ANATOMICAL INTERRELATION BETWEEN THE PHRENIC-NERVE AND THE INTERNAL MAMMARY ARTERY AS SEEN BY THE SURGEON

Paresis of the:diaphragm (especially left-side paresis) is a relativel y frequent finding following cardiac surgery. While, usually, it is a rather benign condition, in exceptional cases it may lead to severe im pairment to death of the patient. The supposed causes of damage to the phrenic nerve include: local myocardial cooling by ice slush; opening of the pleural cavity in connection with local cooling; cross clamp l ength; total hypothermia; central venous cannulation; traction-related damage; mammary artery harvesting. Perhaps the commonest cause of dam age to the phrenic nerve, i.e., the effect of local myocardial cooling by ice slush, and the mode of phrenic nerve protection have been stud ied in considerable detail. The authors focused their attention on the interrelation between the phrenic nerve and the proximal segment of t he mammary artery. Using anatomical preparations, the authors demonstr ate the very intimate relationship of the above entities. The interrel ation of the two anatomical structures basically differs depending on whether the left or right side is concerned. 1) On the left: The phren ic nerve,on entering the thorax, runs between the subclavian artery an d vein laterally from the mammary artery crossing it medially; it part s the latter and continues in mediastinal adipose tissue to run on the pericardium toward the diaphragm. 2) On the right: The phrenic nerve passes between the subclavian vein and artery medially from the mammar y artery. For another 3-4 cm, it runs along the medial and dorsal edge s of the mammary artery. In its further course, the nerve heads medial ly for the pericardium continuing on it towards the diaphragm. In thei r paper, the authors thus pinpoint the areas of potential damage to th e phrenic nerve during mammary artery graft harvesting.