A new method of conduction system staining.

Visualization of the conduction bundle is advantageous in the prevention of surgical trauma to the conduction system during open-heart surgery. Because vital staining using an iodine starch complex has been known to result in tissue damage, we have evaluated the effects of iodine gas on the specialized conduction system. The conduction bundle was stained, well enough to be identified, with iodine tincture, with Lugol's solution, and with iodine gas. However, all these agents except for iodine gas caused marked electrophysiological changes. Similar changes occurred with the use of ethanol and of 10% potassium iodine solution, which are the solvents of iodine tincture and Lugol's solution, respectively. Microscopic examination showed that iodine tincture, Lugol's solution, and their solvents caused marked histological changes in the conduction tissue. However, no significant changes in the conduction tissue were noted from iodine gas spraying. Therefore, tissue damage caused by iodine tincture and Lugol's solution was thought to be due not to a reaction to the iodine starch complex itself, but to their solvents. In a long-term experimental study of 10 dogs, we found that iodine gas caused no electrophysiological disturbances or damage of microscopic tissue. Of the agents we tested, only iodine gas is free from harmful effects and can be used clinically.