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Reviews

Operative Treatment of Coronary Atherosclerosis

Division of Cardiothoracic Surgery, St. Louis University, St. Louis, Missouri

^_* Address correspondence to Dr Barner, St. Louis University Hospital, 3635 Vista, St. Louis, MO 63108 (Email: hbarner{at}slu.edu).

	Abstract

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
The evolution of percutaneous intervention has reduced the prevalence of coronary bypass surgery in a patient population that is older, with more comorbidity and advanced coronary disease. Despite this less favorable group, perioperative mortality has continued to decline as the operation improves. The latter includes off-pump coronary grafting, smaller incisions, better intraoperative myocardial preservation, improving management of cardiopulmonary bypass, perioperative glucose control, and increasing use of arterial conduits as the radial artery comes of age and the gastroepiploic artery is reborn as a free graft. This brief review of the basics of coronary artery bypass is part experience with an effort to be fair-minded and balanced and to include that which is new and promising. It is imperative that we continue to innovate and distil the best from the old so that we can provide the optimal intervention for coronary artery disease.

	Introduction

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Historically the first coronary artery bypass (CAB) conduit was the internal thoracic artery (ITA), and it was placed without cardiopulmonary bypass; the former did not become widely accepted and used until the 1980s, and the latter approach (off-pump) was widely accepted and used a decade later. The purpose herein is to provide a brief review of technical decision-making involved in the treatment of obstructive artery coronary disease by surgical operation.

	Methods

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Forty years of experience documented in the literature form the basis of this report. Appropriate references are cited.

	Indications for Operation

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Coronary bypass grafting is appropriate for several indications, such as three-vessel disease; left main disease with associated distal vessel disease, and isolated left main disease when the distal segment or bifurcation is involved; coronary ostial stenosis; when a pathology is not suitable for percutaneous intervention (ie, total occlusion, circumferential calcification, bifurcation involvement and diffuse or distal lesions); and obstructive coronary artery disease associated with other cardiac conditions requiring operation. In general, the presence of more extensive disease, severe symptoms, and ventricular impairment favor operation. Data supporting operation for obstructive artery coronary disease in diabetics are compelling (American College of Cardiology/American Heart Association 2002 Guide Lines, updated 2004), because the disease process is frequently diffuse, distal, progressive, and associated with sudden death [1].

Atherosclerotic extent (ie, coronary plaque burden) now has a quantitating technique (ie, volumetric intravascular ultrasound), and the predictors of male gender, diabetes mellitus, a history revascularization, and elevated low-density lipoprotein cholesterol.

Although this metric has not been used to define diffuse and distal obstructive artery coronary disease, such a relationship may well exist and prove to be an additional guideline for CAB. Stenting often treats a spot, whereas bypass grafting into the distal third of the coronary treats much of the vessel.

	Choice of Conduit

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Saphenous Veins
The saphenous vein (SV) remains the most widely used conduit because it is usually available, easily harvested, technically favorable, and has acceptable patency for 2.0 mm or larger coronaries. Survival data demonstrate differences between arterial and venous conduits at 6 to 8 years postoperatively, but patency data favors arterial grafts (particularly the left ITA) at any age. Ages greater than 70 to 75 years, moderate to severe left ventricular dysfunction (ie, ejection fractions of less than 25% to 30%), severe pulmonary disease, renal dialysis, severe peripheral vascular disease, malignancy, and associated cardiac disease requiring complex or multiple procedures are rightly associated with greater, but not exclusive, use of venous conduits.

Other Veins
The lesser SV provides comparable results to the greater SV, whereas the arm vein has been abandoned because of poor patency. The lesser SV can be harvested with the patient prone and can also be obtained in the supine position with the hip and knee flexed and the leg rotated, but it requires an assistant to hold the leg.

Arteries
Internal thoracic artery
The left ITA should be used in most patients because of early survival benefit alone. The exceptions are an emergency operation, high-dose chest well radiation, or extremely limited survival potential. Right ITA grafting, which in most instances includes the left, presents the drawbacks of increased harvest time and some increase in mediastinal infection which may be reduced by skeletonizing and clearly by tight glucose control which is a noteworthy evolution [2, 3] . The use of bilateral ITA grafts was 12% in North America in the intake study for the Synergy between percutaneous intervention with Taxus drug-eluting stent and cardiac surgery study of CAB and percutaneous intervention, but was 41% in France [4]. Failure to widely adapt bilateral ITA grafting is in part related to lack of randomized comparison of one and two ITA grafts, which is now being addressed by the Oxford study.

Radial artery
Experience with the radial artery (RA) varies considerably from center to center and surgeon to surgeon without a consensus. There are limited 10-year observational data, but several randomized studies are in progress. Some people believe, including myself, that the RA is second to the ITA and should be used more frequently [5]. The RA is available in 90% of patients, it can be harvested concurrently with other conduits, it will reach any target, and it has an acceptable complication incidence of approximately 10% involving the superficial radial nerve and rarely the median nerve. The major limitations of the RA are thrombosis due to competitive coronary flow if coronary stenosis is less than 80% (perhaps 70% for 1.5 mm coronaries) and harvest induced spasm, which requires perioperative but not subsequent treatment with vasodilators.

Gastroepiploic artery
The right gastroepiploic artery (GEA) is particularly useful as an in situ graft combined with two ITA grafts for off-pump procedures to avoid aortic clamping. It may also be based on the aorta or another arterial conduit. The GEA has greater variability in size than the ITA or RA. It is vulnerable to competitive flow like the RA, and it is more likely to be compromised by proximal atherosclerosis (celiac axis) than the ITA.

Other arteries
Experience with the left gastric, splenic, intercostals, subscapular, thoracodorsal and inferior mesenteric arteries is anecdotal, whereas that with the descending branch of the lateral femoral circumflex is more substantial, but needs confirmation [6]. The ulnar artery is difficult to harvest and shorter than the RA, and it is believed that there is only one report of its use. Although the inferior epigastric artery (IEA) has been reported to have a moderate and favorable experience by a few surgeons, it is limited by significant variability in its relationship to the rectus muscle and usually short length, which limits its predictable use to that of a short Y-graft from another arterial conduit.

	Clinical Pharmacology of Conduits

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Veins
The standard practice of the harvested vein is hydrostatic dilation with saline or balanced salt solution to resolve spasms and identify leaks. Distending pressure of less than 100 mm Hg reduces endothelial and medial injury associated with higher pressures, and salt solution is more protective of the endothelium. Nitrates, calcium channel blockers or phosphodiesterase inhibitors may be added to the storage or irrigating medium, but vein graft spasm after hydrostatic dilation is unusual and pharmacologic vasodilation is unnecessary.

Arteries
Harvest-related spasm is more intense in arteries than veins related to a relatively thicker media and possibly greater sensitivity to spasmogenic stimuli. Hydrostatic dilation is avoided because it requires greater pressure than required for veins that may dissect the ITA, as may the cannula, and will damage the endothelium and the media. Although ITA harvest spasm usually resolves with time, this is not assured so that a pharmacologic approach is safer and necessary for the other arterial conduits that have a more muscular media.

For the ITA, papaverine, nitroglycerin, and nitroprusside are topically effective and moreso when applied intraluminally, but this must be done carefully with the ITA to avoid dissection (Table 1). Papaverine concentration of 1 to 2 mg/mL is appropriate for extraluminal use, whereas 0.5 mg/mL for intraluminal use is optimal to avoid direct endothelial injury. Papaverine in saline has a low pH (approximately 4.0 to 4.5 pH), whereas in blood it is 7.2 pH and will not be injurious to the endothelium. Low, free flow from a spastic ITA can not be distinguished from an intimal flap causing low flow. Therefore, lysis of spasm with resultant good free flow (50 mL/min or greater) is necessary to prove an injury-free conduit. In small patients with small arteries (less than 1.5 mm), a free flow of 25 mL/min is adequate.

	Technical Decisions

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Harvesting
Vein
Interrupted incisions with sharp and blunt dissection are expeditious and result in fewer wound problems than a single incision; low current electrocautery is used for hemostasis, and branches are divided between clips with care to avoid vein wall injury. Ultrasonic dissection will not adequately control most branches and it is slow. Endoscopic harvesting is increasingly used and associated with significant reduction in wound complications and comparable graft patency in several reports. However, the PREVENT IV study reveals reduced graft patency with endoscopic harvest and indicates a need for reassessment of this technique in regard to excessive vein trauma [8]. A novel approach is harvesting the vein with a pedicle of subcutaneous fat surrounding it, leaving the vein in situ until cardiopulmonary bypass has been initiated, and by avoiding hydrostatic or pharmacologic vein dilation. A follow-up report shows patency at 8.5 years equal to that of ITA grafts [9].

Internal thoracic artery
Under direct vision, the endothoracic fascia can be divided with scissors, but low current cautery is more hemostatic particularly for the remainder of the dissection and is faster for branch division than clipping or ultrasonic division. If desired, pedicled branches can be clipped later during "downtime" (ie, cardioplegia infusion).

Skeletonizing may preserve sternal blood flow to a greater degree than pedicle harvest and may reduce sternal complications in bilateral ITA harvesting, providing a longer conduit. The potential for ITA injury is slightly greater, but endothelial and medial injuries were not reported until functional endothelial impairment with ultrasonic harvest was observed [10]. Ultrasonic harvest does not improve sternal flow [11].

Radial artery
A number of approaches have been described to assess collateral circulation to the hand. My method is the continued use of Allen’s test with fist clenching for 20 to 30 seconds and visual determination of capillary refilling of the palm and digits, particularly the thumb, with a cutoff of 12 seconds. Incision length equals the desired artery length. Branch control and dissection have evolved from clips to ultrasound to coagulating forceps; the latter is most expeditious and secures the branches well. Although some harvest the RA endoscopically, my belief is that this requires skill and experience that surgical assistants may lack, and recent negative experience with endoscopic vein harvest suggests that we must proceed cautiously with endoscopic RA procurement [8].

Gastroepiploic artery
The sternotomy incision is extended 4 cm to 8 cm beyond the xiphoid tip and the peritoneal cavity entered. The stomach is pulled up to expose the greater curvature and skeletonizing dissection is initiated with low current cautery or ultrasound, and branches are controlled with clips or ties. The gastric branches are short and may be difficult to control if they bleed. Mobilization extends from the pylorus to the short gastric branches. Routing can be anterior or posterior to the stomach and left lobe of the liver crossing the diaphragm anterior to the inferior vena cava to approach the target in a parallel manner. If the target is farther to the left, the diaphragm crossing can be moved to the left.

Anastomosis
Vein
The vein is marked with indelible ink and the length is measured with the vein distended. The vein is divided transversely and not spatulated unless it is less than 3.0 mm. Running 7-0 polypropylene for distal anastomosis and 6-0 for proximal anastomosis is appropriate. For proximal anastomosis, it is divided transversely and spatulated for a 4 mm or 5 mm punch, both depending on vein size and aortic wall thickness.

Artery
Anastomotic length should be at least 1.5 times the diameter of the coronary to avoid stenosis; the conduit is spatulated 2.0 mm to 3.0 mm with suture bites not too widely spaced, using 7-0 polypropylene with an 8-0 needle. Interrupted fine silk has been used by some, but it is tedious. Interrupted nitinol suture clips may be a little faster, but these are costly. Artery-to-artery anastomosis or artery-to-aorta anastomosis with the same suture may require a larger needle for the aorta and a 3.0-mm to 4.0-mm punch. If the aortic wall is diseased or thick, it is best to use a vein hood, a vein or a pericardial patch, or an in situ arterial conduit for inflow.

Conduit Pattern
Vein
Classic use is a single conduit for each target, but it is well established that sequential grafting improves patency, particularly if the distal anastomosis is to a larger coronary and if side-to-side anastomoses are to smaller vessels. The number of anastomoses is debatable, but if the coronaries are 1.5 mm or smaller, then it is appropriate to include them as side-to-side anastomoses. If they are larger (2.0 mm or greater) it can be argued that they should have separate grafts if they are in different coronary systems, but one graft if they are in the same system. Use of one graft for each coronary system is appropriate; occasionally one graft may supply two systems if the target is small in one system. A single "snake" graft for the entire heart is appropriate if there is no other conduit. A venous Y-graft is useful if there is not enough vein to reach the aorta or alternatively with a Y anastomosis to an arterial conduit.

Artery
Sequential grafting is patency neutral, but it is useful to conserve the conduit, and it is technically more difficult and avoided by some for this reason [12]. Three in situ conduits can achieve all arterial revascularization in some patients and avoid aortic anastomosis, which may be problematic when the aortic wall is thicker or diseased, the conduit is smaller, or the operation is performed off pump. A T-grafting or Y-grafting will achieve the same goal and the former with only two conduits in selected patients by placing the T anastomosis just anterior to the left atrial appendage, which optimally uses both conduits but frequently requires sequential anastomoses with the free graft [13, 14]. One-third of the left ITAs are sequential to the diagonal and left anterior descending arteries [13].

End-to-end anastomosis with the RA, GEA, or IEA on the ITA will extend the length of an in situ or aorta-based conduit to additional targets. Other conduit configurations include horse-shoe, epsilon, and Y on Y anastomosis, all of which have their proponents, but experience and patency data are limited.

Optimal use of the right ITA is to the left side of the heart as a Y-graft from the left ITA [[14, 15] , or using it as an in situ graft to the LAD, or the obtuse marginal artery via the transverse sinus. When it is occasionally placed to the right coronary system, it should usually target the posterior descending artery that often requires a free graft from the aorta with a 10% to 15% patency loss, or the left ITA, as the in situ right ITA does not have adequate length to avoid graft tension. The RA can be based on the aorta or on the in situ ITA and will reach any target as a single graft. If there is more than one side-to-side anastomosis, it may be necessary to use one or two crossing (diamond) anastomoses to have adequate length. Artery grafts should be tacked to the epicardium to relieve anastomotic tension, prevent angulation at the anastomosis, and maintain a smooth source between serial anastomoses.

Endarterectomy
Endarterectomy is considered when there is total proximal occlusion of the coronary and the distal third is smaller than 1.5 mm or not of acceptable quality for grafting. Because some endarterectomized vessels will thrombose in the perioperative interval, there should be reluctance to proceed, but occasionally it is necessary when the coronary artery is not occluded. Multiple segmental coronary lesions with intervening graftable segments may be treated with multiple sequential bypasses to the same vessel. With reasonable ventricular function and ungraftable vessels, endarterectomy is an appropriate alternative to transplantation.

The right coronary is usually opened just proximal to the posterior descending artery, a plane developed with a fine spatula around the core, and the core is transected at the heel of the arteriotomy. Using a coronary spatula, the core is mobilized into each of the branches as far distally as possible with firm traction on the core. The core in the posterolateral branch may be short and may separate easily to allow extraction; if not it should be divided at its origin, and the two branches should be separately treated. If the core should fracture, a second incision is made at the fracture site to dissect and remove the distal core material with feathering, indicating a clean endarterectomy. Reconstruction is done by grafting to the right coronary artery or to a distal incision, or both, with primary or vein patch closure of ungrafted arteriotomies. The left anterior descending coronary artery is approached by a single long incision (ie, 4 to 8 cm) with careful removal of the core material, which is transected at the heel of the arteriotomy, extending into diagonal and perforating branches. Reconstruction can made be with a long tongue of vein or ITA extending from the proximally anastomosed conduit or an isolated vein patch into which it is placed an arterial graft.

The circumflex artery is not usually accessible for endarterectomy, but a ramus or marginal branch which is comprised of 10% of arteries having endarterectomy [16]. A short incision (closed endarterectomy) is made in the proximal or middle third, and the core is distally extracted like the right coronary artery.

Endarterectomy is usually reserved for situations when there are no other grafting options. Circumferentially calcified vessels are not amenable to this technique because the calcium frequently extends to the adventitia and a satisfactory dissection plain can not be established. Operative mortality is greater than for coronary bypass alone, but not significantly so in the last decade. There is a greater but acceptable incidence of perioperative myocardial infarction and ventricular arrhythmia related to perioperative thrombosis of the main vessel or a branch.

Intraoperative Verification
Many verify patency by palpation of a graft pulse, which is of little value until heparin is reversed. The gold standard, angiography, is rarely available intraoperatively. Conduit flow was measured early on with the electromagnetic flow meter. A vein graft flow of less than 20 mL/min was associated with an angiographically verified early closure of 42% rising to 63% at 1 year [17]. This technique has been replaced with transit-time flowmetry (TTFM), which uses mean flow of 10 mL/min or less, diastolic flow index (the percentage of total flow occurring in diastole) of less than 50% of mean graft flow, and a pulsatility index of greater than 4 as predictors of need for graft revision [18].

A newer technique using intraoperative fluorescence imaging (IFI) has more precisely indicated the need for graft revision in one randomized comparison with TTFM [19] Both systems detect occluded grafts well, but greater than 50% stenosis was poorly detected by TTFM, whereas specificity and sensitivity for intraoperative fluorescence imaging was 83.3%. The TTFM quantitates graft flow, but intraoperative fluorescence imaging does not. Graft revision was attempted in 5 of 154 cases, and others were not revised because of poor distal targets [19]. Intraoperative fluorescence imaging has not been part of my practice, but knowledge of graft flow is useful.

Complete or Partial Revascularization
Incomplete revascularization carries the implication of an inadequate or lackadaisical performance by the surgeon. It is axiomatic that arteries with 50% or greater stenosis and 1.5 mm or more in diameter should always by bypassed; occasionally a 40% lesion is deliberately bypassed as may be the case with a 1.0-mm or 1.25-mm vessel when there are no larger targets in a territory. On the other hand, one graft per system was found to be adequate and more than one to the left anterior descending system had negative value [20]. If the operation is complicated by other cardiac procedures, it may be appropriate not to bypass smaller vessels, those with 50% to 60% stenosis, poor quality targets, those requiring endarterectomy, or those amenable to percutaneous intervention to avoid prolonged clamp time.

On-Pump or Off-Pump CAB
Enthusiasm for off-pump CAB has abated somewhat, as a few small randomized clinical trials and large retrospective analyses have not been found to have definite survival benefits or reduction in perioperative stroke. Beneficial trends with off-pump include reduced blood loss and need for transfusion, decline in myocardial enzyme release up to 24 hours after operation, less early neurocognitive dysfunction with no difference at 6 weeks, and reduced renal insufficiency [21]. Fewer grafts are placed in off-pump patients and graft patency may be reduced at 3 months to 1 year [22].

Thus, off-pump CAB has probable benefits for patients with impaired renal function. It is clearly indicated for the calcified or atherosclerotic aorta, but it should be coupled with the use of in situ arterial conduits or use of one or more free arterial conduits attached to in situ grafts. It can be argued that the failure for off-pump CAB to decrease the incidence of perioperative stroke is continued use of partial aortic clamping for proximal anastomosis by most surgeons, which is clearly traumatic to the aortic wall and may result in cerebral embolization as well as acute aortic dissection. Thus, not clamping the aorta is feasible in most patients and should be the goal in all off-pump procedures to reduce stroke and death.

Off-pump CAB is technically more demanding, as reflected in enthusiasm for its use or lack thereof across a broad spectrum of surgeons. Talented surgeons find off-pump CAB beneficial for a majority of their patients, whereas others find it useful for one-vessel or two-vessel disease with easily accessible, noncalcified, nonsubmuscular targets of moderate size.

Minimal Access
Minimal access accomplishes just that and is appropriate for bypassing a particular vessel, usually the left anterior descending coronary artery through a left anterior small thoracotomy, or the right coronary artery through a right-sided incision with or without division or excision of costal cartilage. Harvesting of the ITA for minimally invasive direct coronary surgery can be accomplished with direct vision, which is usually compromised by limited exposure permitting short segment mobilization that may result in conduit injury during a late reoperation. Alternatively more complete ITA mobilization is achieved endoscopically with or without robotic assistance.

Port Access
Failure to achieve enrollment in the National Institutes of Health’s sponsored trial of port access, computer-assisted, robotic CAB discouraged all but a few from use of this innovative approach. Its use has been primarily for left anterior descending bypass, occasionally the ramus intermedius or first obtuse marginal artery, and using the left ITA with or without cardiopulmonary bypass. However, experience to date does not support use of robotic assistance [23].

	Conduit Failure Rates

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Long-term SV patency has improved somewhat for more than 3¹/₂ decades, although the patency in Melbourne, Australia has been significantly better at 5 and 10 years but not at 15 years (Table 3) [24]. However, recent 1-year patency of 74% in the randomized PREVENT IV trial at 104 United States sites gives a realistic indication of current vein graft (VG) patency, which is not different from historical experience [25]. Right and left ITA patency, although clearly superior to VG, has been even better in some centers [8, 24].

Coronary stenosis of less than 60% has a small effect on ITA patency, except in the right system where the effect is greater. Less than 80% stenosis results in a loss of patency for both RA and GEA.

Sequential anastomosis improves patency of side-to-side VG anastomosis and is not associated with loss of patency for ITA conduit [12]. Patency is similar for the right and left ITA and RA directed to the left anterior descending coronary artery or proximal circumflex system, whether in situ or as a Y-graft from the left ITA. Proximal anastomosis to the aorta is patency neutral for the RA, but there is a 10% to 15% patency loss for the right ITA [12].

Patency for the GEA at 10 years was disappointing at 65.5%, but this improved to 87% with skeletonization and selection of targets with at least 90% stenosis [26]. Use of the GEA as a free graft has resulted in 77-month patency equivalent to the ITA to any target [27]. The IEA has good patency off the aorta or as a Y-graft. Enduring patency is the goal of CAB and percutaneous intervention and determines outcome. Arterial conduits are superior in this regard. Bilateral ITA harvest in diabetics has been associated with an increased incidence of mediastinal infection, which may no longer be an issue with glucose control [2]. All arterial grafting is feasible in as many as 90% of patients in some practices [24].

	Reoperation

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Indications
Indications for reoperation are recurrent angina and ischemia after CAB due to VG failure (ie, early thrombosis, early and midterm intimal hyperplasia, and late atherosclerosis) and progression of coronary disease, both of which are more prevalent in those with an earlier age at initial operation (ie, more aggressive disease process); diabetes; poorly treated or persistent hyperlipidemia; failure to control other risk factors, such as hypertension or tobacco use, and taking platelet inhibitors.

Exposure
Reoperation for single-vessel disease can be accomplished through a small anterior thoracotomy for anterior vessels or a lateral thoracotomy for lateral and posterior vessels. Sternotomy is accomplished with groin availability, leaving the sternal wires intact posteriorly, using an oscillating saw with a fan-shaped blade for two-thirds of the sternal thickness and a straight, narrow blade for the inner third (tactile feedback from the blade indicates that the posterior table has been crossed) and with the sternum elevated off the heart with bone hooks or a table-mounted retractor.

Choice of Conduits
Because most reoperations are associated with VG disease, a distinct effort should be made to use multiple arterial conduits that were used in 157 of 1,362 patients (with my own personal experience of more than 11 years) having RA grafting, whereas 27 additional reoperations in that interval did not use arterial conduits. Conduits are selected as previously discussed. The previously used left ITA was recycled in 32 of 157 instances, usually as inflow for the RA and rarely by distal reanastomosis.

Special Problem
The greatest concern is preserving in situ ITA grafts. The most difficult situation is the anterior crossing the right ITA where experience is small but can be successful. Common is the left ITA, which was not positioned in the left pleural space parallel to the phrenic nerve (where all left ITAs should be placed by extending the pericardial incisional laterally across the pulmonic valve to near the phrenic nerve and dividing the overlying mediastinal fat or by making a pericardial window just anterior to the phrenic nerve). The extrapleural ITA courses in the superior mediastinum where it is displaced by the lung and mediastinal fat and lies adjacent to the aorta to which it may be adherent and where it is difficult to identify. Positioning of the ITA is frequently not stated in the operative record, but the anteroposterior view of the angiogram reveals a straight course with intrapleural placement or medial displacement when there is mediastinal location for the ITA. It is relatively easy and safe to find the distal left ITA anastomosis by dissecting it from the apex of the heart proximally along the left anterior descending coronary artery or other target vessel.

Patent but diseased vein grafts should not be handled and are usually divided or ligated, except when being replaced by an arterial graft after the first infusion of antegrade cardioplegia before the grafts are manipulated. Retrograde cardioplegia is routine.

We have been cautioned to not divide patent but diseased vein grafts that are replaced with an arterial conduit because of potentially inadequate flow. One option is to discontinue bypass and when hemodynamically stable, and before giving protamine, temporarily occlude the old VG and observe hemodynamics, the electrocardiogram, left ventricular function by transesophageal echocardiography, and arterial conduit flow by TTFM. If these measurements are stable and graft flow increases it is safe to ligate the old VG.

	Conclusions

Top Abstract Introduction Methods Indications for Operation Choice of Conduit Clinical Pharmacology of... Technical Decisions Conduit Failure Rates Reoperation Conclusions References

 
Longevity of Arterial Grafts
We learned 2 decades ago that if the ITA survives harvest trauma and procedural errors (patent at 1 year) it will likely remain patent at 20 years without evidence of atherosclerosis [28,29]. Although the other arterial grafts do not have equivalent longitudinal and numerical follow-up, the 10-year data do not reveal graft atherosclerosis.

Minimal Incision Surgery
A small anterior thoracotomy is useful for the left anterior descending coronary artery territory and occasionally a proximal circumflex branch, but left ITA mobilization is suboptimal unless it is accomplished endoscopically. Percutaneous coronary intervention frequently precludes the need for isolated left anterior descending coronary bypass, but in combination with percutaneous intervention for other targets it is an appropriate hybrid intervention.

Reduced Morbidity of CPB and Advantages of CPB for Some Patients
Use of heparin-bonded circuits and elimination of cardiotomy suction has not improved clinical outcomes [30]. Despite improving the understanding of the systemic inflammatory response syndrome and evaluation of many specific therapies, clinical benefit has not been forthcoming; however, studies of a combination of anti-inflammatory interventions are needed. Modified ultrafiltration reduced morbidity in one randomized study [31]. Leukocyte depletion may limit pulmonary reperfusion injury in higher risk patients [32], and bypass circuits made with a surface modifying additive can reduce coagulation, fibrinolysis, platelet depletion, and impaired function [33], but well-conducted, randomized studies of sufficient scientific merit to meet the demands of evidence-based medical practice are needed [34].

On-pump CAB is technically less demanding and provides better accessibility to difficult targets and probably better graft patency.

	References

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10. Matsumoto K, Tsuneyoshi I, Iguro Y, Kinjo T, et al. Effects of ultrasonic skeletonization on internal thoracic and gastroepiploic arteries for coronary artery bypass grafting Eur J Thorac Surg 2006;30:592-596.
11. Pektok E, Cikirikcioglu M, Engin C, et al. Harvesting of an internal thoracic artery with an ultrasonic skeletonization have an effect on sternal profusion? J Thorac Cardiovasc Surg 2007;134:442-447.[Abstract/Free Full Text]
12. Dion R, Glineur D, Derouck D, et al. Long-term clinical and angiographic follow-up of sequential internal thoracic artery grafting Eur J Cardio-thoracic Surg 2000;17:407-417.[Abstract/Free Full Text]
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