Haemodynamics of coronary artery - saphenous vein bypass

The velocity distribution of a suspension of red blood cell ghosts in an idealized model of the coronary artery-saphenous vein bypass has been investigated with the aid of laser Doppler anemometry. Pulsatile flow simulated pressure variations in the ascending aorta and ghost cell velocities were determined by the Doppler shift of scattered laser light. Using four different model bypasses it was demonstrated that turbulent flow at the graft-coronary intersection can be delayed by decreasing the discontinuity in diameter between the bypass vein and coronary artery, and also by reducing the bypass vein and host coronary artery intersection angle.     

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.     

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.     

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.     

80岁以上冠心病患者非体外循环不停跳下冠状动脉旁路移植手术治疗的临床特点及疗效

目的:探讨80岁以上冠心病患者采用非体外循环不停跳下冠状动脉旁路移植手术(OPCAB)治疗的临床特点及疗效.方法:2004年8月至2009年8月手术治疗80岁以上冠心病患者24例,占同期冠心病手术的4.5%(12/534),其中男17例,女7例;年龄80～91岁,平均年龄83.7岁.所有患者均经冠状动脉造影诊断为冠状动脉分支多处狭窄,其中陈旧性心肌梗死患者15例,急性冠脉综合征患者9例,采用欧洲心脏病风险评分,4-6分16例,6-8分6例,8分以上2例.手术方式均采用OPCAB,其中急诊手术4例,择期手术20例.同期3例行左室室壁瘤折叠术.结果:24例手术均顺利完成,搭桥1-4支/人,共58支,平均每人2.4支.无手术死亡.术后并发症共4例,占16.7%,其中出现呼吸功能衰竭2例,急性肾功能衰竭1例,一过性意识障碍1例,均经治疗后痊愈.术后随访6-48月,平均28.4月.随访期内1例死亡,死亡原因为大面积脑梗死.其余患者不稳定型心绞痛有明显缓解,心功能NYHA分级恢复为Ⅰ-Ⅱ级.平均住院11d.结论:采用OPCAB治疗80岁以上冠心痛患者,手术安全,疗效确切.尽量减少手术时间,选择主要血管再血管化及注意并发症的防治是治疗的关键.     

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.     

Coronary artery bypass surgery in high-risk patients

Background

In high-risk coronary artery bypass patients; off-pump versus on-pump surgical strategies still remain a matter of debate, regarding which method results in a lower incidence of perioperative mortality and morbidity. We describe our experience in the treatment of high-risk coronary artery patients and compare patients assigned to on-pump and off-pump surgery.

Methods

From March 2002 to July 2004, 86 patients with EuroSCOREs > 5 underwent myocardial revascularization with or without cardiopulmonary bypass. Patients were assigned to off-pump surgery (40) or on-pump surgery (46) based on coronary anatomy coupled with the likelihood of achieving complete revascularization.

Results

Those patients undergoing off-pump surgery had significantly poorer left ventricular function than those undergoing on-pump surgery (28.6 ± 5.8% vs. 40.5 ± 7.4%, respectively, p < 0.05) and also had higher Euroscore values (7.26 ± 1.4 vs. 12.1 ± 1.8, respectively, p < 0.05). Differences between the two groups were nonsignificant with regard to number of grafts per patient, mean duration of surgery, anesthesia and operating room time, length of stay intensive care unit (ICU) and rate of postoperative atrial fibrillation

Conclusion

Utilization of off-pump coronary artery bypass graft (CABG) does not confer significant clinical advantages in all high-risk patients. This review suggest that off-pump coronary revascularization may represent an alternative approach for treatment of patients with Euroscore ≥ 10 and left ventricular function ≤ 30%.     

Comparison between cryopreserved and glycerol-preserved allografts in a partial-thickness porcine wound model

Human skin allografts are one of the best temporary biological coverings for severely burned patients. Cryopreserved (CPA) and glycerol-preserved (GPA) allografts are the most widely used types. This study compared the allograft efficiency of both preservation methods under the same conditions. To simulate actual clinical conditions, we used a porcine wound model. In addition, we evaluated the macroscopic and microscopic scoring of graft performance for each method. Porcine cadaver skin 1 mm thick was obtained from one pig. Cryopreserved skin cell viability was 20.8 %, glycerol-preserved skin was 9.08 %, and fresh skin was 58.6 %. We made ten partial-thickness wounds each in two pigs. The take rates on day 2 were 96.23 and 82.65 % in the GPA and CPA group (both n = 9), respectively. After 1 week, the take rates of both groups were nearly equal. The removal rate at week 5 was 98.87 and 94.41 % in the GPA and CPA group, respectively. On microscopic findings at week 2, inflammation was greater in the CPA group. Other findings such as fibroblast hyperplasia and neovascularization were not significantly different between both groups. At week 5, the score of collagen fiber synthesis was 2.67 ± 0.47 and 2.33 ± 0.47 in the GPA and CPA group, respectively. The epidermal-dermal junction was 2.22 ± 0.79 and 2.00 ± 0.47 in the GPA and CPA group, respectively. These findings suggest that wound healing takes longer in the CPA group. The preservation method of allografts is not a absolute factor in the wound healing process in this wound model.     

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.     

Coronary artery bypass graft surgery in Newfoundland and Labrador

BACKGROUND: Newfoundland and Labrador, like other health care jurisdictions, is faced with widening gaps between the demands for health care and a strained ability to supply the necessary resources. The authors carried out a study to determine the rates of appropriate and inappropriate coronary artery bypass grafting (CABG) in the province and the waiting times for this surgery. METHODS: This retrospective cohort study was performed in the tertiary care hospital that receives all referrals for coronary angiography and coronary artery revascularization for Newfoundland and Labrador. By reviewing the hospital records, the authors identified 2 groups of patients: those in whom critical coronary artery disease was diagnosed on the basis of coronary angiography and who were referred for CABG between Apr. 1, 1994, and Mar. 31, 1995, and those who actually underwent the procedure during that period. By applying specific criteria developed by the RAND Corporation, the authors determined the appropriateness and necessity of CABG in each case. They also compared waiting times for CABG with optimal waiting times; as determined by a consensus-based priority score. RESULTS: A total of 338 patients underwent CABG during the study period. The cases were characterized by multivessel disease and late-stage angina symptoms. Almost all of the patients had high appropriateness scores (7-9), and nearly 95% had high necessity scores (7-9). However, during the study period, the waiting list increased by about 20%, because a total of 391 patients were referred by the weekly cardiovascular surgery conference; the authors identified these and an additional 31 patients as having necessity scores of 7 or more. Only 7 (23%) of 31 patients for whom CABG was considered very urgent underwent surgery within the recommended 24 hours, and only 30 (24%) of the 122 patients for whom CABG was considered urgent underwent surgery within the recommended 72 hours. INTERPRETATION: These results provide evidence that the cardiac surgery program in Newfoundland and Labrador is performing CABG in patients for whom surgical revascularization is highly appropriate and necessary. Access to CABG is less than ideal, however, since the waiting list continues to expand, and many patients wait beyond the recommended time for surgery.     

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.     

Coronary artery bypass grafting is associated with immunoparalysis of monocytes and dendritic cells

Coronary artery bypass grafting (CABG) triggers a systemic inflammatory response that may contribute to adverse outcomes. Dendritic cells (DC) and monocytes are immunoregulatory cells potentially affected by CABG, contributing to an altered immune state. This study investigated changes in DC and monocyte responses in CABG patients at 5 time‐points: admission, peri‐operative, ICU, day 3 and day 5. Whole blood from 49 CABG patients was used in an ex vivo whole blood culture model to prospectively assess DC and monocyte responses. Lipopolysaccharide (LPS) was added in parallel to model responses to an infectious complication. Co‐stimulatory and adhesion molecule expression and intracellular mediator production was measured by flow cytometry. CABG modulated monocyte and DC responses. In addition, DC and monocytes were immunoparalysed, evidenced by failure of co‐stimulatory and adhesion molecules (eg HLA‐DR), and intracellular mediators (eg IL‐6) to respond to LPS stimulation. DC and monocyte modulation was associated with prolonged ICU length of stay and post‐operative atrial fibrillation. DC and monocyte cytokine production did not recover by day 5 post‐surgery. This study provides evidence that CABG modulates DC and monocyte responses. Using an ex vivo model to assess immune competency of CABG patients may help identify biomarkers to predict adverse outcomes.     

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.