Examination of Bypass Grafts

When removing the heart at autopsy, care must be taken to avoid injury to the saphenous vein bypass grafts. A longer segment of the ascending aorta is left in continuity with the heart to enable examination of vein grafts from aortic orifice to distal anastomosis. Twists, as well as excessive tautness between aorta and distal anastomosis, are noted.7 As in the native coronary arteries, the full extent of the saphenous vein grafts is best visualized by barium-gelatin mixture followed by radiography. It is best to inject all the vein grafts simultaneously and to obtain radiographs before injection of the coronary arteries. This enables more detailed study of the native coronary arteries distal to the graft as well as at the coronary graft anastomosis.

Measurements of lumen diameters may be made from the radiographs. In those cases in which the internal mammary artery is anastomosed to the coronary system, the internal mammary artery is injected from where it has been severed during removal of the heart. The native coronary arteries are injected, fixed, and radiographed to evaluate the extent of disease in the remainder of the coronary arterial tree. If, as mentioned previously, it is not feasible to inject the heart with a barium-gelatin mixture, then the heart may be perfusion fixed with formaldehyde from the aortic stump taking care that the graft orifices are below the Lucite plug and the internal mammary artery should be ligated near the site of severance from the chest

The grafts and native arteries may then be removed from the heart, radiographed, and cut at 3- to 4-mm intervals to determine the extent of luminal narrowing, the presence or absence of thrombi, and/or the extent of atherosclerosis in vein grafts and coronary arteries.8-11 In cases where it is not possible to perfusion fix the heart, the heart may be immersion fixed in 10% buffered formaldehyde overnight and dissection of the grafts and native vessels is carried out the next morning. Prior to cutting the arteries and the grafts, it is useful to radiograph and decalcify them when necessary (Figure 2.2.1.3).

When there are no lesions grossly identifiable, random sections of the entire length of the grafts should be taken. Anastomotic sites are sectioned in different ways depending on whether the connection is end to end or end to side (Figure 2.2.1.4). When reporting the findings in the heart, it is important to mention each graft separately; including the location of the aortic orifice, whether it is involved by atherosclerotic ulcerated lesion or not, and if present mention

Coronary Artery Bypass Grafts

Figure 2.2.1.4 Diagram illustrating coronary artery bypass grafts that have end-to-side and side-to-side anastomoses in two separate grafts (shaded area) to left anterior descending and right coronary arteries, respectively. The figure illustrates the method used for sectioning of anastomotic site with end-to-side and side-to-side anastomoses to demonstrate if any of the three mechanisms for obstruction in the anastomotic site are present (i.e., compression or loss of arterial lumen, which may occur if the majority of the arterial wall has been used for anastomosis; thrombosis at the site of anastomosis; and dissection of the native coronary—artery at the site of anastomosis) and if the coronary artery has severe narrowing at the site of anastomosis due to severe atherosclerotic change. (Modified from Bulkley, B.H. and Hutchins, G.M., Pathology of coronary artery bypass graft surgery, Arch. Patrol., 102:273, 1978. From Virmani, R., Ursell, P.C., and Fenoglio, J.J., Examination of the heart, in Virmani, R., Atkinson, J.B., and Fenoglio, J.J., Eds., Cardiovascular Pathology, W.B. Saunders, Philadelphia, 1991, pp 1-20. With permission.)

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