Internal Mammary Artery Bypass Graft Research Articles

Impact of failed mitral valve repair on hospital outcome of redo mitral valve procedures.

The prognostic impact of failed mitral valve repair (FMR) on in-hospital outcome after redo mitral valve surgery has not been thoroughly investigated. Hospital outcomes after redo mitral valve surgery because of an FMR in patients from nine European centres were reported. Logistic regressions identified predictors of mortality in combined or isolated redo mitral valve operations. Hospital outcome was compared between propensity-matched cohorts with FMR and native mitral valves in the context of redo surgery and FMR versus failed prostheses. A total of 246 patients with FMR yielded a 6.5% mortality rate at redo surgery. FMR per se did not impact mortality at multivariable analysis ( P = 0.64). A preoperative Global Initiative for Chronic Obstructive Lung Disease (GOLD) score ≥2 chronic obstructive lung disease (COPD) (OR 15.2, P < 0.01), left ventricular ejection fraction <30% (odds ratio (OR) 21.5, P = 0.005), major injury to cardiovascular structures at re-entry (OR 27.2, P < 0.01) or injury to patent left internal mammary artery-coronary artery bypass graft (OR 7.6, P = 0.03) predicted mortality in the whole FMR population. GOLD ≥ 2 COPD (OR 12.3, P = 0.049), age at surgery (OR 1.15 for each incremental year, P = 0.049) and cardiopulmonary bypass duration (OR 1.02, P = 0.022) predicted mortality in isolated redo mitral valve surgery for FMR. The fourth (> 68 years = 13.8% mortality) and the fifth quintiles of age (≥73.4 years = 14.8%) reported the highest mortality (OR 3.8 and 4.2 respectively, P = 0.002) in this subgroup. Propensity-matched cohorts of FMR and native mitral valves in the context of redo surgery showed no differences in terms of mortality ( P = 0.69) and major morbidity (acute myocardial infarction P = 0.31, stroke P = 0.65, acute kidney injury P = 1.0), whereas more perioperative dialysis ( P = 0.04) and transfusions ( P = 0.02) were noted in propensity-matched failed prostheses compared to FMR. A failed mitral repair does not impact hospital outcome of redo surgery. Given the role of severe left ventricular dysfunction and advanced age on hospital mortality rates, an early indication for redo surgery may improve outcome.

Extensive Dissection of the Left Internal Mammary Artery Graft and Emergency Bail Out

Background: Left internal mammary artery (LIMA) bypass graft to the left anterior descending artery (LAD) have better long-term survival when compared with the use of a venous conduit to the LAD. It is a very important lifeline for coronary artery bypass patients and dissection of the LIMA is often disastrous. This case illustrates an extensive dissection of the LIMA, involving the subclavian artery and aorta after bypass graft angiography. This was followed by an emergency bail out procedure. Case Report: A 60-year-old gentleman presented with unstable angina underwent a routine diagnostic angiogram. Shortly after automated contrast injection of the left internal mammary artery (LIMA) graft, a column of contrast was found trapped in the subclavian artery. A review of the LIMA angiography revealed a spiral dissection extending distally from the ostial to distal LIMA, and also proximally from LIMA to subclavian artery down the aortic arch. Patient immediately deteriorated with hypotension and experienced chest pain. Emergency stenting of the left subclavian artery was performed. However, LIMA remained occluded. Cardiothoracic surgeons were consulted but acute redo coronary artery bypass was considered to be extremely high risk. In an attempt to bail-out the acutely occluded LIMA, we proceed with percutaneous coronary intervention of the native left anterior descending (LAD) artery chronic total occlusion. Fortunately, this was successful and stents were implanted from left main artery to distal LAD..

Coronary-subclavian Steal Syndrome in a Patient with Takayasu Arteritis

A 37-year-old woman who had undergone coronary artery bypass grafting (CABG) surgery for left main and right coronary ostial lesions 2 years prior presented with angina and transient visual dimness. Computed tomography angiography showed a patent left internal mammary artery (LIMA) bypass graft and concentric narrowing with perivascular thickening around the arch vessels. The patient was diagnosed with Takayasu arteritis with coronary subclavian steal syndrome (CSSS). Thoracic angiography revealed severe stenosis of the left proximal subclavian artery (SCA) and reverse flow from the coronary artery to the distal left SCA via the LIMA graft. Successful percutaneous stenting of the left SCA was performed together with stenting of the right common carotid artery (CCA). The patient’s symptoms were completely resolved. This case is informative since it shows that Takayasu arteritis can manifest as angina due to coronary ostial lesions and then can involve arch vessels, which can lead to CSSS in patients with CABG. (Korean J Med 2016;91:37-41)

Invited Commentary

The authors of this study [1Rubens F.D. Chen L. Bourke M. Assessment of the association of bilateral internal thoracic artery skeletonization and sternal wound infection after coronary artery bypass grafting.Ann Thorac Surg. 2016; 101: 1677-1683Abstract Full Text Full Text PDF Scopus (25) Google Scholar] have again verified the safety of bilateral internal thoracic arterial (BITA) grafting in patients requiring coronary revascularization. Their sizeable experience involving a large cohort of patients comparing skeletonized pedicle harvesting with traditional pedicle harvesting techniques demonstrated equivalent rates of sternal infections and other related complications. Over time, arterial conduit use has become the standard of care, relegated to hallowed evidence-based acceptance in appropriately selected patients. However, despite the universal acceptance of single arterial grafting, ElBardissi and colleagues [2ElBardissi A.W. Aranki S.F. Sheng S. O’Brien S.M. Greenberg C.C. Gammie J.S. Trends in isolated coronary artery bypass grafting: an analysis of the Society of Thoracic Surgeons adult cardiac surgery database.J Thorac Cardiovasc Surg. 2012; 143: 273-281Abstract Full Text Full Text PDF PubMed Scopus (345) Google Scholar] revealed that only 4% to 12% of surgical revascularization procedures use BITA; clearly, evidence-based practice is rarely translated into routine clinical practice outside of reporting centers. Previous guidelines supporting arterial grafting with BITA conduits were often dependent on the severity of the native vessel disease; these studies often discouraged the use of BITA when the stenosis was not critical (<90%) [3Hillis L.D. Smith P.K. Anderson J.L. et al.American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines2011 ACCF/AHA guideline for coronary artery bypass graft surgery: executive summary: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines.J Thorac Cardiovasc Surg. 2012; 143: 4-34Abstract Full Text Full Text PDF PubMed Scopus (186) Google Scholar]. In regards to sternal complications, Dorman and coworkers [4Dorman M.J. Kurlansky P.A. Traad E.A. Galbut D.L. Zucker M. Ebra G. Bilateral internal mammary artery grafting enhances survival in diabetic patients a 30-year follow-up of propensity score–matched cohorts.Circulation. 2012; 126: 2935-2942Crossref PubMed Scopus (123) Google Scholar] addressed the effects of diabetes in a high-volume center with extensive BITA use. An even earlier large-scale, multicenter randomized arterial revascularization trial (ART) compared revascularization using BITA for the two most important left-sided target arteries with single internal thoracic artery (ITA) coupled with a combination of radial arteries or venous conduits for the remaining graft sites. This study demonstrated equivalent low 30-day (1%) and 1-year (2.5%) mortality rates, as well as similar rates of stroke and myocardial infarction, and the need for repeat revascularization for BITA grafting compared with the more traditional single ITA grafting strategy. Of note in this study was the increased incidence of sternal wound healing complications requiring reconstruction (1.9% versus 0.6%) in BITA patients compared with single ITA use, especially in diabetic patients. Although this randomized trial used a variety of ITA harvesting techniques, the results suggested that skeletonization of the ITA during harvesting may yield fewer sternal complications [5Taggart D.P. Altman D.G. Gray A.M. et al.ART InvestigatorsRandomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART).Eur Heart J. 2010; 31: 2470-2481Crossref PubMed Scopus (303) Google Scholar]. It is clear that skeletonization affords the surgeon increased arterial conduit length, creating the potential for multiple grafts of the left coronary circulation with a longer left ITA, as well as improving the distal reach of the right coronary arterial target sites with a skeletonized right ITA. Importantly, the known risk factors for suspected increased sternal complications from BITA use (increased body mass index, diabetes, peripheral vascular disease, female sex, and preoperative anemia) are more related to full sternotomy itself, instead of ITA harvesting, and were not significantly different in this report. Bilateral ITA utilization strategies for complex coronary revascularization has clearly demonstrated safety, diminished future interventions, improved graft longevity, and increased patient survival rates. The current report provides further evidence that harvesting techniques matter; hopefully studies like these will prevail over the continued reluctance to commit to more arterial grafting among the cardiac surgery community. The authors are to be congratulated for their excellent results, as well as advancing our understanding of this important topic. Assessment of the Association of Bilateral Internal Thoracic Artery Skeletonization and Sternal Wound Infection After Coronary Artery Bypass GraftingThe Annals of Thoracic SurgeryVol. 101Issue 5PreviewSkeletonization is a technique of bilateral internal thoracic artery (BITA) harvest that preserves sternal blood flow. We sought to identify the relationship of skeletonization and sternal wound infection in a population undergoing BITA harvest. Full-Text PDF

Stenting for left subclavian artery stenosis in patients scheduled for left internal mammary artery-coronary artery bypass grafting.

To evaluate the early and long-term outcomes of stent placement for left subclavian artery stenosis (LSAS) in patients scheduled for left internal mammary artery-coronary artery bypass grafting (LIMA-CABG). Few studies have demonstrated the safety and effectiveness of endovascular therapy for the treatment of LSAS before LIMA-CABG; therefore, use of this therapy requires further exploration and evaluation. Between February 2000 and April 2014, the clinical data of 167 consecutive patients (mean age 64 ± 9 years, 141 males) scheduled for LIMA-CABG with LSAS who were treated by stenting at the Fuwai Hospital were collected and analyzed retrospectively. The technical success rate of the procedure was 97.6% (163/167). The mean stenosis of target lesions decreased from 86.5 ± 9.9% to 7.6 ± 4.6% (P < 0.001). The incidences of death, stroke, and myocardial infarction, as well as the combined incidence of death, stroke, and myocardial infarction from the time of stenting to 30 days after the stenting procedure were 0.6% (n = 1), 1.8% (n = 3), 0% (n = 0), and 1.8% (n = 3), respectively. The 10-year rate of follow-up was 94.6%. The overall survival rate was 98.8% at 1 year, 97.5% at 2 years, 93.9% at 5 years, and 86.2% at 10 years. A total of 14.1% (23/163) of patients developed in-stent restenosis. Stent restenosis-related angina and myocardial infarction were observed in 13 and 3 patients, respectively. The patency rates of the left subclavian artery were 95.7, 93.8, 86.5, and 75.2% at 1, 2, 5, and 10 years, respectively. The target vessel reconstruction rate was 8.0% (13/163). Stenting of LSAS at experienced medical centers for patients scheduled for LIMA-CABG was safe and effective with a low incidence of complication and in-stent restenosis.

Hemodynamics of left internal mammary artery bypass graft: Effect of anastomotic geometry, coronary artery stenosis, and postoperative time

Although the left internal mammary artery (LIMA) bypass graft is the best choice for surgical revascularization, its hemodynamics are still complex and can result in long-term graft failure. Here, we performed a hemodynamic analysis of the LIMA-coronary artery with end-to-side/side-to-side anastomoses based on 15 patient-specific CTA images at various postoperative periods. We hypothesize that hemodynamic patterns are determined by the interplay of LIMA geometry, anastomotic configuration, and severity of native coronary artery stenosis, which are strongly affected by the postoperative time. A 3D finite volume method with the inlet pressure wave and outlet resistance boundary conditions was used to compute the distribution of pressure and flow, from which the time-averaged wall shear stress (TAWSS), oscillation shear index (OSI), time-averaged WSS gradient (TAWSSG), and transverse WSS (transWSS) were determined. To characterize the hemodynamic environment, we defined surface area ratios of low TAWSS (≤4dynes/cm2), high OSI (≥0.15), TAWSSG (≥500dynes/cm3), and transWSS (≥6dynes/cm2) in the LIMA graft and at the anastomosis between LIMA graft and coronary artery. These ratios were determined by the interplay of multiple morphometric parameters in the LIMA-coronary artery, but increased with postoperative time. These findings have significant implications for understanding LIMA graft patency.

50th Anniversary Landmark Commentary on Loop FD, Spampinato N, Cheanvechai C, Effler DB. The Free Internal Mammary Artery Bypass Graft: Use of the IMA in the Aorto-to-Coronary Artery Position. Ann Thorac Surg 1973;15:50–5

50th Anniversary Landmark Commentary on Loop FD, Spampinato N, Cheanvechai C, Effler DB. The Free Internal Mammary Artery Bypass Graft: Use of the IMA in the Aorto-to-Coronary Artery Position. Ann Thorac Surg 1973;15:50–5

In vitro effects of sodium nitroprusside and leptin on norepinephrine-induced vasoconstriction in human internal mammary artery.

SummaryAimThe biological and pharmacological properties of vessels used in coronary artery bypass graft (CABG) surgery are as important as their mechanical properties. The aim of this study was to investigate the possible role of protein kinase C (PKC)-dependent mechanisms in leptin-induced relaxation in the human internal mammary artery (IMA).MethodsIMA rings, obtained from patients undergoing CABG surgery, were suspended in isolated tissue baths containing Krebs-Henseleit solution, which were continuously gassed with 95% O2 and 5% CO2 at 37°C.ResultsThe IMA rings were pre-contracted with increasing concentrations of norepinephrine (NE 10-9–10-4 mol/l) and the relaxation responses to sodium nitroprusside (SNP), a nitrosovasodilator, and leptin were studied in the presence and absence of a PKC inhibitor. Leptin (1 μM) caused a dose-dependent relaxation in NE pre-contracted IMA rings. Pre-treatment with a PKC inhibitor significantly attenuated this vasorelaxatory response to leptin in human isolated IMA.ConclusionIt was found that SNP and leptin caused significant relaxation of the NE pre-contracted human IMA rings, and PKC was probably the sub-cellular mediator for this effect. Our findings may have clinical or pharmacological importance as it could be hypothesised that obese subjects who have a left IMA bypass graft would have better myocardial perfusion.

Minimally invasive epicardial left ventricular lead placement in a case of massive pleural adhesion

BackgroundIn cases of intravenous placement failure of the left ventricular (LV) lead for cardiac resynchronisation therapy (CRT) and obliteration of the left pleural space, the alternative approach of transthoracic placement by video-assisted thoracoscopic surgery (VATS) is difficult and not commonly practiced.MethodsHere, we present a simple technique for transthoracic introduction of an epicardial LV lead using a wound retractor (ALEXIS®) in a patient with heart failure. This wound retractor enables atraumatic tissue retraction without rib spreading, an optimal direct view in the pleural space for surgical pleurolysis and a high degree of safety for the patient.ResultsNo perioperative complications occurred. The tube drainage was removed on the second postoperative day, and the patient was discharged on the third postoperative day.ConclusionsThe decided advantage of this new method is the lack of any need for rib spreading using a mechanical retractor. Especially in patients with a history of open-heart surgery (including internal mammary artery bypass grafting and/or revascularisation of the left lateral wall) or known pleural adhesions (e.g., pleuritis or lung operations), the described technique provides a rapid and save access with minimal surgical effort and greater safety.

Bilateral versus single internal mammary coronary artery bypass grafting in Sweden from 1997-2008.

BackgroundPrior observational studies have suggested better outcomes in patients who receive bilateral internal mammary arteries (BIMA) during coronary artery bypass grafting (CABG) compared with patients who receive a single internal mammary artery (SIMA). The aim of this study was to analyze the association between BIMA use and long-term survival in patients who underwent primary isolated CABG.Methods and ResultsPatients who underwent primary isolated non-emergent CABG in Sweden between 1997 and 2008 were identified. The SWEDEHEART registry and other national Swedish registers were used to acquire information about patient characteristics and outcomes. Unadjusted and multivariable adjusted regression models were used to estimate the association between BIMA use and early mortality, long-term survival, and a composite of death from any cause or rehospitalization for myocardial infarction, heart failure, or stroke in the overall cohort and in a propensity score-matched cohort. The study population consisted of 49702 patients who underwent CABG with at least one internal mammary artery, and 559 (1%) of those had BIMA grafting. In the adjusted analyses, BIMA use was not associated with better survival compared with SIMA use in the overall cohort (hazard ratio (HR) for death: 1.16, 95% confidence interval (CI): 0.97 to 1.37) or in the matched cohort (HR: 1.04, 95% CI: 0.78 to 1.40). The results were similar for early mortality and the composite endpoint. Reoperation for sternal wound complications was more common among BIMA patients (odds ratio: 1.71, 95% CI: 1.01 to 2.88).ConclusionsBIMA grafting was performed infrequently and was not associated with better outcomes compared with SIMA grafting in patients undergoing non-emergent primary isolated CABG in Sweden during 1997–2008.

Spontaneous regression of proximal LAD subocclusive stenosis after left internal mammary artery bypass grafting

Spontaneous regression of proximal LAD subocclusive stenosis after left internal mammary artery bypass grafting

Bilateral internal mammary artery bypass grafting: long-term clinical benefits in a series of 1000 patients

ObjectiveBilateral internal mammary arteries (BIMA) remain widely underused in coronary artery bypass grafting (CABG). In this study, we aim to investigate the early and long-term outcomes of BIMA grafts in...

307: Bilateral internal mammary artery bypass grafting: long-term clinical benefits of a consecutive series of 1000 patients

Bilateral internal mammary arteries (BIMA) remain still widely underutilized in coronary artery bypass grafting (CABG). This historical cohort study evaluated the early and long term outcomes of BIMA grafts in isolated CABG in a single institution. Between 1996 and 2008, we performed elective, isolated, primary, multiple CABG using bilateral internal mammary artery (IMA) grafts and supplemental venous grafts for multivessel coronary disease in 1000 consecutive patients. The mean age of the overall population was 64±15 years. 20% of patients were diabetics with a left ventricular ejection fraction (LVEF) ≤45% in 28% of patients. Comorbidities were represented by chronic renal failure, chronic obstructive pulmonary disease and peripheral artery disease in 11%, 11,5% and 26,9% of cases respectively. Acute coronary syndrome represented the initial clinical presentation in 41% of cases. The 30-day mortality rate was 2.8%. Early postoperative morbidity included myocardial infarction (2,2%), stroke (0,9%), mesenteric ischemia (0,7%), sternitis requiring reintervention (6,7%) and supraventricular arrhythmia (23,1%). The follow-up (between 3 and 14,8 years; mean follow up: 6,4±5 years) revealed 103 deaths. Kaplan-Meier 8-year survival rates for patients <65 and 65 to 74 years of age were 88% and 66% respectively (p<0,01). Multiple regression analysis showed that age ≥ 65 years at baseline (odds ratio (OR): 2,3; 95% confidence interval (CI): 1,3 to 4, p<0,001), acute coronary syndrome (OR: 1,9; 95% CI: 1,1 to 3,4, p=0,02), chronic renal failure (OR: 2,7; 95% CI, 1,4 to 5,2, p<0,001), peripheral artery disease (OR: 3,1; 95% CI, 1,8 to 5,5, p<0,001) and LVEF ≤45% (OR: 2,6; 95% CI, 1,4 to 4,5, p<0,001) were independent predictors of long term cardiovascular mortality. Our longitudinal analysis demonstrates that bilateral IMA grafting has a low operative risk and provides excellent long-term survival.

Innominate vein to left internal mammary artery bypass graft fistula during laser lead extraction: salvage with covered coronary artery stent

A 62-year-old man with a history of ventricular tachycardia and coronary artery bypass graft surgery underwent implantable cardioverter-defibrillator lead extraction with an excimer laser sheath because of a lead failure and inappropriate shocks. The procedure was complicated with an iatrogenic arteriovenous fistula between …

Giant venous aneurysm jeopardising internal mammary arterial graft patency

The authors report a 79-year old man with a history of coronary bypass surgery, presenting with acute heart failure and elevated troponin. Coronarography revealed a giant saphenous vein graft aneurysm, which was compressing the left internal mammary artery bypass graft. This was confirmed by a multislice enhanced-ECG gated cardiac CT, showing the venous aneurysm responsible for external compression of the arterial graft and its functional occlusion. Myocardial ischaemia, the mechanism leading to cardiac failure, was confirmed by hypoperfusion of the sub-endocardial area shown by the CT. The aneurysm was surgically removed without complications. The patient recovered and his cardiac function improved. This is the first recorded case of compression of the left internal mammary artery by an giant saphenous vein graft aneurysm having triggered severe myocardial ischaemia and heart failure. The authors review the incidence and complications of giant venous bypass graft aneurysms reported in the literature.

Coronary artery bypass after Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology, which is the main cause of acquired heart disease in children in developed countries. The main complications result from the development of coronary aneurysms which can lead to ischemic heart disease.We present the case of a teenage boy with a diagnosis of KD at the age of seven. He was treated with gammaglobulin and aspirin and echocardiographic evaluation in the acute phase was apparently normal. At the age of 11, he developed chest pain and exertional dyspnea. Nuclear perfusion scans with exercise revealed hypoperfusion of the left anterior descending (LAD) and right coronary artery (RCA) territories. Cardiac catheterization showed occlusion of the proximal segments of both arteries. He underwent coronary artery bypass graft surgery (internal mammary artery bypass graft to the LAD and saphenous vein graft to the RCA), with a good clinical result.This case report highlights the importance of early diagnosis and treatment of KD and regular cardiological follow-up, bearing in mind the potential late complications of this pediatric disease.

Cirurgia de revascularização coronária após doença de Kawasaki

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology, which is the main cause of acquired heart disease in children in developed countries. The main complications result from the development of coronary aneurysms which can lead to ischemic heart disease.We present the case of a teenage boy with a diagnosis of KD at the age of seven. He was treated with gammaglobulin and aspirin and echocardiographic evaluation in the acute phase was apparently normal. At the age of eleven, he developed chest pain and exertional dyspnea. Nuclear perfusion scans with exercise revealed hypoperfusion of the left anterior descending (LAD) and right coronary (RC) artery territories. Cardiac catheterization showed occlusion of the proximal segments of both arteries. He underwent coronary artery bypass graft surgery (internal mammary artery bypass graft to the LAD artery and saphenous vein graft to the RC artery), with a good clinical result.This case report highlights the importance of early diagnosis and treatment of KD and regular cardiological follow-up, bearing in mind the potential late complications of this pediatric disease.

Single coronary artery giving rise to an intraseptal left coronary artery in a patient presenting with neurocardiogenic syncope

Syncope occurs frequently in adolescents, and is often benign. Potential worrisome syncopal events include those occurring with exertion, concurrent chest pain, dyspnoea or palpitations, and those with focal or diffuse neurologic changes. A 16-year-old female was referred to our institution for a history of exercise-induced spells. She was diagnosed since the age of 2 years with neurocardiogenic syncope and postural orthostatic tachycardia syndrome. She had been evaluated at multiple institutions, and was followed by pediatric neurology for a diagnosis of migraines. Owing to recurrent worsening symptoms and a syncopal episode requiring resuscitation, an echocardiogram was performed. The right coronary was normal, but the left coronary artery ostium could not be identified well. Doppler patterns were suspicious of an abnormal left coronary artery, and computed tomography angiography was performed. This revealed a single coronary artery arising from the right aortic sinus, with the left coronary artery arising from the proximal coronary trunk and coursing through the infundibular septum. This was surgically treated utilising a left internal mammary artery bypass graft to the left anterior descending coronary artery. A year later, she has not experienced any recurrence of syncope, and has returned to athletic activity. This case highlights the index of suspicion that must be present when evaluating any patient with syncope, both clinically and via echocardiography. A computed tomography angiogram is indicated for better evaluation of coronary artery anatomy when an anomalous coronary cannot be ruled out by echocardiography.

Hybrid Coronary Revascularization

The long-term benefits of a left internal mammary artery bypass graft compared to the left anterior descending artery have been well described. The use of drug-eluting stents has minimized the morbidity of revascularization. Hybrid coronary revascularization is the planned use of minimally invasive surgical techniques for left internal mammary artery-left anterior descending artery grafting and the use of percutaneous coronary intervention for nonleft anterior descending coronary artery target revascularization. The optimal timing and order of revascularization in hybrid coronary revascularization remains unclear.

Randomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART)

Randomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART)