No abstract

Background-Radiofrequency ablation of tissues in pulmonary veins can eliminate paroxysmal atrial fibrillation. Objective-To explore the characteristics of normal pulmonary veins so as to provide more information relevant to radiofrequency ablation. Methods-20 structurally normal heart specimens were examined grossly. Histological sections were made from 65 pulmonary veins. Results-The longest myocardial sleeves were found in the superior veins. The sleeves were thickest at the venoatrial junction in the left superior pulmonary veins. For the superior veins, the sleeves were thickest along the inferior walls and thinnest superiorly. The sleeves were composed mainly of circularly or spirally oriented bundles of myocytes with additional bundles that were longitudinally or obliquely oriented, sometimes forming mesh-like arrangements. Fibrotic changes estimated at between 5% and 70% across three transverse sections were seen in 17 veins that were from individuals aged 30 to 72 years. Conclusions-The myocardial architecture in normal pulmonary veins is highly variable. The complex arrangement, stretch, and increase in fibrosis may produce greater non-uniform anisotropic properties. (Heart 2001;86:265-270) Keywords: arrhythmias; catheter ablation; fibrillation; cardiac veins Studies from various groups of investigators have suggested that certain forms of atrial fibrillation are related to the existence of an ectopic discharging focus which is frequently located within the pulmonary veins.1-4 Radiofrequency catheter ablation carried out in the pulmonary veins can eliminate paroxysmal atrial fibrillation in many cases. Stenosis of the vein is a recognised complication following catheter ablation.5 Recurrence of the arrhythmia is also a common problem.4 Both drawbacks of current techniques of catheter ablation in these patients may be avoidable if there is better understanding of the architecture of the pulmonary veins in the human heart.In this study, we explored the walls of the pulmonary veins from the venoatrial junction to the hilum in normal specimens. We then reconstructed our findings so as to provide a three dimensional impression of the architecture of the cardiac muscle, which reinforces to a varying extent the outer layer of the pulmonary veins at their junction with the left atrium. To standardise the orientation of the left and right pulmonary veins, and to emphasise the potential significance of the diVerences in the anatomical arrangements, we viewed the orifices of the veins as they would be seen in a simulated left anterior oblique projection, and used the clock face to describe the sectors of the walls. MethodsWe harvested 65 veins from 20 structurally normal heart specimens that were collected in

The relationship between anatomy and function has long been recognised. Understanding the gross structure, and the myoarchitecture, of the atriums is fundamental to investigations into the substrates and therapy of atrial fibrillation. Based primarily on our experience with normal human hearts, this review provides, firstly, a basis of comparison of gross structures as seen in the clinical situation, and in animals commonly used in experimental studies. Secondly, we discuss the general arrangement of myocardial fibres with respect to gross topography in the normal human heart. The right atrium is dominated by an extensive array of pectinate muscles within the extensive appendage, whereas the left atrium is relatively smooth-walled, with a much smaller tubular appendage. Myoarchitecture displays parallel alignment of fibres along distinct muscle bundles, such as the terminal crest and Bachmann's bundle. Within the smooth wall of the left atrium, there is a marked transmural change in the orientation of the muscular fibres. Abrupt changes in orientation, and mixed arrangements, are common between bundles. Other than Bachmann's bundle, the muscular bridges which provide interatrial connections, and connections between the left atrium and the coronary sinus and inferior caval vein, are highly variable. Inhomogeneities both in gross structure and myoarchitecture are common in the normal heart. These should be taken into account when investigating hearts from patients known to have had a history of arrhythmias, in devising computer models, or when refining diagnostic and therapeutic strategies.

The variability in width and thickness of the LLR, its proximity to Marshall structures and autonomic nerves, and myofibre arrangement may be significant in the fibrillatory process and spread of AF activity.

Background-Esophageal injury is a potential complication after intraoperative or percutaneous transcatheter ablation of the posterior aspect of the left atrium. Understanding the spatial relations between the esophagus and the left atrium is essential to reduce risks. Methods and Results-We examined by gross dissection the course of the esophagus in 15 cadavers. We measured the minimal distance of the esophageal wall to the endocardium of the left atrium with histological studies in 12 specimens.To measure the transmural thickness of the atrial wall, we sectioned another 30 human heart specimens in the sagittal plane at 3 different regions of the left atrium. The esophagus follows a variable course along the posterior aspect of the left atrium; its wall was Ͻ5 mm from the endocardium in 40% of specimens. The posterior left atrial wall has a variable thickness, being thickest adjacent to the coronary sinus and thinnest more superiorly. Behind is a layer of fibrous pericardium and fibrofatty tissue of irregular thickness that contains esophageal arteries of 0.4Ϯ0.2-mm external diameters. Conclusions-The

Atrial structures are important in the current era of cardiac interventions using percutaneous transcatheter procedures. Understanding their locations and component parts helps to reduce risks of procedural-related damage. The general arrangement of the myofibers that make up the atrial walls is reviewed to provide a morphologic basis for atrial conduction and potential substrates of arrhythmias. The right atrium, dominated by its appendage, is characterized by having an extensive array of pectinate muscles. These extend almost perpendicularly from the terminal crest. The left atrium has relatively smooth walls and a small tubular-shaped appendage. The myofibers show changes in orientations when traced through the thickness of the walls. Extensions of atrial myocardium onto the pulmonary veins and the superior caval vein are common. Apart from Bachmann's bundle, there are other muscular bridges of variable numbers and sizes that provide interatrial connections, connections between the left atrium and the coronary sinus, and connections between the muscular sleeves of the right pulmonary veins and the right atrium. The purpose of this review is to summarize the three-dimensional arrangement of gross atrial structures, the myoarchitecture and variations in muscular interatrial connections. These are important features in intra- and interatrial conduction.

The right phrenic nerve is at risk when ablations are carried out in the superior caval vein and the right superior pulmonary vein. The left phrenic nerve is vulnerable during lead implantation into the great cardiac and left obtuse marginal veins.

Atrial arrhythmias, and specifically atrial fibrillation (AF), induce rapid and irregular activation patterns that appear on the torso surface as abnormal P-waves in electrocardiograms and body surface potential maps (BSPM). In recent years both P-waves and the BSPM have been used to identify the mechanisms underlying AF, such as localizing ectopic foci or high-frequency rotors. However, the relationship between the activation of the different areas of the atria and the characteristics of the BSPM and P-wave signals are still far from being completely understood. In this work we developed a multi-scale framework, which combines a highly-detailed 3D atrial model and a torso model to study the relationship between atrial activation and surface signals in sinus rhythm. Using this multi scale model, it was revealed that the best places for recording P-waves are the frontal upper right and the frontal and rear left quadrants of the torso. Our results also suggest that only nine regions (of the twenty-one structures in which the atrial surface was divided) make a significant contribution to the BSPM and determine the main P-wave characteristics.