Adaptive mechanisms of arterial and venous coronary bypass grafts to an increase in flow demand

OBJECTIVE—To compare the mechanisms by which arterial and venous grafts increase their flow during pacing induced tachycardia, early and later after coronary bypass surgery.
DESIGN—43 grafts (13 epigastric artery, 15 mammary artery, 15 saphenous vein) evaluated early (9 (3) days (mean (SD)) after bypass surgery were compared with 41 other grafts (15 epigastric, 11 mammary, 15 saphenous vein) evaluated later after surgery (mean 23 months, range 6 to 168 months) by quantitative angiography and intravascular Doppler velocity analysis during atrial pacing. Controls were 17 normal coronary arteries.
RESULTS—Baseline graft flow tended to be lower later after surgery than early (41 (16) v 45 (21) ml/min, NS). Blood flow increased during pacing by 30 (16)% early after surgery, less than later after surgery (+46 (18)%, p < 0.001) and less than in normal coronary arteries (+54 (27)%, p < 0.001 v early grafts; NS v late grafts). There was no difference between venous and arterial grafts. No significant vasodilatation was observed during pacing early after surgery in arterial and venous grafts. Later after surgery, significant vasodilatation was observed only in arterial grafts (mammary and epigastric grafts), from 2.41 (0.37) to 2.53 (0.41) mm (+5.1% v basal, p < 0.001). Early after surgery and in venous grafts later after surgery, the increase in flow was entirely due to an increase in velocity. In later arterial grafts, the relative contribution of the increase in velocity to the increase in flow during pacing was lower in arterial grafts (70 (22)%) than in venous grafts (102 (11)%, p < 0.001) and similar to normal coronary arteries (68 (28)%).
CONCLUSIONS—Early and later after surgery, arterial grafts and venous grafts both increase their flow similarly during pacing. Early arterial grafts and venous grafts increase their flow only through an increase in velocity. Later after surgery, arterial grafts act as more physiological conduits and increase their flow in the same way as normal coronary arteries, through an increase in velocity and calibre mediated by the endothelium.


Keywords: coronary artery bypass graft; endothelial function     

Nonangiographic assessment of coronary artery bypass graft patency

Coronary artery bypass graft patency can be assessed using the indirect techniques of evaluating patients' symptoms and exercise tolerance, changes in stress electrocardiogram, radioisotope regional perfusion, and myocardial wall contraction. The direct techniques assess graft patency directly by visualizing grafts using conventional computed tomography (CT), ultrafast CT, magnetic resonance imaging, digital subtraction angiography, and echocardiography. The advantages and disadvantages of each of these modalities are reviewed. At the present time, ultrafast CT and possibly magnetic resonance imaging and Doppler appear to be the only techniques besides angiography that can consistently evaluate bypass graft patency. Although they have the advantage of being minimally invasive, they cannot show graft stenosis or sequential graft patency. These techniques are best used in following patients after coronary bypass graft surgery and ruling out graft closure as the source of chest pain.     

A practical approach to MRI of coronary artery bypass graft patency and flow

Direct visualization of coronary artery bypass grafts can be obtained non-invasively by magnetic resonance imaging. Several studies demonstrated a high sensitivity and somewhat lower specificity for detection of vein-graft patency, using the conventional spin-echo and gradient-echo techniques. In addition, the true functional status can be assessed by determining the flowrate within the graft using phase velocity mapping. Important limitations of the previously applied techniques include the inability to accurately evaluate the different segments of jump grafts and the presence of graft stenoses. Further improvement is to be expected from the recent introduction of breath-hold imaging sequences and the forthcoming introduction of bloodpool-avid contrast agents.     

全动脉化冠状动脉旁路移植74例

目的:介绍全动脉化冠状动脉旁路移植（CABG）的早期效果和经验。方法:74例全动脉化CABG的患者。74例患者分别在体外循环（CPB）和非CPB下行CABG。应用左乳内动脉（IMA）1例,左IMA加单挠动脉（RA）14例,左IMA加双RA 54例,双IMA加双RA 3例,双RA 2例。人均搭桥4.7（17）支,序贯吻合66例,“Y”和“T”型吻合分别为15和6例。结果:围手术期无死亡。本组患者随访518（平均12.2）个月,均恢复良好,无心绞痛症状再发。多普勒和16排CT示血管桥无狭窄通畅。结论:全动脉化CABG取得好的早期效果,是一种值得积极推广的方法。     

体外循环与非体外循环下冠脉旁路移植术后的血管桥通畅比较

目的：比较非体外循环下冠状动脉旁路移植术（OPCABG）与常规冠状动脉旁路移植术（CCABG）术后3-4年时血管桥的通畅率。方法：2003年1月-2004年12月间40例单独行冠状动脉旁路移植术（CABG）的患者资料回顾性地被分为OPCABG组和CCABG组。OPCABG组通过胸骨正中切口,在非体外循环心脏不停跳下完成CABG;CCABG组建立常规体外循环,心脏停搏下完成CABG。两组术前的一般情况无明显区别。利用多层螺旋CT（multislice spiral CT,MSCT）造影检查及CT图像后处理,研究两种术式各条血管桥的通畅情况。结果：CCABG及OPCABG组在左乳内动脉（LI MA）到前降支（LAD）的通畅率分别达到94.1%,94.4%,后降支（PDA）为88.2%,91.6%,钝缘支（包括对角支）的通畅率分别为88.9%,90.9%,静脉桥的通畅率为87.8%,88.0%,动脉桥的通畅率为85.7%,91.3%。各组间统计差别均无显著性。结论：OPCABG旁路血管桥的3-4年通畅率可以和CCABG相媲美.OPCAB治疗冠心病的初期结果显示可以减少术后并发症、减少患者术后呼吸机辅助时间和ICU留观时间、住院时间,降低住院费用,它的普及势在必然。     

移植静脉外膜增生与兔血管再狭窄的相关性

目的 探讨冠状动脉旁路移植术后移植静脉外膜增生与血管再狭窄的相关性.方法 构建20例兔颈动脉旁路移植模型,术后当日行血管彩色多普勒检查,检测移植静脉的通畅性.术后30 d,取出移植静脉,组织病理标本切片、HE染色,测量外膜面积和管腔面积.用统计软件分析外膜面积与管腔面积的相关性.结果 术后当日,血管多普勒证明,所有20例模型移植静脉全部通畅.统计软件分析结果显示,移植静脉外膜面积与管腔面积成直线关系.结论 移植静脉外膜增生与血管管腔再狭窄有相关性.移植静脉外膜增生越重,管腔越狭窄.     

冠装动脉移植术患者Q—T离散度与心律失常的关系分析

目的 探讨冠状动脉移植术对Q－T离散度（Q－Td）的影响及Q－Td与术后心律失常的关系。方法 对87例冠状动脉移植术患者（分成Ⅰ组65例：术后无心律失常;Ⅱ组12例：术后伴室性心律失常;Ⅲ组10例：术后伴房性心律失常）术前术后Q－T离散度进行分析。结果 3组Q－Tmax、Q-Tcd、Q－Td在术前、术后3天差异均有显著性意义（P均＜0.05）。在术前,术后3天、1周,室性心律失常组Q－Td均高于下学,而无心律失常组和房性心律失常组基本正常。术后2周室性心律失常组Q－Td也已降至正常,此时3组的Q－Td与术前相比差异均有显著性意义（P＜0.05）。Q－Td和ST－T改变呈显著正相关（P＜0.05）,且与室笥心律失常的发生呈非常显著正相关（P＜0.01）。结论 Q－Td一定程度上反映心肌缺血的程度,可作为冠状动脉移植术后心肌血供改善的一个指标。Q－Td增大对心律失常及猝死有一定预测作用。     

The effect of calcium dobesilate on venous function following saphenectomy in coronary artery bypass grafting

BACKGROUND: The aim of this study was to determine whether prophylactic use of calcium dobesilate (CD) can improve venous function after saphenous vein harvest in coronary artery bypass graft (CABG). MATERIALS AND METHODS: A total of 100 patients who underwent elective CABG were divided into four equal groups. In Group A, the greater saphenous vein (GSV) was harvested below the knee and, in Group B, through the knee till the groin. These patients remained untreated. Group C received CD in a dosage of 1500 mg po daily after the GSV was harvested below the knee. Group D received same dosage of CD after the GSV was harvested through the knee till the groin. Venous function of ipsilateral leg was evaluated clinically and by Doppler ultrasonography in the postoperative first week and second month. RESULTS: Clinical findings of venous insufficiency were observed with a similar rate between groups at both early and late periods. In Groups A and B, after 2 months, flow velocities decreased and reflux periods increased significantly. In groups C and D, treatment with CD for 2 months after saphenectomy resulted in a significant increase in flow velocities and a significant decrease in reflux periods. Patients in Groups B and D have significantly more impaired venous functions. CONCLUSION: Saphenectomy results in ipsilateral leg venous dysfunction, which seems to be unrelated to leg swelling and to be more prominent in patients with high-level saphenectomy. In addition, to be careful about the restriction of the saphenectomy procedure into the most appropriate level, prophylactic use of CD can prevent this deterioration when it was added to varice socks.     

冠状动脉搭桥术后静脉桥狭窄和新生易损斑块形成机制的研究进展

冠状动脉搭桥术术后发生桥血管病变是一种常见的现象,血栓形成、内皮功能障碍、血管痉挛和氧化应激是导致病变的重要机制。相比于动脉桥,静脉桥更易于发生病变,这与静脉本身的解剖形态和功能特征有着很大的关系。急性血栓形成、血管内膜增生和易损斑块形成是静脉桥不同时期发生病变的重要机制。使用抗血小板和调脂药物等冠心病二级预防药物有助于提高桥血管的开通率。寻找桥血管病变的预测因子及相关基因通路有望从细胞及分子学水平为静脉桥疾病提供新的研究方向。本文拟对冠状动脉搭桥术后发生静脉桥狭窄和新生易损斑块病变形成机制的研究进展作一综述。     

正-逆灌并选择性桥血管灌注技术在重症冠状动脉旁路移植术中的价值

目的 总结和分析顺-逆灌并选择性桥血管灌注技术在重症冠状动脉旁路移植术（coronary artery bypass grafting,CABG）中的应用价值.方法 回顾分析2010年6月至2011年12月河南省人民医院收治的重症冠状动脉粥样硬化性心脏病（冠心病）患者152例的临床资料.术前患者均常规行冠状动脉造影术,其中合并左主干病变46例,狭窄程度均大于70％,左前降支完全闭塞51例,前降支及右冠状动脉均完全闭塞29例,三支血管弥漫性病变并血管细小55例;所有手术均在体外循环下进行,术中均经冠状动脉顺灌加冠状静脉窦逆灌并选择性桥血管灌注进行心肌保护.结果 所有患者术中转流平稳,150例自动复跳,2例出现心室颤动,电除颤后顺利复跳,均顺利停机.术后5例出现低心排血量综合征,1例肾功能不全,2例低氧血症,经调整后均恢复,无死亡患者.结论 在重症CABG中,采用顺-逆灌并选择性桥血管灌注技术具有良好的心肌保护效果,能够明显改善患者的预后.     

Detection of patency of internal mammary artery grafts to the left anterior descending artery by transthoracic Doppler echocardiography

BACKGROUND: To determine whether a coronary artery bypass graft (CABG) is patent, we examined the flow of the left internal mammary artery (LIMA) to the left anterior descending artery (LAD) by transthoracic Doppler echocardiography (TTDE). PATIENTS AND METHODS: Eighty-seven patients with CABG (LIMA to distal LAD) were enrolled in the study. The flows from each subject were analyzed by three criteria: mosaic flow at the anastomosis site, distal anterograde flow (ante flow), and proximal retrograde flow (retro flow). RESULTS: On angiography, 79 grafts were patent and eight were not. TTDE study of 79 patent grafts demonstrated mosaic, ante, and retro flow in 63 (79.7%), 74 (93.7%), and 35 grafts (49.4%), respectively. The averaged diastolic peak velocity of ante flow was 26.3 +/- 11.0 cm/sec, significantly higher than that (4.8 +/- 7.1 cm/sec, P < or = 0.0001) in eight patients without patent grafts. These eight patients had no mosaic or retro flow and only three had ante flow. The accuracies to predict patency were 81.6%, 90.8%, and 49.4% for mosaic, ante, and retro flows, respectively. CONCLUSIONS: The existence of mosaic, retro, or sufficient ante flows strongly indicated the patency of LIMA to the LAD. When symptoms are possible to be derived from the occlusion of CABG to LAD, TTDE is a promising method to examine whether a LIMA to LAD bypass is patent.     

Initial experience with 64-slice cardiac CT: non-invasive visualization of coronary artery bypass grafts.

AIMS: The aim of this study was to evaluate the diagnostic accuracy in the assessment of coronary artery bypass grafts using 64-slice computed tomography (CT) technology. METHODS AND RESULTS: CT coronary angiography was performed for 96 bypasses in 31 patients with suspected coronary artery disease using a Siemens Sensation 64-slice CT-scanner and compared with invasive coronary angiography (ICA). Patients with an irregular or fast heart rate despite beta-blocker administration were not excluded from the study. All bypass grafts and 94% of the distal bypass anastomoses could be visualized by CT, non-evaluable distal arterial anastomoses were either due to clip material or calcification artefacts. Forty-two bypass graft occlusions and three significant stenoses were detected by CT and confirmed by ICA. Two venous grafts were missed and one arterial graft was not evaluable with ICA, but both were clearly depicted by multi-slice CT. One false negative and two false positive CT-findings resulted in a sensitivity of 97.8%, a specificity of 89.3%, a positive predictive value of 90%, and a negative predictive value of 97.7%. CONCLUSION: State-of-the-art 64-slice CT coronary angiography demonstrates high diagnostic accuracy in the assessment of arterial and venous bypass graft stenoses.     

冠状动脉旁路移植术后自体血液回输减少血液制品的应用经验

目的总结非体外循环下冠状动脉旁路移植术（OPCABG）后应用自体血液回输以减少血液制品的经验。方法将2007年8月至2011年8月北华大学第二附属医院心脏外科44例OPCABG患者随机分为自体血回输组（试验组）和异体血输血组（对照组）,每组各22例。试验组应用非洗涤过滤式自体引流血回输;对照组未用自体引流血回输。结果试验组自体引流血液回输量（774．9±278．7）ml,输异体红细胞悬液（744．4±．375．5）ml;对照组输异体红细胞悬液（1200．0±357．9）ml。试验组回输自体血量占输血总量的27．8％～96．0％,平均减少了47．9％以上的异体血输入量。术后随访1个月,两组无一例新桥梗阻及血栓形成,无一例再发心绞痛症状。试验组与对照组输异体血量差异有统计学意义（P〈0．01）,而输异体血浆差异无统计学意义（P〉0．05）。结论OPCABG术后应用一次性回输器回收自体引流血可以显著减少异体血输入量。     

Long-term angiographic follow-up of occluded saphenous bypass grafts treated with prolonged urokinase infusion

We report on 10 occluded saphenous vein bypass grafts in nine patients treated with prolonged urokinase infusion. Our purpose was to evaluate the patency of these grafts during long-term follow-up. We retrospectively analyzed consecutive patients treated at a single center. All patients had angiography 0.25 to 54 months after treatment. Results indicated that clot lysis was achieved in all grafts with urokinase infusions of 1,790,000 to 25,920,000 units given over 17 to 108 hours. In two grafts there was no filling of the distal native vessel and in one, a 50% stenosis with ulceration remained. There was a progressive loss of graft patency over the first 18 months, but 50% of the grafts that were opened with prolonged urokinase infusion remain patent. Long-term patency depends upon successful opening without residual obstruction and with good flow into the distal native vessel. Cathet. Cardiovasc. Diagn. 44:291–296, 1998. © 1998 Wiley-Liss, Inc.     

Anti-inflammatory effects of propofol during cardiopulmonary bypass: A pilot study

Introduction:

Propofol has been suggested as a useful adjunct to cardiopulmonary bypass (CPB) because of its potential protective effect on the heart mediated by a decrease in ischemia-reperfusion injury and inflammation at clinically relevant concentrations. In view of these potentially protective properties, which modulate many of the deleterious mechanism of inflammation attributable to reperfusion injury and CPB, we sought to determine whether starting a low dose of propofol infusion at the beginning of CPB would decrease inflammation as measured by pro-inflammatory markers.

Materials and Methods:

We enrolled 24 patients undergoing elective coronary artery bypass graft (CABG). The study group received propofol at rate of 120 mcg/kg/min immediately after starting CPB and was maintained throughout the surgery and for the following 6 hours in the intensive care unit (ICU). The control group received propofol dose of 30-50 mcg/kg/min which was started at the time of chest closure with wires and continued for the next 6 hours in the ICU. Interleukins (IL) -6, -8 and -10 and tumor necrosis factor alpha (TNFalpha) were assayed.

Result:

The most significant difference was in the level of IL-6 which had a P value of less than 0.06. Starting a low dose propofol early during the CPB was not associated with significant hemodynamic instability in comparison with the control group.

Conclusion:

Our study shows that propofol may be suitable as an anti-inflammatory adjunct for patients undergoing CABG.     

Impact of aorto-coronary graft markers on subsequent graft patency: A retrospective review

The use of aorto-coronary graft markers has not been standard, presumably due to concern about possible adverse effects on subsequent graft patency. Our goal was to determine if there was any increased risk of graft occlusion in patients who received circumferential graft markers at the time of their coronary artery bypass (CAB) surgery. A retrospective review of angiograms was performed for patients with prior CAB. Cohorts with and without graft markers were compared. A total of 405 “unmarked” and 311 “marked” grafts were identified in 335 patients meeting inclusion criteria. Patency is reported in divisions of elapsed time since CAB. Overall patency in the “marked” group (71.1%) was significantly higher than in the “unmarked” group (58.0%, P < 0.001). In this retrospective population, there was no increased risk of graft occlusion in patients who received circumferential graft markers at the time of CAB surgery as compared to those patients who did not. Cathet. Cardiovasc. Diagn. 42:259–261, 1997.© 1997 Wiley-Liss, Inc. This article is a US government work and, as such, is in the public domain of the United States of America.     

Long-term patency (9½ years) and atherosclerosis of a polytetrafluoroethylene (Gortex®) coronary artery bypass graft

The patency of a polytetrafluoroethylene (Gortex®) graft 9½ years after coronary artery bypass graft surgery (CABG) is demonstrated. While this material is not commonly used as a conduit because of limited success in the past, this case demonstrates that, given the right circumstances, longterm patency is possible. Since available conduits for CABG are quite often limited, viable alternatives may be lifesaving and require further evaluation. In addition to mechanical considerations such as size, length, and material, anticoagulation and strict management of hyperlipidemia may be critical.     

Endoluminal stenting of narrowed saphenous vein grafts: long-term clinical and angiographic follow-up

From April 1986 through April 1993, 58 intracoronary stents (41 Wall and 17 Wiktor stents) were implanted for the treatment of saphenous vein graft stenosis in 40 symptomatic patients. The indication was a primary stenosis in 44 and restenosis in 14 procedures. In-hospital complications were subacute stent thrombosis (2%), myocardial infarction (2%), and emergency coronary artery bypass grafting (CABG) (2%). Complications during a mean follow-up period of 42±27 months were restenosis (35% by patient, 33% by lesion), myocardial infarction (12%), late bypass grafting (12%), and death (7%). On quantitative coronary angiographic analysis, the mean minimal luminal diameter (and its confidence interval) increased from 1.3 mm (1.1–1.5 mm, preprocedure) to 2.9 mm (2.7–3.1 mm, postprocedure) and 2.2 mm (2.0–2.5 mm, 6 months follow-up, 95% angiographic follow-up). Progression of the underlying coronary artery disease and restenosis were the main reasons for a continual decline of the proportion without cardiac event on a Kaplan-Meier estimate. Restenosis occurred in one-third of cases beyond the first 6 months of follow-up. A relative risk ratio analysis for restenosis, performed on 14 variables, disclosed an increased risk for the following variables: (1) stenting of the proximal, distal or anastomosis part of the vein graft (relative risk 2.41, confidence interval: 1.28–3.59), (2) the implantation of stents <4.5 mm (2.59, 1.18–4.00), and (3) stenting of a redo–CABG vein graft (2.37, 1.17–3.58). Saphenous vein graft stenting seems to be characterized by excellent immediate clinical and angiographic results; in particular, stent thrombosis is rare. In this study, it appears that restenosis rates are lower than after conventional balloon angioplasty, but several procedural factors are related to an increased restenosis risk. Despite a lasting success in the majority of stented lesions, the estimated proportion without cardiac event is low at 5 years follow-up. Progression of the underlying coronary artery disease, a non-procedure-related event, constitutes the major limitation of saphenous vein graft stenting. © 1994 Wiley-Liss,Inc..