Coronary artery and saphenous vein graft remodeling: A review of histologic findings after various interventional procedures—part V

Abstract

Summary:Catheter balloon angioplasty is a well accepted form of nonsurgical treatment of acutely and chronically obstructed coronary artery vessels. It is also the centerpiece for various new intervention techniques. Their morphologic effect on the site of obstruction has been termed "remodeling." Part V of this six-part series focuses on remodeling effects of balloon angioplasty on obstructed young (51 year) and old (>1 year) saphenous vein bypass grafts.Key words: vessel remodeling, coronary angioplasty, restenosis, coronary artery bypass, saphenous vein bypass graft angioplasty, saphenous vein bypass grafl Balloon Angioplasty of Aortocomnary Saphenous Vein Bypass GraftsCoronary embolization as a complication of balloon angioplasty of saphenous vein grafts has been emphasized by several investigators.14 Its frequency, which is higher than that in balloon angioplasty of native coronary arteries, accounts for 2 (1.9%) of 103 cases reported by Saber et aL3 who recently submitted pathologic documentation of coronary embolizdtion after balloon angioplasty of aortocoronary saphe- nous vein bypass grafts. In one of their two cases, a large thromboatheromatous embolus obstructed the proximal left anterior descending artery and was removed at the time of operation. In the second case, embolization of atheromatous and thrombotic debris resulted in obstruction of many intramural coronary artery branches and was considered contributory to the death of the patient.Embolization of thrombotic or atheromatous material probably occurs more frequently after balloon angioplasty than has been recognized since it is clinically asymptomatic in most cases because of the small size and number of emboli. Balloon dilatation of saphenous vein grafts, however, is probably more likely to produce symptomatic embolization because vein grafts and their atheromatous plaques generally are larger than the coronary arteries to whch they are anastomosed. In addition, atherosclerosis in vein grafts tends to be more friable and less fibrocalcific than its counterpart in the native coronary arteries.' Saber e t d 3 recommended that balloon angioplasty of aortocoronary saphenous vein bypass grafts over 1 year of age be performed with the realization that involvement by friable atherosclerosis is likely and that atheroembolization represents a r i~k .~ Balloon Angioplasty of Aortocomnary Saphenous Vein Bypass GraftsMorphologic changes in aortocoronary saphenous vein bypass grafts following balloon angioplasty have been reported.335 This section summarizes clinical and morphologic observations in two patients undergoing percutaneous transluminal coronary angioplasty (PTCA) of saphenous vein bypass grafts early and late after graft in~ertion.~ Operatively excised segments of saphenous vein bypass grafts from two patients undergoing balloon angioplasty of the bypass graft early (young) (5 1 year) and late (old) (>1 year) after aortocoronary bypass surgery was the basis of #is study.

Therapeutic strategies to combat neointimal hyperplasia in vascular grafts

“…Histologic examination of vein grafts that have been treated with angioplasty show intimal thickening with fibrocollagenous tissue, and fibrotic medial and adventitial layers, at both early and late (>1 year) time points. As is the case with native arteries, late restenotic lesions after angioplasty showed changes consistent with recurrent atherosclerosis [39]. The decision to intervene with angioplasty must be weighed against the risk of graft rupture, especially in grafts >1 year old [40], although some reports have demonstrated safety in stenotic but not occluded vein grafts [41].…”

Single-Cell Analyses Offer Insights into the Different Remodeling Programs of Arteries and Veins

“…Arteries and veins differ in histological and cellular organization. Consequently, these vascular conduits have different biomechanical properties [1], develop different types of occlusive lesions, and respond differently to injury [2,3]. Unlike arteries, veins rarely develop atherosclerosis, even under the supra-arterial circulation after the creation of arteriovenous fistulas [4,5].…”

“…On the other hand, the patency of mammary and radial artery grafts is superior to that of the saphenous vein after coronary revascularization surgery [6]. Veins often show higher rates of restenosis and increased fibrotic scarring after balloon angioplasty or stent placement [3,7,8]. Despite clinical and biological evidence, there have been modest efforts to understand the unique cellular and molecular mechanisms responsible for vein remodeling.…”

“…Importantly, there is insufficient knowledge about the healing response of human veins, including the cellular dynamics during the early and late phases of remodeling [3,17,18]. Arguably, the most referenced cell types in vascular remodeling are "synthetic" SMCs, myofibroblasts, and mesenchymal cells, which are derived from phenotypic modulation of contractile SMCs, activated fibroblasts, and transformed ECs, respectively [19][20][21].…”