Is the distance between the internal mammary artery and supplemental vein large?

What is supplemental. What do you mean by vein? The mammary artery is anastomosed to a coronary artery not to a coronary vein. If anastomosed to a coronary vein it will create a fistula with left to right shunting. The distance varies with the particular coronary anatomy and the location of a suitable area in the coronary to be able to anastomose.