Bundle Of His Research Articles

Cardiac Conduction System in Congenitally Corrected Transposition of the Great Arteries and Its Clinical Relevance

Congenitally corrected transposition of the great arteries (ccTGA) is a rare cardiac malformation characterized by the combination of discordant atrioventricular and ventriculoarterial connections.1 The incidence has been reported to be around 1/33 000 live births, accounting for ≈0.05% of congenital heart malformations.2 Although a familial recurrence of heart defects in subjects with ccTGA has been reported,3 the etiology of this malformation is not currently known.1, 4 The morphological right atrium is connected to the morphological left ventricle across the mitral valve, with the left ventricle then connected to the pulmonary trunk; the morphological left atrium is connected to the morphological right ventricle across the tricuspid valve, with the morphological right ventricle connected to the aorta. Because of this “double discordance,” the systemic venous return is pumped to the lungs, while the pulmonary venous return is directed to the body. In the context of usual atrial arrangement (situs solitus), the morphological left ventricle is thus positioned to the right and the aorta, arising from the morphological right ventricle, is more commonly left‐sided. In mirror‐image atrial arrangement (situs inversus), the morphological left ventricle is left‐sided, and the aorta is usually positioned to the right. Most patients have at least 1 associated cardiac anomaly, mainly ventricular septal defect (VSD), subvalvular and/or valvular pulmonary stenosis, or abnormalities of the systemic (tricuspid) atrioventricular (AV) valve with coexisting accessory pathways.4 Because of the unusual position of the atrioventricular node and course of the atrioventricular conduction bundle, cardiac conduction disorders are frequent and markedly alter the natural history and management of the malformation.5, 6, 7 This article provides a comprehensive, up‐to‐date description of the characteristics of the cardiac conduction system in patients with ccTGA, their clinical sequelae, and their contemporary management.

Neuroanatomy of the Pig Cardiac Ventricles. A Stereomicroscopic, Confocal and Electron Microscope Study.

Although the pig is a model for heart disease, the neuroanatomy of cardiac ventricles (CV) in this species remains undetailed. We aimed to define the innervation pattern of pig CV, combining histochemistry for acetylcholinesterase, immunofluorescent labeling and electron microscopy. Forty nine examined pig hearts show that the major nerves supplying the ventral side of CV descend from the venous part of the heart hilum. Fewer in number and smaller in size, epicardial nerves supply the dorsal half of the CV. Epicardial nerves on the left ventricle are thicker than those on the right. Ventricular ganglia of various sizes distribute at the basal level of both CV. Averagely, we found 3,848 ventricular neuronal somata per heart. The majority of somata were cholinergic, although ganglionic cells of different neurochemical phenotypes (positive for nNOS, ChAT/nNOS, or ChAT/TH) were also observed. Large and most numerous nerves proceeded within the epicardium. Most of endocardium and myocardium contained a network of nerve bundles and nerve fibers (NFs). But, a large number of thin nerves extended along the bundle of His and its branches. The majority of NFs were adrenergic, while cholinergic NFs were scarce yet more abundant than nitrergic ones. Sensory NFs positive for CGRP were the second most abundant phenotype after adrenergic NFs in all layers of the ventricular wall. Electron microscopy elucidated that ultrastructure of nerves varied between different areas of CV. The described structural organization of CV provides an anatomical basis for further functional and pathophysiological studies in the pig heart. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1756-1780, 2017. © 2017 Wiley Periodicals, Inc.

Histological topography of the atrioventricular node and its extensions in relation to the cardiothoracic surgical landmarks in normal human hearts.

Atrioventricular (AV) nodal injury which results in cardiac conduction disorders is one of the potential complications of heart valve surgeries and radiofrequency catheter ablations. Understanding the topography of the AV conduction system in relation to the tricuspid and mitral valves will help in reducing these complications. A tissue block of 3cmx4cm, which contain the AV node, bundle of His and the AV nodal extensions, was excised at the AV septal junction in 20 apparently normal human hearts. The block was divided into three equal segments through vertical incisions perpendicular to the insertion of the septal leaflet of the tricuspid valve. Each segment was processed and stained with H&E and Gomori to study the different parts of the AV conduction system. The lower pole of the AV node was located vertically above the tricuspid septal leaflet (TSL) in 100% (20/20) of cases and at the level of the muscular interventricular septum in 65% (13/20) of cases. The upper pole of the compact AV node was located at the level of the mitral valve leaflet (MVL) in 50% (10/20) of cases. The penetrating bundle of His was seen at the level of the TSL, while the branching bundle of His was situated 1.9±1.5 mm inferior to the TSL. The right and left posterior extensions of the AV node spanned from the MVL to 2.9±1.3 mm above the TSL. A rectangular area (2.5 mm × 12 mm) in the Koch's triangle was devoid of AV nodal tissue and could be labeled as a safe area with no risk of conduction defects during valve surgeries. Information on the separation of AV nodal extensions from the TSL, MVL and muscular interventricular septum may play a crucial role in guiding and improving the safety of radiofrequency ablations.

Microscopic Topography of Atrioventricular Conduction System–A Feature of Potential Clinical Significance

ObjectivesProximity of atrioventricular (AV) conduction system to tricuspid, mitral and aortic valves renders it susceptible to injury leading to disturbances in patients undergoing valve operations and radiofrequency catheter ablations. Hence, the knowledge of topography of AV conduction system and its relations with surrounding cardiac structures is indispensible.MethodsIn 20 cases, a tissue block of 3×4 cm at AV septal junction was excised which included the borders of Koch's triangle. The block was divided into three equal segments by parallel vertical incisions made perpendicular to insertion of septal leaflet of tricuspid valve. Each segment was processed for Hematoxylin & Eosin and Gomori stain.ResultsThe upper pole of compact AV node was at the level of mitral valve leaflet in 50% cases. Lower pole of AV node was vertically above tricuspid septal leaflet and at the level of muscular IV septum in 100% and 66.7% cases respectively. The subendocardial depth of upper and lower pole of AV node was 1.45±0.6 mm and 0.92±0.3 mm respectively. Minimum subendocardial depth (0.68±0.2mm) was seen at the center of compact AV node. Penetrating bundle of His was seen at the level of tricuspid septal leaflet just deep to it, while Branching bundle of His was 1.98±1.5 mm below the tricuspid septal leaflet. AV nodal extensions began at the level of mitral valve leaflet while its inferior extension ended 2.92±1.3 mm above tricuspid septal leaflet.ConclusionPrior knowledge of distances of AV conduction system from the surrounding landmarks might help in surgical incision planning, safe suture placement and successful device insertion.Support or Funding InformationFrom Director PGIMER, Chandigarh, India.

Abstract MP083: Autonomic Imbalance at the Level of Atrioventricular Node, but Not at the Level of Sinus Node, is Associated With Sudden Cardiac Death: The Atherosclerosis Risk in Community Study

Introduction: Autonomic imbalance, quantified by decreased heart rate variability (HRV), is associated with increased cardiovascular mortality. It is unknown if autonomic influences on sinus and atrioventricular (AV) nodes are equally important for the risk of sudden cardiac death (SCD). Hypothesis: Autonomic influences on sinus and AV node are equally strongly associated with increased SCD, non-sudden cardiac death (non-SCD), and non-cardiac death. Methods: Baseline visit 10-second ECGs (n=14,250) of the Atherosclerosis Risk in Communities (ARIC) cohort were analyzed. Normalized variance of P-onset to P-onset intervals (PPVN) and QRS-onset to QRS-onset intervals (QQVN) was calculated to assess autonomic influence on sinus and AV node respectively. Normalized variance of Rpeak - Rpeak intervals was determined as HRV measure. Values were log-transformed to normalize distribution. SCD served as primary outcome. Secondary outcomes were non-SCD and non-cardiac death. Three Cox regression models were constructed for dichotomized at 20 th percentile predictor variables. Results: Over median follow-up of 24.4 years, there were 497 SCDs (incidence 1.66 [95%CI 1.52-1.82], 742 non-SCDs (incidence 2.48 [95%CI 2.31-2.67], and 3,753 non-cardiac deaths (incidence 12.6 [95%CI 12.1-13.0]) per 1,000 person-years. In paired analysis, LogPPVN was significantly larger than LogQQVN (-7.28±1.06 vs. -7.72±1.24; P<0.0001). There was no difference between LogQQVN and Log RRVN (-7.72±1.24 vs -7.72±1.23; P=0.364). After full adjustment, LogRRVN and LogQQVN were significantly associated with non-SCD and SCD. Association with non-SCD was stronger. LogPPVN was independently associated with non-SCD but not SCD. No value was associated with non-cardiac death. Conclusion: Autonomic imbalance at the AV node, with likely summary effect at the bundle of His, is associated with SCD and non-SCD. Autonomic imbalance at the SA node is associated with non-SCD only. Autonomic input to SA and AV node should be further studied.

Permanent His Bundle Pacing: The Past, Present, and Future.

Long-term right ventricular (RV) apical pacing has been associated with an increased risk of death, heart failure, and atrial fibrillation (AF). Alternative sites for RV pacing have not proven to be superior to RV apical pacing. Cardiac resynchronization therapy (CRT) using a biventricular (BiV) lead system is indicated for patients with a low left ventricular ejection fraction and QRS prolongation, but there remains about a 25-30% nonresponse rate. CRT has been less effective for nonleft bundle branch block conduction delay and with normal/low normal left ventricular function. Over the past decade, there have been more data on the feasibility and advantages of pacing at the His Bundle (HB) region. We review the anatomy and physiology of the HB, the available data on permanent HB pacing, its current and potential future applications.

Simulation of ventricular rate control during atrial fibrillation using ionic channel blockers

BackgroundThe atrioventricular (AV) node is the only compartment that conducts an electrical impulse between the atria and the ventricles. The main role of the AV node is to facilitate efficient pumping by conducting excitation slowly between the two chambers as well as reduce the ventricular rate during atrial fibrillation (AF). MethodsUsing computer simulations, we investigated excitation conduction from the right atrium to the bundle of His during high-rate atrial excitation with or without partial blocking of the calcium or potassium ionic current. ResultsOur simulations revealed differences in rate reduction and repolarization effects between calcium and potassium current blocking and high degree of potassium current blocking required to reduce the ventricular rate during AF. ConclusionsOur simulation results explain why potassium current blockers are not recommended for controlling ventricular rate during AF.

An Intrinsic Angiogenesis Approach and Varying Bioceramic Scaffold Architecture Affect Blood Vessel Formation in Bone Tissue Engineering <i>In Vivo</i>

Early establishment of angiogenesis is critical for bone tissue engineering. Recently, a technique was introduced, which is based on the idea of using axial vascularization of the host tissues in engineered grafts, namely the “intrinsic angiogenesis chamber” technique, which utilizes an artery and a vein to construct an AV-Bundle. The aim of this study was to evaluate the effect of varying scaffold architecture of calcium alkali orthophosphate scaffolds (CAOP), resulting from two different fabrication procedures, namely 3D printing (RP) or a Schwarzwalder-Somers replica technique (SSM), on angiogenesis in vivo when combining a microvascular technique with bioceramic scaffolds colonized with stem cells for bone tissue engineering. 32 adult female Wistar rats, in which critical size segmental discontinuity defects 6 mm in length were created in the left femur, were divided into 4 groups, group 1 received a RP scaffold colonized with rat stem cells after 7d of dynamic cell culture and an AV-Bundle (AVB), group 2 a SSM scaffold with rat stem cells after 7d of dynamic cell culture and an AVB, group 3 a RP control scaffold (without cells and AVB), group 4 a SSM control scaffold (without cells and AVB). After 3 and 6 months, angiomicro-CT after perfusion with a contrast agent, image reconstruction, histomorphometric and immunohistochemical analysis utilizing antibodies to collagen IV, vWF and CD-31 were performed. At 6 months, a statistically significant higher blood vessel volume%, blood vessel surface/volume, blood vessel thickness, blood vessel density and blood vessel linear density was observed with RP scaffolds with cells and AVB than with the other groups. At 6 mths, RP with cells and AVB displayed the highest expression of collagen IV (score 2.75), CD31 (score 2.75) and vWF (score 2.6), which is indicative of highly dense blood vessels. Both angio-CT and immunohistochemical analysis demonstrated that AVB is an efficient technique for achieving scaffold vascularization in critical size segmental defects after 3 and 6 months of implantation.

Septal Atrioventricular Junction Region: Comprehensive Imaging in Adults.

The septal atrioventricular junction is a centrally located region of the heart where the septal components of the atria and ventricles meet the aortic, mitral, and tricuspid valves. Important structures in this region include the membranous septum, the central fibrous body, the Koch triangle, the inferior pyramidal space, and the base of the interventricular septum. This small area is the home of the atrioventricular node and the atrioventricular conduction axis and has enormous importance to electrophysiologists owing to its prime role in the conduction system of the heart. The atrioventricular node lies within the triangle of Koch; and the atrioventricular bundle, or bundle of His, exits the atrioventricular node and penetrates the right fibrous trigone and runs underneath the membranous septum. The septal atrioventricular junction is a common location for intracardiac shunts such as membranous and perimembranous septal defects. Imaging classification of these defects can have important implications before surgical closure, because the atrioventricular conduction axis passes along the posteroinferior margin of most perimembranous defects. Extracardiac inflammatory and malignant pathologic conditions can extend from the mediastinum toward the inferior pyramidal space in this region through the epicardial fat planes. Although the anatomic structures are complicated, the components can be shown in exquisite detail with computed tomography (CT). In this review, the anatomic boundaries and important anatomic landmarks are examined with CT and magnetic resonance imaging. Also described are the anatomic variants of the membranous septum pertinent to percutaneous aortic valve implantation, the vascular anatomic variants, and commonly encountered pathologic conditions related to the septal atrioventricular junction. ©RSNA, 2016.

Permanent His-bundle pacing in patients with prosthetic cardiac valves

Conduction disease is not uncommon after prosthetic valve (PV) surgery. The feasibility of His-bundle pacing (HBP) in this patient population is not well studied. The purpose of this study was to report our experience with permanent HBP in patients undergoing pacemaker implantation after PV surgery. Permanent HBP was attempted in patients with AV conduction disease after PV surgery referred for pacemaker implantation. Conduction disease was characterized as AV nodal vs infranodal. Feasibility, relationship of HBP lead to PVs, and HBP characteristics were recorded. Thirty patients (47% men, age 74 ± 12 years, left ventricular ejection fraction 49% ± 11%) with AV conduction disease (100% patients; 14 with infranodal block; right bundle branch block 9, left bundle branch block 5, intraventricular conduction delay 1) underwent HBP. PVs included aortic valve replacement (AVR) in 8 patients (infranodal block 6 patients), tricuspid valve (TV) ring with mitral valve replacement or repair (MVR) in 10 patients (AV nodal block 9 patients), transcatheter aortic valve replacement (TAVR) in 4 patients (infranodal block 4 patients), and MVR alone in 6 patients. HBP was successful in 28 patients (93%) (selective HBP 50%). His bundle (HB) recruitment was unsuccessful in 2 patients with TAVR. AVR/TAVR and TV ring served as anatomic landmarks for localizing the HB. Successful sites of HBP were posterior and inferior to AVR/TAVR and distal and septal to the TV ring. Baseline QRSd improved from 124 ± 32 ms to 118 ± 20 ms (P = .39). HBP threshold at implant was 1.45 ± 1 V at 1 ms. Permanent HBP was feasible in 93% of patients with PVs. Patients with AVR/TAVR predominantly developed infranodal block compared to AV nodal block in patients with TV ring/MVR. Location of PV might serve as a landmark for identifying the site of the HB.

Consciousness disorders from cardiological view

Consciousness disorders may have many causes, mainly cardiac arrhythmias. The incidence of bradyarrhythmias (BA) in patients with acute coronary syndrome (ACS) is 0.3-18 % and caused by sinus node dysfunction (SND), high degree atrioventricular (AV) block or bundle branch blocks. SND are sinus bradycardia or sinus arrest. 1st degree AV-block occurs in 4-13 % of patients with ACS caused by rhythm disturbances in atrium, AV node, bundle of His or the Tawara system. 1st or 2nd degree AV block is seen very frequently within 24 hours after beginning of ACS and these arrhythmias are frequently transient and no more present after 72 hours. 3rd degree AV blocks are also frequently transient in pts with infero-posterior myocardial infarction (MI) and permanent in anterior MI patients. Left anterior fascicular block occurs in 5 % of ACS, left posterior fascicular block is observed less frequently (incidence < 0.5 %). Complete bundle branch block is present in 10-15 % of ACS patients and right bundle branch block is more often (2/3) present than left bundle branch block (1/3). In patients with BA atropine i. v. (1-3 mg) is helpful in 70-80 % of ACS patients and will lead to an increased heart rate. The need of pacemaker stimulation (PS) is different in patients with inferior (IMI) or anterior MI (AMI). Tachyarrhythmias are ventricular tachycardia, ventricular flutter or ventricular fibrillation in pts with ACS and it is necessary to terminate these arrhythmias as soon as possible by direct current cardioversion or defibrillation. Other causes of consciousness disorders are valvular heart diseases (aortic stenosis, hypertrophic obstructive cardiomyopathy), myxoma or ion-channel diseases (Brugada syndrome, long and short QT-syndromes). In all cases, a detailed cardiological evaluation is necessary in order to initiate a proper treatment.

Electrophysiological observations of acute His bundle injury during permanent His bundle pacing

BackgroundPermanent His bundle pacing (HBP) is a physiological alternative to right ventricular pacing (RVP). Catheter manipulation during HBP can cause trauma to the His bundle during implantation. We sought to determine acute and long-term incidence of His bundle (HB) injury with HBP. MethodsPatients undergoing permanent HBP at Geisinger Wyoming Valley Medical Center from 2006 to 2014 formed the study group. Patients with pre-existing His-Purkinje disease (HPD) were excluded from the study. Any development of new bundle branch block (BBB) or AV block (B) during acute HBP lead-induced block was recorded. Resolution of AVB and/or BBB was documented. ResultsHBP was attempted in 450 patients. In 358 patients without HPD, 28 (7.8%) developed acute HB injury in the form of complete AVB (4, 1.1%), RBBB (21, 5.9%) or LBBB (3, 0.8%) during HBP lead placement. In all 7 patients with AVB or LBBB, conduction completely recovered. The HB electrogram from the lead displayed injury current in all 7 patients. Lead-induced RBBB resolved in 12 of 21 patients and persisted in 9 (2.5%) patients. Pacing from the HBP lead resulted in correction of acute conduction block in 27 of 28 patients and 8 of 9 patients with chronic RBBB. None of the patients with transient conduction block developed new conduction disease during follow-up of 21±19months. ConclusionsDespite acute trauma to HB in 7.8% of patients undergoing permanent HBP, complete resolution of conduction block occurred in 19 of 28 patients (68%). RBBB persisted in 9 patients (32%) but mostly normalized with HBP.

A case highly suspicious of isolated cardiac sarcoidosis

A 55-year-old Caucasian male without cardiac history presented with a broad-complex tachycardia of a right ventricular origin (Fig. 1a). After successful electrocardioversion, echocardiography and coronary angiogram showed no significant abnormalities. Electrophysiological examination suggested a right ventricular mid-septal origin of the arrythmia, closely to the HIS bundle. Cardiac MRI (Fig. 1b,c) showed extensive late enhancement at the right ventricular part of the interventricular septum (Fig. 1b) and a focal lesion in the epicardial inferolateral wall (Fig. 1c), both showing high uptake on FDG PET-CT (Fig. 1d). In the laboratory findings, soluble interleukin-2 receptor (sIL-2R), a marker for sarcoidosis, was elevated (5276 pg/ml, normal value <3000 pg/ml), making cardiac sarcoidosis highly likely. FDG PET-CT and examination of skin and eyes showed no signs of extracardiac sarcoidosis and pulmonary sarcoidosis was excluded by high-resolution CT and bronchoalveolar lavage, suggesting a case of isolated cardiac sarcoidosis. The prevalence of cardiac involvement in sarcoidosis varies from 5 % in symptomatic patients to up to 30 % in autopsies [1]. Isolated cardiac sarcoidosis is rare and only described in case series [2]. For diagnosis, multimodality imaging is recommended, including MRI and FDG PET [3]. FDG PET is the modality of choice to examine (extra)cardiac sarcoidosis [4]. Giant cell myocarditis can be considered in the differential diagnosis. However the scan results, elevated sIL-2R, young age and dysrhythmia are typical for cardiac sarcoidosis. A two-chamber implantable cardioverter defibrillator was implanted and prednisolone treatment was started. FDG PET-CT after 3 months showed complete normalisation. Although extremely rare, this case illustrates the possible occurrence of mono-organ localisation of sarcoidosis. Fig. 1 a Electrocardiogram showing a broad-complex tachycardia of 240 beats/min, retrograde P waves and right-axis deviation, suggesting a right ventricular origin. Cardiac MRI shows extensive late enhancement at the right ventricular ...

Simultaneous His Bundle and Left Ventricular Pacing for Optimal Cardiac Resynchronization Therapy Delivery: Acute Hemodynamic Assessment by Pressure-Volume Loops.

Previous studies have investigated the role of intrinsic conduction in optimizing cardiac resynchronization therapy. We investigated the role of fusing pacing-induced activation and intrinsic conduction in cardiac resynchronization therapy by evaluating the acute hemodynamic effects of simultaneous His-bundle (HIS) and left ventricular (LV) pacing. We studied 11 patients with systolic heart failure and left bundle-branch block scheduled for cardiac resynchronization therapy implantation. On implantation, LV pressure-volume data were determined via conductance catheter. Standard leads were placed in the right atrium, at the right ventricular apex, and in a coronary vein. An additional electrode was temporarily positioned in the HIS. The following pacing configurations were systematically assessed: standard biventricular (right ventricular apex+LV), LV-only, HIS, simultaneous HIS and LV (HIS+LV). Each configuration was compared with the AAI mode at multiple atrioventricular delays (AVD). In comparison with the AAI, right ventricular apex+LV and LV-only pacing resulted in improved stroke volume (85±32 mL and 86±33 mL versus 58±23 mL; P<0.001), stroke work, maximum pressure derivative, and systolic dyssynchrony at individually optimized AVD. The optimal AVD was close to the P-H interval in the majority of patients. By contrast, HIS-LV pacing improved hemodynamic indexes at all AVD (stroke volume >76 mL at all fixed intervals and 88±31 mL at optimal interval; all P<0.001). Standard right ventricular apex+LV and LV-only pacing enhanced systolic function and LV synchrony at individually optimized AVD close to the measured intrinsic P-H interval. By contrast, HIS+LV pacing yielded improvements, regardless of AVD setting. These findings support the hypothesis of the crucial role of intrinsic right ventricular conduction in optimal cardiac resynchronization therapy delivery.

HIS BUNDLE PACING TO BYPASS LEFT BUNDLE BRANCH BLOCK: THE RELATIONSHIP BETWEEN PRE-PACING QRS AXIS AND PACING-INDUCED QRS NORMALIZATION

His Bundle (HB) pacing to bypass left bundle branch block (LBBB) is increasingly used to achieve electrical synchrony. Based on His-Purkinje System anatomy and the theory of longitudinal dissociation, extreme left axis deviation (LAD) with LBBB could be due to escape of left posterior fascicular

Segregation of Central Ventricular Conduction System Lineages in Early SMA+ Cardiomyocytes Occurs Prior to Heart Tube Formation.

The cardiac conduction system (CCS) transmits electrical activity from the atria to the ventricles to coordinate heartbeats. Atrioventricular conduction diseases are often associated with defects in the central ventricular conduction system comprising the atrioventricular bundle (AVB) and right and left branches (BBs). Conducting and contractile working myocytes share common cardiomyogenic progenitors, however the time at which the CCS lineage becomes specified is unclear. In order to study the fate and the contribution to the CCS of cardiomyocytes during early heart tube formation, we performed a genetic lineage analysis using a Sma-CreERT2 mouse line. Lineage tracing experiments reveal a sequential contribution of early Sma expressing cardiomyocytes to different cardiac compartments, labeling at embryonic day (E) 7.5 giving rise to the interventricular septum and apical left ventricular myocardium. Early Sma expressing cardiomyocytes contribute to the AVB, BBs and left ventricular Purkinje fibers. Clonal analysis using the R26-confetti reporter mouse crossed with Sma-CreERT2 demonstrates that early Sma expressing cardiomyocytes include cells exclusively fated to give rise to the AVB. In contrast, lineage segregation is still ongoing for the BBs at E7.5. Overall this study highlights the early segregation of the central ventricular conduction system lineage within cardiomyocytes at the onset of heart tube formation.

Recruitment of bundle branches with permanent His bundle pacing in a patient with advanced conduction system disease: What is the mechanism?

The patient was a 69-year-old man with coronary artery disease who presented with syncope. His electrocardiogram showed sinus rhythm with a first-degree atrioventricular block, right bundle branch block (RBBB), and left anterior fascicular block (LAFB), and he was referred for an electrophysiology (EP) study. Baseline electrograms suggested intra-Hisian conduction disease, with split His potentials, H′ and H, and an intra-Hisian interval of 78 ms (Figure 1A). It was difficult to maintain His catheter stability during the EP study, and only the distal His signal (H) was consistent, with an His-ventricular (HV) interval of 70 ms (Figure 1A). Decremental atrial pacing demonstrated progressive rate-related HV prolongation up to 280 ms, beyond which HV Wenckebach block occurred (Figure 1B). No arrhythmias were induced with programmed atrial or ventricular stimulation. Given the evidence of infranodal AV conduction disease with probable intra-Hisian disease, we decided to implant a pacemaker. Pacing from the proximal His bundle (HB) position with the His catheter resulted in a wide QRS complex (duration 164 ms) with RBBB/LAFB and a long stimulus-QRS interval, whereas pacing at the distal HB resulted in a narrower QRS using a pacing output of 5 mA at 2 ms (threshold). Given narrowing of the QRS with distal HB pacing, we decided to implant the ventricular lead in the HB region. Unipolar recordings from the tip electrode of a 3830 pace-sense lead (3830, Medtronic Inc., Minneapolis, MN) were used to map the HB region. As seen in Figure 2, recordings from the proximal HB reveal a large A with an HV interval of 64 ms, while recordings from the distal HB reveal a far-field atrial electrogram (A) with a shorter HV interval of 46 ms. Pacing at the distal HB (distal to the site of block/delay resulting in RBBB/LAFB) resulted in para-Hisian (nonselective HB) capture (His + V), evidenced by a narrow QRS of duration 124 ms and presence of a slurred upstroke indicating local myocardial capture. The threshold of para-Hisian capture was 0.5 V at 0.5 ms. The lead was implanted in the distal HB location. What is the mechanism of narrowing of the QRS complex by permanent HB pacing in this patient with conduction disease characterized by RBBB and LAFB? Figure 2Proximal and distal His bundle (HB) recordings (paper speed 50 mm/s) and paced QRS morphology using permanent His bundle lead (3830, Medtronic). A = atrial electrogram; H = His electrogram; V = local ventricular electrogram. View Large Image Figure Viewer Download Hi-res image

A Case of premature ventricular contraction originating from the junction of noncoronary cusp-left coronary cusp, mimicking premature ventricular contraction originating from near the bundle of His.

A Case of premature ventricular contraction originating from the junction of noncoronary cusp-left coronary cusp, mimicking premature ventricular contraction originating from near the bundle of His.

Does Anesthesia Induction during Electrophysiologic Studies Induce Tachycardia in Pediatric Patients

Background: Anesthesia is essential to facilitate the majority of pediatric electrophysiology studies (EPS); however, a risk of an arrhythmia exists during its induction. The purpose of this study was to determine the incidence of arrhythmia during anesthesia induction in pediatric EPS. Methods: IRB approved retrospective review of pediatric EPS from 1/99 to 1/14. Inclusion criteria: Age ≤ 21 years and comprehensive EPS under general anesthesia. Data collected: demographics, EPS results, and anesthesia records. Patients were grouped based upon route of anesthesia administration: Intravenous (IV) agents (propofol, ketamine, and kentanyl) and Inhalational (IH) agents (sevoflurane, isoflurane and desflurane). Sinus Tachycardia (STACH) was defined as variable heart rates of >140 and <180 beats per minute (bpm) originating from sino-atrial node with a duration of ≥5 minutes. Supraventricular Tachycardia (SVT) was defined as an abnormal heart rhythm arising due to abnormal electrical activity of the heart, originating proximal to the bundle of His, with sustained rates ≥ 180 bpm. Results: Inclusion criteria were met by 378 patients, 57% male, median age 14 ± 4 years, with IV induction utilized in 275 (72%) patients. During induction, 39 (10%) developed tachycardia: 38 STACH and 1 SVT. STACH was more common with IH anesthesia when compared to IV (p<0.0001). Patients with Wolff-Parkinson-White (WPW), irrespective of anesthesia type, had twice the risk of developing STACH, 17/114 vs. 21/264 of others (p = 0.02). Conclusion: Sinus Tachycardia occurred in 10% of pediatric electrophysiology cases performed under anesthesia. It was seen more frequently when IH agents were used compared to IV. Patients with WPW have double the risk of developing sinus tachycardia during anesthesia induction when compared to patients with other forms of SVT.

MORPHOMETRIC AND CLINICAL ANALYSIS OF MODERATOR BAND IN HUMANS

Address for Correspondence: Dr. HannahSugirthabai RajilaRajendran, M.S, Ph.D, Professor, Department of Anatomy, Chettinad Hospital & Research Institute, Kelambakkam, Chennai, Tamil Nadu, India. Pin – 603103 Phone No.: +919710403803 E-Mail: ashrajsanada@gmail.com Background: The moderator band has the right bundle of His within the right ventricle. It also is known to prevent the over dilatation of RV. It is important because of its involvement in RV infarcts, in differentiating RV from LV in congenital anomalies, in VPDs & VTs and in VSDs. The present literature is very much lacking in its morphometry. Materials and Methods: Moderator band was looked for in 50 hearts and only in this study did we find it in all the hearts. The length, the thickness, the distance from the tricuspid valve along with the presence of any trabeculations in the septal end or in the papillary muscle end were looked for and recorded. Results: The average length was 14.71±4.99mm, the average thickness was 4.97±1.64 mm, the average distance from the tricuspid orifice was 19.85±5.92 mm. The attachment to the anterior papillary muscle was found to be branched in 8 hearts that is having an incidence of 14% . The septal end were branched and separated as two in only two specimens. Only one specimen had branched attachments on both the apical and septal ends. Conclusion: The distance from tricuspid valve and knowledge of branching are important in corrective surgeries of the VSDs. An awareness of length and thickness helps the clinician to differentiate moderator band from the other structures, which may result in misdiagnosis during echocardiography. Its presence may in fact be of significance in preventing over distension of the heart in RV myocardial ischaemia.