COMPARISON AMONG ARTERIAL GRAFTS AND CORONARY-ARTERY - AN ATTEMPT AT FUNCTIONAL CLASSIFICATION

Various arterial conduits have been used for coronary artery bypass gr afting. However, arterial grafts are not uniform either in anatomy or in function. Some conduits are more spastic than others and there may be possible differences in long-term patency rates. The diverse biolog ic characteristics promote a necessity of classification of arterial g rafts, which may facilitate the understanding of surgeons of biologic characteristics of various arterial grafts and provide a scientific ba sis for searching for new grafts. Another important issue is the compa rison of reactivity between arterial grafts and coronary arteries. In this study, we aim to compare the pharmacologic reactivity among the h uman arteries (grafts and coronary arteries) and to classify arterial grafts. Segments of three arterial grafts (gastroepiploic, internal ma mmary, and inferior epigastric) taken from patients undergoing coronar y artery bypass grafting and coronary arteries taken from explanted he arts were studied in organ baths for the contraction to four vasoconst rictors (endothelin-1, thromboxane A, mimetic U46619, full adrenocepto r agonist norepinephrine, and depolarizing agent potassium) under phys iologic pressure, The diameter of the four arteries at a pressure of 1 00 mm Hg was similar (p > 0.05). However, the gastroepiploic artery co ntracted to higher forces (9.41 +/- 2.0 gm for endothelin, 11.79 +/- 1 .85 gm for U46619, 13.54 +/- 2.7 gm for norepinephrine, and 11.11 +/- 1.97 gm for potassium) than did the coronary artery and internal mamma ry artery (p < 0.05) for ail the tested vasoconstrictors and higher th an the inferior epigastric artery for potassium and norepinephrine (p < 0.05). There was no significant difference among the other three art eries (internal mammary artery, inferior epigastric artery, and corona ry artery) regarding the maximal contraction force to any vasoconstric tor. No difference was detected in regard to the sensitivity (effectiv e concentration causing 50% of the maximal response) to the vasoconstr ictors among the four arteries. This study reveals that among the arte rial grafts and the coronary artery, the gastroepiploic artery has the highest contractility to various vasoconstrictors. On the basis of ou r findings and physiologic and embryologic knowledge we propose a clas sification for arterial grafts: type I (somatic arteries), type II (sp lanchnic arteries), and type III (limb arteries). Types II and III are prone to spasm because of higher contractility whereas type I arterie s are usually less spastic. This classification may have important cli nical implications for the understanding of arterial graft spasm or pa tency and may be useful in the search for new grafts.