Internal Mammary Artery Bypass Research Articles

ＩＭＡ剥離の工夫と冠動脈再建術

ＩＭＡ剥離の工夫と冠動脈再建術

Endothelial hypoxia induction of atherosclerosis: An explanation of patency rates for internal mammary artery and other coronary artery bypass grafts

The major etiological factors of atherosclerosis are reviewed and the case strengthened for endothelial hypoxia being the major initiator. Hypoxia is also shown to be the major cause of coronary artery bypass graft occlusions. The pathophysiological differences between pedicle and free arterial grafts and venous grafts are discussed. Arguments are presented to explain why pedicle internal mammary artery grafts have longer lasting a patency then saphenous vein grafts. It is proposed that free grafts using other systemic arteries should also give very acceptable results and may, in certain circumstances, be desirable over pedicle internal mammary artery grafts. The differences between single, Y and sequential grafts are also discussed to explain differences in patency rates.

Internal mammary artery bypass grafting: Influence on recurrent angina and survival in 2,100 patients

Internal mammary artery (IMA) bypass grafting to the anterior descending coronary artery was performed in 2,100 patients between January 1978 and July 1986. The average number of additional saphenous vein grafts (SVGs) per patient was 1.8. During the same period, 1,753 patients underwent coronary artery bypass grafting using an SVG (average number of grafts per patient, 3.2). The average patient age was similar: 62.3 years for IMA grafts and 64.7 years for SVGs. Men constituted two thirds of each group. Left ventricular function was impaired (ejection fraction < 45%) in 1,071 (51%) of IMA grafts and 847 (48.3%) of SVGs. Other aggregate risk factors, ie, elevated blood pressure, diabetes mellitus, previous myocardial infarction, and congestive heart failure, were similar in each group. Operative results and postoperative mortality of the IMA and SVG patients were comparable. However, the long-term probability of cumulative survival and occlusion-free survival were significantly greater and the probability of recurrent angina and reoperative coronary artery bypass grafting were significantly less in IMA graft patients ( p < 0.015). The relative risk of occlusion in an SVG was 4 to 5 times greater than that of the IMA graft. These data indicate that a patent IMA graft to the anterior descending coronary artery protects against recurrent angina and death from cardiac-related causes, and that the IMA should be the conduit of choice.

Different responses of coronary artery and internal mammary artery bypass grafts to ergonovine and nitroglycerin in variant angina

The dynamic responses of a coronary artery and an internal mammary artery (IMA) graft to pharmacological intervention were examined by arteriography in 5 patients with variant angina who had undergone coronary artery bypass grafting with an in situ IMA to the left anterior descending coronary artery. Preoperative electrocardiographic findings included elevated ST segments in chest leads during attacks of angina, and all patients had severe fixed lesions in addition to marked spasm of the left anterior descending coronary artery after the administration of ergonovine maleate. Postoperatively with ergonovine stimulation, complete occlusion or marked subtotal narrowing was again observed at the primary fixed lesion in the proximal portion of the left anterior descending coronary artery, but the IMA graft and the coronary artery distal to the anastomotic site maintained satisfactory patency with no further occurrence of anginal pain or ST segment elevation. By computer-assisted graphic analysis, which allows highly reproducible measurements of vascular internal diameters, the diameter of the IMA showed only small changes under ergonovine ( p = not significant) or nitroglycerin ( p < 0.05) stimulation in contrast to the marked vascular reactivity of the coronary artery ( p < 0.05 and < 0.01, respectively). These findings indicate that the IMA graft is unresponsive to ergonovine at least in the amount required to produce coronary artery spasm in patients with variant angina and fixed lesions. The IMA graft appears to function well from a clinical and pharmacological viewpoint in patients with variant angina.

“Double Steal” Syndrome

A case is presented of a patient who had undergone internal mammary artery bypass grafting and subsequently developed angina pectoris and cere‐brovascular insufficiency as the result of a single proximal subclavian artery stenosis. The patient's ischemic symptoms resolved following successful angioplasty of the subclavian lesion. The status of the brachiocephalic circulation should be considered in patients presenting with angina following internal mammary artery bypass grafting and preoperatively in patients who are being considered for this procedure. (J Interven Cardiol 1989:2:1)

Thermal coronary angiography: A method for assessing graft patency and coronary anatomy in coronary bypass surgery

Thermal coronary angiography was evaluated in 50 patients undergoing 137 saphenous vein and 48 internal mammary artery bypass grafts. A total of 177 thermal coronary angiograms were performed after completion of the distal anastomoses by injection of cold cardioplegia into the vein or by reperfusion with warmer blood in the internal mammary artery grafts. These angiograms provided details of graft and anastomosis patency, flow directions, and presence of native coronary stenoses. Temperature differences between the injectant and the epimyocardium of greater than 4 °C resulted in high-contrast images. Thermal coronary angiograms were obtained in 173 of the 177 studied bypass grafts; 172 grafts were patent, and 1 internal mammary artery graft was occluded. Unsuspected stenoses wen detected at the site of four distal anastomoses. Subsequently, two anastomoses were successfully revised and three additional grafts performed. Ninety-six native coronary stenoses were located in the recipient coronary arteries. In ten instances, the thermal coronary angiograms were obscured by excess fat or myocardium, thereby impeding correct image analysis. We conclude that thermal coronary angiography can be clinically relevant and helps improve decision making during coronary artery bypass operations.

Internal mammary artery bypass: effect on longevity and recurrent angina pectoris in 2900 patients.

Internal mammary artery bypass (IMA) to the anterior descending coronary artery was performed in 2900 patients from January 1978 to December 1987. The average age of the patients was 64 years. Males accounted for 68% (1972 patients) and 82% (2378 patients) were in New York Heart Association (NYHA) class III. Left ventricular function was impaired in 51%. The average number of additional saphenous vein grafts per patient was 1.8. The operative mortality was 1.6%. Mediastinitis occurred in 29 patients (1%). Reoperation for bleeding was necessary in 32 patients (1.1%). Perioperative myocardial infarction (MI) was seen in 58 patients (2%) and neurological complications occurred in 32 patients (1.1%). Repeat coronary angiography was performed in 703 patients (25%) and demonstrated a patency rate of 96% in IMA grafts and 81% in saphenous vein grafts (SVG). Survival at 9 years was 90% from all causes and 95% when noncardiac deaths were excluded. Recurrence of angina occurred in 522 patients (18%) and reoperation was performed in 15 patients (0.5%). During the same time period, 1783 patients underwent coronary artery bypass utilizing a SVG. Survival at 9 years was 78% from all causes and 83% when noncardiac deaths were excluded. Recurrent angina was present in 546 patients (39%). These data suggest that a patent-IMA to the anterior descending protects against recurrent angina and death from cardiac causes and should be the conduit of choice.

Success of internal mammary bypass grafting can be assessed intraoperatively using myocardial contrast echocardiography

To determine whether the success of internal mammary artery bypass grafting can be assessed intraoperatively using myocardial contrast echocardiography, sonicated Renografin-76 was injected into the aortic root of 11 dogs during the delivery of cardioplegic solution. Studies were performed with the left anterior descending coronary artery patent and totally occluded, and after internal mammary artery bypass grafting distal to the occluded vessel. Flow rate during cardioplegia was constant for all three stages in each experiment. Myocardial contrast echocardiography clearly demonstrated homogeneous myocardial perfusion with the left anterior descending coronary artery patent, lack of perfusion in the left anterior descending artery bed during its occlusion and excellent perfusion of the occluded bed after internal mammary artery bypass grafting distal to the occlusion in 10 of the 11 dogs. In one dog, the bypass graft was technically inadequate and contrast opacification was not noted in the left anterior descending artery bed after internal mammary artery bypass grafting.The exponential function C(t) = Ae−αt+ Be−βtwas fitted to computer-derived time-intensity curves from the myocardium, where α denotes contrast washout and β denotes contrast appearance. Respective values for α and β (mean + 1 SD) were similar for the patent left anterior descending coronary artery and after internal mammary artery bypass grafting distal to the occluded artery (0.11 ± 0.10 versus 0.10 ± 0.10, and 2.5 ± 2.4 versus 1.1 ± 0.56). In conclusion, myocardial contrast echocardiography has potential for intraoperative assessment of the adequacy of coronary artery bypass grafting.

Sensitivity and specificity of assessing coronary bypass graft patency with ultrafast computed tomography: Results of a multicenter study

Because a significant number of all patients seen by cardiologists have had coronary bypass surgery, a relatively noninvasive method of assessing coronary bypass graft patency would be very helpful. Ultrafast computed tomography, by virtue of its rapid data acquisition time and reasonable spatial resolution, may be useful in this regard. To determine the sensitivity, specificity and predictive accuracy of this imaging modality as compared with cardiac catheterization, a multicenter study was undertaken.There were two parts to the study. Part I involved the evaluation of 179 grafts in 74 patients studied in the five participating centers between March 1985 and August 1986. Twenty-nine percent of these graft studies were found to be technically inadequate and were excluded before patency determinations began. The remaining group of 127 bypass grafts in 62 patients had studies adequate for interpretation. Fifty-one grafts werl to the left anterior descending coronary artery or a diagonal branch, 37 to branches of the left circumflex artery and 28 to the right coronary artery or a posterior descending vessel; in addition, there were 11 internal mammary artery bypass grafts primarily into the left anterior descending or diagonal artery distribution. The sensitivity of detecting angiographically open grafts was 93.4%, the specificity of detecting angiographically closed grafts 88.9% and the predictive accuracy was 92.1%. A subsequent study (Part 2) was performed 9 months later to assess the ability to carry out technically adequate examinations. Of the 138 consecutive graft examinations (50 patients) included in this part of the study, 94.2% of the examinations were found to be technically adequate.From these data it is concluded that 1) Ultrafast computed tomography is a very useful, minimally invasive technique for evaluating coronary artery bypass graft patency, and 2) technically adequate studies can be effectively performed in the majority of patients with bypass grafts.

Angiographic demonstration of spasm in a left internal mammary artery used as a bypass to the left anterior descending coronary artery

Spontaneous spasm of native coronary arteries and saphenous vein bypass grafts has previously been demonstrated by coronary angiography.1,2 Direct observation of spasm involving internal mammary artery (IMA) bypass graft has been reported in the immediate postoperative period.3 We present angiographic documentation of spasm in left IMA bypass graft in the late postoperative period.

Early postoperative control of internal thoracic artery-coronary artery anastomoses using intra-arterial DSA

Early postoperative angiographic control is important for prognosis and medical therapy for patients undergoing coronary bypass surgery. Grafts from the internal mammary artery had been shown to be superior to venous bypasses for anastomoses to the left anterior descending coronary artery. Thus, the need for angiographic demonstration of graft patency and function is increasing. We report on the angiographic analyses of 73 patients after left internal mammary artery (LIMA) bypass surgery by filling of the graft via retrograde injection of contrast medium into the left brachial artery. In all cases the bypass, anastomosis and downstream vessel were clearly visualised. No complications or side effects were observed.

Interventional cardiology—An overview

Unt i l 10 years ago, cardiac catheterization was predominantly a diagnostic tool for defining anatomic and functional disease states before cardiac surgical correction. After a decade of tentative exploration with the fixed rigid dilator technique of Dotter, balloon dilatation was developed by Andreas Gruentig in 1974 as a treatment for peripheral atherosclerotic stenosis, ushering in the new field of cardiology. The current supplement to the American Journal of Cardiology is based on a symposium that was sponsored by Advanced Cardiovascular Systems in June 1987 to assess the status of this important new field in which the cardiac catheter is used to render definitive treatment of cardiovascular disease, as well as to provide diagnostic data. The centerpiece of interventional cardiology today is percutaneous transluminal coronary angioplasty (PTCA). During the early years of PTCA (1977 through 1981), relatively crude devices and inexperienced operators limited PTCA to patients with proximal, discrete, subtotal stenosis of a single coronary artery (who comprised only 5 to 10% of the population requiring coronary revascularization), and to a primary success rate of only 60%. In contrast, coronary angioplasty is now being applied routinely to patients with more complex coronary anatomic situations, including distal disease, stenosis of multiple vessels, bifurcation lesions, total occlusions, and diseased saphenous vein or internal mammary artery bypass grafts. Concomitant with this expansion in the anatomic capabilities of coronary angioplasty has been a marked broadening of its clinical indications, which now include patients with chronic stable angina, unstable angina, acute myocardial infarction, clinical features that make bypass surgery unacceptable, and a small subgroup of

A comparison of morphologic and angiographic findings in long-term internal mammary artery and saphenous vein bypass grafts

Internal mammary artery grafts are currently considered the conduits of choice for myocardial revascularization. Comparisons of long-term morphologic changes in internal mammary artery grafts and saphenous vein grafts and correlation with premorlem angiography have not been reported. Eighteen internal mammary artery and 15 saphenous vein grafts that had been in place for 12 to 118 months (mean 56) in 18 patients were removed either surgically or at necropsy and examined hislologkally. Premortem angiograms were performed within 1 month of histologic study in 15 of these patients. Fibrointimai proliferation was more frequent in internal mammary artery than in saphenous vein grafts 8 ([44%] of 18 versus 4 [27%] of 15; p = NS). In contrast, atherosclerosis was common in saphenous vein grafts but was extremely rare in internal mammary artery grafts (10 of 15 versus 1 of 18; p = 0.01). A good correlation was noted between the degree of narrowing estimated by angiographic and histologic measurements in both internal mammary artery grafts (d = 0.99) and saphenous vein grafts (d = 0.71).Acceierated atherosclerosis did not occur in internal mammary artery grafts, but was common in saphenous vein grafts. Fibrointimal proliferation was commonly associated with graft narrowing in internal mammary artery grafts and may be an important factor in late graft closure. This study also confirms that internal mammary artery grafts have greater longevity compared with saphenous vein grafts.

INTERNAL MAMMARY GRAFTS ARE THE BYPASS OF CHOICE.

A randomized trial of internal mammary artery (IMA) versus saphenous vein (SV) bypass grafts will probably never be performed, but this analysis …

Percutaneous transluminal angioplasty involving internal mammary artery bypass grafts: a femoral approach.

Percutaneous transluminal coronary angioplasty is an effective technique for the treatment of selected patients with ischemic heart disease due to coronary artery stenosis. Successful angioplasty in saphenous vein bypass grafts has been documented, but little experience has been reported using angioplasty in internal mammary artery to coronary artery bypass grafts. Nine of ten patients with stenosis in the internal mammary artery to coronary artery anastomosis or in the coronary vessel distal to the anastomosis site were successfully treated with angioplasty. One patient developed restenosis 1 month after the procedure, and a repeat angioplasty was successful. In one patient, the balloon catheter could not be advanced through the left internal mammary artery to the stenosis site. Technical features of internal mammary artery angioplasty are discussed, including the use of specially designed guiding wires, guiding catheters, and balloon catheters that facilitate angioplasty involving internal mammary arteries from the femoral approach.

Improved Technique for the Proximal Anastomosis with Free Internal Mammary Artery Grafts

A method for construction of the proximal aortic anastomosis using an autologous pericardial patch for free internal mammary artery bypass grafts is described. The use of pericardium allows for ease of suturing without the need for saphenous vein harvesting.

Early Postoperative Spasm in Left Internal Mammary Artery Bypass Grafts

Two patients with early postoperative spasm of a left internal mammary artery bypass graft are described. To our knowledge, this entity has not been reported previously. Both patients were characterized by vasomotor collapse secondary to intractable spasm responsive only to local application of vasodilator agents. Although the mechanism of graft spasm is not clear, prophylactic nifedipine therapy in appropriate dose may be of some value. The profound hemodynamic effect of internal mammary artery spasm in the immediate postoperative period may allow no time for anything other than emergency reoperation to assess the nature of the problem and treat it appropriately.

Atresia of the left main coronary artery: Repair with left internal mammary artery bypass

The case of a 17-month-old child with atresia of the left main coronary artery and mitral insufficiency is presented. The child underwent two separate surgical procedures, the first being a left internal mammary-left anterior descending coronary artery bypass and plication of the mitral valve. During the follow-up period the mitral insufficiency progressed, and the child subsequently underwent mitral valve replacement with a Björk-Shiley prosthesis. A selective study of the left internal mammary demonstrated excellent flow into the left coronary artery system. The report illustrates the use of the left internal mammary artery in a small child.

Important Anatomical and Physiological Considerations in Performance of Complex Mammary–Coronary Artery Operations

One or more internal mammary artery (IMA) anastomoses were performed in 87% of 692 consecutive coronary artery bypass operations performed over a 20-month period. One IMA was used in 68% (N = 469) and both IMAs were used in 19% (N = 130). Only saphenous vein grafts were used in 13% (N = 93). The mean number of anastomoses (all types) was 3.5. Fifty-seven patients were having a reoperation; bilateral IMA grafting was performed in 23% (N = 13). In 60 patients, 3 or more IMA anastomoses were performed: 3 IMA anastomoses, 50 patients; 4, 9 patients; and 5, 1 patient. In 27 patients, repeat coronary arteriography was performed within 30 days of operation to evaluate dynamics of IMA, saphenous vein, and native coronary artery flow. Major flow or all flow was through the graft (vs. the native coronary artery) in 62% of in situ IMA bypass grafts, 86% of free IMA grafts and 94% of saphenous vein grafts. Hospital mortality excluding patients having reoperation was 1.7% (11/635); it was less than 1% for patients having either single IMA grafting procedures (4/437) or bilateral IMA grafting procedures (1/117). Hospital mortality for patients receiving only saphenous vein grafts was surprisingly high, 7.4% (6/81). Major determinants of flow through the in situ IMA sequential graft are the size and flow of the IMA, the degree of proximal native coronary artery narrowing, the distally grafted to proximally grafted coronary artery size ratio, and probably the size of the side-to-side anastomosis. Technical factors important for multiple IMA grafts are the length and diameter of the IMA, use of the diamond anastomosis, absence of coronary artery disease at side-to-side anastomoses, epicardial location of the coronary artery, and no angulation distal to the sites of sequential anastomoses. Unless ideal conditions of IMA flow and size are met, an IMA graft supplying more than two coronary arteries might better be done with a free IMA graft.

Left Recurrent Laryngeal Nerve Injury Following Internal Mammary Artery Bypass

To our knowledge, recurrent laryngeal nerve injury has not been reported previously as a complication of internal mammary artery mobilization for coronary artery bypass. We recently experienced this complication and are presenting a case history of the problem and comments.