Conversion and Safety in Off-Pump Coronary Artery Bypass: A System Failure That Needs Re-Emphasis

Off-pump coronary artery bypass grafting is safe and effective in patients with severe left ventricular dysfunction

OBJECTIVES

Severe left ventricular dysfunction (LVD) is associated with increased risk following coronary artery bypass grafting (CABG). Due to a dearth of reports on the choice of CABG technique in patients with LVD, this study aims to compare the outcomes of off-pump CABG (OPCAB) and conventional CABG (ONCAB) in such patients.

METHODS

Retrospective single-centre propensity-matched analysis comparing early- and long-term outcomes of OPCAB and ONCAB in patients with severe LVD. Primary outcome was long-term all-cause mortality.

RESULTS

Between 2002 and 2014, a total of 1161 consecutive patients with severe LVD underwent isolated CABG [442 patients underwent OPCAB and 719 ONCAB (430 matched pairs)]. Incomplete revascularization was observed more frequently among OPCAB than ONCAB patients (35.3% vs 21.6%; P < 0.01). The overall 30-day mortality was 5% and was comparable between the matched groups [OR 0.64 (0.34-1.22); P = 0.18]. OPCAB patients had shorter median hospital stay (11 vs 12 days; P = 0.02) and lower packed red blood cell transfusion rates [2.7 (2.21-3.19) vs 4.4 (3.56-5.24); P < 0.01]. Estimated adjusted survival was 86.0% vs 85.8%, 69.1% vs 65.5% and 59.9% vs 49.1% at 1, 5 and 10 years for OPCAB and ONCAB patients, respectively (P = 0.99). Long-term risk of mortality was similar between groups [hazard ratio (HR) 0.94 (0.66-1.32); P = 0.7]. Incomplete revascularization was weakly associated with increased risk of long-term all-cause mortality [HR 1.33 (0.99-1.77); P = 0.05].

CONCLUSIONS

OPCAB is safe and effective in patients with severe LVD. Although incomplete revascularization is more commonly observed in patients undergoing OPCAB, it is not associated with increased late mortality.

Conversion during off-pump coronary artery bypass graft surgery: A case-control study

Objectives:

Off pump coronary artery bypass (OPCAB) surgery is carried out as an alternative to conventional coronary artery bypass grafting using cardiopulmonary bypass (CPB). At times ‘conversion’ to CPB may be required to bail out a situation resulting from acute decompensation of the heart. It is reported that such conversion carries significant mortality risk. Since we conduct coronary revascularization by OPCAB technique as the preferred technique, we conducted this study with an aim to identify the markers of adverse outcome during conversion in Indian patients.

Design:

Case control retrospective study.

Setting:

Tertiary referral center.

Participants:

We conducted three thousand two hundred OPAB surgeries in the period between 2013 to16. Ninety patients (3.1%) required conversion to complete the revascularization (Con version group). Twice the number of patients who underwent OPCAB surgery without conver sion were chosen as controls (Control group).

Intervention:

OPCAB surgery

Results:

Mortality in the conversion group was 5.56% in contrast to 0.06% in the controls (P = 0.01). The conversion group had higher left ventricular end diastolic pressure, incidence of endarterectomy, and intra-aortic balloon counter pulsation requirement. Female gender was also predictive of conversion. The total chest drain, duration of ventilation, ICU stay and hospital stay were also higher in the conversion group. Conversion was associated with 9.47 times the odds for mortality.

Conclusion:

Conversion during OPCAB is associated with significantly increased mortality. Female gender, increased left ventricular end diastolic pressure and preoperative requirement of Intra-aortic balloon are markers of increased risk of mortality when converted.

Conversion from Off to On-Pump Coronary Artery Bypass Grafting. Is it Avoidable?

Background

With the emergence of new technologies to stabilize the heart off-pump coronary artery bypass grafting (OPCAB), there is an increasing trend that is being observed throughout the world. In certain circumstances, OPCAB needs to be converted to on-pump CABG (ONCAB). In this study, we aim to identify certain risk factors mandating conversions and their associated short-term outcomes.

Methods

After approval from the institutional ethical review committee and exemption from informed consent, retrospective data of 100 patients meeting the inclusion criteria who underwent OPCAB operations at our institution from August 2018 to July 2019 were included. Preoperative, intraoperative, and postoperative variables were recorded and compared in conversion and non-conversion groups. This study was conducted at the National Institute of Cardiovascular Diseases, Karachi, Pakistan.

Results

A total of 100 patients were included in this study, out of which 82% (82) were male, with age ranging between 18 and 77 years with a mean age of 56.34 ± 8.3 years. In nine of the cases, OPCAB was emergently converted to ONCAB due to arrhythmias. In nine (9%) cases, off-pump CABG was emergently converted to on-pump CABG (ONCAB). Emergent conversion was due to arrhythmias in five cases, due to hypotension during OM graft in two cases, and due to hypotension during ramus graft for the remaining two cases. The emergent conversion was significantly associated with higher New York Heart Association (NYHA) functional classification and comorbid conditions such as chronic obstructive pulmonary disease (COPD).

Conclusion

Emergency conversion from off-pump to OPCAB is the most catastrophic event causing higher morbidity and mortality. Conversion rate was observed to be 9% with arrhythmias being the common cause and patients with higher NYHA status and COPD at baseline were found to be at increased risk of emergency conversion. Considering our results in patients with diagnosed COPD and higher NYHA status, the decision for off-pump CABG should be wisely taken carefully weighing the risks and benefits.

Conversion after off-pump coronary artery bypass grafting: the CORONARY trial experience

Objectives

Emergent and late conversions form OFF-to-ON pump coronary artery bypass grafting (CABG) have been associated with worse outcomes, however, it remains unclear as to which risk factors are associated with conversion and how to prevent them.

Methods

Among 4718 patients who randomly underwent off- or on-pump CABG, the incidence of off-pump to on-pump cross-over, or 'OFF-to-ON conversion', was 7.9% (186/2356). The primary outcome was a composite of death, stroke, myocardial infarction, or new renal failure requiring dialysis. We assessed the risk factors and outcomes of converted patients.

Results

Emergent OFF-to-ON conversions, defined as conversions for hypotension or ischaemia, were required for 3.2% of patients ( n  = 75), while most elective conversions were due to small or intramuscular coronaries ( n  = 83). OFF-to-ON converted patients required increased surgery time, blood transfusions, intensive care unit stay, and presented a higher incidence at 1 year of the composite outcome compared with non-converted off-pump patients (all P < 0.01), especially if the conversion was emergent. Conversely, elective conversions outcomes were no different compared with non-converted off-pump patients ( P  = 0.35). Independent predictors of emergent conversions included higher heart rate or chronic atrial fibrillation, urgent surgery, more grafts planned and surgeon experience with off-pump CABG.

Conclusions

Emergent OFF-to-ON conversion is associated with worse outcomes compared with elective conversion or no conversion. In the presence of risk factors for emergent conversion, an early and elective conversion approach is a judicious strategy.

Myocardial revascularization without extracorporeal circulation; Why hasn't it convinced yet?

Extracorporeal circulation has led to a great development in cardiovascular surgery during the last five decades. Its time-proven efficacy and safety have made on-pump coronary artery bypass grafting (CABG) the gold standard method of surgical revascularization. However, coronary revascularization on cardiopulmonary bypass and the accompanying aortic manipulation are related to plenty of deleterious complications. Therefore, off-pump CABG surgery was established to avoid complications. Nevertheless, despite the initial enthusiasm on this technique, only 20% of myocardial revascularization procedures worldwide are performed off-pump. Not only are off-pump cardiac procedures more technically difficult but also they do not provide better results in terms of graft patency, completeness of revascularization, repeat revascularization requirement, cost, and quality of life. Completeness of revascularization and anastomotic quality should not be compromised to avoid cardiopulmonary bypass.

Intraoperative conversion to on-pump coronary artery bypass grafting is independently associated with higher mortality in patients undergoing off-pump coronary artery bypass grafting: A propensity-matched analysis

Context:

One of the main limitations of off-pump coronary artery bypass grafting (OPCAB) is the occasional need for intraoperative conversion (IOC) to on-pump coronary artery bypass grafting. IOC is associated with a significantly increased risk of mortality and postoperative morbidity. The impact of IOC on outcome cannot be assessed by a randomized control design.

Aims:

The objective of this study was to analyze the incidence, risk factors, and impact of IOC on the outcome in patients undergoing OPCAB.

Settings and Design:

Three tertiary care level hospitals; retrospective observational study.

Subjects and Methods:

This retrospective observational study included 1971 consecutive patients undergoing OPCAB from January 2012 to October 2015 at three tertiary care level hospitals by four surgeons. The incidence, patient characteristics, cause of IOC, and its impact on outcome were studied.

Statistical Analysis Used:

The cohort was divided into two groups according to IOC. Univariate logistic regression was performed to describe the predictors of IOC. Variables that were found to be significant in univariate analysis were introduced into multivariate model, and adjusted odds ratio (OR) was calculated. To further assess the independent effect of IOC on mortality, propensity score matching with a 5:1 ratio of non-IOC to IOC was performed.

Results:

The overall all-cause in-hospital mortality was 2.6%. IOC was needed in 128 (6.49%) patients. The mortality in the IOC group was significantly higher than non-IOC group (21 of 128 [16.4%] vs. 31 of 1843 [1.7%], P = 0.0001). The most common cause for IOC was hemodynamic disturbances during grafting to the obtuse marginal artery (51/128; 40%). On multivariate logistic regression analysis, left main disease, pulmonary hypertension, and mitral regurgitation independently predicted IOC. We obtained a propensity-matched sample of 692 patients (No IOC 570; IOC 122), and IOC had OR of 16.26 (confidence interval 6.3–41; P < 0.0001) for mortality in matched population.

Conclusions:

Emergency IOC increases odds for mortality by 16-fold. Hence, identification of patients at higher risk of IOC may improve the outcome.

Analysis of Risk Factors for Conversion from Off-Pump to On-Pump Coronary Artery Bypass Graft

BACKGROUND

Off-pump coronary artery bypass (OPCAB) is performed worldwide, but significant risks are associated with conversion to on-pump surgery. Therefore, we evaluated the composite outcomes between an OPCAB group and a conversion group.

METHODS

From January 2008 to December 2012, 100 consecutive patients underwent OPCAB at Hallym University Sacred Heart Hospital, of whom 84 underwent OPCAB without adverse events (OPCAB group), and 16 were converted to on-pump surgery (conversion group). Early morbidity, early and long-term mortality, and major adverse cardiac and cerebrovascular events (MACCEs) were the primary and long-term composite endpoints.

RESULTS

The mean follow-up period was 55±26 months, with 93% of the patients completing follow-up. The composite outcomes in the OPCAB and conversion groups were as follows: early morbidity, 2.3% versus 12.5%; early mortality, 4.7% versus 0%; long-term mortality, 14.3% versus 25.0%; and MACCEs, 14.3% versus 18.8%, respectively. No composite endpoints showed statistically significant differences. Preoperative acute myocardial infarction (AMI) was identified as an independent risk factor for conversion (p=0.025).

CONCLUSION

The conversion group showed no statistically significant differences in early mortality and morbidity, MACCEs, or long-term mortality compared with the OPCAB group. The preoperative diagnosis of AMI was associated with an increased number of conversions to on-pump surgery.

Nicorandil Infusion During Off-Pump Coronary Artery Bypass Grafting Reduces Incidence of Intra-aortic Balloon Pump Insertion

OBJECTIVE

Off-pump coronary artery bypass grafting in patients with left ventricular dysfunction has proven to be advantageous. However, it carries risk of emergency conversion to cardiopulmonary bypass. We have successfully used an intra-aortic balloon pump to prevent such conversion. The objective of the present study was to evaluate if intravenous nicorandil infusion reduces the incidence of intraoperative intra-aortic balloon pump insertion.

METHODS

Consecutive cases of isolated off-pump coronary artery bypass surgery performed by a single surgeon were studied. Patients were divided into two groups. The first group did not receive nicorandil, and the second group received intraoperative nicorandil infusion (started in the operating room after central line insertion).

RESULTS

A total of 375 patients were included in the study. Four patients in the non-nicorandil group and the patients in nicorandil group were on preoperative intra-aortic balloon pump and hence excluded from the study. After routine use of nicorandil infusion, incidence of intra-aortic balloon pump insertion during off-pump coronary artery bypass surgery decreased from 12.4% (21/169) to 2.9% (6/206).

CONCLUSIONS

Nicorandil infusion significantly (P = 0.007) reduced the incidence of intra-aortic balloon pump insertion in our series. In patients with left ventricular dysfunction (ejection fraction ≤ 30%), this difference (P = 0.008) assumes a special significance as off-pump bypass surgery is considered high risk in this subset. Nicorandil is an inexpensive drug, and the reduction in cost of surgery by avoiding intra-aortic balloon pump insertion is an added advantage. The use of nicorandil infusion during off-pump coronary artery bypass may result in favorable patient outcomes by reducing invasive intra-aortic balloon pump insertion during off-pump coronary artery bypass grafting.

Developments in surgical revascularization to achieve improved morbidity and mortality

Coronary artery bypass graft surgery remains the main treatment modality for multivessel coronary artery disease and has consistently been demonstrated to have significantly lower rates of major adverse cardiac and cerebrovascular events in comparison to percutaneous coronary intervention. In this article we will explore the advances over time and the recent refinements in the techniques of surgical revascularization and how these contribute to the superior outcome profile associated with coronary artery bypass graft surgery. These include the current outcome status of coronary artery bypass grafting; the major landmark trials, registries and meta-analyses comparing coronary artery bypass grafting and percutaneous coronary intervention; the developments in coronary artery disease lesion classification; the techniques for the physiological assessment of coronary artery lesions; bypass grafting using arterial conduits; the role of off-pump coronary artery surgery; the outcomes of reoperative surgery; hybrid techniques for coronary revascularization; minimally invasive coronary artery surgery and finally robotic surgery.

Risk Stratification in Off-Pump Coronary Artery Bypass (OPCAB) Surgery—Role of EuroSCORE II

OBJECTIVES

To evaluate the EuroSCORE II for risk stratification in patients undergoing off-pump coronary artery bypass (OPCAB) surgery.

DESIGN

A retrospective observational study.

SETTING

Two tertiary care hospitals.

PARTICIPANTS

Participants were 1,211 patients undergoing OPCAB surgery.

INTERVENTIONS

No interventions were implemented.

MEASUREMENTS AND MAIN RESULTS

The EuroSCORE II estimated the operative risk for each patient. The calibration of the scoring system was assessed using the Hosmer Lemeshow test, and the discriminative capacity was estimated with area under receiver operating characteristic curves. The incidence, patient characteristics, causes of intraoperative conversion to on-pump coronary artery bypass (ONCAB), and outcome were studied. The all-cause in-hospital mortality was 2.39%. Predicted mortality with the EuroSCORE II was 2.03±1.63. Using the Hosmer Lemeshow test, a C statistic of 8.066 (p = 0.472) was obtained, indicating satisfactory model fit. The calculated area under the receiver operating characteristic curve was 0.706 (p = 0.0002), indicating good discriminatory power. Emergency intraoperative conversion to ONCAB occurred in 6.53% of patients. The mortality in the ONCAB group was significantly higher compared with patients who underwent successful OPCAB surgery (15.18% v 1.5%, p<0.0001). On multiple regression analysis with conversion to ONCAB as the endpoint, associated factors were patients with a higher EuroSCORE II (odds ratio = 1.13, confidence interval = 1.03-1.27) and more-than-trivial mitral regurgitation (odds ratio = 1.84, confidence interval = 1.07-3.06). Net reclassification improvement of 0.714 (p<0.0001) was obtained when on-pump conversion was added to the EuroSCORE II.

CONCLUSIONS

The EuroSCORE II has satisfactory calibration and discrimination power to predict mortality after OPCAB surgery. Intraoperative conversion to ONCAB is a major complication of OPCAB surgery. A higher EuroSCORE II also predicts higher probability of conversion to ONCAB.

Is the evidence from first time off-pump coronary artery bypass graft surgery transferable to re-operative off-pump surgery?

On-pump coronary artery surgery remains the gold standard treatment for multi-vessel disease. The technique of off-pump surgery has evolved since its first use; however, currently less than 20% of all cases worldwide are performed this way. This poor uptake has been both the cause and the effect of widespread scepticism regarding the validity of the data on the technique, as well as criticism regarding the conversion-related adverse outcomes, graft patency and completeness of revascularisation. Consequently, there has been focus on patient selection from subgroups most likely to benefit from the technique. Re-operative patients, by virtue of their advanced age, complex co-morbidities and the technical challenges of re-operation, fall into this category. In this review, the authors will discuss the outcomes of off-pump surgery in comparison to on-pump, explore the potential beneficial effects of off-pump in re-operative surgery and formulate a decision-making strategy in patients undergoing reoperative coronary artery surgery.

Off-pump coronary surgery: current justifications

Although the literature has failed to project an overall superiority of off-pump vs. on-pump surgery, nevertheless, small randomized control trials and large meta-analysis studies have concluded that the incidence of a stroke is less than 1 % when anaortic off-pump techniques are advocated in patients with diseased ascending aorta. Furthermore, off-pump techniques or their combination with hybrid procedures may lead to a reduction of adverse outcome in the aged high-risk population with concomitant poor left ventricular function and co-morbidities. However, despite this, controversy still exists among the cardiac surgery community in terms of the benefit of this technique and its safety; hence, off-pump is becoming out of fashion. In this review paper, by looking at a "marginal group of patients" (elderly, high risks, atherosclerotic aortas) we attempt to re-establish and justify this technique and re-invent its usage.

Intraaortic balloon pump boon for off-pump coronary artery bypass grafting

Background

Off-pump coronary artery bypass techniques have evolved in the past decade, but there are some concerns about hemodynamic decompensation requiring conversion to cardiopulmonary bypass. These conversions are associated with higher morbidity and mortality. We use an intraaortic balloon pump to treat ischemia-induced hemodynamic instability and arrhythmias during off-pump coronary artery bypass. The objective of this study was to assess the impact of intraaortic balloon pump use in off-pump coronary artery bypass to prevent emergency conversion to cardiopulmonary bypass.

Methods

Data of 529 consecutive unselected patients who underwent isolated coronary artery bypass were included in this retrospective study of prospectively collected data and operation notes. Complete revascularization was performed using an off-pump technique. All arterial grafts using bilateral internal mammary arteries, and aortic no-touch technique were preferred. If the clinical situation demanded, vein grafts were used. During the procedure, any hemodynamic compromise not responding to conventional inotropic therapy was treated with intraaortic balloon pump insertion.

Results

Complete revascularization was possible in all 529 patients. An intraaortic balloon pump was inserted in 33 (6.2%) patients to treat hemodynamic instability; in all cases, conversion to cardiopulmonary bypass was avoided and complete revascularization was achieved.

Conclusion

For treating hemodynamic instability during off-pump coronary artery bypass, we recommend intraaortic balloon pump insertion as the preferred bail-out method rather than conversion to cardiopulmonary bypass.

Off-pump surgery: is it beneficial in patients with left ventricular dysfunction?

On-pump coronary artery bypass surgery remains the gold standard for complex multivessel disease. Off-pump revascularization has matured as a technique over the last twenty years, but is used in less than 20% of cases worldwide. The poor uptake has been attributed to the significant learning curve in learning the procedure and conflicting evidence reports, together with concerns over mortality related conversion, graft patency and completeness of revascularization. Given these concerns, patient selection continues to be paramount and the subgroups that benefit most are hotly debated. Patients with left ventricular dysfunction constitute a high-risk subgroup which is enlarging in size. There is some evidence to suggest that avoidance of cardiopulmonary bypass in this group may lead to superior results in terms of early mortality, non-cardiac complications and organ dysfunction. Even with the theoretical risk of incomplete revascularization, the technique may be an attractive option in managing high-risk patients.

Increasing Surgical Experience with Off-Pump Coronary Surgery Does Not Mitigate the Morbidity of Emergency Conversion to Cardiopulmonary Bypass

Objective

Emergency conversion during off-pump coronary artery bypass (OPCAB) confers significant morbidity. We sought to determine whether the outcomes in these patients have changed as our experience with off-pump techniques has increased.

Methods

Between January 1999 and December 2010, 4763 patients underwent coronary artery surgery. An off-pump strategy was attempted in 4415 cases (92.7%). The results of the most recent 50 patients who required emergency conversion were compared with the preceding 50 conversions and with patients who underwent either OPCAB (n = 2737) or on-pump coronary surgery (coronary artery bypass grafting) (n = 268) during the same time frame.

Results

The emergency conversion rate was 2.27% (n = 100), being 2.97% for the first 50 cases and 1.77% for the subsequent 50 patients. The two sequential groups of emergency conversions had similar indications and timing of conversion and comparable outcomes. When compared with patients who underwent OPCAB, the more recent 50 conversions had higher mortality (P = 0.002) and more frequent sternal wound infection (P = 0.036), hemorrhage requiring reoperation (P = 0.003), respiratory failure (P < 0.0001), and all-cause sepsis (P = 0.001). Compared with the on-pump group, the more recent conversions had higher mortality (P = 0.055) and a greater rate of postoperative sepsis (P = 0.002).

Conclusions

The incidence of emergency conversion during OPCAB has decreased with increasing surgical experience; however, the morbidity in these patients remains essentially unchanged. The outcomes in these patients remain worse than those in nonconverted patients. Safer bailout strategies during OPCAB are still warranted.

Off-pump coronary artery bypass grafting in a low-volume center

BACKGROUND

The advantages of off-pump coronary artery bypass grafting (OPCAB) are well documented; however, the conversion of OPCAB to cardiopulmonary bypass (CPB) is associated with higher morbidity and mortality. This issue is of particular concern in low-volume centers or centers that are beginning to use OPCAB. We present an OPCAB methodology that uses a maximum number of arterial grafts.

METHODS

We routinely use OPCAB in every patient unless there is another associated condition. We used the following methods to improve the safety of OPCAB: (1) maintaining normothermia, (2) routine use of a pulmonary artery catheter, (3) routine use of a femoral arterial line, (4) routine use of a cell saver, and (5) complete revascularization.

RESULTS

We included 173 consecutive patients in the study. All patients underwent OPCAB without any conversion to CPB. Hemodynamic compromise in 5 patients (2.89%) required insertion of an intra-aortic balloon pump (IABP). OPCAB was completed in all 5 patients after IABP insertion. Blood transfusions (BTs) were avoided in 55 patients (31.8%), and 68 patients (39.3%) required ≤2 units of blood.

CONCLUSION

The OPCAB technique is still evolving. Low-volume centers have higher rates of conversion to CPB. Hypotension due to an impaired left ventricular function can be successfully treated by using an IABP. Although blood loss can be managed with BTs, use of a cell saver helps to reduce the number of BTs. We conclude that our technique of total arterial OPCAB using a cell saver can be safely performed in a low-volume center.

Wide sternal retraction may impede internal mammary artery graft flow and reduce myocardial function during off-pump coronary artery bypass grafting: presentation of two cases

The internal mammary artery (IMA) is routinely used for grafting of the left anterior descending coronary artery (LAD), providing good flow to the anterior left ventricle (LV) wall. Impeded IMA-to-LAD flow may result in myocardial ischaemia and haemodynamic deterioration. From a study population, we describe two incidents where myocardial ischaemia was observed during off-pump coronary artery bypass surgery (CABG), with a confirmed reduction in the IMA-to-LAD flow in one patient. In patient no. 1, normal IMA flow was assessed by transit-time flow measurement after a complete IMA-to-LAD anastomosis. The anterior LV wall thickening was monitored continuously by epicardial ultrasonic transducers. Normal wall thickening was confirmed after IMA grafting. During a wide sternal opening for circumflex grafting the anterior wall motion displayed an ischaemic pattern, with reduced systolic and increased post-systolic wall thickening. IMA flow was reduced simultaneously. When easing the sternal opening, IMA flow normalized, as did the motion pattern in the anterior LV wall. In patient no. 2, similar changes in wall thickening occurred during a wide sternal opening after IMA-to-LAD grafting. When easing the retractor, the wall thickening normalized. It is important for the surgeon to be aware of this possible cause of myocardial ischaemia, with a risk of subsequent haemodynamic deterioration. This may not only be of great importance during off-pump CABG, but can also be significant for successful weaning from the cardiopulmonary bypass machine.