Beyond the Lens: Unveiling the invisible atrioventricular node in the era of high-density mapping.

Numerous studies have clarified the histological characteristics of the area surrounding the atrioventricular (AV) node, commonly referred to as the triangle of Koch (ToK). Although it is suggested that the conduction of electric impulses from the atria to the ventricles via the AV node involves myocytes possessing distinct conduction properties and gap junction proteins, a comprehensive understanding of this complex conduction has not been fully established. Moreover, although various pathways have been proposed for both anterograde and retrograde conduction during atrioventricular nodal reentrant tachycardia (AVNRT), the reentrant circuits of AVNRT are not fully elucidated. Therefore, the slow pathway ablation for AVNRT has been conventionally performed, targeting both its anatomical location and slow pathway potential obtained during sinus rhythm. Recently, advancements in high-density three-dimensional (3D) mapping systems have facilitated the acquisition of more detailed electrophysiological potentials within the ToK. Several studies have indicated that the activation pattern, the low-voltage area within the ToK obtained during sinus rhythm, and the fractionated potentials acquired during tachycardia may be optimal targets for slow pathway ablation. This review provides an overview of the tissue surrounding the AV node as reported to date and summarizes the current understanding of AV conduction and AVNRT circuits. Furthermore, we discuss recent findings on slow pathway ablation utilizing high-density 3D mapping systems, exploring strategies for optimal slow pathway ablation.

Optimal timing of electrical cardioversion for acute decompensated heart failure caused by atrial arrhythmias: The earlier, the better?

The optimal timing for electrical cardioversion (ECV) in acute decompensated heart failure (ADHF) with atrial arrhythmias (AAs) is unknown. Here, we retrospectively evaluated the impact of ECV timing on SR maintenance, hospitalization duration, and cardiac function in patients with ADHF and AAs. Between October 2017 and December 2022, ECV was attempted in 73 patients (62 with atrial fibrillation and 11 with atrial flutter). Patients were classified into two groups based on the median number of days from hospitalization to ECV, as follows: early ECV (within 8 days, n = 38) and delayed ECV (9 days or more, n = 35). The primary endpoint was very short-term and short-term ECV failure (unsuccessful cardioversion and AA recurrence during hospitalization and within one month after ECV). Secondary endpoints included (1) acute ECV success, (2) ECVs attempted, (3) periprocedural complications, (4) transthoracic echocardiographic parameter changes within two months following successful ECV, and (5) hospitalization duration. ECV successfully restored SR in 62 of 73 patients (85%), with 10 (14%) requiring multiple ECV attempts (≥ 3), and periprocedural complications occurring in six (8%). Very short-term and short-term ECV failure occurred without between-group differences (51% vs. 63%, P = 0.87 and 61% vs. 72%, P = 0.43, respectively). Among 37 patients who underwent echocardiography before and after ECV success, the left ventricular ejection fraction (LVEF) significantly increased (38% [31-52] to 51% [39-63], P = 0.008) between admission and follow-up. Additionally, hospital stay length was shorter in the early ECV group than in the delayed ECV group (14 days [12-21] vs. 17 days [15-26], P < 0.001). Hospital stay duration was also correlated with days from admission to ECV (Spearman's ρ = 0.47, P < 0.001). In clinical practice, early ECV was associated with a shortened hospitalization duration and significantly increased LVEF in patients with ADHF and AAs.

Where is the gap after a 90 W/4 s very-high-power short-duration ablation of atrial fibrillation?: Association with the left atrial-pulmonary vein voltage and wall thickness.

Background: Although pulmonary vein isolation (PVI) for atrial fibrillation (AF) utilizing radiofrequency (RF) applications with a very high-power and short-duration (vHPSD) has shortened the procedure time, the determinants of pulmonary vein (PV) gaps in the first-pass PVI and acute PV reconnections are unclear. Methods: An extensive encircling PVI was performed with the QDOT MICRO catheter with a vHPSD (90 W-4 s) in 30 patients with AF (19 men, 64 ± 10 years). The association of the PV gap sites (first-pass PVI failure, acute PV reconnections [spontaneous reconnections or dormant conduction provoked by adenosine triphosphate] or both) with the left atrial (LA) wall thickness and LA bipolar voltage on the PVI line and ablation-related parameters were assessed. Results: PV gaps were observed in 29 (6%) of 480 segments (16 segments per patient) in 17 patients (56%). The PV gaps were associated with the LA wall thickness, bipolar voltage, and the number of RF points (LA wall thickness, 2.5 ± 0.5 vs. 1.9 ± 0.4 mm, p < .001; bipolar voltage, 2.59 ± 1.62 vs. 1.34 ± 1.14 mV, p < .001; RF points, 6 ± 2 vs. 4 ± 2, p = .008) but were not with the other ablation-related parameters. Receiver operating characteristic curves yielded that an LA wall thickness ≥2.3 mm and bipolar voltage ≥2.40 mV were determinants of PV gaps with an area under the curve of 0.82 and 0.73, respectively. Conclusions: The LA voltage and wall thickness on the PV-encircling ablation line were highly associated with PV gaps using the 90 W/4 s-vHPSD ablation.

Coexistence of a Classical Nodoventricular Accessory Pathway With a Left-Sided Mahaim Accessory Pathway.

The coexistence of 2 Mahaim pathways represents a diagnostic challenge. We present a case in which the SH/HA intervals were useful for identifying concealed nodoventricular or His-ventricular pathways.

Clinical implication of the patient's disease awareness and adherence to medications in patients undergoing atrial fibrillation ablation.

Background: The effects of the patient's disease awareness on the management of postablation of atrial fibrillation (AF) are unknown. Methods: One hundred thirty-three AF patients undergoing an initial ablation were given a disease awareness questionnaire with a score of 16 points (8 points about AF in general and 8 points about oral anticoagulants) for the Jessa Atrial Fibrillation Knowledge Questionnaire (JAKQ) before and 1-year-after ablation. We divided them into the poor disease awareness group and good disease awareness group according to the median value (75%) of the total JAKQ score about AF in general, and compared the baseline patient characteristics and the 1-year changes in the JAKQ score, medication adherence, blood pressure, laboratory data, echocardiographic parameters, and AF/atrial tachycardia (AT) recurrence rate between the two groups. Results: Forty-two (31.6%) patients were classified as having poor disease awareness (<75% of the total JAKQ score), which was closely associated with poor medication adherence, hypertension, diabetes, dyslipidemia, and greater left atrial volume (LAV). These trends in the poor disease awareness group remained unchanged 1 year after the ablation. During the 25.3-month follow-up, the AF/AT recurrence rate was significantly higher in the poor disease awareness than the good disease awareness group (23.8% vs. 7.7%; p = .003 by the log-rank test). Conclusions: Poor disease awareness was linked to poor medication adherence, lifestyle-related diseases, and greater LAV before and even 1 year after the ablation, making it a potential surrogate marker for AF/AT recurrence. These findings highlight the clinical significance of disease awareness in AF management.

Pseudo-slow-fast atrioventricular nodal reentrant tachycardia: Is the fast pathway a criminal or innocent bystander?

The intracardiac electrograms are shown during scanned single premature ventricular extrastimuli with a decreasing coupling interval in a very short RP tachycardia. What is the diagnosis and is the fast pathway essential for sustaining the tachycardia?

Systematic observation-based diagnosis of atrioventricular nodal reentrant tachycardia with a bystander concealed nodoventricular pathway.

Background: This study aimed to establish a systematic method for diagnosing atrioventricular nodal reentrant tachycardia (AVNRT) with a bystander concealed nodoventricular pathway (cNVP). Methods: We analyzed 13 cases of AVNRT with a bystander cNVP, 11 connected to the slow pathway (cNVP-SP) and two to the fast pathway (cNVP-FP), along with two cases of cNVP-related orthodromic reciprocating tachycardia (ORT). Results: The diagnostic process was summarized in three steps. Step 1 was identification of the presence of an accessory pathway by resetting the tachycardia with delay (n = 9) and termination without atrial capture (n = 4) immediately after delivery of a His-refractory premature ventricular contraction (PVC). Step 2 was exclusion of ORT by atrio-His block during the tachycardia (n = 4), disappearance of the reset phenomenon after the early PVC (n = 7), or dissociation of His from the tachycardia during ventricular overdrive pacing (n = 1). Moreover, tachycardia reset/termination without the atrial capture (n = 2/2) 1 cycle after the His-refractory PVC was specifically diagnostic. Exceptionally, the disappearance of the reset phenomenon was also observed in the two cNVP-ORTs. Step 3 was verification of the AVN as the cNVP insertion site, evidenced by an atrial reset/block preceding the His reset/block in fast-slow AVNRT with a cNVP-SP and slow-fast AVNRT with a cNVP-FP or His reset preceding the atrial reset in slow-fast AVNRT with a cNVP-SP. Conclusion: AVNRT with a bystander cNVP can be diagnosed in the three steps with few exceptions. Notably, tachycardia reset/termination without atrial capture one cycle after delivery of a His-refractory PVC is specifically diagnostic.

Characteristics of tissue temperature during ablation with THERMOCOOL SMARTTOUCH SF versus TactiCath versus QDOT MICRO catheters (Qmode and Qmode+): An in vivo porcine study.

INTRODUCTION: High-power short-duration (HPSD) ablation at 50 W, guided by ablation index (AI) or lesion size index (LSI), and a 90 W/4 s very HSPD (vHPSD) setting are available for atrial fibrillation (AF) treatment. Yet, tissue temperatures during ablation with different catheters around venoatrial junction and collateral tissues remain unclear. METHODS: In this porcine study, we surgically implanted thermocouples on the epicardium near the superior vena cava (SVC), right pulmonary vein, and esophagus close to the inferior vena cava. We then compared tissue temperatures during 50W-HPSD guided by AI 400 or LSI 5.0, and 90 W/4 s-vHPSD ablation using THERMOCOOL SMARTTOUCH SF (STSF), TactiCath ablation catheter, sensor enabled (TacthCath), and QDOT MICRO (Qmode and Qmode+ settings) catheters. RESULTS: STSF produced the highest maximum tissue temperature (Tmax ), followed by TactiCath, and QDOT MICRO in Qmode and Qmode+ (62.7 ± 12.5°C, 58.0 ± 10.1°C, 50.0 ± 12.1°C, and 49.2 ± 8.4°C, respectively; p = .005), achieving effective transmural lesions. Time to lethal tissue temperature ≥50°C (t-T ≥ 50°C) was fastest in Qmode+, followed by TacthCath, STSF, and Qmode (4.3 ± 2.5, 6.4 ± 1.9, 7.1 ± 2.8, and 7.7 ± 3.1 s, respectively; p < .001). The catheter tip-to-thermocouple distance for lethal temperature (indicating lesion depth) from receiver operating characteristic curve analysis was deepest in STSF at 5.2 mm, followed by Qmode at 4.3 mm, Qmode+ at 3.1 mm, and TactiCath at 2.8 mm. Ablation at the SVC near the phrenic nerve led to sudden injury at t-T ≥ 50°C in all four settings. The esophageal adventitia injury was least deep with Qmode+ ablation (0.4 ± 0.1 vs. 0.8 ± 0.4 mm for Qmode, 0.9 ± 0.3 mm for TactiCath, and 1.1 ± 0.5 mm for STSF, respectively; p = .005), correlating with Tmax . CONCLUSION: This study revealed distinct tissue temperature patterns during HSPD and vHPSD ablations with the three catheters, affecting lesion effectiveness and collateral damage based on Tmax and/or t-T ≥ 50°C. These findings provide key insights into the safety and efficacy of AF ablation with these four settings.

Termination of slow-fast atrioventricular reentrant tachycardia by a single cryoablation of the slow pathway guided by a fractionation map.

This is a slow-fast atrioventricular nodal reentrant tachycardia (AVNRT) case wherein the fractionation map-guided cryoablation of the slow pathway (SP) successfully terminated the tachycardia. In this case, the Advisor™ HD Grid catheter and fractionation map in the EnSite™ X EP system with relatively high-sensitive settings were useful for detecting the target SP area. Direct AVNRT termination by cryomapping at the fractionated potential area might be a quick and safe ablation strategy, which may provide a new workflow for SP ablation.

Fast-slow atrioventricular nodal re-entrant tachycardia incorporating superior and inferolateral left atrial slow pathways.

BACKGROUND: A 70-year-old man revealed a rare type of atrioventricular nodal re-entrant tachycardia (AVNRT) involving distinct retrograde pathways, superior slow pathway, and inferolateral left atrial slow pathway. RESULT: Radiofrequency ablation was successfully performed on the noncoronary cusp and in the left atrium, respectively, to eliminate the tachycardias. DISCUSSION AND CONCLUSION: Due to the anomalous electrical conduction patterns, careful diagnosis and ablation strategies were necessary to avoid the risk of atrioventricular block. These findings underscore the diversity and complexity of AVNRT and highlight the importance of tailored therapeutic approaches.

External Validation of the HELT-E2S2 Score in Japanese Patients With Nonvalvular Atrial Fibrillation　- A Pooled Analysis of the RAFFINE and SAKURA Registries.

BACKGROUND: The HELT-E2S2score, which assigns 1 point to Hypertension, Elderly aged 75-84 years, Low body mass index <18.5 kg/m2, and Type of atrial fibrillation (AF: persistent/permanent), and 2 points to Extreme Elderly aged ≥85 years and previous Stroke, has been proposed as a new risk stratification for strokes in Japanese AF patients, but has not yet undergone external validation.Methods and Results: We evaluated the prognostic performance of the HELT-E2S2score for stroke risk stratification using 2 large-scale registries in Japanese AF patients (n=7,020). During 23,241 person-years of follow-up (mean follow-up 1,208±450 days), 287 ischemic stroke events occurred. The C-statistic using the HELT-E2S2score was 0.661 (95% confidence interval [CI], 0.629-0.692), which was numerically higher than with the CHADS2score (0.644, 95% CI 0.613-0.675; P=0.15 vs. HELT-E2S2) or CHA2DS2-VASc score (0.650, 95% CI, 0.619-0.680; P=0.37 vs. HELT-E2S2). In the SAKURA AF Registry, the C-statistic of the HELT-E2S2score was consistently higher than the CHADS2and CHA2DS2-VASc scores across all 3 types of facilities comprising university hospitals, general hospitals, and clinics. However, in the RAFFINE Study, its superiority was only observed in general hospitals. CONCLUSIONS: The HELT-E2S2score demonstrated potential value for risk stratification, particularly in a super-aged society such as Japan. However, its superiority over the CHADS2or CHA2DS2-VASc scores may vary across different hospital settings.

Trends over the recent 6 years in ablation modalities and strategies, post-ablation medication, and clinical outcomes of atrial fibrillation ablation.

Background: Ablation strategies and modalities for atrial fibrillation (AF) have transitioned over the past decade, but their impact on post-ablation medication and clinical outcomes remains to be fully investigated. Methods: We divided 682 patients who had undergone AF ablation in 2014-2019 (420 paroxysmal AFs [PAF], 262 persistent AFs [PerAF]) into three groups according to the period, that is, the 2014-2015 (n = 139), 2016-2017 (n = 244), and 2018-2019 groups (n = 299), respectively. Results: Persistent AF became more prevalent and the left atrial (LA) diameter larger over the 6 years. Extra-pulmonary vein (PV)-LA ablation was more frequently performed in the 2014-2015 group than in the 2016-2017 and 2018-2019 groups (41.1% vs. 9.1% and 8.1%; p < .001). The 2-year freedom rate from AF/atrial tachycardias for PAF was similar among the three groups (84.0% vs. 83.1% vs. 86.7%; p = .98) but lowest in the 2014-2015 group for PerAF (63.9% vs. 82.7% and 86.3%; p = .025) despite the highest post-ablation antiarrhythmic drug use. Cardiac tamponade was significantly decreased in the 2018-2019 group (3.6% vs. 2.0% vs. 0.33%; p = 0.021). There was no difference in the 2-year clinically relevant events among the three groups. Conclusion: Although ablation was performed in a more diseased LA and extra-PV-LA ablation was less frequent in recent years, the complication rate decreased, and AF recurrences for PAF remained unchanged, but that for PerAF decreased. Clinically relevant events remained unchanged over the recent 6 years, suggesting that the impact of the recent ablation modalities and strategies on remote clinically relevant events may be small during this study period.

Phenotyping of atrial fibrillation with cluster analysis and external validation.

OBJECTIVES: Atrial fibrillation (AF) is a heterogeneous condition. We performed a cluster analysis in a cohort of patients with AF and assessed the prognostic implication of the identified cluster phenotypes. METHODS: We used two multicentre, prospective, observational registries of AF: the SAKURA AF registry (Real World Survey of Atrial Fibrillation Patients Treated with Warfarin and Non-vitamin K Antagonist Oral Anticoagulants) (n=3055, derivation cohort) and the RAFFINE registry (Registry of Japanese Patients with Atrial Fibrillation Focused on anticoagulant therapy in New Era) (n=3852, validation cohort). Cluster analysis was performed by the K-prototype method with 14 clinical variables. The endpoints were all-cause mortality and composite cardiovascular events. RESULTS: The analysis subclassified derivation cohort patients into five clusters. Cluster 1 (n=414, 13.6%) was characterised by younger men with a low prevalence of comorbidities; cluster 2 (n=1003, 32.8%) by a high prevalence of hypertension; cluster 3 (n=517, 16.9%) by older patients without hypertension; cluster 4 (n=652, 21.3%) by the oldest patients, who were mainly female and with a high prevalence of heart failure history; and cluster 5 (n=469, 15.3%) by older patients with high prevalence of diabetes and ischaemic heart disease. During follow-up, the risk of all-cause mortality and composite cardiovascular events increased across clusters (log-rank p<0.001, p<0.001). Similar results were found in the external validation cohort. CONCLUSIONS: Machine learning-based cluster analysis identified five different phenotypes of AF with unique clinical characteristics and different clinical outcomes. The use of these phenotypes may help identify high-risk patients with AF.

When Is Cardiac Resynchronization Therapy with a Defibrillator Indicated in Patients with Heart Failure, Especially Elderly Patients?

One benefit of an implantable cardioverter-defibrillator is the prevention of sudden cardiac death (SCD). It is recommended for patients with a low left ventricular ejection fraction (LVEF). However, the choice of cardiac resynchronization therapy (CRT) with or without a defibrillator (CRT-D and CRT-P) in elderly patients is controversial. To understand the current situation for proper device selection, we investigated the impact of defibrillators on mortality in elderly patients with heart failure.Consecutive patients who underwent CRT implantation were retrospectively recruited. Baseline characteristics, all-cause mortality, cardiac death, and defibrillator implantation rates were investigated in patients aged > 75 or ≤ 75 years.A total of 285 patients (79 patients aged > 75 years) were analyzed. Elderly patients had more comorbidities, but a lower proportion had ventricular arrhythmia. During the mean follow-up of 47 months, 109 patients died (67 due to cardiac death). Kaplan-Meier analysis showed higher mortality in elderly patients (P = 0.0428) but no significant difference in cardiac death by age group (P = 0.7472). There were no significant differences in mortality between patients with CRT-D versus CRT-P (P = 0.3386).SCD was rare. A defibrillator had no significant impact on mortality. In elderly patients, comorbidities are common and related to mortality. The selection of CRT-D versus CRT-P should take those factors into account.

Intravenous Semaphorin 3A Administration Maintains Cardiac Contractility and Improves Electrical Remodeling in a Mouse Model of Isoproterenol-Induced Heart Failure.

The effects of recombinant semaphorin 3A (Sema3A) on myocardial contractility and electrical remodeling in mice with isoproterenol (ISP) -induced heart failure were investigated.C57BL/6J mice intraperitoneally received ISP (480 mg/kg/day, ISP group; n = 24) or saline (control group; n = 31) for 14 days. Twenty-one ISP-treated mice received 0.5 mg/kg Sema3A intravenously on days 7 and 11 (ISP+Sema3A group). The sympathetic nervous system was activated upon ISP treatment, but was reduced upon Sema3A administration. Greater myocardial tissue fibrosis was observed in the ISP group than in the control group. However, fibrosis was not significantly different between the ISP+Sema3A and control groups. Fractional shortening of the left ventricle was lower in the ISP group than in the control group and was restored in the ISP+Sema3A group (control, 53 ± 8%; ISP, 37 ± 7%; ISP+Sema3A, 48 ± 3%; P < 0.05). Monophasic action potential duration at 20% repolarization (MAPD20) was prolonged in the ISP group (compared to control group), but this was reversed upon Sema3A administration (control, 29 ± 3 ms; ISP, 35 ± 6 ms; ISP+Sema3A, 29 ± 3 ms; P < 0.05). qPCR revealed Kv4.3, KChIP2, and SERCA2 downregulation in the ISP group and upregulation in the ISP+Sema3A group; however, Western blotting revealed similar changes only for Kv4.3 (P < 0.05).Intravenous Sema3A may maintain myocardial contractility by suppressing the sympathetic innervation of the myocardium and reducing myocardial tissue damage, in addition to restoring MAPD via Kv4.3 upregulation.

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.