Arterial grafts for myocardial revascularization; experience of 65 internal mammary artery and gastroepiploic artery graftings

From November, 1984, to February 1987, internal mammary artery (IMA) and gastroepiploic artery (GEA) graftings to coronary arteries were performed in 65 patients. Of these patients, 58 unilateral IMAs, 6 bilateral IMAs, 2 GEAs were utilized. The hospital mortality was 3.2% but no cardiogenic death occurred. Fifty-eight (89%) patients became asymptomatic after surgery. Postoperative angiography performed from 1 to 3 months after operation showed excellent patency in 57 (96%) IMAs and 2 (100%) GEAs. On the other hand, the patency of saphenous vein graft done at the same period were 88%. GEAs were used for 2 reoperated cases and revealed good patency and relief of symptoms without surgical complication. Cavitron ultrasonic surgical aspirator (CUSA) was used to dissect IMA from the chest wall, which was useful to shorten the operative time. In conclusion, arterial grafts, such as IMA and GEA were thought to be excellent coronary bypass conduits even for the small Japanese patient.     

Coronary artery bypass grafting with left internal mammary artery and right gastroepiploic artery, with and without bypass

BACKGROUND: Total arterial and off-pump revascularization are increasingly used in coronary artery bypass grafting. This study describes our experience with the exclusive use of both left internal thoracic artery and gastroepiploic artery by means of a median sternotomy, with and without cardiopulmonary bypass, in a subgroup of patients with two-vessel disease. METHODS: From January 1995 to July 2000, 171 consecutive patients were reviewed in a prospective database. Ninety-one patients underwent coronary artery bypass grafting without cardiopulmonary bypass (group A), and 80 patients were operated on under cardiopulmonary bypass with aortic cross-clamp and cardioplegia (group B). RESULTS: Patient data were similar in both groups except for the Euroscore (mean; 3.4+/-6.1, group A versus 2.5+/-4.5, group B; Euroscore > 6: 26.4%, group A versus 10%, group B; p < 0.05) and ejection fraction (mean, 54.6%+/-15.8%, group A versus 63.1%+/-12.7%, group B; p < 0.001). Severe aortic calcification was present in 6 group A patients, versus no patient in group B. Operative time was shorter in group A (185 versus 213 minutes, p < 0.0001), with less distal anastomoses (2.26 versus 2.5, p < 0.05). Conversion to cardiopulmonary bypass occurred in 1 patient, who was excluded from the study. Bleeding was higher in group A (852.6+/-288 mL versus 712.4+/-274 mL, p < 0.05), but transfusion was similar in both groups. Atrial fibrillation, postoperative inotropic support, and hospital stay were similar in both groups. Myocardial infarction was less frequent in group A (1 versus 4). Postoperative intraaortic balloon pump was used in 2 patients (group B). One patient died (group A) and 1 had an embolic stroke (group B). After discharge, 2 more patients died (group A, day 91; group B day 141), and 1 patient suffered an embolic stroke (group B). One patient in each group presented with dysfunction of the gastroepiploic artery graft requiring successful percutaneous transluminal angioplasty on the right posterolateral artery. CONCLUSIONS: These results suggest that off-pump coronary artery bypass grafting using the left internal thoracic artery and gastroepiploic artery is safe even in high-risk patients. This approach allows an absolute no-touch technique of the aorta.     

Reactivity of gastroepiploic and internal mammary arteries. Relevance to coronary artery bypass grafting.

The gastroepiploic artery is an alternate conduit for coronary artery bypass grafting. To test the hypothesis that its vasoreactive properties are different from those of the internal mammary artery, we obtained gastroepiploic artery segments from human gastrectomy specimens. Trimmed internal mammary artery segments were obtained during coronary artery bypass. Ring segments were mounted on a strain gauge and stretched to optimum resting length (90% of the internal circumference at 100 mm Hg). Potassium chloride, serotonin, and norepinephrine were chosen to simulate physiologic vasospasm induced by depolarization, platelet aggregation, or adrenergic stimulation, respectively. Contractions to potassium and a concentration-response curve to serotonin or norepinephrine were obtained. Sodium nitroprusside was used to assess relaxation. Gastroepiploic artery segments had stronger contractions to the depolarizing agent (potassium chloride), adrenergic stimulation (norepinephrine), and product of platelet aggregation (serotonin). The gastroepiploic and internal mammary arteries showed equal sensitivity, measured by concentration causing half-maximal contraction to norepinephrine and serotonin. There was no difference in relaxation to sodium nitroprusside. These data suggest that prevention of platelet-, adrenergic-, or potassium-induced contraction may be more important when the gastroepiploic artery is used as an alternate conduit for coronary artery bypass, reinforcing consideration of nitrovasodilators and platelet inhibitors in the perioperative interval.     

Vascular reactivity of human internal mammary and gastroepiploic arteries.

Patency rates of bypass graft conduits are thought to be influenced by the determinants of vascular tone. This study has comparatively examined the response of the human internal mammary and gastroepiploic arteries to potassium, noradrenaline, dopamine, 5-hydroxytryptamine, thromboxane, and histamine. The response to potassium was significantly greater in the gastroepiploic artery (Emax = 79.5 +/- 9.6 mN) than in the internal mammary artery (Emax = 27.0 +/- 6.4 mN). Dose-related constrictions were observed in both vessels to all agonists except histamine, which was ineffective in the gastroepiploic artery. Noradrenaline and dopamine produced comparable dose-related constrictions in each vessel, with similar EC50 and Emax (expressed as a percentage of potassium response) values, but 5-hydroxytryptamine (Emax, gastroepiploic = 10.8% +/- 1.9%; internal mammary = 71.8% +/- 21.2%) and thromboxane (Emax, gastroepiploic = 116.7% +/- 4.0%; internal mammary = 169.6% +/- 19.4%) were more efficacious in their constriction of the mammary artery; the potencies were similar. We conclude that there is a heterogeneity of response to some vasoconstrictors between the human internal mammary and gastroepiploic arteries. The internal mammary artery may be more predisposed to events that initiate vasospastic disorders.     

Use of gastroepiploic and internal mammary arteries for myocardial revascularization

Triple coronary artery bypass grafting utilizing the right gastroepiploic artery and both internal mammary arteries was performed successfully in a 37-year-old male, achieving primary myocardial revascularization. All grafts were in situ. The right gastroepiploic artery was anastomosed to the posterior descending artery. The right and left internal mammary arteries were anastomosed to the left anterior descending artery and the posterolateral branch, respectively. The postoperative angiogram showed good patency of all grafts. The patient recovered uneventfully with resolution of his angina pectoris.     

Similar endothelium-dependent relaxation, but enhanced contractility, of the right gastroepiploic artery as compared with the internal mammary artery.

The right gastroepiploic artery is an alternative coronary bypass graft. The excellent graft function of the internal mammary artery has been related to its physiologic properties, particularly to endothelial function. Isolated artery rings were suspended in organ chambers for recording of isometric tension. Norepinephrine and potassium chloride evoked threefold greater contractions in the gastroepiploic artery than in the mammary artery (p less than 0.01 to 0.05), whereas the sensitivity to the catecholamine was comparable. Acetylcholine induced endothelium-dependent relaxations, but the sensitivity (pD2: 6.7 +/- 0.3) and maximal relaxation (81% +/- 9%) were slightly less in the gastroepiploic artery than in the mammary artery (pD2: 7.6 +/- 0.2; 100% +/- 0%; p less than 0.05). Histamine induced endothelium-dependent relaxations with a similar sensitivity (pD2: 7.5 +/- 0.3 and 7.2 +/- 0.1), whereas the maximal relaxation was slightly enhanced in the gastroepiploic artery. The relaxation to the nitric oxide donor SIN-1 was identical in the two arteries. Thus the right gastroepiploic artery exhibits better contractility than the internal mammary artery but comparable endothelium-dependent and endothelium-independent relaxations. The good endothelial function of the gastroepiploic artery might be important for graft function and patency, whereas the enhanced contractility may facilitate vasospasm, especially in the presence of high circulating levels of catecholamines.     

Human gastroepiploic artery has greater chymase activity than the internal thoracic artery

Objective: Recent reports have demonstrated that long-term patency of the gastroepiploic artery (GEA) in coronary artery bypass grafting (CABG) is less satisfactory compared with the internal thoracic artery (ITA). However, the reason has not been fully elucidated. Angiotensin II is known to play an important role in the development of intimal hyperplasia, we hypothesized that the GEA is different from the ITA with respect to angiotensin II-forming ability. Accordingly, we measured activities of angiotensin II-forming enzymes, angiotensin-converting enzyme (ACE) and chymase, in human GEA and ITA. Methods: Remnant of the GEAs and ITAs were obtained from 24 patients who underwent CABG in which both conduits were used simultaneously. Activities of ACE and chymase were measured by using the extract form the GEA or ITA. Sections of the GEA or ITA were immunohistochemically stained with anti-human chymase antibody. Results: The ACE activity of the GEA (0.28 ± 0.16 mU/mg protein) was greater than that of the ITA (0.18 ± 0.11, p < 0.001). The chymase activity of the GEA (11.11 ± 7.15 mU/mg protein) was also greater than that in the ITA (7.13 ± 4.89, p < 0.001). The density of chymase-positive cells in the GEA (3.8 ± 4.2 cells/mm²) was greater than that in the ITA (1.1 ± 1.2, p < 0.01). Conclusion: Activities of both ACE and chymase were significantly greater in the GEA compared with the ITA. The GEA may be different from the ITA with respect to potential ability of angiotensin II-formation.     

Different effects of activated platelets in the right gastroepiploic and internal mammary arteries. Implications for coronary artery grafting.

The right gastroepiploic artery is increasingly utilized as an alternative coronary bypass conduit, although postoperative spasm can represent a problem. Platelet-vessel wall interactions are important determinants of graft function and patency. We studied the effects of activated platelets in porcine and human gastroepiploic and mammary arteries. Arterial rings were suspended in organ chambers for isometric tension recording. In the porcine and human gastroepiploic arteries with or without endothelium contracted with norepinephrine, activated platelets evoked only further and strong contraction. In contrast, in the porcine and human mammary arteries, endothelium-dependent relaxations to platelets mediated by nitric oxide were noted, particularly in rings preincubated with the thromboxane A2 receptor antagonist SQ-30741 and the 5-hydroxytryptamine (5HT2)-serotonergic receptor antagonist ketanserin. Although endothelium-dependent and endothelium-independent relaxation to bradykinin and the nitrovasodilator 3-morpholino sydnonimine were more pronounced in the gastroepiploic than in the mammary artery, norepinephrine, serotonin, and potassium chloride evoked much stronger contractions in the former than in the latter. Thus activated platelets induce pronounced contraction of the gastroepiploic artery that may contribute to postoperative spasm. The administration of antiplatelet drugs and vasodilators that prevent the effects of thromboxane A2 and serotonin may be beneficial for gastroepiploic graft function.     

Similarity between internal thoracic artery and gastroepiploic artery graft: pharmacological point of view

The pharmacological responses of internal thoracic artery (ITA), gastroepiploic artery (GEA) and saphenous vein (SV) obtained from patients receiving coronary artery bypass grafting (CABG) were assessed by isometric contraction records. The concentration-response curves for ergonovine and serotonin showed the leftward shift in SV compared with ITA and GEA. The 50% effective dose values of SV for ergonovine and serotonin were significantly less than those of ITA and GEA. The concentration-response curves for phenylephrine were similar among three kinds of grafts. There were no significant differences in the 50% effective dose values for phenylephrine among them. The effect of 0.4% papaverine chloride on the free graft flow was assessed in 15 patients receiving CABG with mean body surface area of 1.62 +/- 0.12 M2. The free flow of ITA graft was 71 +/- 32 ml/min before intraluminal papaverine injection, and that increased to 112 +/- 41 ml/min after injection. The free flow of GEA graft was 82 +/- 39 ml/min before injection, and that also increased to 128 +/- 40 ml/min after injection. The patency rates at the mean 2.2 months after grafting were 98% in ITA, 93% in GEA, and 88% in SV. In conclusion, both GEA graft and ITA graft can be expected as an excellent conduit in myocardial revascularization.     

The skeletonized internal mammary artery

The internal mammary artery increasingly is being used to construct multiple distal anastomoses. By skeletonizing the pedicle, the artery is functionally lengthened and sequential anastomoses are easier to perform.     

Aneurysm of internal mammary artery.

A fusiform non-sclerotic aneurysm of the left internal mammary artery was found in an otherwise healthy young woman. Aneurysms such as this seem to be extremely rare since no published case could be found.     

Repair of damaged internal mammary artery

The use of the internal mammary artery (IMA) in coronary artery bypass graft surgery is an independent predictor of late survival in all subsets of patients and should not be denied to any subgroup. Therefore damage to the IMA during harvesting is a catastrophic complication after which the graft is usually discarded. We present here a simple and safe technique for repair of a damaged left IMA that allowed its rescue for grafting to the left anterior descending artery.     

Pharmacological studies on internal mammary artery bypass grafts. Action of endogenous and exogenous vasodilators and vasoconstrictors

BACKGROUND: The purpose of this experiment was four-fold: 1) to determine the effect of currently used cardiovascular drugs on internal mammary artery (IMA) vascular tone, 2) to examine IMA reactivity to autacoids and products released from aggregating platelets, 3) to compare the vascular reactivity of the right versus left IMA, and 4) to determine whether the canine IMA was an acceptable physiological model as regards its similarity to the human IMA, which is used routinely for coronary artery bypass grafting. METHODS: To study factors that modulate the tone of IMA, bypass grafts, right and left canine IMAs were studied in vitro in organ chambers (95% O(2)/5% CO(2), pH=7.4). RESULTS: Increasing concentrations (10(-9) to 10(-4M)) of the neurotransmitter acetylcholine (ACH) and the platelet-derived products adenosine diphosphate (ADP) or serotonin (5-HT) induced vasodilatation of contracted right and left IMAs. The vasodilation caused by ACH and ADP was endothelium-dependent while serotonin acted directly on the vascular smooth muscle. Histamine and bradykinin also induced IMA vasodilation, histamine via a direct action on the smooth muscle, and bradykinin through the release of nitric oxide (NO). In canine IMAs, the calcium ionophore A23187 produced endothelium-dependent vasodilation of contracted blood vessels; this vasodilation was blocked by N(G)-nitro-L-arginine (10(-4)M), a competitive inhibitor of nitric oxide synthesis from L-arginine, and by hemoglobin (10(-5)M). Dopamine, dobutamine, and papaverine induced vasodilation of the IMA regardless of the presence or absence of an intact intima, while norepinephrine induced profound IMA vasoconstriction, which was comparable to contraction to potassium ions or the constrictor peptide endothelin. CONCLUSIONS: These experiments establish a pharmacological profile of IMA and demonstrate that endogenous and exogenous compounds can significantly alter its vascular tone.     

Myocardial revascularization with combined arterial grafts utilizing the internal mammary and the gastroepiploic arteries

Coronary artery bypass grafting with a combined arterial graft using both the internal mammary artery and the right gastroepiploic artery was performed in 22 patients during a 21-month period. There were 17 men and 5 women ranging in age from 34 to 73 years (mean age, 53.4 years). Three patients were having a reoperation, and 2 patients had no segment of long saphenous vein available. Twelve patients were less than 55 years old. The mean number of distal anastomoses including vein grafts was 3.2 and the mean number of arterial grafts was 2.5 per patient. The mean aortic cross-clamp time was 63.8 minutes and the mean cardiopulmonary bypass time was 116.7 minutes. There was 1 early and 1 late death. The other 20 patients are alive without angina. Studied within 3 postoperative months, graft patency was 95% (19/20) in internal mammary artery and 93% (14/15) in gastroepiploic artery grafts. It is concluded that the combined arterial graft can be used safely and effectively, and its application facilitates complete revascularization with more arterial and fewer vein grafts.