Differences in the Initial Symptom Burden, Applied Treatment Strategy, and Quality of Life in Japanese Patients With Atrial Fibrillation

IMPORTANCE

The clinical characteristics and outcomes of women and men with atrial fibrillation (AF) are reported to be different. However, whether sex-related differences extend to patients' symptom burden and perceived quality of life (QOL) or the management pattern of AF has been rarely studied, particularly in Asian countries.

OBJECTIVE

To assess the differences in symptoms, treatment, and QOL between Japanese female and male patients with AF.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study using data from the multicenter outpatient registry Keio Interhospital Cardiovascular Studies-Atrial Fibrillation (KiCS-AF), which collects information regarding health status and the treatment of patients with newly diagnosed or referred AF. One-year follow-up data were available for 1534 patients at 11 referral centers in the Tokyo, Japan, area who were enrolled between September 2012 and December 2015. All data available up to the 1-year follow-up examination through July 31, 2017, were included.

MAIN OUTCOMES AND MEASURES

Sex, symptoms, AF treatment, and QOL as determined by Atrial Fibrillation Effect on Quality of Life (AFEQT) questionnaires at their initial visit and 1 year later.

RESULTS

Of 1534 patients, 1076 (70.1%) were men. Compared with men, women were more likely to be older (median age, 73 years [interquartile range {IQR}, 65-78 years] vs 65 years [IQR, 57-73 years], P < .001) and have higher median brain-type natriuretic peptide levels (102.8 pg/mL [IQR, 47.3-235.5 pg/mL] vs 74.1 pg/mL [IQR, 28.5-150.5 pg/mL], P < .001). Women also had lower median AFEQT overall summary scores than men (75 [IQR, 61-85] vs 80 [IQR, 69-90]; P < .001) but similar treatment satisfaction at baseline. During follow-up, women were less likely to be treated with a rhythm control strategy (48.1% [n = 214] vs 58.0% [n = 621], P < .001), including catheter ablation of AF (adjusted hazard ratio, 0.77 [95% CI, 0.62-0.95]; P = .02). At 1-year follow-up, women and men had improved QOL scores, regardless of their baseline characteristics (eg, age or brain-type natriuretic peptide levels) or treatment strategies, yet the sex gap persisted and grew (adjusted change in AFEQT overall summary score during 12 months, 5.89 [95% CI, 2.24-9.54] in women vs 8.94 [95% CI, 5.59-12.30] in men; P = .02).

CONCLUSIONS AND RELEVANCE

In contemporary Japanese clinical practice among unselected patients with AF, women were initially seen with greater QOL impairment, and the sex gap grew 1 year after presentation. The present study underscores the need for focused efforts to better understand and close this observed sex gap over the initial year of treatment for patients with AF.

Prevalence and clinical characteristics of obstructive- and central-dominant sleep apnea in candidates of catheter ablation for atrial fibrillation in Japan

INTRODUCTION

We aimed to study the prevalence and types of sleep apnea (SA) as well as their clinical characteristics in atrial fibrillation (AF) ablation candidates in Japan.

METHODS

Before catheter ablation, 197 consecutive AF patients (age: 60 ± 9 years, body mass index; 25.0 ± 3.0) were evaluated with portable polygraphy. We compared the clinical characteristics, according to the severity of SA as well as its types, as defined by the presence of obstruction and the mixed vs. central apnea indices.

RESULTS

The mean apnea-hypopnea index (AHI) was 17.7 ± 11.9, with 135 AF patients having an AHI ≥10 (68.5%). Patients with an AHI ≥10 had a significantly higher body mass index, plasma brain natriuretic peptide (BNP) level, prevalence of hypertension, and larger left atrial size. Among patients with an AHI ≥10, the incidence of obstructive-dominant SA was 60.9% and that of central-dominant SA was 7.6%. The prevalence of hypertension was significantly higher in obstructive-dominant SA patients (obstructive vs. central: 48.3% vs. 20.0%, P = 0.038). The obstructive apnea index correlated with plasma BNP level and age, but the central and mixed apnea indices did not.

CONCLUSIONS

The prevalence of SA was common in AF ablation candidates, even without an obesity epidemic, and the SA type was predominantly obstructive. Portable polygraphy was useful for detecting undiagnosed SA patients in AF ablation candidates.

A tale of two sisters with hypertrophic cardiomyopathy and recurrent embolism: When is the optimal timing of the intervention for left atrial appendage?

Hypertrophic cardiomyopathy (HCM) is an extremely heterogeneous genetic disease that affects the left ventricle (LV) and has a varied clinical course and phenotypic expression. Here, we report a case of two sisters with HCM who developed a massive refractory left atrial appendage (LAA) thrombus and recurrent embolism. The older sister, who was at a high surgical risk due to progressive LV systolic dysfunction with an ejection fraction of 19%, underwent LAA plication in combination with implantation of an LV assist device after progression to treatment-refractory heart failure at the age of 49. The younger sister underwent surgical thrombectomy, LAA plication, and Maze surgery before deterioration of heart failure at the age of 47. She was free from embolism and atrial fibrillation for 2years after surgery. Individualized therapeutic approaches targeting the LAA at a relatively early stage are required in the subgroups of HCM patients with left atrial dysfunction.

Sex-Dependent Phenotypic Variability of an SCN5A Mutation: Brugada Syndrome and Sick Sinus Syndrome

Background Brugada syndrome ( BS ) is known to be 9 times more prevalent in males than females. However, little is known about the development of sick sinus syndrome in female members with familial BS . Methods and Results Familial BS patients and family members, both from our institutions and collaborating sites that specialize in clinical care of BS , participated in this study. We collected information on their clinical and genetic background, along with the inheritance patterns of BS . Detailed information on each case with familial BS is described. A total of 7 families, including 25 BS patients (12 females and 13 males), were included. Seven were probands and 18 were family members. Ten out of the 12 female patients and none of the 13 male patients developed sick sinus syndrome. Sudden death or spontaneous ventricular fibrillation occurred in 7 out of 13 male patients and 2 out of 12 female patients. Conclusions Familial BS existed in which female patients developed sick sinus syndrome but male patients did not. Some of those female patients with sick sinus syndrome had unrecognized BS . Information should be collected not only regarding a family history of sudden death or BS , but also whether a pacemaker was implanted in female members.

Development of monomorphic ventricular tachycardia in a patient with fever-induced Brugada syndrome

A 50-year-old woman visited the emergency department with a high fever due to pneumonia. Incessant monomorphic ventricular tachycardia occurred and was terminated by intravenous lidocaine. Her ECG during sinus rhythm demonstrated ST segment elevation suggestive of Brugada syndrome (BS). An intensive examination could not detect any structural disease, and typical coved-type ST elevation was unmasked by a pilsicainide injection leading to a diagnosis of BS. An ICD was implanted for secondary prevention of ventricular arrhythmia. The patient has been free from any recurrences of arrhythmia for 3 years.

Dynamicity of hypothermia-induced J waves and the mechanism involved

BACKGROUND

J waves develop during hypothermia, but the dynamicity of hypothermia-induced J waves is poorly understood.

OBJECTIVE

The purpose of this study was to investigate the mechanism of the rate-dependent change in the amplitude of hypothermia-induced J waves.

METHODS

Nineteen patients with severe hypothermia were included (mean age 70 ± 12 years; 16 men [84.2%]). The rectal temperature at the time of admission was 27.8° ± 2.5°C. In addition to prolonged PR, QRS complex, and corrected QT intervals, the distribution of prominent J waves was widespread in all 19 patients.

RESULTS

Nine patients showed changes in RR intervals. When the RR interval shortened from 1353 ± 472 to 740 ± 391 ms (P = .0002), the J-wave amplitude increased from 0.50 ± 0.29 to 0.61 ±0.27 mV (P = .0075). The J-wave amplitude increased in 7 patients (77.8%) and decreased in 2 patients (22.2%) after short RR intervals. The augmentation of J waves at short RR intervals was associated with a significant prolongation of ventricular activation time (35 ± 5 ms vs 46 ± 5 ms; P = .0020), suggesting accentuated conduction delay. Increased conduction delay at short RR intervals was suggested to accentuate the phase 1 notch of the action potential and J waves in hypothermia. None developed ventricular fibrillation, and in 2 of 9 patients with atrial fibrillation, atrial fibrillation persisted after rewarming to normothermia.

CONCLUSION

J waves in severe hypothermia were augmented after short RR intervals in 7 patients as expected for depolarization abnormality, whereas 2 patients showed a bradycardia-dependent augmentation as expected for transient outward current-mediated J waves. Increased conduction delay at short RR intervals can be responsible for the accentuation of the transient outward current and J waves during severe hypothermia.

Improvement in the electrocardiograms associated with right ventricular hypertrophy after balloon pulmonary angioplasty in chronic thromboembolic pulmonary hypertension

Background

Balloon pulmonary angioplasty (BPA) is a treatment option for patients with chronic thromboembolic pulmonary hypertension (CTEPH).

Methods and results

In 60 patients with CTEPH, we examined the hemodynamic data before and after BPA. In addition, the sequential ECG findings for right ventricular hypertrophy (RVH) were assessed. The mean pulmonary arterial pressure (mPAP) decreased from 38 ± 11 to 20 ± 4 mm Hg (p < 0.05). The ROC analysis showed that the S waves in V5, R waves in V1 + S waves in V5, S waves in I, and QRS axis were significant predictors of an mPAP ≧ 30 mm Hg (AUC > 0.75, p < 0.01). The predictive values for the mPAP before the BPA were the S and R waves in lead V6, and P waves in lead II (33.417 + 0.078 × P in II − 0.10 × R in V6 + 0.012 × S in V6). The change in the mPAP (ΔmPAP) correlated with the change in the amplitudes of the ECGs: ΔS wave in lead I (R = 0.544, p < 0.001), ΔR in V1 + S in V5 (R = 0.476, p < 0.001), and ΔP wave in II (R = 0.511, p < 0.001). At 6 months of follow-up, the improvement in an R in V1 + S in V5 of ≧10 mm implied a better functional status.

Conclusion

BPA therapy reduced the pulmonary arterial pressure in patients with CTEPH and was associated with an improvement in the ECG findings related to RVH.

Real-Time Analysis of the Heart Rate Variability During Incremental Exercise for the Detection of the Ventilatory Threshold

Background

It has never been possible to immediately evaluate heart rate variability (HRV) during exercise. We aimed to visualize the real‐time changes in the power spectrum of HRV during exercise and to investigate its relationship to the ventilatory threshold (VT).

Methods and Results

Thirty healthy subjects (29.1±5.7 years of age) and 35 consecutive patients (59.0±13.2 years of age) with myocardial infarctions underwent cardiopulmonary exercise tests with an RAMP protocol ergometer. The HRV was continuously assessed with power spectral analyses using the maximum entropy method and projected on a screen without delay. During exercise, a significant decrease in the high frequency (HF) was followed by a drastic shift in the power spectrum of the HRV with a periodic augmentation in the low frequency/HF (L/H) and steady low HF. When the HRV threshold (HRVT) was defined as conversion from a predominant high frequency (HF) to a predominant low frequency/HF (L/H), the VO₂ at the HRVT (HRVT‐VO₂) was substantially correlated with the VO₂ at the lactate threshold and VT) in the healthy subjects (r=0.853 and 0.921, respectively). The mean difference between each threshold (0.65 mL/kg per minute for lactate threshold and HRVT, 0.53 mL/kg per minute for VT and HRVT) was nonsignificant (P>0.05). Furthermore, the HRVT‐VO₂ was also correlated with the VT‐VO₂ in these myocardial infarction patients (r=0.867), and the mean difference was −0.72 mL/kg per minute and was nonsignificant (P>0.05).

Conclusions

A HRV analysis with our method enabled real‐time visualization of the changes in the power spectrum during exercise. This can provide additional information for detecting the VT.

Real-world monitoring of direct oral anticoagulants in clinic and hospitalization settings

Background:

The monitoring of the effects of direct oral anticoagulants may be beneficial during emergencies and adverse events. We aimed to explore direct oral anticoagulant monitoring in “real-world” settings, in which monitoring methods are limited and loading time can be estimated based on only patient reports.

Methods:

In 164 patients, plasma anti-Xa activity was assessed using a STA^®-Liquid Anti-Xa reagent (Diagnostica Stago, Asnieres, France), and prothrombin time was measured using HemosIL^® RecombiPlasTin 2G (Instrumentation Laboratory, Bedford, MA, USA). The loading time was calculated according to the previous dosing time reported by the patient. In the clinic setting, rivaroxaban and apixaban were administered to 103 patients with atrial fibrillation and a blood sample was tested once during a clinic visit. In the hospitalization setting, edoxaban was administered to 61 patients undergoing arthroplasty for prophylaxis of a venous thrombosis and blood samples were tested 3 and 18 h after the last intake.

Results:

Plasma Xa activity in the clinical setting ranged widely (rivaroxaban: 1.1–424.4 ng/mL, apixaban: 15.4–469.2 ng/mL) during the 11.7 ± 7.0 h following the previous dose. The values varied over a wide range (up to a factor of 2) at the same loading time, especially around the peak period. The plasma anti-Xa activity of rivaroxaban and apixaban showed linear correlations with prothrombin time (R² = 0.828 and 0.717, respectively). Edoxaban administration prolonged the prothrombin time by only 1.6 ± 1.1 s from the trough to the peak, to a degree that was negatively correlated with age, but not with plasma creatinine level, creatinine clearance, or body mass index.

Conclusion:

In real-world settings, plasma anti-Xa monitoring should be interpreted considering the wide variations in data, reflecting the variability in patient-reported loading time and interpatient variability.

Effect of Compliance to Updated AHA/ACC Performance and Quality Measures Among Patients With Atrial Fibrillation on Outcome (from Japanese Multicenter Registry)

Performance measures (PMs) are used to accelerate translation of scientific evidence into clinical practice. However, it remains unknown how they are applied in the real world and whether the compliance to these metrics will lead to improved patient's outcome in atrial fibrillation (AF). Within the Japanese multicenter AF registry (n = 1,874), adherence of the AF PMs (based on 2016 American Heart Association/American College of Cardiology criteria) and its association with quality of life scaling and clinical outcomes was evaluated. The patient was deemed "adherent" when all applicable components of the PMs for outpatient settings (CHA₂DS₂-VASc risk score documentation [PM-4], anticoagulation prescribed [PM-5], and monthly international normalized ratio (INR) for warfarin treatment [PM-6]) were satisfied. The Atrial Fibrillation Effect on Quality of Life (AFEQT) questionnaire was assessed at baseline and 1 year. About a half of patients (46.1%) were adherent to the AF PMs. PMs were more frequently achieved in patients managed with rhythm control compared with rate control. The achievement rate for each component was 53.9% for PM-4, 85.6% for PM-5, and 90.3% for PM-6, respectively. Although AFEQT global scores at baseline were similar (median 79.2 [interquartile ranges 66.7 to 88.5] vs 77.1 [64.8 to 88.0], p = 0.227), AFEQT global scores at 1-year follow-up were significantly greater in adherence group than those in nonadherence group (89.2 [78.5 to 96.6] vs 86.7 [76.7 to 95.0], p = 0.021). This tendency was consistent regardless of therapeutic strategies. There remains an important opportunity to improve the quality of care in patients with AF. Adherence to the AF PMs might lead to the improvement of patient's quality of life.

Flecainide ameliorates arrhythmogenicity through NCX flux in Andersen-Tawil syndrome-iPS cell-derived cardiomyocytes

Andersen-Tawil syndrome (ATS) is a rare inherited channelopathy. The cardiac phenotype in ATS is typified by a prominent U wave and ventricular arrhythmia. An effective treatment for this disease remains to be established. We reprogrammed somatic cells from three ATS patients to generate induced pluripotent stem cells (iPSCs). Multi-electrode arrays (MEAs) were used to record extracellular electrograms of iPSC-derived cardiomyocytes, revealing strong arrhythmic events in the ATS-iPSC-derived cardiomyocytes. Ca²⁺ imaging of cells loaded with the Ca²⁺ indicator Fluo-4 enabled us to examine intracellular Ca²⁺ handling properties, and we found a significantly higher incidence of irregular Ca²⁺ release in the ATS-iPSC-derived cardiomyocytes than in control-iPSC-derived cardiomyocytes. Drug testing using ATS-iPSC-derived cardiomyocytes further revealed that antiarrhythmic agent, flecainide, but not the sodium channel blocker, pilsicainide, significantly suppressed these irregular Ca²⁺ release and arrhythmic events, suggesting that flecainide's effect in these cardiac cells was not via sodium channels blocking. A reverse-mode Na^+/Ca²⁺exchanger (NCX) inhibitor, KB-R7943, was also found to suppress the irregular Ca²⁺ release, and whole-cell voltage clamping of isolated guinea-pig cardiac ventricular myocytes confirmed that flecainide could directly affect the NCX current (I_NCX). ATS-iPSC-derived cardiomyocytes recapitulate abnormal electrophysiological phenotypes and flecainide suppresses the arrhythmic events through the modulation of I_NCX.

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iPS cells are generated from three patients with ATS.

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ATS-iPS cell-derived cardiomyocytes show abnormal electrophysiological phenotypes.

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Flecainide suppresses abnormal electrophysiological phenotypes in ATS-iPS cell-derived cardiomyocytes.