Anatomical Basis for the Cardiac Interventional Electrophysiologist

Figure 10

(a–d) Transverse section of four heart specimens with the roof of the left atrium removed and viewed from above to show the entrance of the pulmonary veins. Note, in (a), the arrangement of four individualized endings of the pulmonary veins into the left atrium. In (b), a separate right middle pulmonary vein (arrow) can be seen, which drains the middle lobe of the lung. (c) showed a conjoined ostia (arrow), a common variant seen in up to 25% of cases, on the left side. In (d) a single left pulmonary vein can be seen. (e) Cross-histological section of the left PVs stained with elastic van Gieson. Note the interpulmonary myocardial connections (double-headed black broken line) between the left superior and inferior veins. Also note a nonuniform in circumferential thickness of the myocardial sleeves in left pulmonary veins. (f) Longitudinal histological section stained with elastic van Gieson showing the thicker atrial wall becoming thinner at the entrance of the left inferior pulmonary vein to form the muscular sleeve, which tapers toward the lung. Note the presence of gaps of connective tissue bridges between the myocytes (arrow). LA = left atrium, LAA = left atrial appendage, LI = left inferior pulmonary vein, LPV = left pulmonary vein, LS = left superior pulmonary vein, RAA = right atrial appendage, RI = right inferior pulmonary vein, RS = right superior pulmonary vein, and SCV = superior cava vein.

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