[Thickness of the muscle layer of the gastroepiploic artery and the internal mammary artery--a presumable factor of flow instability in GEA during the perioperative period].

Unlabelled: Recently the right gastroepiploic artery (RGEA) is often used for coronary bypass grafting. Although patency rate of the RGEA is as high as that of the IMA, instability of blood flow through the RGEA during the perioperative period is reported. We assumed that the RGEA is more predisposed to spasm than the internal mammary artery (IMA). This study was carried out to verify the following two points. 1. The GEA has a smaller internal diameter and thicker muscle layer than the IMA. 2. The contractile force of the muscle layer of the GEA are stronger than those of the IMA under the same transmural pressure due to the greater thickness o the muscle layer of the GEA.

Methods: The RGEA was obtained at its full length from gastorectomy cases due to gastric cancer (n = 25). The distal section of the IMA was obtained from the left IMA during bypass grafting (n = 23). All specimens were stained by the Masson-trichrome method and examined microscopically. The thickness of the smooth muscle layer of the media and the internal radius were compared between the RGEA and the IMA.

Results: The thickness of the muscle layer was 274.0 +/- 13 microns in the RGEA, and 169.1 +/- 8 microns in the IMA (p < 0.01) that is the thickness in the GEA was 1.62 times greater in the IMA. Although a significant difference was not obtained, the internal radius of GEA (563.7 +/- 21.8 microns) was smaller than that of IMA (583.1 +/- 12.0 microns). Based on the internal diameter-elastic wall tension relationship and the Laplace law, internal diameter and elastic tension in both arteries were obtained at the same blood pressure. Mean elastic tension and internal diameter in the GEA were considered to be smaller than than those in the IMA. The values of the internal diameter of the arteries obtained from the theoretical view point were correlated well with those obtained by the histometoric methods. As the muscle layer of the arterial wall of the GEA is thicker than that o the IMA, and the internal diameter of the GEA tends to be smaller than that of the IMA, the stronger contraction o the muscle layer, when induced, would reduce the blood flow in much greater extent in the GEA than the IMA.

Conclusion: These results support the assumption that the RGEA reacts strongly than the IMA to constructor agents and physical stimuli, thereby inducing a greater instability of blood flow. Therefore, RGEA grafts should be carefully handled during bypass grafting.