Atrioventricular Junction Research Articles

Interatrial Block, Bayés Syndrome, Left Atrial Enlargement, and Atrial Failure

Interatrial block (IAB) is defined by the presence of a P-wave ≥120 ms. Advanced IAB is diagnosed when there is also a biphasic morphology in inferior leads. The cause of IAB is complete block of Bachmann’s bundle, resulting in retrograde depolarization of the left atrium from areas near the atrioventricular junction. The anatomic substrate of advanced IAB is fibrotic atrial cardiomyopathy. Dyssynchrony induced by advanced IAB is frequently a trigger and maintenance mechanism of atrial fibrillation (AF) and other atrial arrhythmias. Bayés syndrome is characterized by the association of advanced IAB with atrial arrhythmias. This syndrome is associated with an increased risk of stroke, dementia, and mortality. Advanced IAB frequently produces an alteration of the atrial architecture. This atrial remodeling may promote blood stasis and hypercoagulability, triggering the thrombogenic cascade, even in patients without AF. In addition, atrial remodeling may ultimately lead to mechanical dyssynchrony and enlargement. Atrial enlargement is usually the result of prolonged elevation of atrial pressure due to various underlying conditions such as IAB, diastolic dysfunction, left ventricular hypertrophy, valvular heart disease, hypertension, and athlete’s heart. Left atrial enlargement (LAE) may be considered present if left atrial volume indexed to body surface is > 34 mL/m2; however, different cut-offs have been used. Finally, atrial failure is a global clinical entity that includes any atrial dysfunction that results in impaired cardiac performance, symptoms, and decreased quality of life or life expectancy.

Morphology of the mural and commissural atrioventricular junction of the mitral valve

ObjectiveThis study investigates mitral annular disjunctions (MAD) in the atrial wall-mitral annulus-ventricular wall junction along the mural mitral leaflet and commissures.MethodsWe examined 224 adult human hearts (21.9% females, 47.9±17.6 years)...

Abstract 17978: Validation of Contemporary Administrative Codes for Identifying Pulmonary Vein Isolation Procedures

Introduction: Use of pulmonary vein isolation (PVI) to treat atrial fibrillation continues to grow. Despite great interest in leveraging administrative data for real-world analyses, contemporary procedural codes for identifying PVI have not been validated. Methods: Inpatient PVIs were identified among US Medicare fee-for-service beneficiaries using Current Procedural Terminology (CPT) code 93656 in the Carrier Line Files. Each patient was cross-matched by procedure date with claims from Medicare Provider Analysis and Review Files (MedPAR), in order to compare CPT claims with International Classification of Diseases-10 th Revision Procedure Coding System (ICD-10 PCS) claims submitted by healthcare facilities to bill for each PVI. We performed the reverse for commonly matched ICD-10-PCS codes, to identify their corresponding CPT-billed procedures. Results: We identified 20,388 inpatient PVIs from 1/2017 to 12/2020, of which 14,468 (71%) were linked to MedPAR by same-day procedure date. Of these, 13,156 (91%) were billed as ICD-10 02583ZZ “ Destruction of Conduction Mechanism, Percutaneous Approach ”, with lower use of other codes. However, the reverse process yielded heterogeneous results: among 75,003 procedures billed as ICD-10 02583ZZ, only 15,691 (21%) matched with CPT 93656 (PVI), as several other procedures were interchangeably billed under this same ICD-10 code (Figure). Conclusions: Compared with CPT codes as a gold standard, the ICD-10-PCS code most commonly associated with CPT-billed PVI procedures actually refers to ablation of the atrio-ventricular junction. Yet this same ICD-10-PCS code also matches with a wide range of other procedures distinct from PVI. We conclude that ICD-10-PCS codes alone are not sensitive or specific for identifying PVI in claims, and cannot be reliably used in isolation for health services research on this important procedure.

Defining the Spectrum of Hypoplastic Left Heart Syndrome (HLHS).

The 2021 International Paediatric and Congenital Cardiac Code and the Eleventh Revision of the International Classification of Diseases provide the following definition for hypoplastic left heart syndrome (HLHS): "Hypoplastic left heart syndrome (HLHS) is defined as a spectrum of congenital cardiovascular malformations with normally aligned great arteries without a common atrioventricular junction, characterized by underdevelopment of the left heart with significant hypoplasia of the left ventricle including atresia, stenosis, or hypoplasia of the aortic or mitral valve, or both valves, and hypoplasia of the ascending aorta and aortic arch." Although HLHS with intact ventricular septum (HLHS + IVS) and HLHS with ventricular septal defect (HLHS + VSD) are different cardiac phenotypes, both of these lesions are part of the spectrum of HLHS.

Spontaneous Sinus Rhythm Restoration in Patients With Refractory, Permanent Atrial Fibrillation Who Underwent Conduction System Pacing and Atrioventricular Junction Ablation

Ablate and pace (A&P) with conduction system pacing (CSP) improves outcomes in patients with symptomatic permanent atrial fibrillation (AF). Data on spontaneous sinus rhythm restoration (SSRR) in this setting are lacking. This study aimed to assess the incidence and the predictors of SSRR in a population of patients with permanent AF who underwent A&P with CSP. Prospective, observational study, enrolling consecutive patients with symptomatic permanent AF (of documented duration >6months) and uncontrolled, drug-refractory high ventricular rate, who underwent A&P with CSP. The incidence and predictors of SSRR were prospectively assessed. A total of 107 patients (79.0 ± 9.1years, 33.6% male, 74.8% with New York Heart Association class ≥III, 56.1% with ejection fraction <40%) were enrolled: 40 received His' bundle pacing, 67 left bundle branch area pacing. During a median follow-up of 12months SSRR was observed in 14 patients (13.1%), occurring a median of 3months after A&P (interquartile range 1 to 6; range 0 to 17). Multivariable analysis identified a duration of permanent AF <12months (hazard ratio 7.7, p=0.040) and a left atrial volume index <49ml/m2 (hazard ratio 14.8, p=0.008) as independent predictors of SSRR. In patients with coexistence of both predictors the incidence of SSRR was of 41.4%. In a population of patients with symptomatic, permanent AF, treated with A&P with CSP, SSRR was observed in 13% of patients during follow-up. A duration of permanent AF <12months and a left atrial volume index <49 ml/m2 were independent predictors of this phenomenon.

Conduction system pacing after atrioventricular junction ablation for atrial fibrillation patients with heart failure: a new approach to an old strategy

Conduction system pacing after atrioventricular junction ablation for atrial fibrillation patients with heart failure: a new approach to an old strategy

Computed tomographic analysis of the morphometrics and dynamics of the tricuspid annulus in secondary functional tricuspid regurgitation

ObjectivesSecondary functional tricuspid regurgitation (FTR) management remains controversial mainly due to the lack of knowledge in its pathogenesis and the difficulties to measure the actual dimensions of tricuspid annulus (TA) with current imaging methods. Using a novel method based on multiphase cardiac computed tomography (CT) scan acquisition to accurately analyze the right atrioventricular junction size, we sought to explore modifications of TA morphometry and dynamics in secondary FTR. MethodsEchocardiographic and cardiac CT studies were obtained from 21 patients with severe mitral regurgitation (MR group) and 21 patients with dilated cardiomyopathy (DCMP group). Using an in-house software, a 3-dimensiontal (3D) semiautomated delineation of the TA perimeter was assessed. Modifications of diameters, 2-dimensional/3D areas and perimeters were analyzed through time. These 2 groups of patients were compared with 30 healthy subjects, considering the presence of a significant (≥2+) versus nonsignificant (<2+) FTR in each group. ResultsMaximum TA 3D areas were 7.0 ± 1.2 cm2/m2 in healthy subjects at mid-to-late diastole and were smaller than in the MR group (9.8 ± 2.1 cm2/m2, P < .001) and the DCMP group (9.2 ± 3.0 cm2/m2, P < .001). In the MR group, patients with FTR <2+ had also larger TA areas and diameters than healthy patients (P < .01 for all 3D/2-dimensional parameters). TA shape was more circular only in the DCMP group with FTR ≥2+ compared with other patients (P < .05 for eccentricity). In multivariate analysis, both RA area (P < .001) and RV volume (P = .002) were independently related to TA dilatation. ConclusionsBased on multiphase CT image analyses, TA dilatation was directly related to RV and RA enlargement. Patients with severe mitral myxomatous disease and nondysfunctional tricuspid valve had yet dilated TA, which questioned the current cut-off recommendation for concomitant tricuspid annuloplasty in this specific population.

Abstract EC.10: Transcriptional Heterogeneity Of The Postnatal Cardiac Conduction System

The cardiac conduction system (CCS) is a network of specialized cardiomyocytes responsible for the coordinated spreading of electrical impulses throughout the heart for synchronized contractions. The CCS is largely made up of the sinoatrial node (SAN), atrioventricular node (AVN) and the fast-conducting ventricular conduction system (VCS), which is further divided into the His bundle, Bundle branches and Purkinje fibers. Although these CCS structures were anatomically discovered &gt;100 years ago, their molecular constituents are not fully known. In this study, CCS cells, making up ~0.05% of myocytes (~500 cells/heart), were isolated from early postnatal hearts (postnatal day 1 to 4) of fluorescent reporter mice (Cntn2-Cre;Rosa26TdTomato), purified using fluorescence-activated cell sorting, and subjected to single-cell RNA-sequencing. Unbiased cluster analysis on ~7000 CCS cells demonstrated distinct transcriptomic profiles in the SAN, AVN, proximal VCS ( His bundle, bundle branches) and distal VCS ( Purkinje fibers). Conforming to previous studies, global conduction markers, such as Cntn2 and Id2, were present throughout the entire CCS, while a VCS-specific transcription factor, Irx3 , was expressed only in the VCS. A comparison between proximal and distal VCS components revealed enrichments of Igfbp7 , Lyz2 and Sfrp5 in the proximal VCS, and Scn10a , Psd3 and Wisp1 in the distal VCS. Sub-clustering analysis followed by validation with immunostaining further identified unique molecular profiles of the SAN ( Shox2 , Vsnl1 ), AVN ( Rspo3 ), His bundle ( S100a6 , Pcp4 ) and bundle branches ( Nppa , Mest ). Data integrating publicly available ATAC-seq in SAN, AV junction, and atrial and ventricular cardiomyocytes as well as Tbx3-ChIP-seq, suggested that these regional markers are possibly regulated by two CCS-specific transcription factors, Irx3 and Tbx3 . More importantly, overexpressing Irx3 and/or Tbx3 in cultured neonatal mouse atrial and ventricular myocytes recapitulated these region-specific expression patterns in a dish. Together, our study provides a comprehensive view of the molecular profiles within the postnatal CCS at a high-resolution and show Irx3 and Tbx3 as genetic regulators establishing heterogeneities of the CCS.

Pacing of Specialized Conduction System.

Right ventricular pacing for bradycardia remains the mainstay of pacing therapy. Chronic right ventricular pacing may lead to pacing-induced cardiomyopathy. We focus on the anatomy of the conduction system and the clinical feasibility of pacing the His bundle and/or left bundle conduction system. We review the hemodynamics of conduction system pacing, the techniques to capture the conduction system and the electrocardiogram and pacing definitions of conduction system capture. Clinical studies of conduction system pacing in the setting of atrioventricular block and after AV junction ablation are reviewed and the evolving role of conduction system pacing is compared with biventricular pacing.

Atrioventricular septal defect: An extended approach to prenatal sonographic imaging of the atrioventricular valves

AbstractAn atrioventricular septal defect (AVSD) is diagnosed with prenatal sonography using the 4‐chamber view (4CV) of the fetal heart. Prenatal 2D sonographic imaging of normal and AVSD short axis (SAX) atrioventricular (AV) valve views have not been well described. The aim is to describe the 2D sonographic 4‐chamber and SAX view of the AV valves when an AVSD is present compared to normal AV valves. The 4CV AVSD heart demonstrates no offset of AV valves due to the abnormal valve structure. Complete and intermediate AVSD has a septum primum defect and inlet ventricular septal defect (VSD). The partial AVSDs have either a septum primum defect or just an inlet VSD with an intact primum septum. The SAX view of AVSD demonstrates the common AV junction and the bridging leaflets. In ventricular diastole valves have a “figure 8” and “dumbbell” shape in partial and complete AVSD, respectively. These appearances are not seen in the normal heart in SAX as both tricuspid and mitral valve are separate valves. The SAX view can be obtained by locating a sagittal aortic arch view and then scanning slightly towards the left side of the fetus, near the base of the heart and the AV valves. An in‐depth interrogation of the abnormal fetal heart is obtained without specialised 4D capable ultrasound machines providing information to assist in counselling during the pregnancy and for postnatal surgical planning. Future research to assess the feasibility of incorporating the SAX view into routine practice and by general sonographers is suggested.

Autopsy for Medical Diagnostics: Finding the Cause of Sudden Unexpected Death through Investigation of the Cardiac Conduction System by Serial Sections.

Sudden unexpected death (SUD) is a fatal event that occurs in an apparently healthy subject in a way that such an abrupt outcome could have not been predicted. SUD-including sudden intrauterine unexplained death (SIUD), sudden neonatal unexpected death (SNUD), sudden infant death syndrome (SIDS), sudden unexpected death of the young (SUDY), and sudden unexpected death in the adult (SUDA)-occurs as the first manifestation of an unknown underlying disease or within a few hours of the presentation of a disease. SUD is a major unsolved, shocking form of death that occurs frequently and can happen at any time without warning. For each case of SUD, a review of clinical history data and performance of a complete autopsy, particularly focused on the study of the cardiac conduction system, were carried out according to the necropsy protocol devised by the Lino Rossi Research Center, Università degli Studi di Milano, Italy. Research cases collected and selected for this study were represented by 75 SUD victims that were subdivided into 15 SIUD, 15 SNUD, 15 SUDY, and 15 SUDA victims. After a routine autopsy and clinical history analysis, death remained unexplained, and hence a diagnosis of SUD was assigned to 75 subjects, which included 45 females (60%) and 30 (40%) males ranging in age from 27 gestational weeks to 76 years. Serial sections of the cardiac conduction system disclosed frequent congenital alterations of the cardiac conduction system in fetuses and infants. An age-related significant difference in distribution among the five age-related groups was detected for the following anomalies of the conduction system: central fibrous body (CFB) islands of conduction tissue, fetal dispersion, resorptive degeneration, Mahaim fiber, CFB cartilaginous meta-hyperplasia, His bundle septation, sino-atrial node (SAN) artery fibromuscular thickening, atrio-ventricular junction hypoplasia, intramural right bundle branch, and SAN hypoplasia. The results are useful for understanding the cause of death for all SUD cases that were unexpected and would have otherwise remained unexplained, so as to motivate medical examiners and pathologists to perform more in-depth studies.

A randomized comparison of retrograde left-sided versus anterograde right-sided ablation of the atrioventricular junction.

Catheter ablation of the atrioventricular node (AVN) is an effective treatment for patients with symptomatic atrial fibrillation. This study compares the success rate, procedure time, radiation time, and complication rates of retrograde left-sided (LSA) and anterograde right-sided (RSA) AVN ablation in a randomised controlled trial. Thirty-onepatients undergoing AVN ablation were randomized to either LSA (15 patients) or RSA (16 patients). Crossover occurred after six unsuccessful radiofrequency (RF) applications. The LSA cohort had a mean age of 77.00 ± 5.17 and the RSA cohort was 79.44 ± 6.08 (p = .0240). There were five crossovers from LSA to RSA and there was one crossover from RSA to LSA. There was no significant difference in ablation time between LSA and RSA (210.40 ± 179.77vs. 192.19 ± 130.29 seconds, p = .748). There was no significant difference in procedure time, fluoroscopy time, radiation dose, or number of RF applications between the two groups. There was 1 (6.67%) serious adverse event in the LSA group and 1 (6.25%) in the RSA group due to femoral hematomas requiring blood transfusion or intervention. There was no significant difference in patient-reported discomfort between LSA and RSA (16.43 ± 20.67 vs. 17.87 ± 28.08, p = .877). The study was stopped before full recruitment due to futility. Retrograde LSA of the AVN does not reduce RF applications, procedure time, or radiation exposure compared with conventional RSA and cannot be recommended as a first-line clinical approach.

P480 SUBMITRAL LEFT VENTRICULAR ANEURYSM AND STROKE IN A YOUNG CAUCASIAN WOMAN

Abstract Submitral aneurysms are infrequent and they are generally described in populations from Subsaharian Africa. The aetiology is still unclear: it has been proposed that they could be caused by congenital alterations of ventricular wall, infectious events, chest trauma, cardiac surgery or Myocardial Infarction. Submitral aneurysms can induce arrhythmias, stroke, heart failure secondary to mitral insufficiency, and can facilitate infections. We report the case of a 39–year–old Caucasian woman who was hospitalized in our Institution after relapsing fever episodes, presenting with altered state of consciousness. The ECG showed sinus rhythm and normal morphology. When she was hospitalized, laboratory test findings included normocytic anaemia (Hb 9,8 g/dl), thrombocytopenia (94x103 platelets), neutrophilia (81% neutrophils), ESR 32 mm/h, CRP 8,84, low electolyte level, procalcitonin 11,54 ng/ml. Blood culture was positive for Candida Albicans. A transthoracic echocardiogram showed normal left ventricle dimensions and wall thickness, without abnormalities of global or segmental wall motion, thickening of mitral valve leaflets, which appeared slightly hyperechogen. It was found an aneurysmatic area in correspondence of subvalvular apparatus of mitral valve, between mitral annulus and posterior papillary muscle. Mitral annulus was shifted toward the atrial roof. These findings were confirmed by a thransesophageal echocardiogram. The aneurysm measured 33x22 mm in correspondence to the atrio–ventricular junction. A cardiac MRI confirmed these morphologic alterations without evidence of infarction areas, supposing the presence of an infectious lesion. A brain MRI showed multiple and diffuse areas of altered signal referred to stroke. The patient was referred to the Heart Surgery of our Institution. Intraoperatively, a large aneurysm arose from submitral area; moreover, the posterior leaflet of the mitral valve was characterized by some fissures. The aneurysm was excluded by a direct suturing and the mitral valve was replaced with a biological valve. In our patient, mitral annulus dislocation was evident, supporting the hypothesis of a congenital malformation that can have promoted a mycotic infection and the formation of thrombi responsible for the cerebral disease. In patients with cardiac arrhythmias or embolic events, without other motivating factors, it’s necessary to pay attention and to make a differential diagnosis with these types of aneurysms.

MP-453086-7 ATRIOVENTRICULAR JUNCTION ABLATION AND CARDIAC RESYNCHRONIZATION THERAPY IN PATIENTS WITH NONOBSTRUCTIVE HYPERTROPHIC CARDIOMYOPATHY AND PERMANENT ATRIAL FIBRILLATION

Atrial fibrillation (AF) is the most common arrhythmia encountered with hypertrophic cardiomyopathy (HCM) and is associated with adverse cardiovascular outcomes. The outcomes of ablate-and-pace strategy for the management of refractory AF in HCM patients are unclear. The objective of this retrospective study was to investigate the incremental benefit and safety of atrioventricular junction (AVJ) ablation and biventricular pacing (CRT) in patients with nonobstructive (NO) HCM and symptomatic permanent AF. Between January 2016 and December 2021, 20 patients with NO-HCM underwent AVJ ablation + CRT for uncontrolled permanent AF. The control group included 86 NO-HCM patients with permanent AF treated by the best medical rate-control therapy. A 1:1 propensity score (PS) matching analysis weighted on clinical (age, gender, hypertension, diabetes, recent hospitalization for heart failure [HF], cerebrovascular accident, chronic kidney disease, NYHA class) and imaging characteristics (left ventricle [LV] ejection fraction [EF], left atrial dimension, estimated pulmonary hypertension, maximal wall thickness, late gadolinium enhancement extension) was performed to compare outcomes between groups. The primary endpoint was a composite of all-cause mortality and hospitalization due to HF during follow-up. PS matching yielded 40 patients, 20 patients with AVN ablation + CRT (Group 1), and 20 patients in best medical rate-control therapy (Group 2). CRT was achieved in all patients (100% CRT-D). No acute procedure-related complications were noted. The mean paced QRS duration was 119±12 ms. Within the matched cohort, mean age was 64±7 years, the median time since AF diagnosis was 2 years (IQR 0.8-2.3 years), the mean LV EF was 53%±5%. During a median follow-up period of 23 months (IQR 19-27 months), patients in Group 1 had a lower risk of primary outcomes (HR 0.7; 95% CI 0.47-0.92; p=0.04), mainly driven by a significantly lower risk of HF hospitalization (HR 0.4; 95% CI 0.23–0.75; p=0.02). Compared to Group 2, Group 1 experienced a significant improvement in LV EF (55%±5% [Group 1] vs 48%±6% [Group 2], p=0.03) and improvement in NYHA class. No long-term device-related complications were noted. Ablation of AVJ + CRT was safe and superior to medical therapy in reducing HF hospitalization in patients with NO-HCM and permanent AF.

Fetal Supraventricular Tachycardia: Histologic Evidence of Accessory Pathways Due to Incomplete Annulus Fibrosus Formation.

Atrioventricular (AV) reentrant tachycardia is a common type of supraventricular tachycardia (SVT) that occurs in the fetus and neonate. Although many tachycardias resolve within several weeks of birth or respond to medical management, disruptions in the cardiac annulus fibrosus and development of additional accessory pathways may lead to refractory dysrhythmia resulting in fetal hydrops and ultimately, fetal death. While accessory pathways have been well documented anatomically in adult and childhood tachyarrhythmias, there are no reports of the histology of these pathways in human fetuses with SVT. This is a small case series of 2 fetuses with a history of SVT that resulted in fetal hydrops. In both cases, examination of the cardiac conduction system was unremarkable and examination of the atrioventricular junction revealed a focally thinned and/or discontinuous annulus fibrosus with documented direct continuity between the atrial and ventricular myocardium in 1 case. This case series demonstrates that thinning or absence of the annulus fibrosus is a feature seen in fetal SVT, and the development of subsequent aberrant AV connections due to defective formation of the annulus fibrosus suggests a possible cause for these arrhythmias.

The impact of rate and rhythm control strategies on quality of life for patients with atrial fibrillation: a protocol for a systematic review

BackgroundAtrial fibrillation (AF) is the most common heart arrhythmia globally and it adversely affects the quality of life (QoL). Available rate and rhythm control strategies equally reduce mortality but may impact QoL differently. A number of systematic reviews have focused on the impact of specific strategies on QoL, though a 2006 review synthesized the evidence on the effect of all strategies on QoL, allowing for a clinically important comparison between the types of strategies. Many trials have been published since the review undertook the search in 2005; therefore, an update is needed. This systematic review aims to provide an update to the 2006 review on the impact of all rate and rhythm control strategies on QoL in people with AF.MethodsThe following four databases and three clinical trial registries will be searched for primary studies: CENTRAL, MEDLINE, Embase, CINAHL, WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, and ClinicalTrialsRegister.eu. No language restriction will be applied. The search will be limited to 2004 or later publication year to allow overlap with the search conducted by the 2006 review authors. Any randomized control trial that reports the QoL of adult (≥ 18 years) AF patients following an eligible rate or rhythm control intervention will be eligible for inclusion. Eligible interventions (and comparators) include pacing, atrioventricular node junction and bundle of HIS ablation, pharmacological therapy, radio frequency catheter ablation, cryoablation, pulmonary vein isolation, maze operation, pace maker implantation, and defibrillator implantation. Two reviewers will independently screen for eligible studies, extract the data using a piloted tool, and assess bias by QoL outcome using the RoB 2 tool. The suitability of conducting a meta-analysis will be assessed by the clinical and methodology similarities of included studies. If it is feasible, standardized mean differences will be pooled using a random-effects model and assessed appropriately.DiscussionThe findings from this review will allow for meaningful comparisons between various rate and rhythm control strategies regarding their impact on QoL. This review will be useful for a wide range of stakeholders and will be crucial for optimizing the overall wellbeing of AF patients.Systematic review registrationPROSPERO CRD42021290542

Junctional ectopic tachycardia as an AVNRT catheter ablation complication in children

Junctional ectopic tachycardia (JET) occurs postoperatively or after catheter ablation in the region of Koch's triangle. The post-ablation incidence of JET reported in the medical literature is very low. We report the case of a 13-year-old female patient who underwent catheter ablation of the slow pathway for atrioventricular node reentrant tachycardia and subsequently developed JET. An accelerated automatic ectopic focus was found in the atrioventricular junction area due to radiofrequency applications. Treatment with metoprolol, ivabradine, propafenone, and amiodarone was ineffective in stopping the arrhythmia. However, JET resolved within 30 days without other antiarrhythmic drugs.

Expression of Stem Cell Niche-Related Biomarkers at the Base of the Human Tricuspid Valve.

Stem cell niches have been thoroughly investigated in tissue with high regenerative capacity but not in tissues where cell turnover is slow, such as the human heart. The left AtrioVentricular junction (AVj), the base of the mitral valve, has previously been proposed as a niche region for cardiac progenitors in the adult human heart. In the present study, we explore the right side of the human heart, the base of the tricuspid valve, to investigate the potential of this region as a progenitor niche. Paired biopsies from explanted human hearts were collected from multi-organ donors (N = 12). The lateral side of the AVj, right atria (RA), and right ventricle (RV) were compared for the expression of stem cell niche-related biomarkers using RNA sequencing. Gene expression data indicated upregulation of genes related to embryonic development and extracellular matrix (ECM) composition in the proposed niche region, that is, the AVj. In addition, immunohistochemistry showed high expression of the fetal cardiac markers MDR1, SSEA4, and WT1 within the same region. Nuclear expression of HIF1α was detected suggesting hypoxia. Rare cells were found with the co-staining of the proliferation marker PCNA and Ki67 with cardiomyocyte nuclei marker PCM1 and cardiac Troponin T (cTnT), indicating proliferation of small cardiomyocytes. WT1+/cTnT+ and SSEA4+/cTnT+ cells were also found, suggesting cardiomyocyte-specific progenitors. The expression of the stem cell markers gradually decreased with distance from the tricuspid valve. No expression of these markers was observed in the RV tissue. In summary, the base of the tricuspid valve is an ECM-rich region containing cells with expression of several stem cell niche-associated markers. Co-expression of stem cell markers with cTnT indicates cardiomyocyte-specific progenitors. We previously reported similar data from the base of the mitral valve and thus propose that human adult cardiomyocyte progenitors reside around both atrioventricular valves.

A conversion CRT strategy combined with AVJA may be a perspective alternative for heart failure patients with persistent atrial fibrillation.

Heart failure (HF) combined with persistent atrial fibrillation (AF) often coexist and may promote the pathological conditions of cardiac dysfunction, leading to poor prognosis. Cardiac resynchronization therapy (CRT) combined with atrioventricular junction ablation (AVJA) is a highly effective treatment for HF patients with underlying AF who either have failed or are not suitable for catheter ablation. The CRT-AVJA combination therapy can improve clinical outcomes in HF patients. Currently, clinical CRT methods are categorized into biventricular pacing (BVP) - based and conduction system pacing (CSP) - based methods. These procedures have inherent advantages and disadvantages, in addition to their considerable differences in clinical applications. This article aims to review the clinical progress of AVJA combined with different CRT strategies for treating HF patients with persistent AF and propose that conversion CRT strategy (BVP/CSP-CRT) combined with AVJA may be a perspective alternative. Meanwhile, we generalize that 7 categories of HF patients with persistent AF may need to consider the CRT-AVJA combination therapy.

PS-R02-9: A PATIENT HAS THE ONLY CONNECTION BETWEEN THE ATRIUM AND VENTRICLE IS AN ACCESSORY PATHWAY

Case report: A 62-year-old woman without cardiovascular risk factors such as hypertension, diabetes, smoking and hyperlipidemia was admitted to our cardiology outpatient clinic with palpitations and syncope history. Her electrocardiography showed preexcitation possible posteroseptal accessory pathway. We performed electrophysiological study and found posteroseptal accessory pathway. Tachycardia was not induced in inductions. ERP detected below 240 msn. The area where the shortest V-A interval was detected. His signal was not detected in this region. We determined that it was anatomically far from the AV node. We started radiofrequency ablation and in the 5. second of ablation, we saw that the patient entered 3. degree AV block. Ablation was immediately stopped then sinus rhythm restored in patients qucikly. We search his signal with ablation catheter in right atrium but could not find the signal. We detected that the AV block and accessory pathway were found together in the patient. Since the patient had a history of syncope and ERP &lt; 250 ms was detected, we planned ablation after pacemaker implantation in the patient. We implant DDDR pacemaker and 2 weeks later we make successfully accessory pathway ablation. Discussion: In these patients, atrioventricular conduction is done only, and entirely, via the accessory route. A complete block, nodal or sub-Hissian, underlying, will only be visible on the ECG if there is concomitant blockage of the atrioventricular conduction through the accessory pathway. The appearance of atrioventricular conductive disorders after radiofrequency ablation of an accessory pathway, located at a distance from the atrioventricular junction, is not considered by some authors to be a real complication of this procedure. It would rather be a prior conductive disorder having been unmasked following the blockage of the accessory pathway thanks to ablation. It is therefore logical to review the indication for the removal of the accessory pathway in these cases, especially in asymptomatic patients who have never reported a history of palpitation attacks. The only possible tachycardia remains atrial fibrillation on WPW. Only the study of anterograde refractory periods makes it possible to specify the correct indication for ablative treatment. The indication for the implantation of a pacemaker is still appropriate given the risk of progressive and subsequent degeneration of the accessory pathway. In addition, conduction via the accessory pathway, whether continuous or intermittent, would help prolong the longevity of the pacemaker by inhibiting ventricular pacing in the event of atrioventricular conduction through the accessory pathway.