Search

Background: This study determined the histological features of the atrial myocardium connecting the coronary sinus and the left atrium in humans., Methods and Results: Ten necropsied hearts were studied by performing serial longitudinal sections parallel to the long axis of the coronary sinus that extended its full length using a large microtome. In all specimens, the venous wall of the coronary sinus was surrounded by a cuff of striated muscle extending 40+/-8 mm from the ostium. Striated myocardial connections of varying number and morphology left this coronary muscle cuff and connected to the left atrium; they ranged from 1 to 2 fascicles to a widely intermingled continuum (thickness, 2.79+/-2 mm; width, 2.91+/-3.5 mm). These connections originated 8.8+/-5.7 mm from the coronary sinus ostium and inserted 18+/-11 mm distally into the left atrium. The insulating compartment in which the connections traversed between the left atrium and the coronary sinus was mostly formed of adipose tissue. The valve of Vieussens was found in 6 hearts at a mean distance of 3.4+/-3.2 mm from the distal extremity of the coronary sinus muscle cuff., Conclusions: In the human heart, a consistent but morphologically variable left atrial coronary sinus myocardial connection was found. This emphasizes the need for surgical dissection or catheter ablation in or around the coronary sinus to eliminate these connections.

A 25 year old patient presented with several types of paroxysmal tachycardia. Analysis of the recordings and the results of endocavitary electrophysiological investigation suggest the presence of nodoventricular and atrio-ventricular fibres. These two accessory pathways were latent in sinus rhythm but formed part of reentry loops. The reciprocating rhythms used the Kent bundle in the retrograde direction, and either the normal nodo-hisian or the Mahaim fibres in the anterograde direction. Simple echos ascending by the nodo-hisian pathway and descending by the nodo-ventricular pathway were also observed. The patient died of an unassociated cause and a pathological examination of the heart was performed. This confirmed the presence of a left posterior paraseptal Kent bundle and the presence of fibres relaying the inferior part of the atrioventricular node to the septal ventricular myocardium, this being made possible by a dehiscence of the central fibrous body.

A study has been conducted into the morphological arrangement of the atrioventricular junctional area of human heart. The area was investigated in infantile, child, young adult, middle-aged, and old nodes. Although marked individual and ageing variations were observed, a general pattern of nodal architecture could be distinguished. The junctional area was therefore divided into four areas: (1) a transitional zone, (2) the compact node, (3) the penetrating bundle, and (4) the branching bundle. The transitional zone was intermediate between atrial myocardium and compact nodal specialized myocardium, but itself exhibited specialized characteristics. An important connection of the zone was to the myocardium of the left side of the interatrial septum. The compact node was itself composed of two segments which approached each other anteriorly from the mitral and tricuspid extremities of the septal anulus fibrosus. The junction of compact node and penetrating bundle could not be distinguished using cytological criteria. It was arbitrarily defined as the last point to make contact with transitional cells. Tissue distal to this was considered as penetrating bundle. A bypass tract was defined as any fiber contacting the bundle distal to this point, but such tracts were not observed in normal hearts. The branching bundle originated at the point of bifurcation of the penetrating bundle.

A 58 year old man who died of metastatic carcinoma had undergone electrophysiological investigation 4 years previously for a Wolff-Parkinson-White syndrome (Rosenbaum Type A, Frank and Boineau Type IV) associated with supraventricular tachycardia (SVT) at 180/mn, atrial fibrillation and flutter and slow junctional (or low atrial) rhythm at 70-80/mn. Atrial extrasystoles or appropriate atrial stimulation not only induced and terminated the SVT but also the junctional rhythm and allowed passage from one arrhythmia to another. These studies showed the presence of a left lateral Kent bundle responsible for orthodromic SVT with retrograde conduction through the accessory pathway, and suggested that the junctional rhythm might be due to longitudinal dissociation of the AV node. Autopsy findings confirmed the presence of the left posterolateral Kent bundle in an almost horizontal position, parallel to the mitral annulus (it might therefore have escaped eventual surgical section) and the longitudinal dissociation of the AV node.

Symptomatic supraventricular tachycardias developed in a 58-year-old man not long before he also was found to have metastatic cancer. During electrophysiological studies, type A Wolff-Parkinson-White syndrome was defined and at least four different forms of supraventricular tachycardias were documented. When he died of his cancer, autopsy studies included special examination of his heart and its conduction system. There was a slender connection between the left atrium and left ventricle posterior to the margo obtusus, composed of ordinary working myocardial cells. There was also persistent fetal dispersion of the atrioventricular (AV) node within the central fibrous body, forming a suitable anatomical substrate for reentrant tachycardias originating entirely there. The anatomical and electrophysiological findings are discussed relative to the question of surgery in such patients, since cutting the lateral AV connections might eliminate the delta wave but not the supraventricular tachycardias.