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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 1  |  Issue : 2  |  Page : 50-55

Off-pump coronary artery bypass surgery: Intra-aortic balloon pump aides multivessel revascularization in high-risk patients


1 Department of Surgery, Wellstar Atlanta Medical Center, Atlanta, USA
2 Section of Cardiology, Morehouse School of Medicine, Atlanta, USA
3 Wellstar Kennestone Regional Medical Center, Marietta, GA, USA

Date of Web Publication16-Dec-2016

Correspondence Address:
Jonathan Nwiloh
Department of Surgery, Wellstar Atlanta Medical Center, Atlanta, GA
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2468-7391.195929

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  Abstract 

Objective: Off-pump coronary artery bypass (OPCAB) has been demonstrated to be a safe technique with similar outcomes to on-pump coronary artery bypass (ONCAB) in low-risk patients, while its role and benefits in high-risk patients are the subject of ongoing clinical trials. This review compares our high-risk patients aided by intra-aortic balloon pump (IABP) with low-risk patients undergoing OPCAB to identify any differences in outcomes. Materials and Methods: One hundred and twenty-four patients who underwent OPCAB surgery between January 2004 and December 2013 were retrospectively reviewed. 61.3% were males, 57.3% were African Americans, mean age was 62.7 ± 13.3, and range was 30-90 years. Patients were divided into Group 1, 26 (21.0%) patients with IABP and Group 2, 98 (79.0%) patients without IABP. Group 1 patients had higher risk profile with mean ejection fraction (EF) 26.0 ± 10.8 and EF ≤20 present in 46.1% compared to 45.2 ± 11.9 and 5.1%, respectively, in Group 2 (P < 0.001). Results: 92.35% of Group 1 and 82.7% of Group 2 patients had multivessel disease with a mean number of bypass grafts 2.9 ± 0.97 versus 2.75 ± 0.8, respectively (P < 0.364). Left internal mammary artery (LIMA) to left anterior descending (LAD) was performed in all Group 1 and 97.9% of Group 2 patients, with saphenous vein graft (SVG) to the left circumflex and right coronary arteries in 73.1% versus 62.2% and 57.7% versus 52.0% of Groups 1 and 2, respectively. Complete revascularization occurred in 88.5% and 90.8% of Groups 1 and 2, respectively (P < 0.990). 4.0% were converted to ONCAB for either hemodynamic instability or intramyocardial coronary artery. Major morbidities were re-exploration for bleeding 3.8% versus 1.0%, stroke 3.8% versus 2.0%, acute kidney injury 11.5% versus 0%, and prolonged intubation 15.4% versus 2.0% in Groups 1 and 2, respectively. Euroscore II predicted (P) versus observed (O) mortality was 4.56% versus 4.03%, for Group 1, 7.82% versus 7.69% and Group 2, 3.64% versus 3.06%, and O/P ratios 0.88, 0.98 and 0.84 respectively. Two (2.0%) females in Group 2 with single LIMA to LAD underwent repeat revascularization with SVG to the LAD within 90 days. Conclusion: IABP helps stabilize hemodynamics during OPCAB in high-risk patients with moderate to severe left ventricular dysfunction. Mean number of bypass grafts and predicted versus observed mortality were similar between the low- and high-risk groups.

Keywords: Coronary artery disease, Intra-aortic balloon pump, off-pump coronary artery bypass surgery


How to cite this article:
Nwiloh J, Oduwole A, Hernandez E. Off-pump coronary artery bypass surgery: Intra-aortic balloon pump aides multivessel revascularization in high-risk patients. Niger J Cardiovasc Thorac Surg 2016;1:50-5

How to cite this URL:
Nwiloh J, Oduwole A, Hernandez E. Off-pump coronary artery bypass surgery: Intra-aortic balloon pump aides multivessel revascularization in high-risk patients. Niger J Cardiovasc Thorac Surg [serial online] 2016 [cited 2020 Dec 5];1:50-5. Available from: http://www.nigjourcvtsurg.org/text.asp?2016/1/2/50/195929


  Introduction Top


Coronary artery disease (CAD) is the leading cause of cardiovascular death in developed nations, and it's incidence is also rising in underdeveloped nations with modernization and adoption of western lifestyles. [1] Coronary artery bypass graft surgery (CABG) for treatment of CAD was first performed in 1964 by Garrett et al. [2] in Houston although not reported until 1973. Subsequently, Favalaro from the Cleveland Clinic independently performed the first saphenous vein bypass graft in May 1967 and by December had accumulated the largest clinical series in the World of 171 patients. [3],[4] Subsequently, balloon angioplasty evolved and was first successfully performed in humans by Andreas Gruentzig in September 1977, [5] and presently, percutaneous coronary intervention (PCI) is the most common revascularization strategy for ischemic heart disease, with surgery reserved mainly for complex multivessel disease. Off-pump coronary artery bypass surgery (OPCAB) later developed in the early 1990s [6] was promoted as been less invasive than on-pump coronary artery bypass surgery (ONCAB) and therefore likely to reduce the morbidity and mortality associated with cardiopulmonary bypass.


  Materials and Methods Top


The medical records of 124 patients who underwent OPCAB surgery by a single surgeon from January 2004 to December 2013 were retrospectively reviewed. There were 76 (61.3%) males and 48 (38.7%) females with a mean age of 62.7 ± 13.3, range 30-90 years. Seventy (57.3%) patients were African Americans and 53 (42.7%) patients Caucasians. Twenty patients (16.1%) had left main stenosis >50% and 65 (52.4%) patients had triple vessel disease. The mean ejection fraction (EF) was 41.0 ± 14.1 and Euroscore II (ES) was 4.56 ± 4.90. Majority of the surgeries were urgent in 120 (96.8%) patients and emergent in 4 (3.2%) patients. The baseline preoperative demographics are summarized in [Table 1]. All surgeries were performed through a full median sternotomy and standard monitoring with radial arterial line, Swan-Ganz catheter, and transesophageal echocardiogram. The left internal mammary artery (LIMA), saphenous vein, and radial artery were harvested in the standard fashion and used as bypass conduits. Eight French sheathless intra-aortic balloon pump (IABP) with 35 or 40 ml balloon were inserted mostly percutaneously through the femoral artery before sternotomy in patients with moderate to severe left ventricular (LV) dysfunction deemed at higher risk for hemodynamic instability with manipulations and elevation of the heart. Cut down for exposure of the femoral artery was required in a few patients with unsuccessful attempts at percutaneous placement. IABP was inserted preoperatively in the cardiac catheterization laboratory in two patients with acute myocardial infarction complicated by cardiogenic shock and cardiac arrest, respectively. Intravenous heparin 1 mg/kg was administered to maintain activated clotting time >300 s. The distal anastomoses in target vessels were constructed with one of the stabilizing devices after occluding the coronary artery proximal to the arteriotomy site with deep myocardial bites using 5/0 Prolene suture looped twice around the coronary vessel and weighted down the side with 2-3 hemostat clamps. CO 2 blower was used as an adjunct to keep the operative field dry during construction of the anastomoses, and intracoronary shunts were not used. The LIMA to left anterior descending artery (LAD) anastomoses was usually performed first, followed by the left circumflex artery (LCX) and right coronary artery (RCA) territories. The proximal anastomoses were initially constructed in the early years with the hamstrings device but subsequently done with partial occluding clamp on the ascending aorta and making an aortic punch hole. Heparin was reversed with protamine on completion of all anastomoses. Patients were generally extubated within hours of surgery in the intensive care unit, and IABP weaned and removed within the next 24-48 h if patients were hemodynamically stable and on low-dose inotropes. All patients were started postoperatively on aspirin and Plavix if no known contraindications. Plavix was continued for 3 months after surgery and aspirin indefinitely. Operative mortality (OM) was regarded as death within 30 days of surgery or within the same hospitalization. All collected data were entered into an Excel Spreadsheet and then imported into the Sigma Plot (Systat Software Inc., San Jose, CA, USA) for statistical analysis. Categorical variables were reported as frequencies and percentages, whereas continuous variables were expressed as mean ± standard deviations. Univariate analysis by unpaired Student's t-test with two-tailed distribution was used for continuous variables, and Chi-square exact test or Fisher's exact test was used for categorical variables. P < 0.05 was considered statistically significant.
Table 1: Preoperative baseline demographics

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  Results Top


The overall mean number of grafts performed was 2.79 ± 0.84. There was no statistical difference in number of grafts between Group 1, 2.92 ± 0.97 versus 2.75 ± 0.81 in Group 2 (P < 0.364). LIMA was utilized in 100% of Group 1 and 97.9% of Group 2 patients. The LAD/diagonal territory was grafted in all patients in both groups, followed by the LCX in 73.1% and 62.2%, RCA in 57.7% and 52.0% of Groups 1 and 2, respectively [Table 2]. Complete revascularization was achieved in 88.5% and 90.8% of Groups 1 and 2, respectively. The reasons for incomplete revascularization were primarily due to either small coronary vessels <1 mm, diffuse disease, poor quality, or limited conduits. There was no statistically significant difference in the territories grafted or rate of incomplete revascularization between the two groups. The only one radial artery used was grafted to the LAD in a redo patient with an occluded LIMA from 6 years earlier. One patient with small OM vessels unsuitable for grafting had transmyocardial laser revascularization to the LCX territory. Another patient with complete occlusion of the left internal carotid artery and near complete occlusion of the right internal carotid artery deemed unsuitable for carotid endarterectomy and at high risk for perioperative stroke had LIMA to the LAD followed postoperatively by PCI of the LCX. Five (4.0%) patients comprising one Group 1 and four comprising Group 2 patients were converted to on-pump for either hemodynamic instability or intramyocardial coronary anatomy. All ONCAB conversions were done on an empty beating heart except for one female with small intramyocardial LAD that required aortic cross-clamping with ischemic cardioplegic arrest. Three (11.5%) patients in Group 1 developed acute kidney injury (AKI) compared to none in Group 2 (P < 0.007). However, only one of the patients required temporary dialysis. Prolonged intubation was required in 15.4% of Group 1 compared to 2.0% of Group 2 (P < 0.021). Overall stroke rate was 2.4%. A watershed infarct occurred in one Group 1 patient, and two patients both 83 years old had a stroke in Group 2; 1 minor and 1 major with hemiplegia. Another 83-year-old patient in Group 2 who was converted to ONCAB for ventricular tachycardia and hypotension after the LIMA to LAD anastomosis had hypoxic encephalopathy on electroencephalogram postoperatively, and care was subsequently withdrawn as per patient's living will. Re-exploration for bleeding occurred in two (1.6%) patients, one of whom was on Plavix preoperatively. There were no complications associated with the IABP. Observed mortality was slightly lower than predicted by ES II, with overall OM 4.03% compared to 4.56% predicted, and in Group 1, 7.69% versus 7.82% and Group 2, 3.06% versus 3.64%. The observed to predicted ratios were overall 0.88, Group 1 0.98 and Group 2 0.84 [Table 3]. Two (2.0%) female patients in Group 2 both with small vessels had undergone previous single LIMA to LAD and returned within 90 days with recurrent angina and non-ST elevation myocardial infarction. Cardiac catheterization revealed anastomotic stenosis and LIMA spasm and both underwent redo surgical revascularization with saphenous vein graft (SVG) to LAD.
Table 2: Operative variables

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Table 3: Morbidity and mortality

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  Discussion Top


OPCAB surgery was reintroduced into clinical practice in the early 1990s with the hope that eliminating the risks of cardiopulmonary bypass associated with ONCAB would lead to lower morbidity and mortality. However, after several reports of higher rates of incomplete revascularization, lower graft patency, and higher repeat revascularization with OPCAB, the initial enthusiasm among surgeons began to wane. According to an abstract presented at the 2016 AATS annual meeting, Bakaeen et al. [7] in a review of 2,137,841 isolated CABGs from 1997-2012 in the STS database observed a decline in OPCAB over the last 5 years with fewer than 1 in 5 patients undergoing OPCAB. They also found that 86% of surgeons did 20 or less OPCAB a year in the US. Similarly, a status review of OPCAB by Abu-Omar and Taggart [8] estimates 20%-25% of patients undergo OPCAB in Europe, compared to a review of the Japanese experience by Yaku et al. [9] showing that over 60% of CABGs performed were OPCAB. Abu-Omar and Taggart [8] speculate that the reasons for this wide geographic disparity between the West and Asia are multifactorial and possibly may include socioeconomic, political, and clinical considerations. There are several reviews in the literature both for and against OPCAB, with rates of adoption varying depending on local practices. One of the strong advocates and early pioneers of OPCAB from Emory, Puskas et al. [10] reported excellent comparable results with no statistically significant difference in 1-year graft patency of 93.6% in OPCAB compared to 95.8% in ONCAB. Similarly, a multicenter randomized trial from the Netherlands found 1-year graft patency of 93% for ONCAB and 91% for OPCAB and concluded there was no difference in 1-year cardiac outcomes in low-risk patients. [11] However, a Veterans Affairs randomized trial of ON/OFF Bypass (ROOBY) [12] reported significantly worse outcomes with off-pump bypass. They observed complete revascularization in 50.1% versus 63.9%, 1-year arterial graft patency of 85.8% versus 91.4%, and SVG patency 72.7% versus 80.4% for off- and on-pump cohorts, respectively. Furthermore, the Danish multicenter randomized study (DOORS) found inferior 6-month vein graft patency 79% versus 86% in OPCAB and ONCAB, respectively, but similar LIMA patency of 95% in both cohorts. [13] While the debate and controversies on the advantages and disadvantages of OPCAB versus ONCAB continue, both revascularization strategies will likely continue to play a role in surgical revascularization depending on clinical and patient characteristics. [14],[15] Abu-Omar and Taggart [8] had noted that many of the early conducted randomized trials were on low-risk patients who are less likely to be negatively affected by the deleterious systemic effects of cardiopulmonary bypass and may not include the real world experience of many practicing surgeons who operate on higher risk patients. The full benefits of OPCAB they argue, therefore, maybe in high-risk elderly patients with significant atherosclerotic aorta with increased risk of stroke. Patel and Angelini [16] similarly agree that the greatest benefits of OPCAB with respect to morbidity and mortality are in high-risk patients which in their opinion includes ES >5, LV dysfunction, atherosclerotic aorta, age >75 years, left main stenosis, preoperative cerebrovascular disease, diabetes, renal failure, COPD, and acute myocardial infarction. They are hopeful that their ongoing OPCAB CRISP trial of high-risk patients with ES >5 will likely shed more light on the benefits in these group of patients. Meanwhile, the German GOPCABE trial enrolling 2539 elderly patients older than 75 years reported similar 30 days mortality, stroke, AKI requiring dialysis for OPCAB and ONCAB, but noted fewer bypass grafts and incomplete revascularization in the off-pump group. [17] The reasons for incomplete revascularization with OPCAB likely include hemodynamic instability, diffuse atherosclerotic disease, and small coronary arteries. Manipulation and lifting of the heart during OPCAB can cause significant fluctuations in filling pressures and cardiac output with resultant hemodynamic instability. [18] This impairment is likely to be less tolerated in the presence of severe LV dysfunction. To ameliorate these reductions in cardiac function and hemodynamic instability, many surgeons have used mechanical support with IABP as an adjunct to vasopressors in these high-risk patients to help achieve complete revascularization. [19],[20],[21],[22] IABP enabled completion of OPCAB in all Group 1 patients except one who had persistent hemodynamic instability and later required conversion to ONCAB on an empty beating heart to complete his quadruple bypass. The patient had a complicated postoperative course with AKI requiring temporary dialysis and later died. Another Group 2 patient who also required conversion to ONCAB following ventricular arrhythmia and severe hypotension developed hypoxic encephalopathy and died postoperatively. Overall five patients (4%) had conversion from OPCAB to ONCAB with two deaths (40%). The reported conversion rates are 1%-3% in centers specializing in OPCAB [23],[24] although the VA ROOBY trial reported a 12% conversion. Conversiton to ONCAB is known to increase morbidity and mortality as we also observed in our series. [23],[25] It is, therefore, crucial to select from the outset patients based on pathological anatomy likely to successfully undergo OPCAB, and to convert early to ONCAB if difficulties are encountered to reduce postoperative morbidity and mortality associated with persistent hypotension. Higher rates of myocardial infarction and repeat revascularization have been noted to occur with OPCAB in several series. [26],[27] The two patients in our series undergoing repeat revascularization within 90 days were females with small coronaries and LIMA, and one had both spasm of the LIMA and anastomotic stricture [Figure 1],[Figure 2] and [Figure 3]. It is possible that ONCAB might have resulted in a better anastomosis, but unclear if this would have made any difference in the persistent distal LIMA spasm despite intracoronary vasodilator seen on cardiac catheterization. Strong consideration should be given to converting scheduled OPCAB to ONCAB if unexpected small coronary artery, especially when intramyocardial is encountered after opening the chest. Despite the higher risk profile of Group 1 patients with approximately half having EF 20 or less, we observed no significant difference with the number of grafts and completeness of revascularization compared with the lower risk Group 2 patients. The observed mortality rates in both groups were also within that predicted by ES II. One of the added advantages of the OPCAB technique is the lower cost compared to ONCAB, with reported estimated savings per patient ranging between 14% and 25%. [11],[28],[29] This may be particularly of great importance in low-resource countries in developing countries where cost is a major obstacle to accessing high-tech medical interventions and surgeries. Although OPCAB is technically more challenging, with increasing surgical experience most patients with 1 or 2 vessels disease not amenable to PCI can probably undergo OPCAB in these low-resource countries, thereby allowing more patients receive care with lower cost. There is of course the added downside risk of possible lower graft patency with OPCAB compared to ONCAB. Although this review is limited due to small numbers and been retrospective, our results are consistent with some others showing that multivessel OPCAB can be performed in high-risk patients with ES >5 with mortality within predicted.
Figure 1: Preoperative left main coronary angiogram.

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Figure 2: Postoperative left internal mammary artery to left anterior descending angiogram.

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Figure 3: Postoperative saphenous vein graft to left anterior descending injection 6 years later.

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  Conclusion Top


Despite the relatively high-risk profile of Group 1 patients with very poor EF 20 or less in approximately half, the use of IABP aided multivessel OPCAB grafting of the three major coronary artery territories with lower than predicted mortality by ES II.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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