Asian Cardiovasc Thorac Ann 2008;16:473-478
© 2008 Asia Publishing EXchange Ltd
Off-Pump Coronary Revascularization for Left Main Coronary Artery Stenosis
Gopichand Mannam, FRCS(CT),
Lokeswara R Sajja, MCh,
Satya BR Dandu, MCh,
Satyendra N Pathuri, MCh,
Krishnamurthy VSS Saikiran, MCh,
Sriramulu Sompalli, MD1
Division of Cardiothoracic Surgery
1 Division of Cardiac Anesthesiology, CARE Hospital, The Institute of Medical Sciences, Hyderabad, India
For reprint information contact: Lokeswara R Sajja, MCh Tel: 91 40 6666 1935 Fax: 91 40 2332 7025 Email: sajjalr{at}yahoo.com, Division of Cardiothoracic Surgery, CARE Hospital, The Institute of Medical Sciences, Road No.1, Banjara Hills, Hyderabad-500034, India.
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ABSTRACT
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Experience of on- and off-pump coronary artery bypass in 379 patients with significant left main coronary artery stenosis was retrospectively reviewed. Beating-heart operations were performed on 219 patients between January 2001 and October 2007. Their results were compared with 160 who underwent revascularization under cardiopulmonary bypass during the same period. All patients had multivessel grafting via a median sternotomy. Both groups were comparable demographically. Off-pump patients received significantly fewer grafts per patient (3.21 ± 0.86 vs 3.74 ± 0.82). The use of moderate or high doses of inotropics (> 5 µ g · kg–1 · min–1) was more frequent in the on-pump group (44% vs 26%). Postoperative blood transfusion requirement was lower in off-pump patients, and fewer of them experienced worsening of preexisting renal insufficiency. There were 2 operative deaths in the on-pump group and 1 in the off-pump group. The off-pump procedure is safe and effective in patients with left main coronary artery disease.
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INTRODUCTION
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The first clinical description of left main coronary artery (LMCA) disease was by James Herrick1 in 1912. Several observational and randomized studies have documented that patients with LMCA stenosis have improved survival following surgery, compared to those treated medically.2,3 Left main cornary artery stenosis has been identified as an independent predictor of postoperative morbidity and mortality after coronary artery bypass grafting (CABG).4,5 However, significant (
50%) LMCA stenosis is considered a definite indication for surgical myocardial revascularization, regardless of symptoms. Off-pump coronary artery bypass (OPCAB) has emerged as an effective alternative to conventional CABG using cardiopulmonary bypass (CPB).6,7 CPB has been associated with risks of coagulopathy, neurological dysfunction, and increased release of inflammatory mediators.8–10 Until recently, LMCA stenosis was considered to be a relative contraindication to OPCAB, but it is now increasingly performed in such cases.11–13 This retrospective study was undertaken to evaluate the feasibility and safety of OPCAB in patients with significant LMCA stenosis.
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PATIENTS AND METHODS
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Between January 2001 and October 2007, primary CABG was carried out in 4,199 patients at our institution, of whom 379 had significant LMCA stenosis, defined as > 50% stenosis, in accordance with the Society of Thoracic Surgeons’ National Database. Preoperative, intraoperative, and postoperative data were collected in the Dusk Database (developed in Microsoft Access). Early outcomes were compared in patients who underwent OPCAB and those who had on-pump CABG (conventional CABG, CCAB). All except 22 patients were eligible for revascularization by either technique. Patient characteristics did not deliberately influence their assignment to a specific technique. The patients choose OPCAB or CCAB under CPB after the merits and drawbacks of both procedures were explained to them. The surgeons choose on-pump CABG in 18 patients with small and diffusely diseased epicardial coronary arteries. On 4 occasions, OPCAB was chosen by the surgeons because the ascending aorta was severely atherosclerotic. Of the 379 patients with LMCA disease, 219 (58%) had OPCAB and 160 (42%) underwent CABG under CPB.
All patients were operated on through a standard median sternotomy. The internal thoracic artery and long saphenous vein were harvested in the standard fashion, and radial artery conduits were harvested by our extrafascial technique.14 In OPCAB, elevation of the heart was accomplished using 3 deep pericardial traction sutures: 2 were placed on the left side 1 cm anterior and parallel to left phrenic nerve, and the 3rd to the left of the inferior vena cava. A Medtronic Starfish cardiac positioner (Medtronic, Inc., Minneapolis, MN, USA) was used to aid access to the coronary arteries. A Medtronic Octopus version 3 or 4 stabilizing device was employed to achieve target coronary artery stabilization. The mean systemic arterial pressure was maintained at 65–70 mm Hg throughout the procedure. An intracoronary shunt was used while constructing all coronary anastomoses. A humidified carbon dioxide blower/mister (Medtronic, Inc., Grand Rapids, MI, USA) was employed to disperse blood from the anastomotic site while constructing the distal anastomoses. The left anterior descending coronary artery (LAD) was grafted first using the left internal thoracic artery (LITA), followed by the obtuse marginal branches of the left circumflex artery, or the right coronary artery or its branches, whichever was most critically narrowed, followed by arteries with less critical stenoses. The LAD anastomosis was easily accomplished with minimal manipulation of the heart and without significantly compromising hemodynamics. When more than 1 critically stenosed obtuse marginal branch was to be bypassed, completion of the first distal anastomosis with a vein graft was followed by proximal anastomosis of the graft to the ascending aorta, and subsequent distal anastomoses of other obtuse marginal branches. For patients with left ventricular dysfunction, this strategy works better because lifting the left ventricle vertically for a longer period to complete 2 or more distal anastomoses to the obtuse marginal branches may not be well tolerated. When performing on-pump CABG, every effort was made to minimize the deleterious effects of CPB. All diabetic patients received infusions of insulin-glucose-potassium solution throughout the procedure. Myocardial protection was achieved with either intermittent ischemic fibrillatory arrest or cold blood cardioplegia. The patients were cooled to 32°C. A Myotherm cardioplegia system (Medtronic, Inc., Minneapolis, MN, USA) was used to deliver intermittent cold (4°C–8°C) blood high-potassium (4:1) cardioplegia antegradely.
Comparisons of baseline characteristics between groups were carried out using the Student t test for continuous variables and the chi-squared test for categoric variables. Standard statistical tests were used to calculate odds ratios and 95% confidence intervals. The p values were calculated by Fisher’s exact test. The results are reported as mean ± standard deviation or as absolute frequencies and proportions. Statistical significance was defined as a p value < 0.05.
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RESULTS
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Preoperative data are given in Table 1
. Either LITA or right internal thoracic artery (RITA) was used to graft the LAD in all patients in both groups. RITA was used to graft the LAD in 12 patients, and the RITA limb of a LITA and RITA Y-graft was used to graft obtuse marginal branches in 9 patients. Fourteen patients in the OPCAB group and 18 in the CCAB group received radial artery grafts to obtuse marginal branches. Intraoperative details are listed in Table 2. The OPCAB group spent less time in the operating room. Two (0.9%) OPCAB patients were converted to on-pump CABG; both remained in the OPCAB group for comparison as this was an intention-to-treat analysis. Both patients survived the procedure. Postoperative adverse outcomes are listed in Table 3. There was no significant difference in the incidence of new-onset renal failure, but significantly more patients suffered worsening of preexisting renal insufficiency in the conventional CABG group. The odds for nondiabetic patients, non-hypertensive patients, emergency or urgent surgery, and preoperative balloon pump use were significantly different for inotropic requirement between off-pump and on-pump groups (Table 4). The incidence of a trial fibrillation (AF) was similar in both groups, except for nondiabetic patients (Table 4). Preoperative left ventricular ejection fraction, glomerular filtration rate, functional class, emergency or urgent surgical priority had no influence on the incidence of AF, but patients without peripheral vascular disease in the OPCAB group had a lower incidence of AF. There was significantly lesser use of homologous blood in OPCAB patients, although there was no difference in the protocol for blood transfusion requirements between groups; all patients with hemoglobin < 9.0 g · dL–1 were given homologous blood. Aprotinin was not used routinely in either group, and only 3 patients in the on-pump group received aprotinin postoperatively for excessive mediastinal bleeding.
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Table 4. Postoperative Data According to Procedure, Adjusted for Propensity Score for Postoperative Inotropic Usage and Atrial Fibrillation
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DISCUSSION
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The specific clinical significance of critical LMCA stenosis within the context of atherosclerotic coronary disease has been highlighted over the past 2 decades. The fact that the left ventricle receives approximately 80% of its blood supply from the LMCA renders its critical stenosis potentially the most lethal form of coronary disease. The natural history of critical LMCA stenosis has revealed a poor prognosis in non-surgically treated patients; critical LMCA stenosis remains a primary indication for surgical revascularization.2,15,16
There has been a surge in off-pump CABG in the last decade as mechanical stabilizers have become available, and reports from institutions performing large numbers of revascularization procedures without CPB have confirmed the safety and efficacy of this procedure, with mortality rates of 0%–2.5%.6,17,18 Nathoe and colleagues16 concluded that OPCAB was more cost effective than on-pump CABG, and there was no significant difference in cardiac outcomes between the 2 groups; their 1-year mortality rate was 1.4% in the OPCAB group.
The mortality rate of 0.5% in our OPCAB group was less than the Society of Thoracic Surgeons’ predicted mortality (4.2%) for this population. We postulated that hemodynamic disturbances would be overcome by revascularizing the LAD using LITA as the first anastomosis, which would transform LMCA disease to non-LMCA disease. In addition, implementation of newer stabilizing devices, pericardial traction sutures, and positioning the operating table as necessary to maintain hemodynamic stability, as well as the vigilance of cardiac anesthesiologists adept at using inotropics, pressors, and vasodilators, have further ensured smooth operative courses.
Hemodynamic fluctuations that occur while performing revascularization on a beating heart are well documented and have led to a reluctance of surgeons to perform OPCAB on patients with critical LMCA stenosis. Once perfusion of the LAD by the LITA graft has started, the patient tolerates revascularization of the lateral and inferior target coronary arteries in a similar fashion to that of patients with non-LMCA stenosis, even when the heart is lifted perpendicularly. The OPCAB group required inotropic support less frequently than the on-pump group, and this difference was more significant in nondiabetic patients. The incidence of postoperative AF in nondiabetic patients was also significantly less in the OPCAB group. In addition, the off-pump technique is more renoprotective than CABG under CPB because fewer patients showed worsening of preexisting renal insufficiency, in agreement with our earlier report.19 The safety and efficacy of OPCAB has been reported by several authors, and comparative data are shown in Table 5.20
It is evident that an increasing number of surgeons are realizing the widespread applicability of the OPCAB technique, particularly in patients with multiple comorbidities. LMCA stenosis is no longer a contraindication to OPCAB, and early outcomes of this technique are comparable to those of conventional on-pump CABG. Furthermore, OPCAB is better for preserving renal function in patients with preexisting renal insufficiency.
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ACKNOWLEDGMENTS
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We sincerely thank Mr A Nadamuni Naidu, MSc(Stat), Head (Rtd), Department of Statistics National Institution of Nutrition, ICMR, Hyderabad, India, for statistical analysis of the data, Mr N Subba Rao, BCom, of CARE Foundation, Hyderabad, and Mr G Arun Babu, MBA, Star Hospitals, Hyderabad for preparation of the manuscript.
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ABSTRACT
INTRODUCTION
