Version May 2024
INTRODUCTION — Standard coronary artery bypass graft surgery (CABG) employs a midline incision through the sternum, placement of the patient on cardiopulmonary bypass, and arrest of the heart with cardioplegia. This approach allows for optimal exposure of the coronary arteries and a motionless (non-beating) heart, both of which optimize the suturing of the distal anastomoses of the bypass.
This approach may contribute to an increased risk of adverse outcomes in certain clinical scenarios. For example, patients requiring a repeat CABG are at risk of damage to a previously placed left internal mammary bypass graft during a repeat sternotomy and patients with calcified aortas may be at increased risk of cerebral embolization with cross-clamping of the aorta during cardiopulmonary bypass.
This topic will discuss outcomes after off-pump and minimally invasive direct CABG, two approaches that have been evaluated as potential alternatives to standard CABG. Complications of CABG using any technique, technical issues related to minimally invasive CABG, and minimally invasive approaches to valvular surgery are discussed separately. (See "Early noncardiac complications of coronary artery bypass graft surgery", section on 'Prevention of complications' and "Minimally invasive coronary artery bypass graft surgery: Definitions and technical issues" and "Minimally invasive aortic and mitral valve surgery".)
OFF-PUMP CABG — Off-pump CABG (sometimes abbreviated as "OPCAB") refers to CABG without the use of cardiopulmonary bypass. The rationale for developing this procedure, which is also called "beating heart surgery," was to avoid the morbidity associated with cardiopulmonary bypass (induction of a systemic inflammatory response, activation of platelets, and of cross-clamping the aorta). (See "Minimally invasive coronary artery bypass graft surgery: Definitions and technical issues", section on 'General principles' and "Thromboembolism from aortic plaque" and "Management of cardiopulmonary bypass" and "Initiation of cardiopulmonary bypass".)
For most patients undergoing CABG, we perform on-pump rather than off-pump CABG. Studies that evaluated mortality suggest, but do not definitively show, higher long-term mortality with off-pump CABG. The rate of repeat revascularization, often due to less complete revascularization or worse graft patency, is also higher with off-pump CABG. (See "Coronary artery bypass graft surgery: Graft choices", section on 'Off-pump versus on-pump CABG'.)
The off-pump technique is technically more challenging and requires additional training. Thus, surgeon experience with off-pump CABG is of vital importance with increased operative risk and higher conversion rates with off-pump CABG in low-volume centers with low-volume surgeons.
It has been chosen by some practitioners for high-risk patients with contraindications to conventional CABG, such as those with extensive ascending aortic atheromatous or calcific changes that might preclude safe aortic instrumentation. A potential disadvantage of off-pump surgery is the difficulty of performing distal anastomoses on a beating heart; this might lead to incomplete revascularization if exposure of the back of the heart is challenging or decreased graft patency because of suboptimal conditions during the construction of the distal anastomosis.
Patient selection — The following factors should be taken into account when deciding between the on- and off-pump CABG [1,2]:
●Expertise of the surgeon in performing OPCAB. An analysis has documented a significant surgeon-volume relationship with an estimated 5 percent decrease in mortality risk in surgeons who performed the highest volume of OPCAB (p<0.01) [3].
●The extent of atheromatous involvement of the ascending aorta [4-9]. (See 'Off-pump CABG' above and 'Neurologic dysfunction' below.)
●The extent of technically challenging anatomy, which might occur in patients with small, diffusely diseased or calcified vessels or intramyocardial vessels [10], marked cardiomegaly, diffuse intramyocardial coronary disease, or hemodynamic instability [11]. In addition, patients with heart failure or significant mitral regurgitation are less likely to tolerate the cardiac displacement that occurs during this procedure. We prefer on-pump CABG when any of these factors are present.
●The greater need for repeat revascularization with off-pump CABG. (See "Coronary artery bypass graft surgery: Graft choices", section on 'Total arterial revascularization' and 'Survival and repeat revascularization' below.)
●The presence of serious comorbidities such as significant renal or pulmonary dysfunction [4-9].
●The likelihood of achieving complete revascularization with an off-pump strategy is of the utmost importance. Long-term survival is significantly lower for patients in whom complete revascularization was not achieved with an off-pump approach [12].
Most surgeons consider using off-pump CABG in patients with isolated proximal left anterior descending (LAD) coronary artery disease and occasionally with LAD and proximal right coronary artery disease.
Off-pump CABG can be used as part of a hybrid revascularization approach in cases where complete revascularization cannot be achieved. (See 'Hybrid revascularization procedures' below.)
Outcomes
Survival and repeat revascularization — In the aggregate, the studies that have compared off-pump to on-pump CABG have found an increase in long-term mortality and an increased risk for repeat revascularization with the former.
Although initial observational studies with off-pump CABG suggested similar or better outcomes compared with conventional on-pump CABG [13-23], conclusions were likely flawed due to multiple sources of bias. Other randomized trials have been too small to demonstrate conclusive clinical superiority of either surgical approach [1,24-31].
A 2012 meta-analysis and systematic review of 86 randomized trials compared the two surgical techniques [32]. Off-pump CABG significantly increased all-cause (long-term) mortality in all trials and in the 10 trials (nearly 5000 patients) at low risk of bias (3.7 versus 3.1 percent; relative risk [RR] 1.24; 95% CI 1.01-1.53 and 6.2 versus 4.6 percent; relative risk 1.35; 95% CI 1.07-1.70, respectively).
The following three trials were not included in or published after the meta-analysis:
●The ROOBY trial (2009) randomly assigned 2203 relatively low-risk patients scheduled for elective or urgent CABG to either an off- or on-pump procedure [24]. The rate of the primary outcome (a composite of death from any cause, a repeat revascularization procedure, or a nonfatal myocardial infarction within one year after surgery) was significantly higher in the off-pump group (9.9 versus 7.4 percent, RR 2.5, 95% CI 1.01-1.76), including a significant increase in the rate of death from cardiac causes (2.7 versus 1.3 percent). The proportion of patients with fewer grafts completed than originally planned was significantly higher in the off-pump group (17.8 versus 11 percent).
At five years, the rate of death was higher with off-pump CABG (15.2 versus 11.9 percent; RR 1.28, 95% CI 1.03-1.58) [33]. Approximately, 43 percent of the deaths were cardiac related. The rate of the other five-year primary end point (a composite of death from any cause, repeat revascularization, or nonfatal myocardial infarction) was also higher with off-pump CABG (31.0 versus 27.1 percent; RR 1.14, 95% CI 1.00-1.30).
An angiographic follow-up study of 1370 patients enrolled in ROOBY evaluated graft patency [34]. At one year, graft patency was significantly worse in those who received off-pump CABG (82.6 versus 87.8 percent), attributable primarily to a lower overall patency in saphenous vein grafts (76.6 versus 83.8 percent). The one-year adverse cardiac event rate (death, nonfatal myocardial infarction, or repeat revascularization) was significantly lower in patients with effective, compared with ineffective, revascularization (5.9 versus 16.4 percent). Effective revascularization was defined as follows: All three major coronary territories with significant disease (at randomization) were revascularized with a patent graft, which was placed in proper position relative to the native disease, and there were no new postanastomotic lesions.
●The CORONARY trial (2012) randomly assigned 4752 patients scheduled to undergo isolated CABG surgery to either an off- or on-pump procedure [35]. The patients represented a higher-risk group than those enrolled in ROOBY, and the surgeons as a group had a higher level of expertise with off-pump techniques.
At one year, there was no significant difference in the rate of the primary composite outcome (12.1 versus 13.3 percent, respectively; hazard ratio 0.91, 95% CI 0.77-1.07) [36,37]. In addition, there were no significant differences in the rates of the individual components of the composite outcome or in measures of quality of life or neurocognitive function. However, there was a trend toward a higher rate of revascularization with off-pump CABG.
At five years, there were no significant differences between the off- and on-pump groups in the rate of the composite end point of death, stroke, myocardial infarction, renal failure, or repeat coronary revascularization (23.1 and 23.6 percent, respectively; hazard ratio 0.98, 95% CI 0.87-1.10) [38].
●The GOPCABE trial (2013) randomly assigned 2539 higher-risk patients (mean logistic Euroscore 8.3 and older than the age of 75 years) to test the hypothesis that off-pump CABG would be superior to on-pump CABG in these patients. In comparison to ROOBY and CORONARY trials, surgeons were more experienced, with median off-pump CABG experience of 322 cases [37].
At 30 days and 12 months, the composite end point of death, MI, stroke, repeat revascularization, and new renal replacement therapy were no different between the groups. Mean number of grafts was marginally but statistically significantly lower in off-pump CABG, and crossover was nearly twice as high. Mean operative time, and length of ICU and hospital stay were the same, and there was a higher need for repeat revascularization in the off-pump group at 30 days.
Five-year follow-up of the GOPCABE trial [39] showed no difference between the two groups in the composite outcome of death, repeat revascularization, and myocardial revascularization. There was greater incomplete revascularization in the off-pump versus the on-pump group (34 versus 29 percent, p<0.001). In summary, at 30 days, one year, and five years there was no difference between the groups in survival or other primary end points. Incomplete revascularization was associated with a lower five-year survival, irrespective of the type of surgery.
A 2014 meta-analysis of 22 studies (randomized trials and observational studies), enrolling a total of more than 100,000 patients, found a 7 percent increase in long-term all-cause mortality with off-pump relative to on-pump CABG [40]. A 2018 meta-analysis of six randomized trials (N = 8145) that reported outcomes at four years or longer showed higher mortality in the off- versus on-pump group (13.9 versus 12.3 percent; odds ratio = 1.16; 95% CI 1.02-1.32) but no difference in angina, myocardial infarction, need for revascularization, or stroke [41].
A further meta-analysis published in 2018 analyzed randomized trials that reported long-term outcomes. This study concluded that there was significantly lower incidence of mortality in the on-pump CABG group compared with off-pump at greater than four-year follow-up. There was no difference between the groups in the incidence of myocardial infarction, angina, revascularization, and stroke [41].
Similar findings were reported in another meta-analysis of randomized controlled trials, which demonstrated a significant long-term mortality benefit in patients undergoing on-pump compared with off-pump CABG. This benefit was seen after five-year clinical follow-up and may have been driven by a higher rate of repeat CABG in off-pump CABG patients. No differences were seen in rate of stroke, myocardial infarction, or cardiac death at any time-point between surgical strategies [42].
Three large observational studies provide "real world" outcomes with the two approaches:
●In a 2014 review of the Society of Thoracic Surgeons database, off-pump CABG was associated with less morbidity and shorter length of stay, but similar mortality risk compared with on-pump approaches [43].
●In a 2014 registry study of 5203 patients who underwent isolated CABG between 1989 and 2012, the adjusted overall mortality was higher in the off-pump group at a median follow-up duration of 6.4 years (hazard ratio 1.43, 95% CI 1.19-1.71) [44].
●In a 2016 retrospective cohort analysis of 13,226 patients (5882 underwent off-pump and 7344 underwent on-pump CABG) at a single institution with expertise in performing off-pump CABG, there was no difference in 1, 5 and 10-year survival [45].
OFF-PUMP VERSUS ON-PUMP REVASCULARIZATION IN LEFT MAIN STEM DISEASE — A post-hoc retrospective analysis from the EXCEL trial compared the outcomes following off-pump and on-pump surgery for left main disease. Among 923 CABG patients, 652 and 271 patients underwent on-pump and off-pump surgery, respectively. Despite a similar extent of disease, off-pump surgery was associated with a lower rate of revascularization of the left circumflex and right coronary arteries. At three-year follow-up, off-pump surgery was associated with a significantly increased risk of three-year all-cause death compared with on-pump surgery [46].
Neurologic dysfunction — Meta-analyses of randomized trials published in 2005 and 2006 found a significant decrease in the risk of stroke with off-pump CABG [47] but no significant difference in the risk of neurocognitive dysfunction with off-pump CABG [48].
The 2009 ROOBY trial (see 'Outcomes' above), which was published after the above meta-analyses, randomly assigned over 2200 patients to either on- or off-pump procedures. There was no difference between the two groups in neuropsychological outcomes with test measures at baseline and at one year [24]. (See 'Off-pump CABG' above.)
CORONARY and GOPCABE trials, which addressed the limitations and criticisms levelled at the ROOBY trial, showed no difference in stroke rates between the two groups. To date, no randomized trials have shown a difference in stroke rate between on- and off-pump CABG.
A 2018 post-hoc analysis of a randomized trial compared the rate of major adverse cardiovascular events in 2394 elderly (≥75 years) patients undergoing on- or off-pump CABG. There was no significant difference in the rate of stroke within 30 days after surgery between the two groups [49].
A related issue is whether surgical techniques applied during off-pump CABG that reduce manipulation of the aorta lower the rate of stroke. These techniques include an "anaortic" approach which completely avoids manipulation of the aorta, a partial clamping technique, or use of the clampless Heartstring device. (See "Minimally invasive coronary artery bypass graft surgery: Definitions and technical issues", section on 'Possible disadvantages'.)
A 2017 network meta-analysis of 37,720 patients from 13 observational, non-randomized, and randomized studies found that the anaortic or no-touch aorta technique for off-pump approach significantly decreased the risk of postoperative stroke more than on-pump CABG, or off-pump CABG with partial clamping technique, and the Heartstring device [50]. Anaortic off-pump CABG also reduced the risk of mortality, renal failure, atrial fibrillation, and bleeding. However, these results may have been influenced by selection bias, as the meta-analysis included observational and nonrandomized trials.
MIDCAB — The term minimally invasive direct CABG (MIDCAB), also called minimal or limited access CABG, is applied to procedures that use alternative incisions to standard median sternotomy. In most instances, MIDCAB is performed off-pump.
MIDCAB is performed through a limited anterior thoracotomy and generally without cardiopulmonary bypass. In many instances, this approach typically involves only an anastomosis between the left internal mammary artery (LIMA) and left anterior descending (LAD) coronary artery or some use of a composite graft off the LIMA to other coronary arteries.
Outcomes — LIMA-to-LAD coronary artery MIDCAB with off-pump bypass is associated with angiographic patency ranges from 86 to 97 percent, a low incidence of postoperative complications (approximately 2 percent), and rapid recuperation [51-54]. In an observational study of 274 patients, the one-year mortality rate was 2 percent and the reintervention rate was 2.9 percent [52]. However, there is little high-quality evidence to suggest that it is superior to a median sternotomy for outcomes of death, stroke, non-fatal myocardial infarction, or repeat revascularization [55-57].
Early randomized trials compared MIDCAB with percutaneous coronary intervention (PCI), but the ability to apply their conclusions to current practice is limited due to factors such as the predominant use of bare metal stents (compared with drug-eluting stents), relatively short follow-up, and inconsistent use of current adjunctive medical therapies such as aggressive antiplatelet therapy [58-60]. In three small randomized trials of patients with isolated LAD disease, MIDCAB was associated with a marked reduction in the need for target vessel revascularization consequent to restenosis at six months compared with PCI with bare metal stents [58,60]. This has not markedly changed with the use of drug-eluting stents [61]. Otherwise, the results were comparable over a 10-year period [62]. In addition, it can approach lesions that cannot be treated with PCI, such as those that have excessive length, angulation, tortuosity, or complex lesions.
Although incisions that are alternatives to median sternotomy are thought to be less invasive, the incidence of wound complications, such as incisional hernia, dehiscence, seroma formation, and infection, with an anterior thoracotomy (MIDCAB) incision is significant (9 versus 1 percent with standard median sternotomy) and may have been underreported [63]. In addition, a thoracotomy incision generally is a more painful incision compared with a midline sternotomy. However, thoracoscopic or robotic-assisted MIDCAB, which do not need rib spreading for access and rely on soft-tissue retraction only, are significantly less painful and allow early return to normal activities, including work.
While several surgical approaches are utilized to achieve a MIDCAB, reports of midterm outcomes and the incidence of major adverse cardiovascular events in patients undergoing robotically-assisted minimally invasive CABG demonstrate acceptable procedural success and excellent five-year survival, which is comparable to historic reports [64].
Patient selection — We believe that a sternal approach allows for more complete revascularization in most instances. However, MIDCAB may be preferable to median sternotomy in the following circumstances:
●The surgeon and the center are experienced with this approach, and MIDCAB is performed on a regular routine basis [65].
●Patients for whom the LAD coronary artery is the only target vessel.
●Patients for whom a long sternal incision is cosmetically problematic or for whom the shorter recovery after MIDCAB is preferable.
●Patients who require reoperation, but in whom a repeat sternotomy carries risk due to an underlying bypass graft or cardiac structure adherent to the sternum, previous sternal wound infection or mediastinal radiation therapy, or calcified or diffusely atherosclerotic aorta. This approach may be limited in its access to the heart. This approach may be preferable if a bypass graft to the lateral wall of the heart needs to be revised and is thought to be feasible to perform without cardiopulmonary bypass.
●Patients in whom a hybrid approach to coronary revascularization is entertained. (See 'Hybrid revascularization procedures' below.)
Hybrid revascularization procedures — MIDCAB is used by some surgeons when an attempt is made at complete revascularization using CABG and PCI. This is often referred to as a hybrid coronary artery revascularization procedure (HCR) [66]. HCR is discussed separately. (See "Revascularization in patients with stable coronary artery disease: Coronary artery bypass graft surgery versus percutaneous coronary intervention", section on 'Multivessel disease'.)
RECOMMENDATIONS OF OTHERS — No major societal guidelines have made specific recommendations for the use of off-pump CABG since 2011 [67].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Coronary artery bypass graft surgery".)
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 5th to 6th 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 10th to 12th 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)")
●Beyond the Basics topics (see "Patient education: Coronary artery bypass graft surgery (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Background – Standard coronary artery bypass graft surgery (CABG) may contribute to an increased risk of several adverse outcomes. For example, patients requiring a repeat CABG are at risk of damage to a previously placed left internal mammary bypass graft during a repeat sternotomy and patients with calcified aortas may be at increased risk of cerebral embolization with cross-clamping of the aorta during cardiopulmonary bypass. (See 'Introduction' above.)
●Off-pump CABG – Off-pump CABG (sometimes abbreviated as "OPCAB") refers to CABG without the use of cardiopulmonary bypass. The rationale for developing this procedure, which is also called "beating heart surgery," was to avoid the morbidity associated with cardiopulmonary bypass (induction of a systemic inflammatory response, activation of platelets, and of cross-clamping the aorta). (See 'Off-pump CABG' above.)
●Outcomes – The 30-day and one-year results of off- and on-pump CABG are comparable for composite outcomes that include death, stroke, and nonfatal myocardial infarction. However, at one year, the rate of revascularization appears to be increased with off-pump CABG. (See 'Outcomes' above.)
●Patient selection – For most patients who are referred for CABG and who do not have extensive ascending aortic atheromatous or calcific changes that might preclude safe aortic instrumentation, we recommend an on-pump as opposed to off-pump procedure (Grade 1B).
Patients felt to be at high risk of stroke due to aortic manipulation may reasonably choose off-pump CABG after taking into account the expertise of the surgeon and outcomes at a particular institution. Patients choosing to undergo off-pump surgery should be made aware of the higher mortality associated with emergent intraoperative conversion from off- to on-pump CABG.
●Minimally invasive CABG – The term minimally invasive direct CABG (MIDCAB), also called minimal or limited access CABG, is applied to procedures that use alternative incisions to standard median sternotomy. In most instances, MIDCAB is performed off-pump.
The choice between the two approaches likely depends on local expertise and the revascularization necessary. In patients undergoing left anterior descending coronary artery bypass, a MIDCAB may be preferable, whereas a sternal approach may be a better choice in patients undergoing multivessel bypass. (See 'MIDCAB' above.)
Likely benefits of MIDCAB include faster recovery in the case of robotic/thoracoscopic MIDCAB and superior cosmetic results.
ACKNOWLEDGMENT — The UpToDate editorial staff would like to thank Drs. John M. Stulak and David M. Holzhey for their contributions as authors to previous versions of this topic review.
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