Radiographic anatomy of the internal mammary arteries

The radiographic anatomy of the IMAs is described based on bilateral selective arteriography in 100 patients with coronary artery disease. The right and left IMAs were identical in caliber in their mid portions in 94% of cases. Fifteen percent of the IMAs measured less than 2 mm in luminal diameter at the level of the fourth costal cartilage. The side branches showed a great deal of variability and asymmetry in their origin and distribution. The understanding of the radiographic anatomy of the IMA and its branches is helpful in preoperative appraisal and is crucial for postoperative evaluation of the IMA grafts.     

Vasorelaxant properties of isolated human radial arteries: comparison with internal mammary arteries

Radial arteries, used in revascularisation surgery, are prone to spasm. We have examined the ability of nitrovasodilators, calcium channel blockers, and K_ATP channel openers to cause vasodilation, and to attenuate contractions due to depolarisation and receptor activation in radial and mammary arteries used in coronary artery bypass graft surgery. Two to three millimetre rings of artery obtained from patients at surgery were studied in organ baths in vitro. Constriction to KC1 and phenylephrine was examined before and again after treatment of the rings with drug or vehicle. Calcium channel blockers were the only compounds to inhibit contractions to both KC1 and phenylephrine. Sodium nitroprusside attenuated constriction to phenylephrine but not KC1 in both vessels. K_ATP channel openers similarly attenuated constriction to phenylephrine in radial arteries but were much less effective in mammary arteries. These studies support the continued use of calcium blockers after revascularisation with radial artery but suggest that other classes of drug may be as effective at minimising spasm due to receptor mediated constriction.     

Triple arterial coronary revascularization using the radial artery and bilateral internal mammary arteries versus the gastroepiploic artery and bilateral internal mammary arteries.

Arterial grafts are frequently used in modern coronary artery bypass grafting (CABG) and the benefit of the 2 internal mammary arteries (IMA) has already been established. However, the choice of the third arterial conduit, in addition to the IMA, is controversial. We have retrospectively analized perioperative and the follow-up results of patients who underwent CABG with triple arterial bypass using either the radial artery (RA) or the gastroepiploic artery (GEA) in conjunction with the bilateral IMA (BIMA). Between December 1995 and June 2001, 1,516 consecutive isolated CABG operations were performed at Shin-Tokyo Hospital. Among them the RA and BIMA were used in 96 patients (78 males, 18 females; mean age, 63.2+/-6.7 years, group R), and the GEA and BIMA in 123 patients (101 males, 22 females; mean age, 61.0+/-11.6 years, group G). Their perioperative and follow-up data were studied. The preoperative risk factors were similar between the 2 groups, except that there were significantly fewer patients with renal dysfunction in group R. The surgical results did not differ between the 2 groups; however, the GEA was more commonly used for revascularization of the right coronary artery, while the RA was used for the diagonal, circumflex or right coronary arteries. Surgical mortality and morbidity rates were not significantly different. During the follow-up period of 2.3+/-1.6 years, the event-free rates as well as the survival rates were not significantly different. CABG with either the RA or the GEA in conjunction with the BIMA can be performed safely. The surgical results as well as the follow-up results were acceptable and no significant differences between the 2 groups were observed.     

Nonselective preoperative digital subtraction angiography of internal mammary arteries

In preparation for coronary bypass surgery, digital subtraction angiography (DSA) was used to assess the caliber of the left and right internal mammary arteries and to exclude stenoses of their feeding arteries. In 100 patients (86 males, mean age 56 +/- 9 years) DSA was performed with a Siemens Digitron 2 device. A frontal projection was used in 18 patients, and a 10-20 degree right anterior oblique projection was used in 82 patients. The flow was 10 to 25 ml/sec; 20 ml was injected in 45 patients, 30 ml in 41, 40 ml in 5, 50 ml in 8, and 60 ml in 1 patient. Judged on the proximal third, visualization of the left and the right internal mammary artery was good in 80 and 72, fair in 17 and 20, and bad in 3 and 8 arteries, respectively. The diameter (mm) was 2.7 +/- 0.4 (range 1.8-3.4) and 2.7 +/- 0.3 (range 2.0-3.5), and visible length (cm) was 8 +/- 5 (range 1-24) and 9 +/- 4 (range 2-22) for the two arteries, respectively. The 10-20 degree right anterior oblique view separated the left internal mammary artery better from the descending aorta than the frontal view. In more pronounced right anterior oblique views the ascending aorta interfered with the right internal mammary artery. The quality was not different with 20 ml or 30 ml injections. The feeding arteries could not be assessed in 4 patients. One left subclavian artery was found occluded at the orifice. Incidentally, 2 distal right subclavian stenoses and 2 carotid stenoses were detected.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phenotype of smooth muscle cells in internal mammary arteries

The volume fraction of synthetic organelles in smooth muscle cells (SMCs) from the intima and media of human internal mammary artery (IMA) was examined by ultrastructural morphometry. The distal ends of 8 IMAs were collected peroperatively from coronary bypass patients aged 43 to 67 years. The thickness of the intimas ranged from 3 to 49 microns. Even the thickest parts had only a few cell layers, the majority of which were SMCs. In most patients, the cytoplasmic volume fraction of synthetic organelles was significantly lower in the media than in the intima (0.11 and 0.21 respectively). The high degree of differentiation of the SMCs agrees with the absence of atherosclerosis in the IMAs.     

Percutaneous transluminal angioplasty of internal mammary arteries in patients with rest angina

Angioplasty of the internal mammary artery (IMA) bypass graft has been shown to be a safe and effective revascularization procedure. However, angiographic and long term clinical outcomes in the high-risk group of patients presenting with rest angina has not been well documented. We report the results of IMA angioplasty in 20 patients with rest angina out of 614 (3.2%) who received a left IMA graft at our institution between April 1987 and September 1994. All patients were admitted with rest angina, 12 patients demonstrated persistent ischemia despite medical therapy, two patients were in heart failure, and one patient was in cardiogenic shock. Balloon angioplasty was successful in 15 of 20 patients (75%). Failed angioplasty was associated with either severe IMA tortuousity (three patients) or inability to cross the anastomotic stenosis with the guide wire (two patients). Each of these five patients required angioplasty of either the native left anterior descending artery or other saphenous vein grafts for clinical stabilization. No patient suffered a major complication (myocardial infarction, emergent coronary bypass surgery, death). Clinical follow-up was obtained in all 20 patients (6 months, 7 years, mean 27 months). Twelve patients (60%) were asymptomatic or had stable angina at follow-up, and 8 returned with anginal symptoms. Four patients required repeat angioplasty for disease in other vessels, two were treated medically for angina, one underwent repeat CABG, and cardiac transplantation was performed in one patient for refractory heart failure. Angiographic follow up was obtained in 10/15 (66%) successful angioplasty patients, and only one patient demonstrated restenosis at the treated site (10%). During follow up one patient developed an IMA stenosis at a previous dissection site in the body of the graft that was treated with angioplasty. These results suggest that IMA angioplasty in patients with rest angina is associated with excellent long term patency and clinical efficacy, as well as low procedural risk. © 1996 Wiley-Liss, Inc.     

Skeletonized bilateral internal mammary arteries for total arterial myocardial revascularization

BACKGROUND: Bilateral internal mammary artery (IMA) grafting is associated with an improved long-term survival, low rates of recurrence of angina and late myocardial infarction. However, because of the inadequate length of the conduit, use of bilateral internal thoracic artery grafting occasionally is not suitable for complete revascularization. To overcome this limitation, extra length can be obtained by skeletonization of both IMAs. We decided to prospectively assess the safety of this technique. METHODS: One hundred patients with a mean age of 52.5 +/- 13.1 years underwent complete revascularization with skeletonized bilateral internal mammary arteries on cardiopulmonary bypass (CPB). The right internal mammary artery (RIMA) was used as a free graft connected to the in situ left IMA (LIMA) in 88 patients. A free LIMA was attached to in situ RIMA in 12 patients. The average number of grafts was 3.2 per patient (range: 2-4 grafts per patient). Mean left ventricular ejection fraction was 60% (range: 25-80%). RESULTS: No patient required reexploration for bleeding, and no patient died within 30 days after operation. On the basis of electrocardiographic changes, three patients sustained a perioperative myocardial infarction. One patient had a sternal wound infection. Mean follow-up was 24 months (range: 6-36 months). The actuarial survival rate was 99 +/- 1% at 3 years. No myocardial infarctions were reported during the follow-up. Three patients had recurrent angina with conduit occlusion diagnosed on coronary angiography. CONCLUSION: Complete myocardial revascularization with skeletonized bilateral internal mammary arteries is a safe and reliable technique with excellent early and mid-term results.     

Discontinuities in the internal elastic lamina: a comparison of coronary and internal mammary arteries

The internal elastic lamina (iel.) of the anterior descending branch of the left coronary artery, and the internal mammary artery, were studied in 166 unselected subjects of different ages and races. The coronary artery showed substantial defects in the iel. even in the first few years of life, while the iel. of the mammary artery showed only minimal defects in all age groups. The defects in the iel. were associated with the presence of medial cells in the intima, and the thickness of the intima was correlated with the magnitude of the defects in the iel. (Correlation coefficient 0.95 for the coronary artery and 0.80 for the mammary artery). Small arteries involved in chronic inflammatory or neoplastic disease showed a similar relationship if the vessel were present in an edematous area. These vessels which do not usually show intimal thickening, displayed a thickened intima in the vicinity of defects of the iel. It is suggested that the pronounced difference in the incidence of arteriosclerosis between the coronary and internal mammary arteries is related to these defects in the internal elastic lamina.     

Endothelin receptor blockade improves endothelial function in human internal mammary arteries

OBJECTIVE: Endothelial dysfunction, specifically endothelium-derived contracting factors have been implicated in the development of arterial conduit vasospasm. The potent vasoconstrictor endothelin-1 (ET-1) has received much attention in this regard. The present study was designed to evaluate the role of ET-1 in the development of endothelial dysfunction in human internal mammary arteries (IMA). To this aim, we examined the effects of specific and non-specific ET-receptor antagonists on endothelial function (assessed using acetylcholine (ACh)-induced vasodilation) in segments of IMA obtained during coronary artery bypass graft (CABG) surgery. METHODS: Vascular segments of IMA were obtained from 51 patients undergoing elective coronary artery bypass graft (CABG) surgery and in vitro endothelium-dependent and -independent responses to ACh and sodium nitroprusside (SNP) were assessed. Isometric dose response curves (DRC) to ACh and SNP were constructed in pre-contracted rings in the presence and absence of bosentan (ET(A/B) receptor antagonist, 3 microM), BQ-123 (ET(A) antagonist, 1 microM) and BQ-788 (ET(B) antagonist, 1 microM) using the isolated organ bath apparatus. Percent maximum relaxation (%E(max)) and sensitivity (pEC(50)) were compared between interventions. RESULTS: ACh caused dose-dependent endothelium-mediated relaxation in IMA (%E(max) 43+/-4, pEC(50) 6. 74+/-0.12). In the presence of bosentan, BQ-123 and BQ-788 ACh-induced relaxation was significantly augmented (%E(max) bosentan 60+/-3, BQ-123 56+/-4, BQ-788 53+/-5 vs. control 43+/-4, P<0.05) without affecting sensitivity. The effects of these antagonists were endothelium-specific since endothelium-independent responses to SNP remained unaltered. Furthermore, the beneficial effects were independently and maximally mediated by ET(A) and ET(B) receptors (%E(max) BQ-123 56+/-4 vs. BQ-788 53+/-5 vs. bosentan 60+/-3, P>0. 05). CONCLUSIONS: These data uncover, for the first time, beneficial effects of ET receptor blockade on endothelial-dependent vasorelaxation in human IMA.     

Attenuation of lipopolysaccharide-induced hyperreactivity of human internal mammary arteries by melatonin

Reactive oxygen species (ROS) are thought to be important mediators in ischaemia/reperfusion injury following coronary vasospasm. The most ubiquitous action of melatonin is that of a free radical scavenger. Therefore, we investigated the action of melatonin by monitoring changes in the tone on ring preparations from human internal mammary arteries (IMA). In quiescent IMA rings melatonin (0.1 nm-10 microm) never elicited any change in baseline tension but 1-100 nm melatonin enhanced significantly maximal responses to noradrenaline (NA) in arteries with endothelial function. In NA (1 microm) precontracted arteries inhibition of nitric oxide (NO(*)) formation by N(G)-monomethyl-L-arginine (l-NMMA, 100 and 400 microm) eliminated 43 +/- 7 and 61 +/- 7% of the acetylcholine (ACH) effect. Melatonin (100 and 400 nm) attenuated maximal endothelium-dependent relaxant responses to ACH slightly by 23 +/- 9 and 17 +/- 9% leaving responses to direct stimulation of soluble guanylate cyclase by sodium nitroprusside unchanged. Incubation of IMA for 20 hr at 37 degrees C with 1 microg/mL lipopolysaccharide (LPS) enhanced maximal NA effects to 147 +/- 18% (n = 22, P < 0.01) whereas 50 microg/mL LPS reduced the NA maxima to 68 +/- 9% (n = 10, P < 0.01) of the control effects. The LPS-induced potentiation was completely attenuated by coincubation with melatonin (400 nm) and significantly reduced by coincubation with the thromboxane synthase inhibitor dazoxiben (10 microm). It is suggested that the LPS-induced hyperreactivity of vascular smooth muscle is mediated through enhanced release of ROS and prostanoids and that melatonin inhibits the vascular hyperreactivity through selective scavenging of ROS.     

Use of both internal mammary arteries; not everything is advantageous

The internal mammary artery is considered the elective graft for performing aortocoronary by-pass as its long-term results have proven better than those obtained with the internal saphenous vein. Our results in a series of 21 patients in whom both internal mammary arteries were used are reported. Four patients (19.04%) needed reoperation for sternal dehiscence and two of them had mediastinitis (9.52%). Those patients were successfully treated by continuous povidone-iodine flushing. A clear statistical difference was found between this group of patients, in whom both internal mammary arteries were used, and the rest of the patients (182 patients) in whom just the internal saphenous vein and/or only one internal mammary artery was used. The second group presented 8 cases of sternal dehiscence (4.39%) and 1 mediastinitis (0.55%).     

Expanded use of the right and left internal mammary arteries for myocardial revascularization

While the use of the left internal mammary artery (IMA) has become routine in many cardiac surgery units there is some reluctance to utilize the right IMA. The reasons for this are the higher morbidity and mortality observed in the initial experience with bilateral IMA grafting, the limited length of the right IMA, and its potential injury in reoperations when used to revascularize the left anterior descending artery. In this series of 50 patients the right IMA was used as a conduit for myocardial revascularization. One hundred and fifty-nine coronary vessels were grafted (3.2 per patient) 67.3% with IMA and only 32.7% with vein grafts. The right IMA was used for 51 anastomoses and the left for 56, either as simple, sequential or Y type grafts. The refinement of techniques for constructing the IMA grafts used in this series show that the right IMA can reach in most of the cases the anastomotic sites of the right coronary artery beyond the acute margin of the heart, and it is hoped that the lateral positioning of the IMA pedicles will lessen the chance of graft injury at reoperation. On the basis of early clinical results (2% mortality and 4% sternal complications), the application of the right IMA seems justified electively for the revascularization of both left and right coronary artery systems or as a free graft in conjunction with the left IMA.     

Results of angioplasty (with or without stent) at the site of a narrowed coronary anastomosis of the left internal mammary artery graft or via the internal mammary artery

During the past 6 years, 50 patients underwent percutaneous transluminal coronary angioplasty (PTCA) of a narrowed coronary anastomosis of a left internal mammary artery (LIMA) graft or PTCA of a left anterior descending coronary artery stenosis via LIMA grafts at the investigators' institution. The success rate was high at 88%. Thirty-four of the 44 successfully treated patients (77%) underwent repeat angiography, which showed restenosis in 14 patients (41%). In cases of stent implantation at the coronary LIMA graft anastomosis angioplasty site, the restenosis rate was 80%, but it was only 14% in cases of pure balloon dilation (p = 0.001). Therefore, in cases of coronary LIMA graft anastomosis, stent implantation should be avoided, because it implicates an excessively high restenosis rate.