Effect on blood flow of rotation and position of the internal mammary artery pedicle

The internal mammary artery is the preferred conduit for coronary artery bypass grafts. The effect on flow through the artery of both rotation and position of the artery pedicle was tested in an in-vitro setting on 20 arteries using a perfusate closely approximating the normothermic viscosity of blood. It was found that the effect of rotation on blood flow was highly significant (p < 0.0004) and that this occurs after a degree of rotation that is dependent on the pedicle length. The critical degree of rotation required to significantly affect blood flow is 30 degrees for each centimeter of pedicle length. The degree of rotation required to stop flow altogether is 45 degrees per unit length. Flow through the arteries was found to be inversely proportional to the length of the artery but was not affected by changes in the position of the artery provided there was not a rotational component. Tension of the pedicle did not influence flow in either a linear or rotated position. These results were verified in a clinical setting. This study supports that a 180-degree rotation of the internal mammary artery pedicle in any clinical setting will not alter blood flow. For rotations of 360 degrees or greater, however, the effect on flow becomes significant when this is 12 cm or less. Although flow is independent of linear pedicle deformity, as flow is inversely proportional to length, excess pedicle length is best avoided.