The role of magnetic resonance in the evaluation of functional results after CABG/PTCA

Magnetic resonance imaging (MRI) is a non-invasive modality which can be used for direct visualization of coronary artery bypass grafts. Spin-echo and gradient-echo (cine-MRI) techniques are now available on standard MR machines and provide information on graft morphology and graft patency with a 90% accuracy. By combining the standard techniques with MR phase velocity mapping, the flow rate in the graft can be measured, thereby offering a unique non-invasive assessment of the graft function. Newer techniques include MR coronary angiography, pharmacologically induced stress MRI, ultrafast MRI of the first-pass (perfusion) of a paramagnetic contrast agent through the myocardium, and³¹P MR spectroscopy of high-energy phosphate metabolism of the myocardium. All of these may develop into valuable diagnostic tools for the assessment of functional results after CABG or PTCA, but still require clinical validation. At present, MRI is a useful screening procedure for assessment of graft patency and function in post-operative pain syndromes and in late graft occlusion or stenosis.     

Transthoracic 2D echo color Doppler assessment of internal mammary artery to left anterior descending coronary artery graft

For noninvasive evaluation of anatomy and flow characteristics of internal mammary artery graft (IMA-graft), 2D echo-Color-Doppler (CDE) was performed in 60 patients (54 M, 6 F, mean age 54.1±6.9 y), who underwent coronary angiography 20.1 ±13 months after a coronary artery bypass graft (CABG). CDE was performed, using an echocardiographic unit equipped with a 5 MHz linear transducer. In all patients, measurements of IMA-graft diameter (mm), and peak systolic and diastolic flow velocity (cm/sec) were obtained at baseline and also in 16 patients after dipyridamole infusion (0.54 mg/Kg/min) and in 10 patients after sublingual nitroglycerin (NTG) (0.4 mg). Angiography showed the IMA-graft patency in 58/60 patients (96.8%). A typical biphasic flow was displayed by CDE in 49/58 patients (84.4%) with angiographic patency. Dipyridamole infusion increased both IMA-graft diameter and peak diastolic flow velocity (PDFV) from 2.28 ±0.51mm to 2.9 ±0.42mm and from 19.4 ±6.2 cm/sec to 93.9 ±29 cm/sec, respectively (p<0.0001). No significant modifications of peak systolic flow velocity (PSFV) were observed. NTG increased PDFV from 29.11 ±8 cm/sec to 41.88 ±7.20 cm/sec (p<0.005), while diameter and PSFV showed no statistically significant modifications. CDE is a useful diagnostic tool for noninvasive evaluation of IMA-graft patency both early after surgery and during long-term follow-up. CDE pharmacological stress improves the sensibility of the technique and it can provide indirect information about pathophysiology of recipient coronary vessel.     

常规超声结合冠脉血流显像技术评价冠状动脉搭桥术后桥血管通畅性

目的应用常规超声结合冠脉血流显像技术评价冠状动脉搭桥术后桥血管通畅性.方法行冠状动脉搭桥术(左乳内动脉原位转流至左前降支)患者46例;术后检查乳内动脉桥起始段、桥血管远段(吻合口近端)、吻合口、远端及近端左前降支.分别测量各段收缩期峰值流速、舒张期峰值流速、收缩期流速时间积分、舒张期流速时间积分.结果乳内动脉原位转流术后, 桥血管起始段显示率95.65%;桥血管与自体左前降支吻合口显示率80.43%.通过测量并计算吻合口与吻合口近端桥血管流速时间积分比值以及舒张期峰值流速比值评价吻合口是否存在狭窄.结论常规超声结合冠脉血流显像技术可提供评价桥血管通畅性的直接证据,为临床随访提供一种新的无创的方法.     

Disturbed Endothelial Function of the Internal Thoracic Artery in Patients with Coronary Artery Disease

Objectives and Background The internal thoracic artery is an established arterial graft for myocardial revascularization. It never had been investigated, whether there are functional differences in this vessel between patients with or without coronary artery disease. Methods We investigated the left internal thoracic artery of 28 patients (15 with and 13 without coronary artery disease) with a duplex-system at rest and with a handgrip exercise. Results Concerning the measured flow velocities at rest there was only a significant difference between the diastolic mean and peak velocity between the two groups, the other investigated parameters demonstrate no significant difference. The peak diastolic and the mean diastolic velocity was less in patients with coronary artery disease during the handgrip-test. The flow reserve was decreased in patients with coronary artery disease (12.6±24.0% vs. 32.3±30.9%, P < 0.05). Conclusions We demonstrated, that patients with coronary artery disease have a higher peripheral resistance and a lower diastolic velocity of the internal thoracic artery during stress testing. This corresponds to a disturbed vasomotion and may be an early marker of arteriosclerosis.     

应用超声定量组织速度成像(QTVI)技术评价冠心病患者PTCA支架置入术后局部心肌运动的临床研究

目的探讨超声定量组织速度成像（QTW）技术评价冠心病患者VIVA支架置入前后局部心肌运动速度的临床应用价值。方法26例接受左前降支（LAD）支架置入术的冠心病患者，在术前1天内、术后1周内以及3个月时分别行QTVI检查。结果与术前相比，术后一周内LAD对应节段（前间隔，前壁，室间隔中段和心尖段）的收缩期峰值速度（PSMV）、舒张早期峰值速度（PDMV）明显增高。结论成功的冠状动脉内支架置入术后左室局部室壁运动显着改善，超声QTVI技术能提供新的定量评价指标。     

组织速度成像对冠心病早期缺血心肌再灌注后舒张时间变化的研究

目的探讨组织速度图像测定早期缺血心肌再灌注后舒张功能变化特征。方法选择43例冠心病患者，分别于经皮冠状动脉成形术＋支架植入术前、术后1周及术后1～3个月观察心尖两腔、四腔及长轴观的组织多普勒图像，测量左室二尖瓣环的舒张时间间期。结果冠心病患者术后1周及1～3个月与术前对照，等容舒张时间、舒张晚期达峰时间显著缩短，快速充盈时间、快速充盈达峰时间、心房收缩时间明显延长，等容舒张期出现的收缩后收缩波峰值速度、加速度、减速度以术后1周增高最为明显。结论冠心病患者组织速度图早期缺血心肌再灌注后舒张时间有显著改变，以术后1周改变最为明显。     

Transesophageal echocardiographic assessment of systolic and diastolic dysfunction during percutaneous transluminal coronary angioplasty

Left ventricular short-axis cross-sections at the level of the papillary muscles and transmitral flow were obtained with transesophageal echocardiography during percutaneous transluminal coronary angioplasty (PTCA) in 15 patients who had received anesthesia and who all demonstrated new areas of or more severe wall motion abnormality 10.2 +/- 4.3 seconds after initiation of balloon inflation. Both systolic (percentage area reduction and ejection fraction of the ischemic segment) and diastolic (early to atrial peak flow ratio and time velocity integral) function parameters and end-systolic wall stress changed significantly during PTCA. These changes were most profound during PTCA of the left anterior descending artery than they were during PTCA of the right coronary artery. Systolic and diastolic dysfunction are therefore invariably linked during transient ischemia, and PTCA of the left anterior descending artery consistently produced more profound dysfunction.     

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.     

冠状动脉搭桥术前后乳内动脉的超声检查

目的：研究冠状动脉搭桥术前后乳内动脉（ＩＭＡ）血流动力学的改变,为临床提供安全可靠的检查方法。方法：５０名ＩＭＡ－冠状动脉前降支（ＬＡＤ）搭桥术的患者于手术前后作了ＩＭＡ的超声检查。测量ＩＭＡ的收缩期峰值与舒张末期流速之比（Ｓ／Ｄ）,搏动指数（ＰＩ）,阻力指数（ＲＩ）,计算舒张期流速时间积分分数（ＤＶＴＩＦ）。将与ＬＡＤ吻合的ＩＭＡ手术前后的测值进行比较,并将术后两侧ＩＭＡ的测值进行比较,作统计学处理。结果：手术前后转流侧ＩＭＡ测值比较,血流动力学发生改变。Ｓ／Ｄ,ＰＩ,ＲＩ及ＤＶＴＩＦ均有显著性差异（Ｐ＜０．０１）。手术后转流侧ＩＭＡ与对侧比较,以上各项血流动力学测值同样有非常显著性差异（Ｐ＜０．０１）。ＩＭＡ的血流由术前的收缩期优势型转变为术后的舒张期优势。结论：超声检查在术前对ＩＭＡ可进行筛选,术后是随访转流血流通畅性可靠的无创方法。     

Assessment of coronary artery bypass graft patency by multidetector computed tomography and electron-beam tomography

This case report describes the use of retrospectively ECG-gated 16-slice multidetector computed tomography (MDCT) and electron-beam tomography (EBT) for assessing bypass graft patency in two patients with recurrent angina after coronary artery bypass graft surgery. The results of each tomographic modality were compared to the findings of traditional coronary angiography. In the first patient MDCT showed occlusion of the left internal mammary artery (LIMA) and saphenous vein graft after the second anastomosis. Coronary angiography confirmed these findings. In the second patient EBT showed patency of the LIMA and saphenous vein graft. After the first anastomosis of the saphenous vein graft, the connected vessel filled poorly. Coronary angiography confirmed both grafts to be patent, and detected an occlusion distal to the first anastomosis. These findings support the evidence that both MDCT and EBT are suitable techniques for establishing bypass graft patency by non-invasive means.     

CT血管造影分析体外循环与非体外循环冠状动脉旁路移植后的桥血管通畅率

背景:近年来,非体外循环冠状动脉旁路移植后桥血管通畅率是否与传统的体外循环冠状动脉旁路移植相同存在争议.目的:探讨体外循环与非体外循环冠状动脉旁路移植后桥血管时间通畅率的差异性.方法:选取同一操作者行体外循环冠状动脉旁路移植患者100例,按其临床特征及桥血管病变危险因素匹配抽取非体外循环冠状动脉旁路移植患者137例.采用64排多螺旋CT血管造影分析冠脉搭桥后1个月,1年,2年,3年,4年的桥血管通畅情况.结果与结论:共对641条桥血管进行评价,两组中左侧乳内动脉桥血管时间通畅率均高于大隐静脉桥,两组左侧乳内动脉桥和人隐静脉桥血管时间通畅率比较差异均无显著性意义.说明非体外循环与体外循环冠状动脉旁路移植后患者桥血管时间通畅率相似,对于某些适当的患者来说,非体外循环冠状动脉旁路移植不失为一个良好的选择.     

Noninvasive assessment of left and right internal mammary artery graft patency with high-frequency transthoracic echocardiography.

OBJECTIVES: The aim of this study was (1) to visualize internal mammary artery grafts (IMAG) on coronary artery by transthoracic echocardiography and (2) to assess the patency of the grafts. METHODS: Twenty-three patients (21 men, 56 +/- 6 years) with previous coronary artery bypass grafting were studied at baseline and after they underwent low-dose dipyridamole infusion. The parameters obtained were systolic (SPV) and diastolic (DPV) peak velocities and their ratio (DPV/SPV); the dipyridamole infusion to baseline ratio of DPV was an index of IMAG blood flow reserve (FR). Two groups of patients were selected at baseline: group A, (n = 12) with a DPV/SPV >1, and group B (n = 11), with a DPV/SPV <1. RESULTS: The IMAG was identified in all patients. Intraluminal flow signals obtained with pulsed wave Doppler showed a biphasic pattern (1 systolic and 1 diastolic wave). After dipyridamole infusion was administered, flow velocities increased in 11 of 12 patients in group A and in 5 of 11 patients in group B. In group A the DPV/SPV increased from 1.79 +/- 0.47 to 1.8 +/- 0.43 (P = not significant), and the FR was 1.8 +/- 0.4. In group B the DPV/SPV increased from 0. 46 +/- 0.05 to 0.5 +/- 0.09 (P = not significant), and the FR was 1. 3 +/- 0.41. Coronary angiography showed the graft patency in all patients in group A and in 5 patients in group B with increased flow velocity after dipyridamole infusion. In the identification of graft stenosis at baseline, DPV/SPV showed 100% sensibility and 58% specificity, and FR showed 92% sensibility and 84% specificity. CONCLUSION: Doppler echocardiographic evaluation of the IMAG is a simple noninvasive method to assess the functional impairment of the vessel.     

The flow-function relationship in patients with chronic coronary artery disease and reduced regional function: a Doppler transesophageal and bidimensional transthoracic echocardiography study

Background: Infra-low dose dipyridamole allows one to selectively explore myocardial viability. Transesophageal echocardiography Doppler measurement of left anterior descending coronary artery flow at baseline and following dipyridamole is an efficient tool to assess coronary flow response. Aim of this study was to determine the flow-function relationship during coronary vasodilatory stress in patients with coronary artery disease and baseline dysfunction. Methods and results: Twelve patients with resting dyssynergies and 6 controls underwent assessment of regional function and of left anterior descending blood flow velocity. Flow and function were evaluated at rest and following infra-low dose dipyridamole (0.28?mg/Kg over 4?min). Controls showed a normal function at rest and after dipyridamole. Six patients (‘Responders’) with resting dyssynergies showed an improvement in segments of left anterior descending artery territory, whereas the other six ones (‘Non-responders’) showed no functional change. Controls and ‘Responders’ had similar values of resting peak diastolic left anterior descending artery flow velocity both at rest and after dipyridamole, whereas ‘Non-responders’ showed a blunted flow response to dipyridamole. Conclusion: Myocardial segments with a resting dysfunction and a contractile reserve more often exhibit a residual flow response, whereas segments with fixed pattern show a flat flow response during coronary vasodilator stress.     

运动核素心肌灌注断层显像评估PTCA疗效

本文总结31例经皮冠状动脉腔内血管成形术(PTCA)前后作运动核素心肌灌注断层显像,PTCA前冠状动脉平均狭窄82.58±16.04%,术后为17.7±6.21%,26例(83.9%)运动心肌灌注断层显像显示PTCA术后心肌缺血完全消失及明显改善。90.3%病例PTCA术后运动试验较术前进步。认为运动心肌灌注断层显像可做为判断PTCA疗效的有效方法。     

Assessment of transmural coronary blood flow with intraoperative transesophageal color Doppler echocardiography during coronary revascularization.

Intraoperative color Doppler transesophageal echocardiography with a 4- to 7-MHz transducer was performed on 28 consecutive patients who underwent coronary artery bypass grafting to image and evaluate the transmural coronary blood flow before and after cardiopulmonary bypass. The transmural coronary flow was visualized in 26 (92.8%) of 28 patients in the inferior wall and in 13 (46.4%) of 28 patients in the lateral wall. The peak diastolic flow velocity of the transmural coronary artery in the inferior and lateral wall was significantly increased after coronary revascularization in patients with a successful bypass graft to the right coronary artery (from 34.0 +/- 19.7 to 64.9 +/- 30.9 cm/s, P <.001, n = 10) and to the left circumflex coronary artery (from 35.1 +/- 18.6 to 62.1 +/- 21.1 cm/s, P <.001, n = 10). No significant changes were observed in patients with no bypass graft to the right or left circumflex coronary artery. Coronary blood flow can be mapped and the velocity measured with Doppler transesophageal echocardiography with a high-frequency (4- to 7-MHz) transducer. Assessment of the transmural coronary flow may provide valuable information and aid in decision making during surgical revascularization.     

Assessment of flow velocity in a bypass graft of the gastroepiploic artery by contrast-enhanced transabdominal Doppler echocardiography: a case report.

An 81-year-old man with effort angina pectoris underwent coronary artery bypass grafting operation using the bilateral internal thoracic arteries and the right gastroepiploic artery (GEA). Angiography after operation showed that the bilateral internal thoracic arteries were patent. Abdominal angiography showed severe ostial stenosis in the celiac trunk. The GEA was not opacified by the celiac trunk but by the superior mesenteric artery, by collaterals. GEA flow could be detected from the epigastric lesion by contrast-enhanced Doppler echocardiography, and moreover, the flow velocity reserve of the graft was 2.4. This case suggests that the GEA graft can provide sufficient blood flow to the coronary artery despite ostial stenosis of the celiac trunk.     

桡动脉作为冠状动脉旁路移植术桥血管的安全性评估

目的比较二维及多普勒超声和Allen试验2种方法筛选冠状动脉旁路移植术(CABG)移植血管的准确性。方法51例患者CABG术前联合Allen试验与超声检查评价尺(UA)、桡动脉(RA)间侧支循环状况。结果47例经超声检查证实UA、RA间存在完善的侧支循环的患者,无论Allen试验结果阴性或阳性,术后均未发生手部缺血。2例Allen试验阴性结果,但超声检查认为UA不能代偿供血的患者,发生了不同程度的手部缺血表现。2例因不符合条件被排除。结论超声检查与Allen试验比较,对手掌部UA、RA间侧支循环评估的准确性更高,是一项很有意义的前瞻性检查。     

经胸彩色多普勒冠状动脉血流显像技术对冠状动脉左前降支心肌桥的初步研究

目的 利用经胸冠状动脉血流显像技术研究左前降支（LAD）心肌桥患者的壁冠状动脉血流频谱特征以及硝酸甘油对血流频谱的影响;探讨应用经胸冠状动脉血流显像技术诊断心肌桥的可行性.方法 取32例冠状动脉造影检出的心肌桥患者作为研究对象,其中31例心肌桥位于LAD中段,1例位于远段, 静息及舌下喷服硝酸甘油后观察壁冠状动脉及其近、远端彩色多普勒及频谱多普勒特点,比较壁冠状动脉与其近、远端血流参数及诱发前后壁冠状动脉血流参数.结果 硝酸甘油诱发前后LAD中段彩色多普勒总显示率87.1%.静息状态12例患者壁冠状动脉段出现特征性的＂拇指征＂频谱,列为静息阳性组,诱发后出现＂拇指征＂频谱的10例患者列为诱发阳性组.诱发前彩色多普勒检出1例壁冠状动脉起始处舒张期花色血流,诱发后增加显示6例,其中1例出现收缩期反向蓝色血流,多普勒检查示诱发前后拇指征频谱与其近、远端比较舒张期峰值流速、舒张期平均流速、加速度差异有统计学意义;诱发前后＂拇指征＂频谱比较舒张期峰值流速、舒张期平均流速、加速度差异有统计学意义,壁冠状动脉受压时间差异无统计学意义.诱发后2例测及收缩期反向波频谱.结论 经胸冠状动脉血流显像技术是诊断心肌桥的一种新方法,应用硝酸甘油可提高心肌桥的检出率.     

The statistical analysis of graft patency data in a clinical trial of antiplatelet agents following coronary artery bypass grafting

Because most coronary artery bypass patients receive more than one graft at surgery, it is most important to determine whether statistical analysis of graft patency should be performed on the premise that the multiple grafts within patients are dependent or independent experimental units. Veterans Administration Cooperative Study No. 207 was a multicenter clinical trial comparing four different antiplatelet regimens to placebo in the prevention of graft occlusion following coronary artery bypass grafting. Using the results from the 1-week postoperative angiograms from the Veterans Administration Cooperative Study No. 207, in which there were 3.2 distal anastomoses per patient, we have tested the hypothesis that grafts within patients tend to act dependently with respect to patency or occlusion by comparing the graft patency data to a binomial distribution (i.e., that distribution that would have been manifest if grafts were independent). Because the graft patency results in Study No. 207 significantly deviated from the binomial distribution (p = 0.0003), a more appropriate analysis for graft patency data was applied using a ratio estimate as applied to cluster sampling. The statistical methods used in 11 previous clinical trials of antithrombotic therapy after coronary artery bypass grafting were examined. Only one of the previous studies used such an analysis, and three additional reports attempted to correct for dependency of grafts within patients in their analyses using other statistical methods. In seven of the studies the investigators did not address the potential problem of a dependent relationship between multiple grafts within patients. We conclude that grafts within patients act as dependent experimental units and that the ratio estimate as applied to cluster sampling may be appropriately applied to these data.     

CT血管造影分析体外循环与非体外循环冠状动脉旁路移植后的桥血管通畅率

背景：近年来,非体外循环冠状动脉旁路移植后桥血管通畅率是否与传统的体外循环冠状动脉旁路移植相同存在争议。目的：探讨体外循环与非体外循环冠状动脉旁路移植后桥血管时间通畅率的差异性。方法：选取同一操作者行体外循环冠状动脉旁路移植患者100例,按其临床特征及桥血管病变危险因素匹配抽取非体外循环冠状动脉旁路移植患者137例。采用64排多螺旋CT血管造影分析冠脉搭桥后1个月,1年,2年,3年,4年的桥血管通畅情况。结果与结论：共对641条桥血管进行评价,两组中左侧乳内动脉桥血管时间通畅率均高于大隐静脉桥,两组左侧乳内动脉桥和大隐静脉桥血管时间通畅率比较差异均无显著性意义。说明非体外循环与体外循环冠状动脉旁路移植后患者桥血管时间通畅率相似,对于某些适当的患者来说,非体外循环冠状动脉旁路移植不失为一个良好的选择。