Endothelium-dependent relaxation in perforating branch of human internal mammary artery

The purpose of the present study was to examine the effect of acetylcholine on perforating branch of the human internal mammary artery (HIMA). Acetylcholine (10(-9)-10(-5)M) induced concentration- and endothelium-dependent relaxation (pEC(50)=7.54+/-0.03, maximal response was 98+/-1.3%) of the precontracted arterial segments. Indomethacin, 4-aminopyridine (10(-5)M) and precontraction with K(+)-rich Krebs-Ringer-bicarbonate solution had no effect on acethylcholine-induced relaxation. N(G)-monomethyl-L-arginine (L-NMMA) (10(-5)M) inhibited relaxation evoked by acetylcholine. Indomethacin applied together with L-NMMA lead to further inhibition of acethylcholine-induced relaxation. Even in the presence of both L-NMMA and indomethacin, 4-aminopyridine had no provoked further inhibition of acetylcholine-induced relaxation of perforating branch of HIMA. It was concluded that the acethylcholine-induced relaxation of isolated perforating branch of HIMA is probably mediated via endothelial production of nitric oxide. However, when NO-synthase is inhibited, acetylcholine-induced vasorelaxation may be, in part, mediated through activation of cyclooxygenase pathway and consequent production and release of prostacyclin or some other cyclooxygenase products.     

The internal mammary bypass graft: a superior second coronary artery.

In a study of the initial 1,004 consecutive patients who had direct coronary artery bypass at Ochsner Medical Institutions, computer methods of data processing were used to compare the clinical results between patients who had saphenous vein (SV) grafts and those who had internal mammary artery (IMA) grafts. The factors compared were the long-term mortality rates, nonfatal myocardial infarction rates, relief or persistence of angina, and the percentage of patients who acquired congestive heart failure. A simple comparison showed the patients with IMA grafts did better in all four categories; however, in a subsequent analysis in which maldistributed factors were removed, the rates of anginal relief and congestive heart failure were not significantly improved. The major benefit appears to be an increase in longevity among patients who had IMA bypasses.     

Free internal mammary artery graft as canine femoral artery substitute

Both right and left internal mammary artery (IMA) were dissected free in six dogs via median sternotomy, the left together with 2 cm-wide surrounding tissue and the right as naked artery. Free IMA grafts (3 cm long) were anastomosed end-to-end to the femoral arteries as bypass. Graft patency was assessed by palpation and Doppler analysis twice monthly. At 6 months all grafts were patent. They were harvested for light and scanning electron microscopy (SEM). Intimal thickening was seen in one specimen from each side. Medial fibrosis was more common in the IMA grafts with surrounding tissue. SEM showed endothelium in all grafts, but with some degeneration of endothelial cells. The study thus demonstrated maintenance of patency in free IMA grafts, which did not differ if the graft had been taken with or without surrounding tissue.     

乳内动脉-冠状动脉旁路移植术53例

作者对１９９４年１月～１９９６年１２月本院所作的５３例乳内动脉（ＩＭＡ）－冠状动脉旁路移植术进行了总结。全部患者均为经内科治疗效果不满意者。其中４４例发生过一次以上的心肌梗塞；１６例合并室壁瘤形成。除１例为非体外循环行单纯左ＩＭＡ与左前降支吻合外，其余均行左ＩＭＡ吻合前降支及大隐静脉序惯“蛇形”桥。全组平均做冠脉吻合口４．２８支。同期左室室壁瘤切除４例。手术死亡４例。３５例随访６个月～１年半，其中３０例症状消失，５例症状减轻，活动量增加。随访结果提示，ＩＭＡ冠脉旁路移植术可取得满意疗效。作者还对ＩＭＡ冠脉旁路移植术的技术要点、适应证等进行了讨论。     

乳内动脉—冠状动脉和移植术53例

作者对１９９４年１月－１９９６年１２月本院所作的５３例乳内动脉（ＩＭＡ）－冠状动脉旁路移植术进行了总结。全部患者均为经内科治疗效果不满意者。其中４４例发生过一次以上的心肌梗塞;１６例合并室壁瘤形成。除１例为非体外循环单纯左ＩＭＡ与左前降支史合外,其余元首地左ＩＭＡＫ吻合前降支及大陷序惯“蛇形”桥。全组平均做冠脉吻合口４．２８支。同期左室壁瘤切除４例。３５例随访６个月－１年半,其中３０例症状消失,５     

Weak beta-adrenoceptor-mediated relaxation in the human internal mammary artery

The function of beta-adrenoceptors in the human internal mammary artery was studied in vitro to predict the way in which the internal mammary artery graft would respond to beta-adrenergic agonists and antagonists given in the perioperative period. Ring segments of the distal internal mammary artery obtained from patients not receiving beta-blocker therapy were mounted in organ baths and isometric wall force was measured. For comparison, similar experiments were conducted on segments of canine coronary artery, a vessel known to have powerful beta-adrenoceptor function. All arteries were precontracted with potassium or the thromboxane mimetic agent, U46619, before isoproterenol cumulative concentration-relaxation curves were constructed. In the human internal mammary artery, the maximum relaxation induced by isoproterenol was only 14% of the potassium-induced contraction and 24% of the U46619-induced contraction. These responses were weak compared with 54% and 86% for beta-adrenoceptor relaxation measured in corresponding experiments in the canine coronary artery. In all experiments, propranolol antagonized the relaxation induced by isoproterenol. These studies suggested that the human internal mammary artery has only a small number of beta-adrenoceptors. We conclude that beta-adrenoceptors would contribute little to the reactivity of the human internal mammary artery graft to sympathomimetic drugs.     

The free internal mammary artery bypass graft. Use of the IMA in the aorta-to-coronary artery position

Transposition of the internal mammary artery (IMA) into the aorta-to-coronary artery position is described, and 4 patients who underwent this operation are reported. Currently, this type of bypass graft is reserved for those patients who have unsuitable or stripped saphenous veins. The free IMA grafts can be connected to any of the major coronary vessels, and in most instances optical assistance is not necessary. There was no significant difference in recorded blood flow between these free grafts and a large group of in situ IMA-to-coronary artery bypass grafts.     

Coronary artery bypass with inverted internal mammary artery: angiographic evidence of late graft patency

The internal mammary artery (IMA) is currently considered as the graft of choice for myocardial revascularization procedures. We report on two patients who underwent successful coronary artery bypass surgery using retrograde IMA flow. We provide, for the first time, angiographic evidence of late patency of an inverted IMA graft.     

Coronary artery bypass using internal mammary artery branches.

The excellent long-term patency rates achieved with use of the internal mammary artery (IMA) to bypass the left anterior descending coronary artery have stimulated a variety of approaches to expand the use of this conduit in coronary bypass surgery. In this report we document our results using the two terminal branches of the IMA to bypass two arteries in a Y configuration. Sixty-seven patients received IMA Y grafts during a 6-month period in 1987. A total of 150 IMA branch anastomoses were performed (8 patients received bilateral IMA Y grafts). Fourteen of 67 patients were revascularized using IMA grafts only. Operative mortality was 2 of 67 (3%), and follow-up mortality was 5 of 67 (7.5%). Fifty-eight patients could be evaluated 37 +/- 2.7 months later. Clinically 36% of patients reported some recurrence of angina and 12 of 47 (25%) had a positive electrocardiographic stress test. Four patients were reoperated on (2 redo coronary artery bypass grafting, 2 transplants). Sixty (40%) of the 150 branch anastomoses could be evaluated objectively and 30 (50%) were patent. Five (8.5%) were stenotic and 25 (41.5%) were occluded (overall patency rate, 58.5%). We conclude that although the use of IMA Y grafts is a technically feasible means to increase IMA usage, extended application of this technique cannot be recommended unless improved patency rates can be demonstrated.     

The internal mammary artery as a graft material for coronary artery bypass surgery. Histopathologic and biochemical studies of its atherosclerotic changes

To evaluate the usefulness of the internal mammary artery (IMA) as a graft material for coronary artery bypass surgery, 1) the whole length of 26 bilateral IMAs and 13 left anterior descending coronary arteries (LADs) harvested at autopsies were comparatively examined on atherosclerosis from the histological point of view, and 2) the lipid (total cholesterol, triglyceride and phospholipid) contents of 12 IMA segments and 11 LAD segments excised at other autopsies were also comparatively examined from the biochemical standpoint. 1) The histologic index of atherosclerotic involvement was expressed as intima-to-media ratio (R) representing the severity of the intimal thickening. The severity of atherosclerosis was graded from I to IV according to the R value. Of all 274 IMA sections grade IV (R greater than or equal to 3.0) atherosclerosis was found in only one section (1/26 IMAs, 3.8%). The mean R value of all IMAs (0.30 +/- 0.36) was approximately one tenth of that of all LADs (3.01 +/- 2.05) (p less than 0.01). The histologic examination for whole segments of the IMAs revealed that atherosclerosis of the IMA was equally slight in every part of the IMA with no laterality. On the other hand, atherosclerosis of the LAD was characteristically severer in the proximal segment of the artery than the distal segment. 2) The contents of total cholesterol, triglyceride and phospholipid of the IMA and the LAD were 5.5 +/- 1.8 (IMA) vs 17.8 +/- 13.6 (LAD) micro g/mg wet wt. (p less than 0.05), 90.4 +/- 90.3 (IMA) vs 114.4 +/- 117.2 (LAD) micro g/mg wet wt. and 7.4 +/- 3.9 (IMA) vs 11.2 +/- 3.9 (LAD) micro g/mg wet wt. (p less than 0.05) respectively. The lipid content of the IMA was significantly smaller than that of the LAD. 3) The low incidence of atherosclerosis of the IMA in contrast to frequent atherosclerosis of the LAD was proven histologically as well as biochemically in the present study. This is the first report to describe the histologic examination of atherosclerosis on the whole length of the IMA and the biochemical analysis for the lipid content of the IMA in Japanese population.     

Free internal mammary artery for coronary bypass.

An improved technique of free internal mammary artery (IMA) to ascending aorta anastomosis for coronary bypass is described. A small patch vein with a suitable side branch or branches is interposed, connecting the proximal end of a detached IMA to the ascending aorta. A single or double free IMA alone or in combination with an additional saphenous vein graft was performed in 77 patients. A total of 125 free IMA grafts were done. The hospital mortality was 2-7% and late mortality 1-4%. Seventy-one of the 74 surviving patients had no angina and returned to a normal life. Postoperative coronary arteriography in 65 patients showed a patency rate of 96%. On year's experience with this technique is very encouraging. However, prolonged follow-up is necessary to determine if free IMA, as used by us, will increase the long-term patency rate.     

胸腔镜辅助与前正中开胸非体外循环下冠状动脉旁路移植术乳内动脉桥猪模型的对比研究

目的建立一种能模拟胸腔镜辅助非体外循环下冠状动脉旁路移植术乳内动脉桥的家猪模型,与前正中开胸手术进行对比研究。方法 16头家猪,随机分为2组,VACAB组为胸腔镜辅助组,采用胸腔镜辅助的方法行非体外循环下左乳内动脉-前降支(LIMA-LAD)旁路移植术,MTCAB组为前正中开胸组,采用前正中开胸的方法行非体外循环下左乳内动脉-前降支旁路移植术。比较两组手术时间、左乳内动脉(LIMA)游离时间,LIMA-LAD吻合时间,和不同时间点的血液监测指标:肌酸磷酸激酶(CK)、磷酸肌酸激酶同工酶(CK-MB)、肌钙蛋白I(cTnI)。结果 VACAB组的手术时间、LIMA游离时间及LIMA-LAD吻合时间均较开胸组延长,且差异具有统计学意义。两组动物LIMA桥流量差异无统计学意义。两组之间CK、CK-MB、cTnI的差异无统计学意义。结论电视胸腔镜辅助非体外循环下冠状动脉旁路移植术是一种现实可行、效果良好的微创手术,采用动物模型进行VACAB训练有助于临床实践。     

Prevention of radial artery graft vasospasm after coronary bypass

Background. Pharmacologic prophylaxis for prevention of notorious radial artery (RA) spasm is critical because of the increasingly routine use of the RA conduit during coronary bypass. Therefore, we investigated the vasodilatory effect of calcium antagonist in combination with nitroglycerin (NTG) RA segments.

Methods. We evaluated the vasodilatory effect of nifedipine alone, verapamil alone, diltiazem alone, NTG alone, and calcium antagonist in combination with in endothelin-1 (ET-1)-, angiotensin II (AII)-, 5-hydroxytryptamine (5-HT)-, and norepinephrine (NE)-precontracted human RA rings mounted in organ baths.

Results. Nifedipine (10⁻⁵ M) alone, diltiazem (10⁻⁵ M) alone, verapamil (10⁻⁵ M) alone, and NTG (10⁻⁵ M) alone showed maximum vasodilatory effect in either 10⁻⁷ M ET-1-, 10⁻⁷ M AII-, 10⁻⁵ M NE-, or 10⁻⁴ M 5-HT-precontracted RA segments. The 10⁻⁵ M NTG alone-induced vasodilation (88.5% ± 7.7%) in ET-1-precontracted segments was the highest vasodilation (ANOVA, p = 0.0008) among NTG alone-induced vasodilatory effects in RA. The relaxing effect of any of the calcium antagonists alone varied from 32.7% ± 13.2% to 76.5% ± 20.5% in RA precontracted with different vasoconstrictors. Nearly 200% vasodilation was observed with calcium antagonist in combination with NTG in AII-precontracted vessels. Nonetheless, the vasodilatory effect of calcium antagonist in combination with NTG in RA segments precontracted with different vasoconstrictors other than AII was nearly 100%.

Conclusions. A calcium antagonist in combination with NTG is more potent than calcium antagonist alone or NTG alone in prevention of human RA vasospasm after coronary bypass.     

Right internal mammary artery and radial artery composite in situ pedicle graft in coronary artery bypass grafting

Background. The use of two internal mammary artery grafts in coronary artery bypass grafting has been associated with decreased risks of death, reoperation, and angioplasty. However, bilateral internal mammary artery takedown is associated with higher incidence of sternal wound infection, particularly in people with diabetes and in elderly and obese patients. This study was conducted to explore the feasibility of using right internal mammary artery (RIMA) and radial artery (RA) as a composite graft while preserving the distal two thirds of the RIMA to leave the sternal blood supply intact.

Methods. Eighteen patients underwent coronary artery bypass grafting using proximal RIMA and RA composite graft as one of the bypass conduits. The distal two thirds of the RIMA was left intact to preserve sternal blood supply. The graft-free flows of the RIMA and RA composite graft and of the left internal mammary artery graft and the length of the composite graft had been measured. The graft patency and the flow in the distal part of the unharvested RIMA was evaluated postoperatively 2 weeks after the procedure. In 6 of these patients the graft patency was evaluated by selective angiography.

Results. There was no hospital mortality or incidence of perioperative myocardial infarction. None of the patients needed intraaortic balloon pump support postoperatively. There was no sternal wound infection. The vessels grafted were distal right coronary artery (n = 7), posterior descending artery (n = 8), obtuse marginal branches (n = 3), and posterolateral ventricular branch (n = 1); 1 patient received the composite graft as a sequential graft to the posterior descending artery and posterolateral left ventricular branches. The mean graft-free flow of the RIMA and RA composite graft was 98.06 ± 16.93 mL/min compared to left internal mammary artery flows of 55.80 ± 8.99 mL/min. All 16 patients who had a good echo window showed patent grafts when evaluated by two-dimensional echocardiography and color Doppler echocardiography. All of the 6 patients in whom the angiogram was repeated postoperatively showed patent RIMA and RA grafts.

Conclusions. Myocardial revascularization using proximal RIMA and RA in situ pedicle graft was safe in patients with diabetes and in obese and chronic obstructive pulmonary disease patients. This graft was useful to revascularize posterior descending artery, posterolateral ventricular branches of right coronary artery, and obtuse marginal branches where a left internal mammary artery and RA composite graft cannot be used because of technical reasons. Its usage was not associated with sternal wound infection.