Double grafting of the left anterior descending artery: is the distance between the internal mammary artery and supplemental vein graft anastomoses relevant in graft survival?

Introduction: Under certain conditions (small internal mammary artery (TMA) or large runoff), double grafting of the left anterior descending (LAD) artery system is necessary to avoid the ominous consequences of myocardial hypoperfusion. Previous studies have shown that a saphenous vein (SVG) adjacent to an IMA graft leads to failure of the IMA. This study compares IMA flow patterns when adjacent (<1 cm) and separated (3-4 cm) from a SVG placed on a proximally occluded LAD. Methods: A SVG and right IMA (PIMA) to proximal LAD (2.5-3 mm) coronary bypass were performed in 12 mongrel dogs. The left IMA (DIMA) was anastomosed to the distal LAD (1.5 mm). All anastomoses were carried out without cardiopulmonary bypass. The native LAD was occluded proximally to the PIMA anastomosis, and all graft flows were measured in competitive and non-competitive Bow conditions. Results: Isolated graft to LAD Bow's were similar for the three conduits. There was a drop in flow in both the PIMA and DIMA when placed in competition with the SVG (10.1 +/- 3.0 vs. 19.1 +/- 4.6 ml/min; P < 0.05). The total drop in flow was significantly greater in the PIMA (67.6 vs. 39.9%; P < 0.05). Diastolic flow was better preserved in the distal IMA graft (19.6 +/- 5.6 vs. 10.2 +/- 3.0 ml/min; P < 0.05). The patterns of flow were much different during competition and there was significant retrograde systolic Bow in all PIMA grafts while there was no (n = 5) or minimal retrograde flow (n = 7) in the DIMA grafts. Conclusion: An IMA graft, when adjacent to a SVG, sustains a significant decrease in both total and diastolic flows and develops an oscillating pattern of Bow in early systole (retrograde then antegrade). Placing the IMB mon distally on the LAD improves Bow and decreases retrograde flow. In clinical situations requiring double grafting on the LAD, distance between grafts may be an important factor in maintaining IMA patency. (C) 1998 Elsevier Science B.V.