Coronary artery bypass graft surgery: Graft choices

INTRODUCTION — Coronary artery bypass graft surgery (CABG), compared with medical therapy or percutaneous coronary intervention (PCI), is recommended for patients with coronary artery disease when survival will be improved. In addition, patients with angina refractory to medical therapy may receive a recommendation for CABG if PCI cannot be performed. (See "Revascularization in patients with stable coronary artery disease: Coronary artery bypass graft surgery versus percutaneous coronary intervention", section on 'Our approach' and "Left main coronary artery disease", section on 'Significant left main disease'.)

CABG involves the placement of one or more grafts between the aorta and coronary artery circulation. Arterial and venous grafts are used as bypass grafts and most patients receive some combination of the two. However, long-term graft patency is significantly better with the former. Potential consequences of graft failure (loss of patency) include the development of angina, myocardial infarction, or cardiac death.

This topic will discuss the choice of arterial and venous grafts. The following issues are discussed elsewhere:

●Operative mortality. (See "Operative mortality after coronary artery bypass graft surgery".)

●Early noncardiac complications. (See "Early noncardiac complications of coronary artery bypass graft surgery".)

●Early cardiac complications. (See "Early cardiac complications of coronary artery bypass graft surgery".)

●Medical therapy to prevent complications. (See "Coronary artery bypass surgery: Perioperative medical management".)

●Vein graft stenosis.

●Late recurrent angina. (See "Late recurrent angina pectoris after coronary artery bypass graft surgery".)

●Graft patency is an important determinant of long-term survival. (See "Coronary artery bypass graft surgery: Long-term clinical outcomes", section on 'Possible predictors of mortality'.)

●Prevention, presentation, and management of saphenous vein graft stenosis. (See "Coronary artery bypass graft surgery: Prevention and management of vein graft stenosis".)

VEIN GRAFTS — The saphenous vein is the most common venous graft used for bypassing the coronary circulation. However, relative to arterial grafts, failure rates are high, perhaps 10 to 25 percent in the first 12 to 18 months (movie 1) [1]. Failure is often in the form of vein graft stenosis. The clinical consequences of saphenous vein graft (SVG) stenosis are presented elsewhere. (See "Coronary artery bypass graft surgery: Prevention and management of vein graft stenosis", section on 'Clinical presentation' and "Coronary artery bypass graft surgery: Long-term clinical outcomes", section on 'Possible predictors of mortality'.)

SVG patency is dependent on the distal runoff of the coronary artery bypassed; distal runoff is largely determined by the size of the native coronary artery. The left anterior descending coronary artery is the largest coronary artery and therefore patency rates are much better even when a vein is used.

Early occlusion — SVG occlusion occurs within 30 days of coronary artery bypass graft surgery (CABG) in approximately 10 percent of grafts. This complication is usually due to technical failure (such as kinks from excessive length of the graft), conduit characteristics (such as a diameter <1.5 mm or prior vein pathology), or poor distal runoff [2]. Each of these may contribute to stasis within the graft, leading to thrombosis. Hypercoagulability, if present, may also contribute.

Occlusion within the first 12 to 18 months — The rates and causes of vein graft failure (VGF) were evaluated in a 2014 post-hoc, retrospective analysis of the more contemporary PREVENT IV trial [3]. In this multicenter study, 1828 patients from the trial underwent either protocol-mandated follow-up angiography at 12 to 18 months or angiography for a clinical indication. VGF was defined as a ≥75 percent stenosis or occlusion. VGF was seen in about 43 percent of patients and about 25 percent of vein grafts had failed. After multivariable adjustment, the following factors predicted failure: longer surgical duration, endoscopic vein harvesting, poor target artery quality, and postoperative use of a platelet P2Y₁₂ receptor blocker. Among the patients with VGF, only 7.1 percent were identified by early repeat angiography for clinical symptoms, meaning VGF is silent in the majority of patients. (See "Coronary artery bypass graft surgery: Long-term clinical outcomes", section on 'Vein graft failure'.)

The pathophysiology of SVG failure during 12 to 18 months includes platelet aggregation, growth factor secretion, endothelial dysfunction due to reduced endothelial production of nitric oxide and prostacyclin, decreased local fibrinolytic potential resulting from upregulation of plasminogen activator inhibitor-1, inflammation, luminal foam cell accumulation, and marked intimal hyperplasia [4-10]. Damage to the vein graft at the time of transplantation is postulated as an initiator of these changes [3].

Late occlusion — Late occlusion after the first 12 to 18 months occurs when areas of intimal hyperplasia develop lipid deposition and finally an atherosclerotic-like plaque [10]. From the end of year one to year six, SVGs obstruct at the rate of approximately 2 percent per year; the subsequent closure rate rises to 4 to 5 percent per year.

The predictors of late occlusion have been evaluated in several studies of which the following are representative [10-13]:

●In a study of 266 patients with 656 grafts that were patent 7 to 10 days after surgery, the only factors that were predictive of graft patency at three years were vein preservation solution temperature ≤5ºC, serum cholesterol, the number of proximal anastomoses (≤2), and recipient artery diameter >5 mm [12].

●In a study of 1248 patients (who underwent angiography at baseline 1 to 11 years after CABG and 4.3 years later), factors independently associated with the progression of disease, in order of importance, were maximal stenosis of the graft at baseline angiography, time after CABG, prior myocardial infarction, elevated triglyceride levels, small minimum graft diameter, low high density lipoprotein-cholesterol concentration, high low density lipoprotein-cholesterol concentration, elevated mean arterial pressure, reduced left ventricular ejection fraction, male sex, and current cigarette smoking [13].

A vein graft can be used for single or multiple distal anastomoses; concerns have been raised about the possibility of worse outcomes when performed for the latter [14]. These concerns are based on a greater likelihood of technical failure and their more frequent use with poor distal coronary targets (see 'Early occlusion' above). The issue of whether long-term outcomes differ with single or multiple distal anastomoses was evaluated in a post-hoc, substudy of the PREVENT IV trial, which randomly assigned 3014 patients undergoing first CABG with at least two planned SVGs to either a novel agent used to prevent neointimal hyperplasia or placebo [15]. The use of SVG conduits with multiple distal anastomoses was associated with a significantly higher rate of SVG failure (defined as a ≥75 percent angiographic stenosis) at one year (adjusted odds ratio 1.24, 95% CI 1.03-1.48) and a trend toward a higher rate of the adjusted composite of death, myocardial infarction, or revascularization at five years (hazard ratio 1.15, 95% CI 1.00-1.31).

Off-pump versus on-pump CABG — The number of off-pump CABG operations continues to decrease, as the expected benefits have been largely marginal or absent, with the possible exception of patients with predicted very high-risk surgical scores for whom the risk of stroke was lower with off-pump CABG [16].

There are studies that have suggested a significant superiority for on-pump CABG with regard to SVG patency when compared with off-pump surgery [17-20]. (See "Off-pump and minimally invasive direct coronary artery bypass graft surgery: Clinical use", section on 'Outcomes'.)

ARTERIAL GRAFTS — Arterial grafts into the coronary circulation are much more durable than venous grafts and have been associated with better patient survival in some studies. An attempt is made to place at least one arterial graft in every patient who undergoes coronary artery bypass graft surgery (CABG). We attempt to place a second arterial graft in many patients, particularly those who are younger than 60 years of age. Patients in whom placement of a single arterial graft is reasonable include those:

●With a life expectancy of less than 10 years

●Person with obesity

●Dialysis patients

●Those with more than moderate emphysema

●Those with poorly controlled diabetes

●Those undergoing emergency surgery

Single arterial graft — When one arterial graft is placed, it is usually the left internal thoracic artery (ITA), which is also referred to as the internal mammary artery. The preference for the left ITA as the first arterial graft, compared with the right ITA or another arterial graft, is due to the broad experience with it and the relative ease with which it can be used. The left ITA is usually anastomosed to the left anterior descending coronary artery (LAD).

Unlike vein grafts in which long-term patency is problematic (see 'Late occlusion' above), patency rates for arterial grafts at 10 years are as high as 98 percent, and arterial graft patency is associated with higher long-term survival [21-25]. There are a number of anatomic and physiologic differences between saphenous veins and ITAs that contribute to this difference (table 1) [10].

The early patency of a left ITA graft was almost 99 percent in a study with a mean follow-up of about 11 days [26]. Early patency for a right ITA, when anastomosed to a major branch of the left circumflex artery, is approximately 94 percent [27]. Early arterial failure is related to operative issues (ie, technical harvest problems; distal anastomotic technique; and perioperative management, including the variable use and timing of antiplatelet therapy, vasospasm, and statin therapy) and patient-related anatomical issues (proximal stenosis, presence of competitive flow in the bypassed vessel, size of distal vessel, as well as plaquing and diffuse disease in the bypassed vessel).

The frequency and predictors of ITA mid-term graft failure were evaluated using information in the PREVENT IV trial database [28]. Among 1539 patients who underwent ITA-LAD revascularization and had 12- to 18-month angiographic follow-up, the rate of ITA failure was 8.6 percent, a rate higher than that seen in other series (see next paragraph). Predictors of failure were LAD coronary artery stenosis of <75 percent, additional bypass graft to the diagonal branch, and not having diabetes. Individuals who had graft failure had a significantly higher incidence of subsequent acute (<14 days) clinical events likely due to a higher rate of repeat revascularization.

Long-term graft patency is much higher with left ITA than venous grafts [1,11,23,29,30]. ITA graft patency is over 95 percent at five years and slightly lower at 10 years, particularly if the graft is placed to the LAD [29-31]. Right ITA graft patency is similar at five years, but falls below 90 percent at 10 years, particularly if it is placed to the right coronary artery.

Study-to-study differences in reported graft failure rates may be related to population differences, as well as differences in the age of the venous grafts.

Two arterial grafts — In patients undergoing CABG who have tight, proximal stenosis in two or more coronary arteries, placement of two rather than one arterial graft should be attempted in those with a life expectancy of greater than 7 to 10 years. Although the use of two arterial grafts, compared with one, has not been clearly shown to be superior, potential benefits include better long-term patency, lower rate of repeat revascularization and myocardial infarction, and possible longer survival.

The observation of benefit from the placement of single arterial grafts has led to the use of combinations of multiple arterial grafts, including bilateral (right and left) ITA grafts, left ITA and radial artery grafts, and "total arterial revascularization" [32] (see 'Total arterial revascularization' below). Long-term patency for multiple arterial grafts is high, and there is some evidence of improved survival [33]. The placement of two arterial grafts is attempted in many patients.

In most cases, the first graft will be the left ITA and the second either a radial artery or the right ITA. There is no convincing evidence that one is superior to the other. The choice between the two will depend on factors such as the patient’s risk for sternal wound infection (being in an obese weight category, active smoking, poorly controlled insulin dependent diabetes, or immunosuppressive therapy such as with glucocorticoids) and the availability of a radial artery for grafting. (See "Early noncardiac complications of coronary artery bypass graft surgery", section on 'Sternal wound infection and mediastinitis' and "Surgical management of sternal wound complications", section on 'Risk factors for sternal wound complications'.)

The following evidence from randomized trials supports the use of two compared with one arterial graft:

●A 2018 patient-level meta-analysis of six randomized trials (n = 1036) evaluated outcomes at 60 months in patients who received either a radial artery or an SVG as a supplement to left ITA grafting [34]. There was a lower rate of the primary outcome of death, myocardial infarction, or repeat revascularization at 60 months in patients who received a radial artery graft (hazard ratio [HR] 0.67, 95% CI 0.49-0.90, respectively). The incidence of all-cause death was similar in the two groups (HR 0.90, 95% CI 0.59-1.41, respectively). At follow-up angiography at a mean of 50 months, radial artery grating was associated with a significantly lower risk of occlusion (HR 0.44, 95% CI 0.28-0.70) and a lower incidence of repeat revascularization (HR 0.50, 95% CI 0.40-0.63).

At a median follow-up of 10 years, the use of the radial artery was associated with a reduction in the primary composite outcome (41 versus 47 events per 1000 patient-years; HR 0.73, 95% CI 0.61-0.88) [35]. In a post-hoc analysis, the mortality was lower in the radial artery group (24 versus 27 events per 1000 patient-years; HR 0.73, 95% CI 0.57-0.93).

These 5- and 10-year analyses are limited in part due to the relatively small number of events. For example, there were only 128 deaths at 10 years.

●In the 2016 ART trial, which randomly assigned 3102 patients scheduled to undergo CABG to bilateral or single ITA grafting, the rate of death was not different between the two groups (8.7 versus 8.4 percent; HR 1.04, 95% CI 0.81-1.32) at 5 and 10 years (20.3 versus 21.2 percent; HR 0.96, 95% CI 0.82-1.12) [36,37].

In addition to the evidence above from randomized trials, most observational studies suggest that long-term survival is better with two or more, as opposed to one, arterial grafts [32,36,38-44].

Total arterial revascularization — Total arterial revascularization refers to the use of two or more arterial grafts without placement of SVG. The use of only arterial grafts for CABG markedly reduces the risk of stenosis or occlusion associated with SVG [29,31,45-48]. However, this approach is technically demanding and takes longer to perform than other types of CABG. We consider total arterial revascularization in patients with one or more of the following: age <60 years, multiple arteries with stenoses >90 percent and no significant distal disease, and poor-quality veins.

In a review of 3220 patients undergoing total arterial coronary revascularization at the Royal Melbourne Hospital, the operative mortality was 0.7 percent, and angiographic graft patency was 97 and 89 percent at five years for left and right ITA grafts and 91 percent at one year for radial artery grafts (only 65 patients) [31].

The safety of total arterial revascularization was also noted in a report from 27 centers in the United Kingdom that included 71,470 patients who underwent CABG [48]. Total arterial revascularization was performed in 5401 (7.6 percent); the frequency increased over time from 3.2 in 1992 to 11.7 percent in 2001, with variability among centers. Propensity analysis revealed a nonsignificant small increase in in-hospital mortality with total arterial revascularization (1.74 versus 1.51 percent for one artery and veins). The potential benefits from total arterial revascularization are discussed separately. (See "Coronary artery bypass graft surgery: Long-term clinical outcomes", section on 'Two arterial grafts'.)

Total arterial revascularization reduces the incidence of early cardiac events compared with standard CABG that includes SVGs. This was illustrated in a trial of 200 patients who were randomly assigned to either total arterial or standard CABG [45]. At one year, the total arterial group had significantly lower rates of recurrent angina (2 versus 13 percent for standard CABG) and percutaneous coronary intervention (PCI) (0 versus 8 percent), and a significantly higher actuarial rate of freedom from death, myocardial infarction, angina recurrence, graft occlusion, or PCI (96 versus 67 percent).

Radial artery graft — The radial artery is increasingly being used in CABG procedures. While long-term patency has been established, no study has shown significantly higher survival rates [34]. The benefit from its use as a second arterial conduit is discussed above. (See "Coronary artery bypass graft surgery: Long-term clinical outcomes", section on 'Two arterial grafts'.)

The long-term outcome with radial artery grafts has been excellent in most [29,38,49-51] but not all observational series [52], with patency rates as high as 96 percent at one year and 89 percent at four years [29]. The rate of radial artery patency is higher when grafted to a native coronary artery with more than 80 percent stenosis [29,53].

The issue of whether the radial artery or the right ITA is a better second arterial graft has been evaluated in the following two studies:

●In the RAPCO-RITA trial, 394 patients who received a left ITA were randomly assigned to receive either RA of free RITA graft on the second most important coronary target [54]. The estimated 10-year patency was 89 and 80 percent in the two groups, respectively (hazard ratio for graft failure 0.45, 95% CI 0.23-0.88). Survival was improved in the RA group, but the number of events was small.

●An observational study evaluated outcomes in 1001 patients undergoing first nonemergent CABG and who received one of these two in addition to a left ITA [55]. After a median follow-up of about 58 months, long-term overall survival and major adverse cardiac and cerebrovascular events-free survival (a combined endpoint including myocardial infarction, stroke, cardiac-related death, and repeat revascularization) were significantly better with bilateral ITA compared with left ITA plus RA (hazard ratio 0.23, 95% CI 0.07-0.81 and 0.18, 95% CI 0.08-0.42, respectively).

Use of the radial artery requires an evaluation for adequate ulnar artery flow to prevent the loss of hand function. There are usually only minimal changes in hand function after CABG, manifested by a small amount of forearm numbness and tingling, but no change in motor function or tolerance to temperature or pain [31,49,56,57]. These symptoms are self-limited in the majority of patients [58].

One drawback with the use of the radial artery is the development of spasm of the graft, which has been reported to occur in 4 to 10 percent of radial grafts immediately after surgery [59,60]. The radial artery is particularly prone to spasm, possibly because of its large medial cross-sectional area [61]. A variety of vasodilator agents, most commonly calcium channel blockers, have been used to prevent spasm of radial grafts after implantation [62].

If possible, radial artery grafts should be avoided in patients with chronic renal disease who are at risk for requiring dialysis. Harvesting of a radial artery in such patients precludes use of the ipsilateral arm for vascular access.

INCOMPLETE REVASCULARIZATION — "Complete" revascularization refers to a successful attempt to bypass important stenoses of the major epicardial coronary arteries. It is not technically possible to surgically improve myocardial blood flow caused by disease in small vessels.

While complete revascularization has been the usual goal for coronary artery bypass graft surgery, the evidence to support superiority of complete revascularization compared with incomplete revascularization is not consistent, with studies suggesting that incomplete revascularization may be equally safe and effective. This issue is discussed separately. (See "Coronary artery bypass graft surgery: Long-term clinical outcomes", section on 'Incomplete revascularization'.)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)

●Basics topics (see "Patient education: Recovery after coronary artery bypass graft surgery (The Basics)" and "Patient education: Coronary artery bypass graft surgery (The Basics)")

●Beyond the Basics topic (see "Patient education: Coronary artery bypass graft surgery (Beyond the Basics)" and "Patient education: Recovery after coronary artery bypass graft surgery (CABG) (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Saphenous vein graft patency declines significantly starting at the time of surgery. Rates below 90 percent are common at one year. (See 'Vein grafts' above.)

●In patients undergoing coronary artery bypass graft surgery (CABG), long-term graft patency is excellent with internal thoracic artery bypass grafts. Rates exceeding 90 percent at 5 to 10 years are common.

An attempt should be made to place at least one arterial graft in all patients undergoing CABG. (See 'Arterial grafts' above.)

●The evidence suggests that, in addition to improved long-term graft patency, survival is improved with arterial grafting compared with saphenous vein bypass grafting particularly when the left anterior descending is grafted with an artery. (See 'Arterial grafts' above.)

●For patients with multivessel disease in whom it is technically possible to place multiple arterial grafts, we recommend an attempt at placement of two rather than one arterial graft (Grade 1B). (See 'Two arterial grafts' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff thank Dr. Julian M. Aroesty for his contributions as an author to prior versions of this topic review.