Coronary artery bypass with glycerol-preserved saphenous vein allografts

Over a 2-year period, 19 patients whose autologous saphenous veins were either unsuitable or unavailable underwent myocardial revascularization with saphenous vein allografts (SVAs) at our institution. All SVAs had been preserved in 98% glycerol at room temperature for at least 3 weeks (average, 7 weeks); before use, they were rinsed with saline and antibiotic solution. One operative death (5.2%) and three late deaths (16.6%) occurred. Fourteen of the long-term survivors have been observed for 24 to 48 months (average 32.2 months) postoperatively. Nine are asymptomatic, whereas four complain of angina, and one reports exertional dyspnea with-out chest pain. Only three patients have been restudied (7, 10, and 18 months after surgery, respectively); in each of these patients, angiography has shown occlusion of all SVAs. However, histologic examination of glycerol-preserved SVAs has not revealed pathologic changes that would suggest potential graft failure. Despite fairly satisfactory clinical results, preliminary hemodynamic data indicate that glycerol-preserved SVAs are unsuitable for myocardial revascularization in the absence of autologous saphenous veins.     

Endoscopic lesser saphenous vein harvesting for coronary artery bypass grafting: first reported case

Endoscopic vessel harvesting has become a widely used modality for harvesting venous and arterial conduits for coronary artery bypass grafting. Specifically, it has been used to harvest the greater saphenous vein, internal thoracic artery, and the radial artery. A case of endoscopic lesser saphenous vein harvesting for coronary artery bypass grafting is reported.     

Manual pressure distension of the human saphenous vein changes its biomechanical properties-implication for coronary artery bypass grafting

Patency rates of saphenous vein grafts following coronary artery bypass grafting (CABG) depend on multiple factors. Information regarding the impact of biomechanical properties of vein grafts on patency rates is not available. The objective of the present study was to evaluate whether uncontrolled manual pressure distension during routine preparation of the saphenous vein in CABG-induced changes in the biomechanical properties of the vein. The morphometric and stress-strain properties were studied in isolated segments of the saphenous vein from 12 patients undergoing elective CABG. Six segments were manually distended without pressure control and six were not distended. The mechanical test was performed as a ramp inflation using syringe pump. The vein dimensions were obtained from digitised images at different pressures as well as at the no-load and zero-stress states. The circumferences, the wall and lumen area, the wall thickness, and the outer diameter as function of the applied pressure were largest in the segments with uncontrolled manual distension compared to those without distension (P<0.05). The opening angle and the absolute value of the residual strains were lower (P<0.01) and the circumferential stress-strain curve shifted to the left, indicating the wall became stiffer with uncontrolled manual distension compared to those without distension (P<0.05). In conclusion, manual pressure distension changed the morphometric and biomechanical properties of the saphenous vein. The perspective is that studies on biomechanical properties on the saphenous vein may guide surgeons how to handle graft material without causing major changes of the biomechanical properties during harvesting and preparation.     

Simultaneous endoscopic radial artery and great saphenous vein harvesting for redo coronary artery bypass grafting. A report of two cases

Aim: An ageing population and increase in patient co-morbidities are forcing cardiac surgeons to meticulously consider the benefits and risks of respective conduits and their harvesting techniques. Case reports: Two cases of simultaneous endoscopic radial artery and great saphenous vein harvesting, for redo coronary artery bypass grafting, are presented. A shortage of venous conduits after previous bypass grafting, as well as the presentation of several risk factors of wound-healing complications, favoured simultaneous utilisation of both endoscopic techniques. Conclusion: Endoscopic vessel harvesting together with the pre-harvesting duplex study is able to gain not only high-quality conduits but also minimize the risk of wound-healing and neurological disturbances associated the saphenous vein and radial artery harvesting.     

Vasa vasorum inside out/outside in communication: a potential role in the patency of saphenous vein coronary artery bypass grafts

The saphenous vein (SV) is the most commonly used conduit for revascularization in patients undergoing coronary artery bypass surgery (CABG). The patency rate of this vessel is inferior to the internal thoracic artery (ITA). In the majority of CABG procedures the ITA is removed with its outer pedicle intact whereas the (human) SV (hSV) is harvested with pedicle removed. The vasa vasorum, a microvessel network providing the adventitia and media with oxygen and nutrients, is more pronounced and penetrates deeper towards the lumen in veins than in arteries. When prepared in conventional CABG the vascular trauma caused when removing the hSV pedicle damages the vasa vasorum, a situation affecting transmural flow potentially impacting on graft performance. In patients, where the hSV is harvested with pedicle intact, the vasa vasorum is preserved and transmural blood flow restored at graft insertion and completion of CABG. By maintaining blood supply to the hSV wall, apart from oxygen and nutrients, the vasa vasorum may also transport factors potentially beneficial to graft performance. Studies, using either corrosion casts or India ink, have shown the course of vasa vasorum in animal SV as well as in hSV. In addition, there is some evidence that vasa vasorum of hSV terminate in the vessel lumen based on ex vivo perfusion, histological and ultrastructural studies. This review describes the preparation of the hSV as a bypass conduit in CABG and its performance compared with the ITA as well as how and why its patency might be improved by harvesting with minimal trauma in a way that preserves an intact vasa vasorum.     

Human saphenous vein and coronary bypass surgery: ultrastructural aspects of conventional and "no-touch" vein graft preparations

Coronary artery bypass graft surgery (CABG) is routinely used to restore blood flow to diseased cardiac muscle due to coronary artery disease. The patency of conventional grafts decreases with time, which is due to thrombosis and formation of neointima. A primary cause of graft failure is the mechanical damage inflicted to the graft during harvesting, including removal of surrounding tissue accompanied by high pressure saline distension to overcome vasospasm (both causing considerable mechanical trauma). The aim of this study was to compare the ultrastructural features of human saphenous vein (SV) grafts harvested conventionally and grafts prepared using an atraumatic 'no-touch' harvesting technique introduced by Souza (1996). The results of this study showed a better preservation of the lumenal endothelium and medial vascular smooth muscle (SM) in 'no-touch' versus conventional grafts. A 'fast' (within 30 min) response of SM cells to conventional harvesting was noted where features of both SM cell division and apoptosis were observed. It is concluded that the 'preserved' nature of the 'no-touch' aortocoronary SV grafts renders them less susceptible to thrombotic and atherosclerotic factors than grafts harvested conventionally. These features are suggested to contribute to the improved early patency rate described using the no-touch technique of SV harvesting.     

CD68 expression in aortocoronary saphenous vein bypass grafts

Atherosclerosis commonly affects the arteries harvested from patients 70 years of age or older. Saphenous vein grafts appear to maintain a higher patency rate after coronary artery bypass grafting in these subjects. The infiltration of macrophages is an early step in saphenous vein graft atherosclerosis; however, little is known regarding the underlying mechanisms of infiltration. The objective of the present report is to evaluate the presence of CD68-positive cells in the saphenous vein wall and correlate initial CD68-positive infiltration to specific clinical and biochemical parameters and the graft patency rate as estimated in patients undergoing coronary artery bypass grafting. A total of 309 patients were allocated into two groups: A1 patients, who were between 50 and 70 years of age, and A2 patients, who were 70 years or older at the time of vein harvesting. CD68 expression was evaluated by immunohistochemistry. There were no significant differences between A1 and A2 patients regarding macrophage expression within any of the analyzed vascular regions. Saphenous vein macrophages were never present in the tunica intima unless they were also expressed in the media or the adventitia. The patients with CD68-positive cells in the tunica intima had a significantly higher number of bypass stenoses when compared with the subjects who did not have CD68-positive cells in this layer. These findings suggest that the CD68-positive cells (those that have not yet developed into foam cells) present in the intima of saphenous vein grafts might serve as a very early marker of graft occlusion.     

Haemodynamics in the first seconds after coronary artery occlusion.

The changes in cardiac and in total haemodynamics, occurring during the first seconds of occlusion and the subsequent desocclusion of coronary arteries were studied on 28 dogs. The most intensive changes were observed after the trunk occlusion of the left coronary artery. Simultaneously with decreasing blood inflow into the myocardium its contractility and the systolic pressure in the left ventricle and the outflow from the coronary sinus began to fall rapidly. The systolic pressure in the left ventricle decreased within the first 10 s from 24 to 13-15 kPa (180 to 100-110 mm Hg), which means that the systolic pressure fell about 1 kPa (7-8 mm Hg) per second, or 0.5-0.6 kPa (4-5 mm Hg) per systole. At the same time the end-diastolic pressure in the left ventricle also increased from zero to 3-4 kPa (25-30 mm Hg). After the trunk desocclusion of the left coronary artery the systolic pressure in the left ventricle proceeded to fall by about 2-3 kPa (15-22 mm Hg). Only then, 20-25 s after the desocclusion, blood flow in the left coronary artery began to rise intensively and 4-6 s later the myocardial contractility and the systolic pressure in the left ventricle also increased. After unclamping (50-60 s), there was an overshoot of haemodynamic values above preocclusive values and then followed the compensatory phase. This phase lasted 80-90 s and on its peak the pressure and flow parameters increased by about 50-60% above preocclusive values. During the occlusion of ramus interventricularis anterior or ramus circumflexus for 30-60 s the haemodynamic parameters changed only slightly. The same was observed during trunk occlusion of the right coronary artery (30-60 s), but in that case many extrasystoles occurred.     

Angiotensin II,as well as 5-hydroxytriptamine,is a potent vasospasm inducer of saphenous vein graft for coronary artery bypass grafting in patients with diabetes mellitus

Diabetes mellitus (DM) is an important risk factor for adverse outcomes of coronary artery bypass grafting. The bypass grafts harvested from patients with DM tend to go into spasm after their implantation into the coronary circulation. To clarify the contribution of 5-hydroxytriptamine (5-HT) and angiotensin II (AngII) in the bypass graft spasm, we examined the contractile reactivity to 5-HT or AngII of isolated human endothelium-denuded saphenous vein (SV) harvested from DM and non-DM patients. The 5-HT-induced constriction of the SV was significantly augmented in the DM group than in the non-DM group, which is similar to our previous report. AngII-induced constriction of the SV was also significantly augmented in the DM group than the non-DM group. Especially in the non-DM group, the AngII-induced maximal vasoconstriction was markedly lower than the 5-HT-induced one. Meanwhile, the increasing rates of AngII-induced vasoconstriction in the DM group to the non-DM group were significantly greater than those of 5-HT-induced vasoconstriction. These results indicate that 5-HT is a potent inducer of SV graft spasm in both DM and non-DM patients, while AngII is a potent inducer of SV graft spasm only in patients with DM. Furthermore, the protein level of AngII AT₁ receptor (AT₁R), but not the protein level of 5-HT_2A receptor, in the membrane fraction of the SV smooth muscle cells of DM patients was significantly increased as compared with that of the non-DM patients. These results suggest that the mechanism for hyperreactivity to AngII in the SV from DM patients is due to, at least in part, the increase in the amount of AT₁R on membrane of the SV smooth muscle cells.     

Economics of coronary artery bypass grafting.

To decide whether the number of operations for coronary artery bypass grafting should be increased, maintained at the present levels, or decreased we need to know how cost effective they are relative to other claimants on the resources of the National Health Service. For this purpose effectiveness is taken to be the effect on life expectancy adjusted for the quality of life. In an assessment of the cost per quality adjusted life year gained coronary artery bypass grafting rates well for cases of severe angina and extensive coronary artery disease. The cost, however, rises sharply for less severe cases. Bypass grafting seems to compare favourably with valve replacement for aortic stenosis and implantation of pacemakers for heart block; it is distinctly better than heart transplantation and the treatment of end stage renal failure but is probably less cost effective than hip replacement. If the number of operations for coronary artery bypass grafting were to increase it would be a fairly strong claimant only if restricted to the most severe cases. The data on which these judgments are based are crude and in need of refinement. The methodology is powerful, far reaching, and open to comment.     

Levels of l-ascorbic acid and cadmium in the saphenous vein of patients with coronary artery disease are negatively correlated

BackgroundThe aim of this study was the simultaneous determination of levels of cadmium and l-ascorbic Acid (AA) in human saphenous vein (SV) used in coronary artery bypass grafting (CABG) and check whether there is a relationship between these levels.MethodsHuman SV were collected from 40 patients (20 men and 20 women; age, 40–75 years) at the time of routine coronary artery surgical revascularization. The concentration of cadmium in the tissue was determined according to the GF AAS—atomic absorption method. The concentration of AA was assayed in supernatant by FIA method with spectrophotometric detection.ResultsAA concentration (mean ± SD); men: 98,7 ± 13,18 μg/g tissue, women: 96,06 ± 11,98 μg/g tissue. Cadmium concentration(mean ± SD); men: 309 ± 103,71 ng/g tissue, women: 348,5 ± 255,71 ng/g tissue. Correlations among concentrations of AA and cadmium were insignificant negative in the group of men (Pearson r = −0,1504, p = 0,5269) and in the group women (Pearson r = −0339, p = 0144).ConclusionsNegative correlations among concentrations of AA and cadmium in human SV obtained in our study may indicate a protective effect of this vitamin in relation to toxic cadmium.     

Platelet regeneration time and late occlusion of aortocoronary saphenous vein bypass grafts.

The half-time for platelet regeneration was estimated in 16 patients with aortocoronary vein grafts by the use of a non-radioisotopic technique based on the permanent inhibition by acetylsalicylic acid of lipid peroxidation by platelets. Ten patients had patent grafts after 6 years; in the other six at least one graft had become occluded between 2 and 6 years after the operation as shown by serial angiography. The mean half-time (+/- the standard error) for platelet regeneration was reduced to 2.5 +/- 0.2 days (P less than 0.002) in the group with occluded grafts as compared with 3.3 +/- 11 healthy volunteers. These results suggest a relation between late graft occlusion and platelet turnover and support the idea that patients with aortocoronary vein grafts could benefit from platelet suppressive therapy. Finally, the method employed appears to be a useful and simple way of evaluating platelet function in vivo.     

Management of dyslipidemia after coronary artery bypass grafting

The results of serial angiographic studies and intervention trials in patients after coronary artery bypass artery grafting have provided ample evidence that abnormalities of the plasma lipoprotein system are one of the most significant risk factors for a rapid atherosclerotic attrition of saphenous vein grafts. In addition to confirming the well recognized role and contribution of cholesterol-rich LDL or lipoprotein B particles to the progression of atherosclerotic lesions, intervention trials have also provided strong evidence for the atherogenic capacity of some intact and partly delipidized triglyceride-rich very low density lipoprotein and intermediate density lipoprotein (lipoprotein B complex) particles, and the protective effect of some (high density lipoprotein 3) but not all high density lipoprotein particles. Most importantly, those studies have emphasized the need for an early, aggressive treatment of dyslipoproteinemias with pharmacological agents as the most efficient therapeutic approach to delaying, if not preventing, the detrimental effect of atherosclerosis on saphenous vein grafts.