Left Internal Mammary Artery Harvesting: The Skeletonization Technique

This video shows the basic technique of skeletonized left internal mammary artery (LIMA) harvesting. Skeletonization is an advanced technique of graft harvesting for coronary artery bypass grafting (CABG), and while it requires meticulous attention, it has many advantages. For example, skeletonization of the IMA can minimize sternal ischemia and lower the risk of mediastinitis, and the graft is longer and larger than a pedicled IMA.

A conventional median sternotomy is performed in the usual manner. A Favaloro retractor is then used to provide exposure. Care should be taken when opening the retractor as the lower part is pushing on the right ventricle and this may cause hemodynamic instability in a fragile patient. The pleura is then freely dissected from the chest wall. Superiorly, the subclavian vein should be exposed clearly. The authors prefer dissecting using an electric cautery rather than sweeping the pleura with a gauze because this may damage the small branches of the mammary vessels and cause some bleeding, making it more difficult to expose the artery. With the left chest wall elevated and the parietal pleura and pericardium dissected free, the course of the internal mammary artery and vein can be identified clearly. A parallel cut is made in the inner chest wall fascia about 5 mm medial to the visualized mammary vein. This dissection plane can be started at the middle, approximately the level of the third rib, and extended superiorly until the right subclavian vein and inferiorly toward the xiphoid process.

The posterior rectus sheath is freed from the undersurface of the sternum and costal cartilages, allowing more extensive retraction with improved exposure of the IMA. As the fascia is pulled down with forceps, the vein is exposed using the electrocautery tip. When the under-surface of the vein is clearly exposed, the artery subsequently becomes visible. The cautery tip gently separates the vein and IMA. The trunk of the IMA is separated from the chest wall gradually. This allows exposure of the perforating branches to cut. The authors do not have the harmonic scalpel for LIMA harvesting yet, so electrocautery is used to cut down the collaterals. When hemoclips are used, scissors should be used to divide the vessels. If electrocautery were to be used, the heat and the electric current could conduct through the metal clip and cause a burn injury.

Because the internal mammary artery is a delicate structure, any undue stretching, clamping, or misplaced clips results in permanent vascular injury and therefore unsatisfactory short- and long-term results. Excessive traction during mobilization should be avoided as it can lead to dissection of the vessel wall. The dissection of the LIMA is then continued distally until the bifurcation is reached.

Proximally, the mammary vein may be clipped and divided, clearing the view for the artery. The IMA is then dissected free from the subclavian vein, one can go 1 cm further from the inferior border of this vein. Also at this level, care should be taken not to damage the phrenic nerve, which crosses the artery. The first intercostal branch of the internal mammary artery must be identified and divided to avoid any possible steal phenomenon from the internal mammary flow.

The dissection should be continued until the artery is completely freed from the parasternal tissues to the level of the bifurcation. After finishing the procedure, papaverine is sprayed gently over the LIMA. Only after full dose heparin is given is the LIMA clipped at the bifurcation and divided, and the adequacy of the arterial flow is then checked. The CABG procedure is then performed in a conventional manner.

The authors hope that this video is beneficial. Please do not hesitate to contact them if you have any questions about this video.

Suggested Reading

1. Asai T, Suzuki T, Nota H, et al. Off-pump coronary artery bypass grafting using skeletonized in situ arterial grafts. Ann Cardiothorac Surg. 2013;2(4):552-556.

This video is part of the Cardiac Surgery Essentials Series, brought together by CTSNet Guest Editor Dr Tsuyoshi Kaneko. Find the whole series here.