Anatomical Basis for the Cardiac Interventional Electrophysiologist

Figure 9

(a) Dissection to show Bachmann’s bundle, crossing the anterior interatrial groove and branching toward the left atrial appendage (white lines), and the septopulmonary bundle, which arises from the interatrial groove underneath Bachmann’s bundle, fanning out to line the pulmonary veins and to pass longitudinally over the dome (yellow lines). (b) Dissection of the subendocardium showing the abrupt changes of subendocardial fiber orientation (asterisks) of the septoatrial bundle at the level of the posterior wall of the left atrium, left atrial appendage, and orifices of the pulmonary veins. (c) Cross-histological section (Masson’s trichrome stain) shows Bachmann’s bundle and its rightward extension toward the sinus node. (d) Cross-histological section showing a muscular bridge (arrow) across the anterior interatrial groove connecting the right atrium to the left atrium. (e) Cross-histological section showing a muscular bridge below Bachmann’s bundle crossing the anterior interatrial groove (arrow). (f) Cross-histological section (Masson trichrome stain) through the CS demonstrates the coronary sinus and left atrial muscle connection (asterisk) at the distal end of the coronary sinus. Often there is continuity between musculature of the coronary sinus sleeve and left atrial wall (arrow). BB = Bachmann’s bundle, ICV = inferior cava vein, LA = left atrium, LAA = left atrial appendage, LI = left inferior pulmonary vein, LS = left superior pulmonary vein, MV = mitral valve, OF = oval fossa, RA = right atrium, RI = right inferior pulmonary vein, RS = right superior pulmonary vein, SCV = superior cava vein, and SPB = septopulmonary bundle.

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