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Cardiac Electrophysiology Clinics Dec 2020Accessory pathways that bypass all or part of the normal atrioventricular conduction system traverse the atrioventricular junction. The atrioventricular junction... (Review)
Review
Accessory pathways that bypass all or part of the normal atrioventricular conduction system traverse the atrioventricular junction. The atrioventricular junction comprises of a limited septal component and much more extensive right and left parietal components. Its composition forms a plane of insulation between atrial and ventricular myocardium, preventing direct continuity between them. Typical accessory atrioventricular pathways located anywhere along the atrioventricular junction are muscle bundles or may involve muscle around the walls of coronary sinus aneurysms or coronary veins. Increasingly, variants or unusual accessory pathways, some involving an accessory node, are reported in clinical studies.
Topics: Accessory Atrioventricular Bundle; Adolescent; Adult; Atrioventricular Node; Heart Atria; Heart Conduction System; Heart Ventricles; Humans; Male
PubMed: 33161994
DOI: 10.1016/j.ccep.2020.07.001 -
Current Opinion in Cardiology Jan 2021Atrioventricular node reentrant tachycardia (AVNRT) is the most common mechanism of supraventricular tachycardia. Radiofrequency ablation has been the most prevalent... (Review)
Review
PURPOSE OF REVIEW
Atrioventricular node reentrant tachycardia (AVNRT) is the most common mechanism of supraventricular tachycardia. Radiofrequency ablation has been the most prevalent method for slow pathway ablation but carries risk of atrioventricular node injury. Focal cryoablation has been utilized as an alternative ablation modality; however, there has been concern about decreased efficacy, resulting in a higher rate of recurrence postablation. We also report outcomes from two international centers using an 8-mm cryocatheter and complete a thorough comparison of existing data on ablation of AVNRT.
RECENT FINDINGS
Previous reviews included studies from 2006 onward. These studies included use of the 4 mm focal cryocatheter, which has largely been abandoned in current adult practice. We will cite more contemporary studies within the past 10 years, which also includes use of the 6 and 8 mm cryocatheter.
SUMMARY
The use of focal cryoablation allows for reversible injury during AVNRT ablation, providing safety from permanent atrioventricular node injury. With the appropriate ablation endpoints, 8 mm focal cryoablation is more effective for permanent lesion formation, leading to lower recurrences.
Topics: Adult; Atrioventricular Node; Catheter Ablation; Cryosurgery; Humans; Recurrence; Tachycardia, Atrioventricular Nodal Reentry; Treatment Outcome
PubMed: 33093311
DOI: 10.1097/HCO.0000000000000820 -
Europace : European Pacing,... May 2020The anatomic substrates for atrioventricular nodal re-entry remain enigmatic, but require knowledge of the normal arrangement of the inputs and exist from the...
AIMS
The anatomic substrates for atrioventricular nodal re-entry remain enigmatic, but require knowledge of the normal arrangement of the inputs and exist from the atrioventricular node. This knowledge is crucial to understand the phenomenon of atrioventricular nodal re-entry.
METHODS AND RESULTS
We studied 20 human hearts with serial sections covering the entirety of the triangle of Koch and the cavotricuspid isthmus. We determined the location of the atrioventricular conduction axis and the connections between the specialized cardiomyocytes of the conduction axis and the adjacent working atrial myocardium. The atrioventricular node was found at the apex of the triangle of Koch, with entry of the conduction axis to the central fibrous body providing the criterion for distinction of the bundle of His. We found marked variation in the inferior extensions of the node, the shape of the node, the presence or absence of a connecting bridge within the myocardium of the cavotricuspid isthmus, the connections between the compact node and the myocardium of the atrial septum, the presence of transitional cardiomyocytes, and the 'last' connection between the working atrial myocardium and the conduction axis before it became the bundle of His.
CONCLUSION
The observed variations of the inferior extensions, combined with the arrangement of the 'last' connections between the atrial myocardium and the conduction axis prior to its insulation as the bundle of His, provide compelling evidence to support the concept for atrioventricular nodal re-entry as advanced by Katritsis and Becker.
Topics: Atrioventricular Node; Heart Atria; Heart Rate; Humans; Myocardium
PubMed: 32304217
DOI: 10.1093/europace/euaa031 -
Advances in Experimental Medicine and... 2024The electrical impulses that coordinate the sequential, rhythmic contractions of the atria and ventricles are initiated and tightly regulated by the specialized tissues...
The electrical impulses that coordinate the sequential, rhythmic contractions of the atria and ventricles are initiated and tightly regulated by the specialized tissues of the cardiac conduction system. In the mature heart, these impulses are generated by the pacemaker cardiomyocytes of the sinoatrial node, propagated through the atria to the atrioventricular node where they are delayed and then rapidly propagated to the atrioventricular bundle, right and left bundle branches, and finally, the peripheral ventricular conduction system. Each of these specialized components arise by complex patterning events during embryonic development. This chapter addresses the origins and transcriptional networks and signaling pathways that drive the development and maintain the function of the cardiac conduction system.
Topics: Animals; Humans; Atrioventricular Node; Gene Expression Regulation, Developmental; Heart Conduction System; Myocytes, Cardiac; Signal Transduction; Sinoatrial Node
PubMed: 38884712
DOI: 10.1007/978-3-031-44087-8_10 -
Radiographics : a Review Publication of... 2016The 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... (Review)
Review
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.
Topics: Anatomic Landmarks; Atrioventricular Node; Cardiac Imaging Techniques; Diagnosis, Differential; Heart Atria; Heart Septal Defects; Heart Ventricles; Humans; Image Enhancement; Magnetic Resonance Imaging; Tomography, X-Ray Computed
PubMed: 27740897
DOI: 10.1148/rg.2016160010 -
Cardiac Electrophysiology Clinics Jun 2019Several arrhythmogenic substrates may generate narrow QRS complex tachycardia, frequently encountered in clinical practice. Some narrow QRS complex tachycardias,... (Review)
Review
Several arrhythmogenic substrates may generate narrow QRS complex tachycardia, frequently encountered in clinical practice. Some narrow QRS complex tachycardias, however, are sustained by an uncommon arrhythmogenic mechanism. Although rare, these forms should be taken into account in the differential diagnosis to avoid misdiagnosis and improper patient management. Dual atrioventricular node physiology can be responsible for different uncommon forms of narrow QRS complex tachycardia, also nonreentrant in mechanism. A ventricular origin also is possible, if the tachycardia site is located in the upper ventricular septum with fast ventricular propagation to the specific conduction system and narrowing of the QRS complex.
Topics: Atrioventricular Node; Electrocardiography; Humans; Tachycardia
PubMed: 31084851
DOI: 10.1016/j.ccep.2019.02.003 -
Circulation Research Jul 2020ZO-1 (Zona occludens 1), encoded by the tight junction protein 1 () gene, is a regulator of paracellular permeability in epithelia and endothelia. ZO-1 interacts with...
RATIONALE
ZO-1 (Zona occludens 1), encoded by the tight junction protein 1 () gene, is a regulator of paracellular permeability in epithelia and endothelia. ZO-1 interacts with the actin cytoskeleton, gap, and adherens junction proteins and localizes to intercalated discs in cardiomyocytes. However, the contribution of ZO-1 to cardiac physiology remains poorly defined.
OBJECTIVE
We aim to determine the role of ZO-1 in cardiac function.
METHODS AND RESULTS
Inducible cardiomyocyte-specific deletion mice (; ) were generated by crossing the floxed mice and transgenic mice. Tamoxifen-induced loss of ZO-1 led to atrioventricular (AV) block without changes in heart rate, as measured by ECG and ex vivo optical mapping. Mice with tamoxifen-induced conduction system-specific deletion of () developed AV block while tamoxifen-induced conduction system deletion of distal to the AV node () did not demonstrate conduction defects. Western blot and immunostaining analyses of AV nodes showed that ZO-1 loss decreased Cx (connexin) 40 expression and intercalated disc localization. Consistent with the mouse model study, immunohistochemical staining showed that ZO-1 is abundantly expressed in the human AV node and colocalizes with Cx40. Ventricular conduction was not altered despite decreased localization of ZO-1 and Cx43 at the ventricular intercalated disc and modestly decreased left ventricular ejection fraction, suggesting ZO-1 is differentially required for AV node and ventricular conduction.
CONCLUSIONS
ZO-1 is a key protein responsible for maintaining appropriate AV node conduction through maintaining gap junction protein localization.
Topics: Animals; Atrioventricular Node; Connexin 43; Connexins; Heart Rate; Humans; Male; Mice; Mice, Inbred C57BL; Myocytes, Cardiac; Myosin Heavy Chains; Potassium Channels, Voltage-Gated; Zonula Occludens-1 Protein; Gap Junction alpha-5 Protein
PubMed: 32347164
DOI: 10.1161/CIRCRESAHA.119.316415 -
Circulation. Arrhythmia and... Dec 2016Heart block is associated with pulmonary hypertension, and the aim of the study was to test the hypothesis that the heart block is the result of a change in the ion...
BACKGROUND
Heart block is associated with pulmonary hypertension, and the aim of the study was to test the hypothesis that the heart block is the result of a change in the ion channel transcriptome of the atrioventricular (AV) node.
METHODS AND RESULTS
The most commonly used animal model of pulmonary hypertension, the monocrotaline-injected rat, was used. The functional consequences of monocrotaline injection were determined by echocardiography, ECG recording, and electrophysiological experiments on the Langendorff-perfused heart and isolated AV node. The ion channel transcriptome was measured by quantitative PCR, and biophysically detailed computer modeling was used to explore the changes observed. After monocrotaline injection, echocardiography revealed the pattern of pulmonary artery blood flow characteristic of pulmonary hypertension and right-sided hypertrophy and failure; the Langendorff-perfused heart and isolated AV node revealed dysfunction of the AV node (eg, 50% incidence of heart block in isolated AV node); and quantitative PCR revealed a widespread downregulation of ion channel and related genes in the AV node (eg, >50% downregulation of Ca1.2/3 and HCN1/2/4 channels). Computer modeling predicted that the changes in the transcriptome if translated into protein and function would result in heart block.
CONCLUSIONS
Pulmonary hypertension results in a derangement of the ion channel transcriptome in the AV node, and this is the likely cause of AV node dysfunction in this disease.
Topics: Animals; Atrioventricular Node; Disease Models, Animal; Down-Regulation; Echocardiography; Electrocardiography; Electrophysiologic Techniques, Cardiac; Heart Block; Hypertension, Pulmonary; Ion Channels; Male; Monocrotaline; Polymerase Chain Reaction; Rats; Rats, Wistar; Transcriptome
PubMed: 27979911
DOI: 10.1161/CIRCEP.115.003432 -
Current Opinion in Cardiology Jan 2018Atrial fibrillation and heart failure are commonly encountered in current clinical practice. This review aims to revisit the complex interaction of these two common... (Review)
Review
PURPOSE OF REVIEW
Atrial fibrillation and heart failure are commonly encountered in current clinical practice. This review aims to revisit the complex interaction of these two common situations and the best treatment whenever both occurs, especially focusing on heart failure patients undergoing cardiac resynchronization therapy (CRT).
RECENT FINDINGS
It has been recently confirmed that in patients undergoing cardiac resynchronization therapy, 100% biventricular pacing percentage should be pursued. Large observational studies confirmed that atrioventricular junction ablation is very often the only way to gain 100% biventricular pacing in atrial fibrillation.
SUMMARY
On the basis of the recent observational extensive data, in patients presenting intermediate or elevated atrial tachycardia-atrial fibrillation burden, atrioventricular junction ablation may represent a fundamental tool to achieve full CRT delivery, thus, conferring marked improvements in global cardiac function, and by extension, in survival. Atrial fibrillation patients should not be excluded from CRT, provided that maximal biventricular pacing is warranted.
Topics: Adrenergic beta-Antagonists; Amiodarone; Anti-Arrhythmia Agents; Atrial Fibrillation; Atrioventricular Node; Cardiac Resynchronization Therapy; Catheter Ablation; Digoxin; Heart Failure; Humans; Treatment Outcome
PubMed: 29045344
DOI: 10.1097/HCO.0000000000000472 -
Texas Heart Institute Journal Dec 2016
Topics: Action Potentials; Anti-Arrhythmia Agents; Atrial Flutter; Atrioventricular Node; Catheter Ablation; Electrocardiography; Flecainide; Heart Rate; Humans; Male; Middle Aged; Predictive Value of Tests; Tachycardia, Supraventricular; Treatment Outcome
PubMed: 28100969
DOI: 10.14503/THIJ-16-6088