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A 55-year-old man presented with occasional shortness of breath and palpitations for the last 6 months. Holter monitoring revealed intermittent complete heart block and junctional escape rhythm. Transthoracic echocardiography was unremarkable. Cardiac MR was performed to look for any scar or any

Objectives This study sought to describe the electrophysiologic properties and catheter ablation outcomes for T-AVRT. Background Although catheter ablation for atrioventricular (AV) reciprocating tachycardia via twin AV nodes (T-AVRT) is an established entity, there are few data on the electrophysiological properties and outcomes of this procedure. Methods An international, multicenter study was conducted to collect retrospective procedural and outcomes data for catheter ablation of T-AVRT. Results Fifty-nine patients with T-AVRT were identified (median age at procedure, 8 years [interquartile range, 4.4-17.0 years]; 49% male). Of these, 55 (93%) were diagnosed with heterotaxy syndrome (right atrial isomerism in 39, left atrial isomerism in 8, and indeterminate in 8). Twenty-three (39%) had undergone Fontan operation (12 extracardiac, 11 lateral tunnel). After the Fontan operation, atrial access was conduit or baffle puncture in 15 (65%), fenestration in 5 (22%), and retrograde in 3 (13%). Acute success was achieved in 43 (91%) of 47 attempts (targeting an anterior node in 23 and posterior node in 24). There was no high-grade AV block or change in QRS duration. Over a median of 3.8 years, there were 3 recurrences. Of 7 patients with failed index procedure or recurrent T-AVRT, 6 (86%) were associated with anatomical hurdles such as prior Fontan or catheter course through an interrupted inferior vena cava–to–azygous vein continuation (P = 0.11). Conclusions T-AVRT can be targeted successfully with low risk for recurrence. Complications were rare in this population. Anatomical challenges were common among patients with reduced short and long-term efficacy, representing opportunities for improvement in procedural timing and planning.

The peculiar electrophysiological properties of the sinoatrial node and the cardiac conduction system are key components of the normal physiology of cardiac impulse generation and propagation. Multiple genes and transcription factors and metabolic proteins are involved in their development and regulation. In this review, we have summarized the genetic underlying causes, key clinical findings, and the latest available clinical evidence. We will discuss clinical diagnosis and management of the genetic conditions associated with conduction disorders that are more prevalent in clinical practice, for this reason, very rare genetic diseases presenting sinus node or cardiac conduction system abnormalities are not discussed. Sin financiación No data JCR 2021 0.422 SJR (2021) Q3, 200/356 Cardiology and Cardiovascular Medicine No data IDR 2021 UEM

Atrioventricular (AV) nodal conduction is decremental and very prone to alterations in autonomic tone. Conduction through the His-Purkinje system (HPS) is via fast channel tissue and typically not that dependent on autonomic perturbations. Applying these principles, when the sinus rate is stable and then heart block suddenly occurs preceded by even a subtle slowing of heart rate, it typically is caused by increased vagal tone, and block occurs in the AV node. Heart block with activity strongly suggests block in the HPS. Enhanced sympathetic tone and reduced vagal tone can facilitate induction of both AV and atrioventricular node reentry.

Delayed atrioventricular (AV) conduction most commonly occurs in the AV node, resulting from AH prolongation on an intracardiac electrocardiogram and PR prolongation on a surface electrocardiogram. AV conduction may be blocked in a 2:1 manner, with a normal PR interval and wide QRS suggesting infranodal disease, whereas a prolonged PR interval and narrow QRS are more suggestive of AV nodal disease. Block within the His is suspected when there is 2:1 AV block with normal PR and QRS intervals. Complete heart block occurs when the atrial rhythm is totally independent of a junctional or lower escape rhythm.

PR prolongation (first-degree AV block) is defined primarily as delayed conduction through the atrioventricular (AV) node, but can also signify delayed electrical impulse propagation through any part of the specialized conduction system. The prevalence of PR prolongation ranges from 1-5% in patients younger than 50 years of age, with increasing prevalence, particularly after the sixth decade of life and in patients with organic heart disease. While classical studies suggest no adverse associations linked to PR prolongation, contemporary studies have documented increased risk of atrial arrhythmias, heart failure, and mortality in patients with PR prolongation. Future studies are needed to risk stratify elderly patients with PR prolongation who may be at increased risk of adverse outcomes and determine the optimal monitoring strategy for future follow-up.

The funny current, I f, was first recorded in the heart 40 or more years ago by Dario DiFrancesco and others. Since then, we have learnt that I f plays an important role in pacemaking in the sinus node, the innate pacemaker of the heart, and more recently evidence has accumulated to show that I f may play an important role in action potential conduction through the atrioventricular (AV) node. Evidence has also accumulated to show that regulation of the transcription and translation of the underlying Hcn genes plays an important role in the regulation of sinus node pacemaking and AV node conduction under normal physiological conditions - in athletes, during the circadian rhythm, in pregnancy, and during postnatal development - as well as pathological states - ageing, heart failure, pulmonary hypertension, diabetes and atrial fibrillation. There may be yet more pathological conditions involving changes in the expression of the Hcn genes. Here, we review the role of I f and the underlying HCN channels in physiological and pathological changes of the sinus and AV nodes and we begin to explore the signalling pathways (microRNAs, transcription factors, GIRK4, the autonomic nervous system and inflammation) involved in this regulation. This review is dedicated to Dario DiFrancesco on his retirement.

Aims Accurate determination of intra-atrial conduction velocity (CV) is essential to identify arrhythmogenic areas. The most optimal, commonly used, estimation methodology to measure conduction heterogeneity, including finite differences (FiD), polynomial surface fitting (PSF), and a novel technique using discrete velocity vectors (DVV), has not been determined. We aim (i) to identify the most suitable methodology to unravel local areas of conduction heterogeneities using high-density CV estimation techniques, (ii) to quantify intra-atrial differences in CV, and (iii) to localize areas of CV slowing associated with paroxysmal atrial fibrillation (PAF). Methods and results Intra-operative epicardial mapping (>5000 sites, interelectrode distances 2 mm) of the right and left atrium and Bachmann’s bundle (BB) was performed during sinus rhythm (SR) in 412 patients with or without PAF. The median atrial CV estimated using the DVV, PSF, and FiD techniques was 90.0 (62.4–116.8), 92.0 (70.6–123.2), and 89.4 (62.5–126.5) cm/s, respectively. The largest difference in CV estimates was found between PSF and DVV which was caused by smaller CV magnitudes detected only by the DVV technique. Using DVV, a lower CV at BB was found in PAF patients compared with those without atrial fibrillation (AF) [79.1 (72.2–91.2) vs. 88.3 (79.3–97.2) cm/s; P Conclusions Areas of local conduction heterogeneities were most accurately identified using the DVV technique, whereas PSF and FiD techniques smoothen wavefront propagation thereby masking local areas of conduction slowing. Comparing patients with and without AF, slower wavefront propagation during SR was found at BB in PAF patients, indicating structural remodelling.

Objectives This study set out to examine outcomes from pediatric supraventricular tachycardia ablations over a 20-year period. This study sought to examine success rates and repeat ablations over time and to evaluate whether modalities such as 3-dimensional (3D) mapping, contact force, and cryotherapy have improved outcomes. Background Ablation of supraventricular tachycardia in pediatric patients is commonly performed in most congenital heart centers with excellent long-term results. Methods Data were retrieved from the NICOR (National Institute of Clinical Outcomes Research) database in the United Kingdom. Outcomes over time were evaluated, and procedure-related details were compared. Results There were 7,069 ablations performed from January 1, 1999, to December 31, 2018, at 10 centers. Overall, ablation success rates were 92% for accessory pathways, 97% for atrioventricular node re-entry tachycardia, and 89% for atrial tachycardia. There was an improvement in procedural success rates over time (p Conclusions Overall success rates from pediatric ablations are excellent and compare favorably to other registries. Introduction of newer technologies have likely made procedures safer and reduced radiation exposure, but they have not changed success rates or the need for a repeat procedure.

Atrial flutter (AFL) is a large reentrant circuit located in the right atrium. Anti-arrhythmic drugs (AADs) can provoke AFL with 1:1 atrioventricular conduction (AVC) to cause hemodynamic collapse. We elucidated the characteristics of patients with AFL exhibiting spontaneous 1:1 AVC. Fifteen patients (1:1 AFL group; 11 males, 52.4 ± 13.7 years old) who documented AFL with 1:1 AVC were enrolled and compared to 153 patients without 1:1 AVC (Control group; 137 males, 68.9 ± 11.2 years old). AFL cycle length during maximum AVC was significantly longer in the 1:1 AFL group than in the control group (274.7 ± 37.0 vs. 216.2 ± 25.6 ms, p

Aims The exact circuit of atrioventricular nodal re-entrant tachycardia (AVNRT) remains elusive. To assess the location and dimensions of the AVNRT circuit. Methods and results Both typical and atypical AVNRT were induced at electrophysiology study of 14 patients. We calculated the activation time of the fast and slow pathways, and consequently, the length of the slow pathway, by assuming an average conduction velocity of 0.04 mm/ms in the nodal area. The distance between the compact atrioventricular node and the slow pathway ablating electrode was measured on three-dimensionally reconstructed fluoroscopic images obtained in diastole and systole. We also measured the length of the histologically discrete right inferior nodal extension in 31 human hearts. The length of the slow pathway was calculated to be 10.8 ± 1.3 mm (range 8.2–12.8 mm). The distance from the node to the ablating electrode was measured in five patients 17.0 ± 1.6 mm (range 14.9–19.2 mm) and was consistently longer than the estimated length of the slow pathway (P Conclusion Successful ablation affects the tachycardia circuit without necessarily abolishing slow conduction, probably by interrupting the circuit at the septal isthmus.

Background: His bundle pacing (HBP) is a physiological alternative to biventricular (BiV) pacing. We compared short-term results of both pacing approaches in symptomatic atrial fibrillation (AF) patients with moderately reduced left ventricular (LV) ejection fraction (EF ≥35% and

INTRODUCTION In patients with uncontrolled atrial fibrillation, atrioventricular (AV) node ablation after permanent His bundle pacing (p-HBP) could be a therapeutic option for heart rate (HR) control. We aimed to demonstrate the advantages of AV node ablation with p-HBP, and to describe its effectiveness and safety. METHODS This descriptive observational study included patients with uncontrolled permanent atrial arrhythmias who were candidates for HR control (January 2019 to July 2020) and underwent p-HBP and AV node ablation. RESULTS A total of 39 patients were included. The median left ventricular ejection fraction (LVEF) was 55% (45-60); 46.1% in NYHA class II and 43.6% in NYHA class III. p-HBP was achieved in 92.3% (n = 36), and AV node ablation was successfully performed in all patients. The LVEF improved in patients with reduced LVEF (baseline, 35% [23.8-45.3%]; follow-up, 40% [35-56.5%], p

A model of the cardiac conduction system is considered. The model provides an insight into the electrical processes in the myocardium under normal and pathological conditions. The model takes into account the involvement of the atria in generating the sinus rhythm of the heart and the sinus rhythm disorders in arrhythmia. The role of the atrioventricular node in reducing the risks associated with the cardiac conduction disorders in the sinoatrial region is considered. This includes frequency filtering of impulses transmitted from atria to ventricles and the activity of the second-order automatism node. The model can include units for simulating third- and fourth-order automatism nodes and a source of impulses that can cause premature ventricular contraction.

Background Exercise capacity is an important aspect of quality of life in patients undergoing pacemaker implantation. Device algorithms for ventricular pacing avoidance have been developed to avoid unnecessary and potentially harmful effects of right ventricular pacing. However, little data exists on the immediate response of these algorithms to sudden AV block during exercise.Methods The ventricular pacing avoidance algorithms of four pacemaker manufacturers were tested in an ex-vivo model. The RSIM-1500-USB Device-Interactive Heart Simulator (Rivertek Medical Systems, Inc.) was used to simulate three different scenarios: the first one starting with an initially conducted atrial pacing rate of 60 min(-1), the second one starting with an atrial rate of 120 min(-1) and finally a scenario starting with an atrial rate of 150 min(-1). In all three scenarios, the initially conducted atrial rate was followed by a sudden, long lasting episode of third-degree AV-block. The response to those scenarios was recorded for each of the (brand-specific) ventricular pacing avoidance algorithms.Results In the first scenario, the simulation resulted in a ventricular pause of 1333 ms (Boston Scientific), 2000 ms (Medtronic and Microport), and 2340 ms (Biotronik). In the second and third scenario, different results were observed across devices. All simulations of the second and third scenario resulted in repetitive 2:1 block response (during eight cycles) in Boston Scientific and Biotronik devices. These scenarios were confirmed in patient cases.Conclusion Simulator based observations of unanticipated pacemaker-induced 2:1 block response during exercise may explain clinical symptoms experienced by some patients having a two-chamber pacemaker.

Electrical activity in the heart exhibits 24-hour rhythmicity, and potentially fatal arrhythmias are more likely to occur at specific times of day. Here, we demonstrate that circadian clocks within the brain and heart set daily rhythms in sinoatrial (SA) and atrioventricular (AV) node activity, and impose a time-of–day dependent susceptibility to ventricular arrhythmia. Critically, the balance of circadian inputs from the autonomic nervous system and cardiomyocyte clock to the SA and AV nodes differ, and this renders the cardiac conduction system sensitive to decoupling during abrupt shifts in behavioural routine and sleep-wake timing. Our findings reveal a functional segregation of circadian control across the heart’s conduction system and inherent susceptibility to arrhythmia., Cardiac function fluctuates greatly across the day and night, but this is not simply a consequence of our changing behaviour. The authors highlight the role of the body’s circadian clock in regulating the heart electrical activity, including a time-of-day dependent susceptibility to cardiac arrhythmias.

Background A 61-year-old female patient requested a homeopathic therapy as an alternative to a pacemaker for a non-acute myocardial infarction, high-grade atrioventricular node block (HG-AVNB) with a narrow QRS complex. Methods Homeopathic Digitalis purpurea (Digitalis) was employed to accelerate the patient's heart rate. Results Digitalis caused within 3 days a pulse rate of about 90 beats per minute (bpm) which is represented on the electrocardiogram (ECG) by an accelerated junctional rhythm (AJR).The AJR compelled seeking a medicine to reduce its rate. Homeopathic Arsenicum album (Arsenicum) reduced its rate and also seemed to have assisted in the unanticipated recovery of the atrioventricular node (AVN). Conclusions This case report represents, an ECG documented case of a medical treatment modality which could be an alternative to pacemakers for patients with a HG-AVNB with a narrow QRS complex. Digitalis has been safe and effective during its 3 and a half year employment.

Sudden deaths in young active people and athletes are distinctly uncommon and frequently related to highly visible cardiovascular conditions including hypertrophic cardiomyopathy and congenital coronary anomalies. Myocarditis is also a cause of sudden death in the young, but frequently under-recognized clinically, and therefore deserving of the present analysis. Two large registries were interrogated for cases of myocarditis, and clinical, demographic, and pathologic findings were assessed. Of 97 cases of myocarditis identified, ages were 19.3 ± 6.2 years, 76% male, and 58 were physically active at or near the time of death. Almost one-half of the 97 cases (47%) had a viral prodrome or symptoms (i.e., syncope, malaise, chest pain or palpitations). Nine were evaluated by cardiologists, but in none was a diagnosis of myocarditis established before death. The inflammatory cellular infiltrate was predominantly lymphocytic (67%), was most frequently multifocal (59%) and involved the conduction system (including atrioventricular node), 38%. In conclusion, myocarditis is an important but under-recognized cause of sudden death in young people including competitive athletes. Clinical diagnosis is difficult because symptoms are nonspecific and often ignored, requiring high index of suspicion for diagnosis. Our data support the ACC/AHA consensus guidelines recommending removal of individuals with myocarditis from competitive sports during recovery. Selective examination of conduction systems showed a number of cases with involvement of myocarditis, suggesting a novel mechanism for sudden death.

BACKGROUND: A significant percentage of patients that acutely develop high-grade atrioventricular block following valve surgery will ultimately recover, yet the ability to predict recovery is limited. OBJECTIVES: The purpose of this analysis was to evaluate the cost effectiveness of two different management strategies for the timing of permanent pacemaker implantation for new heart block following valve surgery. METHODS: A cost effectiveness model was developed using costs and probabilities of short and long-term complications of pacemaker placement, short-term atrioventricular node recovery, intensive care unit stays, and long-term follow up. We aggregated the total expected cost and utility of each option over a 20 year time period. Quality-adjusted survival with a pacemaker was estimated from the literature and institutional patient-reported outcomes. Primary decision analysis was based on an expected recovery rate of 36.7% at 12 days with timing of pacemaker implantation: early placement (5 days) versus watchful waiting for 12 days. RESULTS: A strategy of watchful waiting was more costly ($171,798 ± $45,695 vs $165,436 ± $52,923, p

The University of Manchester Museum of Medicine and Health holds of collection of drawings of human hearts by anatomist Sir Arthur Keith (1866–1955). The specimens were provided by the cardiologist, Sir James Mackenzie (1853–1925) who was using a polygraph to investigate patients with cardiac arrhythmias. Keith’s dissections helped to establish the anatomy and pathology of the atrioventricular conduction system and assisted Mackenzie to interpret his polygraph recordings and understand the origin of cardiac arrythmias.

Context Management of atrial fibrillation includes either rhythm control that aims at establishing a sinus rhythm or rate control that aims at lowering the ventricular rate, usually with atrioventricular nodal blocking agents. Another potential strategy for ventricular rate control is to induce a negative dromotropic effect by augmenting cardiac vagal activity, which might be possible through noninvasive and nonpharmacologic techniques. Thus, the hypothesis of this study was that occipitoatlantal decompression (OA-D) and transcutaneous auricular vagus nerve stimulation (taVNS) not only increase cardiac parasympathetic tone as assessed by heart rate variability (HRV), but also slow atrioventricular conduction, assessed by the PQ-interval of the electrocardiogram (EKG) in generally healthy study participants without atrial fibrillation. Objectives To test whether OA-D and/or transcutaneous taVNS, which have been demonstrated to increase cardiac parasympathetic nervous system activity, would also elicit a negative dromotropic effect and prolong atrioventricular conduction. Methods EKGs were recorded in 28 healthy volunteers on three consecutive days during a 30 min baseline recording, a 15 min intervention, and a 30 min recovery period. Participants were randomly assigned to one of three experimental groups that differed in the 15 min intervention. The first group received OA-D for 5 min, followed by 10 min of rest. The second group received 15 min of taVNS. The intervention in the third group that served as a time control group (CTR) consisted of 15 min of rest. The RR- and PQ-intervals were extracted from the EKGs and then used to assess HRV and AV-conduction, respectively. Results The OA-D group had nine participants (32.1%), the taVNS group had 10 participants (35.7%), and the CTR group had nine participants (32.1%). The root mean square of successive differences between normal heartbeats (RMSSD), an HRV measure of cardiac parasympathetic modulation, tended to be higher during the recovery period than during the baseline recording in the OA-D group (mean ± standard error of the mean [SEM], 54.6 ± 15.5 vs. 49.8 ± 15.8 ms; p Conclusions The lengthening of the PQ-interval in the OA-D and taVNS groups was accompanied by an increase in RMSSD. This implies that the negative dromotropic effects of OA-D and taVNS are mediated through an increase in cardiac parasympathetic tone. Whether these findings suggest their utility in controlling ventricular rates during persistent atrial fibrillation remains to be determined.

Introduction: In patients with supraventricular arrhythmias and high ventricular rate, unresponsive to rate and rhythm control therapy or catheter ablation, atrioventricular (AV) node ablation may be performed. Objectives: To assess long-term outcomes after AV node ablation and to analyze predictors of adverse events. Methods: We performed a detailed retrospective analysis of all patients who underwent AV node ablation between February 1997 and February 2019, in a single Portuguese tertiary center. Results: A total of 123 patients, mean age 69±9 years and 52% male, underwent AV node ablation. Most of them presented atrial fibrillation at baseline (65%). During a median follow-up of 8.5 years (interquartile range 3.8-11.8), patients improved heart failure (HF)functional class (NYHA class III-IV 46% versus 13%, p=0.001), and there were reductions in hospitalizations due to HF (0.98±1.3 versus 0.28±0.8, p=0.001) and emergency department (ED) visits (1.1±1 versus 0.17±0.7, p=0.0001). There were no device-related complications. Despite permanent pacemaker stimulation, left ventricular ejection fraction did not worsen (47±13% vs. 47%±12, p=0.63). Twenty-eight patients died (23%). The number of ED visits due to HF before AV node ablation was an independent predictor of the composite adverse outcome (OR 1.8, 95% CI 1.24-2.61, p=0.002). Conclusions: Despite pacemaker dependency, the clinical benefit of AV node ablation persisted at long-term follow-up. The number of ED visits due to HF before AV node ablation was an independent predictor of the composite adverse outcome. AV node ablation should probably be considered earlier in the treatment of patients with supraventricular arrhythmias and HF, especially in cases that are unsuitable for selective ablation of the specific arrhythmia. Resumo: Introdução: Nos doentes com disritmias supraventriculares e frequência ventricular elevada, irresponsivos à terapêutica para controlo da frequência e do ritmo, ou à ablação por catéter, a ablação do nódulo auriculoventricular (ANAV) pode ser realizada. Objetivos: Avaliar os resultados em longo prazo após a ANAV e analisar preditores de eventos adversos. Métodos: Análise retrospetiva detalhada, dos doentes submetidos à ANAV entre fevereiro 1997 e fevereiro 2019, num centro terciário português. Resultados: Foram submetidos 123 doentes à ANAV: idade média 69 ± 9 anos e 52% homens. A maioria apresentou fibrilhação auricular (65%). Num período mediano de seguimento de 8,5 anos (intervalo interquartil 3,8-11,8), houve melhoria da classe funcional de insuficiência cardíaca (IC) (classe NYHA III-IV 46% versus 13%, p = 0,001) e redução dos internamentos por IC (0,98±1,3 versus 0,28±0,8, p=0,001), redução dos recursos ao serviço de urgência (SU) (1,1±1 versus 0,17±0,7, p=0,0001). Não houve complicações relacionadas ao dispositivo. Apesar da estimulação permanente de pacemaker, a FEVE não agravou (47%±13 versus 47%±12, p=0,63). Faleceram 28 doentes (23%). O número de recursos ao SU por IC antes do procedimento foi preditor independente do composto de eventos adversos (OR 1,8, IC95%, 24-2,61, p=0,002). Conclusões: Apesar da dependência de pacemaker, o benefício clínico da ANAV persistiu a longo prazo. O número de recursos ao SU por IC antes do procedimento foi preditor do composto de eventos adversos. Provavelmente, a ANAV deveria ser considerada mais cedo no tratamento de doentes com disritmias supraventriculares e IC, sobretudo nos casos em que a ablação seletiva da disritmia seja inapropriada.

We present the case of a 58-year-old patient admitted for wide QRS tachycardia (200 bpm). There was no delta wave on a 12-lead surface electrocardiogram during sinus rhythm. During the electrophysiological study, stimulation of the high right atrium and the proximal coronary sinus resulted in decremental anterograde conduction through the atrioventricular node, whereas pacing at the right ventricular apex led to retrograde conduction through the atrioventricular node. Conduction through an anterograde accessory pathway was revealed during pacing at the distal site of its atrial insertion. Some nonmanifest accessory pathways may be unmasked by differential pacing maneuvers.

There is minimal data regarding antegrade-only accessory pathways in young patients. Given evolving recommendations and treatments, retrospective analysis of the clinical and electrophysiologic properties of antegrade-only pathways in patients

In the human heart, the atrioventricular node is located toward the apex of the triangle of Koch, which is also at the apex of the inferior pyramidal space. It is adjacent to the atrioventricular portion of the membranous septum, through which it penetrates to become the atrioventricular bundle. Subsequent to its penetration, the conduction axis is located on the crest of the ventricular septum, sandwiched between the muscular septum and ventricular component of the membranous septum, where it gives rise to the ramifications of the left bundle branch. In contrast, the bovine conduction axis has a long non‐branching component, which penetrates into a thick muscular atrioventricular septum having skirted the main cardiac bone and the rightward half of the non‐coronary sinus of the aortic root. It commonly gives rise to both right and left bundle branches within the muscular ventricular septum. Unlike the situation in man, the left bundle branch is long and thin before it branches into its fascicles. These differences from the human heart, however, have yet to be shown in three‐dimensions relative to the surrounding structures. We have now achieved this goal by injecting contrast material into the insulating sheaths that surround the conduction network, evaluating the results by subsequent computed tomography. The fibrous atrioventricular membranous septum of the human heart is replaced in the ox by the main cardiac bone and the muscular atrioventricular septum. The apex of the inferior pyramidal space, which in the bovine, as in the human, is related to the atrioventricular node, is placed inferiorly relative to the left ventricular outflow tract. The bovine atrioventricular conduction axis, therefore, originates from a node itself located inferiorly compared to the human arrangement. The axis must then skirt the non‐coronary sinus of the aortic root prior to penetrating the thicker muscular ventricular septum, thus accounting for its long non‐branching course. We envisage that our findings will further enhance comparative anatomical research.

We compared dl-sotalol-induced electrocardiographic responses in intact dogs using a repeated-measures design among 1% halothane anesthesia, 1.5% isoflurane anesthesia with nitrous oxide (N2O), and conscious state to clarify influences of the anesthetics (n = 4). Basal PR interval was longer in halothane than either in isoflurane with N2O or in conscious state, reflecting sympathetic nerve suppression for the atrioventricular node by halothane. Both anesthetics exhibited longer basal QRS width than conscious state, suggesting their ventricular INa inhibition. Also, both anesthetics showed longer basal QT interval, QTcF and Tpeak-Tend than conscious state, indicating their ventricular IKr inhibition. Meanwhile, dl-sotalol prolonged PR interval similarly in isoflurane with N2O and in conscious state, which was less great in halothane, suggesting further sympathetic nerve suppression for the atrioventricular node might be limited in halothane. dl-Sotalol prolonged QT interval and QTcF >3 times greater in either of the anesthetics than in conscious state; moreover, dl-sotalol prolonged Tpeak-Tend similarly in both anesthetics, but hardly altered it in conscious state; indicating isoflurane with N2O as well as halothane may have reduced the repolarization reserve to increase the sensitivity of ventricle toward IKr suppression. Thus, isoflurane with nitrous oxide could be useful for in vivo IKr assay like halothane.

Up to one-third of patients who undergo cardiac resynchronization therapy do not obtain clinical benefit. A systematic approach can identify treatable causes in many nonresponding patients. We present a case of nonresponse to cardiac resynchronization therapy that resolved by ablation of the atrioventricular node in a patient with complete atrioventricular block. (Level of Difficulty: Advanced.), Graphical abstract

Introduction A middle-age woman underwent an electrophysiologic study due to recurrent atypical atrial flutter. Methods and result Radiofrequency ablation of cavotricuspid isthmus and anterior mitral line was performed. During energy delivery on the anterior left atrial wall, interatrial dissociation and complete block of the sinus impulse to the atrioventricular (AV) node was observed. AV node activation became dependent on a subsidiary left atrial rhythm. Conclusion Anatomical location of intra and inter-atrial connections must be taken into account when performing extensive ablation procedures, specially in cases with prior cardiac surgeries.

A retrospective study included 93 patients who underwent a drug conversion of the heart rhythm with amiodarone. They were divided into comparison groups. The first group consisted of 58 patients who received monotherapy with amiodarone. The second group consisted of 35 patients in whom propranololol was added to amiodarone. A comparative analysis was conducted to establish the efficacy and safety of medication conversion of rhythm with these treatment options. It was found that atrial fibrillation supplementation with amiodarone in combination with propranololol is registered more frequently and in a shorter time than with amiodarone alone. However, this treatment option is associated with a more pronounced reduction of conductivity in the atrioventricular node and the development of more pronounced bradycardia in 8.6% of cases.

Aims His-bundle pacing (HBP) combined with atrioventricular node (AVN) ablation has been demonstrated to be effective in patients with atrial fibrillation (AF) and heart failure (HF) during medium-term follow-up and there are limited data on the risk analysis of adverse prognosis in this population. In this study, we aimed to evaluate the long-term performance of HBP following AVN ablation in AF and HF. Methods and results From August 2012 to December 2017, consecutive AF patients with HF and narrow QRS who underwent AVN ablation and HBP were enrolled. The clinical and echocardiographic data, pacing parameters, all-cause mortality, and heart failure hospitalization (HFH) were tracked. A total of 94 patients were enrolled (age 70.1 ± 10.5 years; male 57.4%). Acute HBP were achieved in 89 (94.7%) patients with successful permanent HBP combined with AVN ablation in 81 (86.2%) patients. Left ventricular ejection fraction (LVEF) improved from 44.9 ± 14.9% at baseline to 57.6 ± 12.5% during a median follow-up of 3.0 (IQR: 2.0–4.4) years (P Conclusion His-bundle pacing combined with AVN ablation was effective in patients with AF and drug-refectory HF. High PASP, high Scr, or low LVEF at baseline was independent predictors of composite endpoint of all-cause mortality or HFH.

A 56‐year‐old female with manifest Wolff‐Parkinson‐White (WPW) syndrome was sent to emergency room because of preexcited atrial fibrillation (AF) and became sinus rhythm after cardioversion. Then, she received catheter ablation of a left‐sided lateral accessory pathway. The patient immediately developed Wenckebach atrioventricular (AV) block and left bundle branch block (LBBB) during the initial ablation. The ECG still showed LBBB 1 hour after ablation. The LBBB became narrow QRS (The QRS complex in the electrocardiogram. The QRS complex includes the Q wave, R wave, and S wave) 1 day later. Two weeks later, Holter's ECG showed normal sinus rhythm with 1:1 AV conduction even at the maximum heart rate of 125 beats/min. Transient LBBB and poor AV nodal conduction could occur during ablation by the trans‐aortic approach., A 56‐year‐old female with manifest Wolff‐Parkinson‐White (WPW) syndrome was sent to emergency room because of atrial fibrillation with rapid wide QRS tachycardia and became sinus rhythm after cardioversion. After she received catheter ablation of a left‐sided lateral accessory pathway for 1 hour, the ECG showed LBBB, and the LBBB became narrow QRS 1 day later. Eliminating the accessory pathway could recover the AV nodal and His‐Purkinje conduction.