Highly flexible nitinol mesh to encase aortocoronary saphenous vein grafts: first clinical experiences and angiographic results nine months postoperatively
ABSTRACT Saphenous vein graft patency is frequently limited by degeneration. Experimental studies have indicated that rigid external support of venous grafts by a flexible, tubular nitinol mesh may improve graft patency. The study presented was part of a prospective, randomized, multicenter first-in-man trial investigating the safety and effectiveness of nitinol-supported venous grafts in coronary artery bypass graft (CABG) surgery. From our clinic, 25 subjects with multivessel coronary artery disease requiring saphenous vein graft CABG of the right coronary artery (RCA) and the circumflex artery were entered into the trial. Subjects were randomized to receive a mesh-supported graft on one of these arteries; the other vessel received an untreated vein graft. Graft patency was assessed by coronary angiography nine months after surgery. The implantation of mesh grafts was simple and safe. In 10 cases, a nitinol mesh-supported venous graft was anastomosed to the circumflex artery and in 15 cases to the RCA. All patients survived the observation period. A total of 72% of the patients underwent control coronary angiography. The patency rate of mesh-supported grafts was 27.8% nine months postoperatively. Conventional vein grafts showed an 85.7% patency, and arterial grafts had a 100% patency. No complications directly related to the implantation of mesh-supported grafts were observed. The promising experimental results of mesh-supported venous grafts could not be reproduced in the study presented. A critical item seems to be correct selection of nitinol mesh diameter, the anastomotic method and fixation of the mesh tube to the venous graft.
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ABSTRACT: OBJECTIVES: Different flow patterns and shear forces were shown to cause significantly more luminal narrowing and neointimal tissue proliferation in coronary than in infrainguinal vein grafts. As constrictive external mesh support of vein grafts led to the complete suppression of intimal hyperplasia (IH) in infrainguinal grafts, we investigated whether mesh constriction is equally effective in the coronary position. METHODS: Eighteen senescent Chacma baboons (28.8 ± 3.6 kg) received aorto-coronary bypass grafts to the left anterior descending artery (LAD). Three groups of saphenous vein grafts were compared: untreated controls (CO); fibrin sealant-sprayed controls (CO + FS) and nitinol mesh-constricted grafts (ME + FS). Meshes consisted of pulse-compliant, knitted nitinol (eight needles; 50 μm wire thickness; 3.4 mm resting inner diameter, ID) spray attached to the vein grafts with FS. After 180 days of implantation, luminal dimensions and IH were analysed using post-explant angiography and macroscopic and histological image analysis. RESULTS: At implantation, the calibre mismatch between control grafts and the LAD expressed as cross-sectional quotient (Q(c)) was pronounced [Q(c) = 0.21 ± 0.07 (CO) and 0.18 ± 0.05 (CO + FS)]. Mesh constriction resulted in a 29 ± 7% reduction of the outer diameter of the vein grafts from 5.23 ± 0.51 to 3.68 ± 0 mm, significantly reducing the calibre discrepancy to a Q(c) of 0.41 ± 0.17 (P < 0.02). After 6 months of implantation, explant angiography showed distinct luminal irregularities in control grafts (ID difference between widest and narrowest segment 74 ± 45%), while diameter variations were mild in mesh-constricted grafts. In all control grafts, thick neointimal tissue was present [600 ± 63 μm (CO); 627 ± 204 μm (CO + FS)] as opposed to thin, eccentric layers of 249 ± 83 μm in mesh-constricted grafts (ME + FS; P < 0.002). The total wall thickness had increased by 363 ± 39% (P < 0.00001) in CO and 312 ± 61% (P < 0.00001) in CO + FS vs 82 ± 61% in ME + FS (P < 0.007). CONCLUSIONS: In a senescent non-human primate model for coronary artery bypass grafts, constrictive, external mesh support of saphenous veins with knitted nitinol prevented focal, irregular graft narrowing and suppressed neointimal tissue proliferation by a factor of 2.5. The lower degree of suppression of IH compared with previous infrainguinal grafts coincided with a lesser reduction of calibre mismatch in the coronary grafts.European Journal of Cardio-Thoracic Surgery 01/2013; 44(1):64-71. DOI:10.1093/ejcts/ezs670 · 2.81 Impact Factor
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ABSTRACT: Saphenous vein remains a widely used conduit in coronary surgery. However, the long-term success of surgical myocardial revascularization is largely limited by the development of neointimal hyperplasia and superimposed atherosclerosis in vein grafts. Although strategies for preventing vein graft failure have been constantly explored, few therapeutic interventions to date have shown sustained benefits in the clinical setting. The application of external support has emerged as a promising strategy for modulating the overall biomechanical responses in venous wall. Nonetheless, clinical translation of this intervention has been formerly challenged, primarily due to several technique limitations. The purpose of the current review is to summarize the possible mechanisms involved in the external support strategy for preventing vein graft failure. Furthermore, several previously tested biomaterials and delivery techniques are also highlighted.Asian cardiovascular & thoracic annals 10/2012; 20(5):615-22. DOI:10.1177/0218492312456980
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ABSTRACT: Purpose of review To address the most recent evidence bases for coronary artery bypass grafting (CABG) and stenting in patients with multivessel and left main coronary artery disease (CAD) and for optimizing the performance of CABG with particular reference to multiple arterial grafts, off-pump and less invasive CABG, graft flow measurements and external stenting of vein grafts. Recent findings Current evidence confirms that CABG results in markedly superior survival to stenting for most patients with multivessel and/or left main stem CAD, as well as a significant reduction in subsequent myocardial infarction and repeat revascularization. Whereas there is strong circumstantial evidence of important survival benefits with bilateral internal mammary arteries, there is no evidence for clinical benefits of off-pump CABG, except perhaps in higher-risk patients. There appears to be increasing justification for routine graft flow measurements, while minimally invasive and robotic CABG remains as a niche specialty. Summary CABG remains the most effective revascularization strategy in terms of survival and freedom from myocardial infarction and repeat revascularization in most patients with multivessel and/or left main stem CAD. There is a strong case for much wider use of bilateral internal mammary arteries during CABG, and off-pump CABG may be beneficial in higher-risk patients with particular reference to reducing neurologic injury. There is a strong rationale for the routine use of graft flow measurement, and particularly when using composite arterial grafts. There is a potential role for the development of an external stent to reduce the development of intimal hyperplasia in vein grafts.Current Opinion in Cardiology 08/2014; 29(6). DOI:10.1097/HCO.0000000000000111 · 2.59 Impact Factor