Vein graft occlusion

Westaby S, Katsumata T. Aprotinin and vein graft occlusion—the controversy continues. J Thorac Cardiovasc Surg 1998 116(5) 731-3. 

Looking at safety of these concentrates, analysis of 3 studies found adverse events in 3 of 26 patients receiving fibrinogen concentrate, whereas 12 of the 27 control patients experienced an adverse event [120 ]. The three reported adverse events were subclinical PE, vein graft occlusion and postoperative atrial fibrillation. One of the studies included in this analysis did not report safety data. Going forward, it will be important for studies to consider issues of threshold, clinical situation, role of testing and documentation of adverse events [121 ]. 

Apart from its role in atherogenesis, recent observations suggest that high Lp(a) levels are also associated with early occlusion of coronary artery bypass grafts and femoropopliteal vein grafts (H33, W17). In this situation, however, a thrombotic rather than an atherogenic mechanism may be responsible for the events. 

Chesebro, H.J., Lam, J.Y.T. and Fuster, V. (1986). The pathogenesis and prevention of aortocoronary vein bypass graft occlusion and restenosis after arterial angioplasty role of vascular injury and platelet thrombus deposition. ]. Am. Coll Cardiol, 8, 57B-66B... 

Fig. 21.10a,b. CTA of coronary bypass grafts, a Cross-sectional image of a patent saphenous vein graft (arrows) exhibiting severe calcified wall changes. Data of another patient (b) who presented with acute chest pain shows two venous grafts, with thrombus formation (small arrows) and total occlusion of one graft (arrowhead)... 

Coronary artery bypass graft surgery Thoracic surgery whereby parts of a saphenous vein from a leg or internal mammary artery from the arm are placed as conduits to restore blood flow between the aorta and one or more coronary arteries to bypass the coronary artery stenosis (occlusion). 

G. W. Stone, C. Rogers, J. Hermiller, R. Feldman, P. Hall, R. Haber, A. Masud, P. Cambier, R. P. Caputo, M. Turco, R. Kovach, B. Brodie, H. C. Herrmann, R. E. Kuntz, J. J. Popma, S. Ramec and D. A. Cox, Randomized comparison of distal protection with a filter-based catheter and a balloon occlusion and aspiration system during percutaneous intervention of diseased saphenous vein aorto-coronary bypass grafts, Circulation 108, 548-553 (2003). 

Reversed segments of autologous saphenous vein can be used as appropriate conduits. Particularly in coronary revascularization, the internal mammary arteries and the radial arteries have widely been used [3]. However, autologous vessels may be insufficient for multiple or repeated bypasses and/or saphenous veins may have varicose degenerative alterations. Therefore, allograft arteries and veins as well as synthetic tubes have been developed, but they proved to be less satisfactory as conduits [4, 5] particularly, synthetic grafts with an internal diameter of 6 mm or less are prone to thrombus induction and occlusion [6]. 

This may be achieved by neointima formation or the use of antithrombogenic biomaterial. In the former case the thrombi formed on the surface are expected to organize into the pseudoneointima, which should be fixed on the material surface and viable for a long period. This is the common method used for vascular grafts of arteries with a diameter larger than about 6 mm. For substitutes of veins and arteries with a smaller diameter, this stable neointima formation is hardly expected because the conduit undergoes occlusion by the thrombi formed almost instantly when the surface comes into contact with blood, or because the neointima grows continuously to occlude entirely the conduit of small diameter. 

Cavitation is probably the dominant mechanism responsible for the increase in clot lysis with microbubbles. This ultrasound-mediated methodology is frequently referred to as sonothrombol-ysis. We and others have conducted a number of studies using microbubbles for sonothrombolysis, both in pre-clinical and clinical studies for thrombosed dialysis grafts, deep vein thrombosis (DVT), peripheral artery occlusions (PAO), and stroke. ... 

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