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ORIGINAL CONTRIBUTIONS |
| Department of Cardiovascular Surgery Escorts Heart Institute and Research Centre New Delhi, India |
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| For reprint information contact: Zile S Meharwal, MCh Tel: 91 11 682 5000 Fax: 91 11 682 5013 email: meharwal{at}hotmail.com Department of Cardiovascular Surgery, Escorts Heart Institute and Research Centre, Okhla Road, New Delhi 110025, India. |
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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CABG without CPB is gaining popularity, and the results are encouraging.8 This technique is now being used for high-risk patients, including patients with poor ventricular function, advanced age, renal dysfunction, and a history of stroke. The morbidity and mortality have been reported to be lower than in patients operated on CPB.9
In the present study, we analyze our results of off-pump CABG (OPCAB) in terms of perioperative morbidity and mortality and compare them with conventional CABG on CPB (CCAB).
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PATIENTS AND METHODS |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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In addition to routine preoperative investigations required for CABG, all patients had carotid artery duplex scanning for associated carotid artery disease and transesophageal echocardiography (TEE) to detect atheromatous disease in the aorta.
In OPCAB, the patient was operated through a median sternotomy. The left internal mammary artery (LIMA) was harvested as a pedicled graft in most patients together with its veins by standard techniques using hemoclips. The patient was heparinized with a dose of 1.5 mgákg–1. An Octopus tissue stabilization system (Medtronic, Inc., Minneapolis, MN, USA) or a CTS MIDCAB Access Platform and Stabilizer (Cardiothoracic Systems, Cupertino, CA, USA) was used to stabilize the target coronary vessel. An intracoronary shunt (Anasta Flo Intravascular Shunt; Baxter Healthcare, Irvine, CA, USA) was used for most of the distal anastomoses together with an oxygen blower. Hemodynamics were monitored through a Swan-Ganz catheter, with continuous measure-ments of arterial pressure, central venous pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac index, stroke volume, and systemic vascular resistance. Global and regional left ventricular function before, during, and after surgery was evaluated by TEE.
The sequence of grafting was individualized based on the patient’s hemodynamics. In most cases, the left anterior descending (LAD) artery was the first to be grafted, followed by the right coronary artery and lastly the vessels on the lateral and posterior walls. The LAD and the right coronary artery can be grafted without much displacement of the heart. To expose the circumflex vessels, 3 pericardial traction sutures were used to pull the heart vertically. The right pleura was opened, followed by vertical pericardio-tomy to allow the heart to herniate to the right chest under the sternum. Other maneuvers, such as the Trendelenburg position and tilting the table, were performed as required. Inotropes were used as and when necessary during surgery. The distal anastomosis was made using 7/0 or 8/0 polypropylene sutures.
Proximal anastomosis was performed using standard techniques. The aorta was palpated before applying a partial occlusion clamp. Aortic atherosclerosis was assessed by intraoperative TEE. Recently, we have also started using epiaortic scanning to assess the proximal aorta. If there was any evidence of significant aortic atherosclerosis, aortic clamping was avoided and anastomosis to the LIMA pedicle was made. The aortic pressure was reduced to a systolic pressure of 70 to 80 mm Hg before applying the partial occlusion clamp. Sutures of 6/0 polypropylene were used for anastomosis.
In CCAB, CPB was established using ascending aortic and two-stage venous cannulation. The LIMA and veins were harvested by standard techniques. The patient was not actively cooled, but temperature was allowed to drift. Most of the patients (94.3%) were operated under warm-blood cardioplegic arrest using antegrade or a combination of antegrade and retrograde cardioplegia. Cardioplegia was repeated after every distal anastomosis. The other patients (5.7%) were operated on CPB without arresting the heart (empty beating heart). Hemodynamics were monitored as in OPCAB.
Data are reported as mean ± standard deviation. Categorical variables were analyzed by the chi-squared test and Fisher’s exact test. Unpaired Student’s t test was used to compare intergroup means. A p value < 0.05 is considered significant. Variables that are not normally distributed were compared using the Mann-Whitney U test.
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RESULTS |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. The groups were comparable in preoperative risk factors. The findings of coronary angiography were comparable between the groups (Table 2). Triple-vessel disease was found in 87.6% of OPCAB patients and 88.7% of CCAB patients.
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). The average number of grafts in the CCAB group was significantly higher than in the OPCAB group. This difference was more marked in the first 2 years of study, but there was no statistically significant difference in the last 2 years of study. This reflects more caution in the initial period of off-pump surgery. Total operating time was significantly shorter in the OPCAB group.
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). Many patients in this group required some inotropic support during anastomosis to the vessels on the lateral and posterior walls, although with proper positioning of the heart and utilization of appropriate maneuvers, most anastomoses could be performed with minimal or no inotropic support.
Postoperative results are shown in Table 4. Operative mortality was lower in the OPCAB group, but it did not reach statistical significance. There were 18 deaths in the CCAB group. Low cardiac output was the most common cause of death, occurring in 8 patients, 5 of whom had left ventricular ejection fraction < 30%. The other causes of death were stroke in 1 patient, mesenteric ischemia in 2, respiratory failure in 3, septicemia in 1, renal failure in 1, and multiorgan failure in 2. Of the 4 deaths in the OPCAB group, 2 were due to low cardiac output and 1 each to septicemia and respiratory failure. The OPCAB group fared better in intubation time, length of intensive care unit stay, reoperation for bleeding, postoperative blood loss, the need for transfusion of blood or blood products, the incidence of postoperative atrial fibrillation (AF), and the total hospital stay.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The incidence of postoperative complications was lower in our OPCAB group, as has been found by other studies.9,12 The greater need for blood transfusion in the CCAB group is likely related to inflammatory and coagulopathic sequelae intrinsic to CPB as well as the hemodilution effect of the pump-priming fluid. We tend to use the blood cell saver in patients who have low preoperative hematocrit.
Boyd and colleagues12 reported a lower incidence of AF and low output syndrome in OPCAB. We too observed a lower incidence of AF in OPCAB patients. AF is considered a major factor for increased morbidity and mortality and prolonged hospital stay after CABG.13 The length of stay in the intensive care unit and in the hospital was shorter in our OPCAB group.
Adverse cerebral outcomes after CABG increase dramatically in elderly patients and are believed to be largely due to CPB and aortic manipulation. One study reported a 9.3% stroke rate in octogenarians operated on CPB but zero in the off-pump group.14 None of our OPCAB patients had stroke, while it occurred in 0.5% of the CCAB patients. The causes of perioperative stroke are multifactorial and include a history of stroke, age, CPB and aortic crossclamping time, aortic atherosclerosis, urgency of operation, and hypertension.15
The incidence of neurologic injury, in particular neuropsychologic impairment, was found to remain high after CPB. One-third of patients exhibited long-term cognitive deficit, and the principal cause of impairment is thought to be diffuse microischemia secondary to cerebral embolism.16 One study found that neurocognitive function was impaired in both off-pump and on-pump patients at discharge, but it improved significantly in both groups at 3 months.17 Another study reported that CCAB was associated with a substantial risk of protracted neurobehavioral decline, the magnitude of which was significantly greater than that observed in the age-matched general population.18
OPCAB avoids cannulation and crossclamping of the aorta, but partial occlusion clamping is used in proximal anastomosis. Proper screening of the aorta for atherosclerosis in elderly patients is therefore important to prevent embolization during the application and release of the partial occlusion clamp. TEE and epiaortic scanning are important tools for evaluating the aorta. Although palpation of the aorta, especially when the pressure is low, is fairly sensitive in identifying calcification or signifi-cant discrete atheroma, it is a poor technique for identifying diffuse atheromatous thickening or soft endophytic lesions.19 Epiaortic scanning has been found to be a sensitive means of identifying aortic pathology.20 The surgical technique can be modified according to aortic pathology, and this can decrease the incidence of stroke.
Concerns have been raised regarding the completeness of revascularization with OPCAB. These concerns have been based mainly on the difficulty of grafting vessels on the lateral and inferior walls of the heart. In our study, the average number of grafts in the OPCAB group was less than in the CCAB group in the initial period, but there is now no difference. Complete myocardial revascularization on the beating heart can be accomplished safely and effectively using currently available mechanical stabilizers, intracoronary shunts, and suitable maneuvers.
In summary, OPCAB is safe and effective in elderly patients. It is associated with lower perioperative morbidity and mortality. Proper assessment of the aorta using TEE and epiaortic scanning is important.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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This article has been cited by other articles:
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  S. G Raja and G. D Dreyfus Current Status of Off-pump Coronary Artery Bypass Surgery Asian Cardiovasc Thorac Ann, April 1, 2008; 16(2): 164 - 178. [Abstract] [Full Text] [PDF]
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 T. Athanasiou, O. Aziz, O. Mangoush, A. Weerasinghe, S. Al-Ruzzeh, S. Purkayastha, J. Pepper, M. Amrani, B. Glenville, and R. Casula Do off-pump techniques reduce the incidence of postoperative atrial fibrillation in elderly patients undergoing coronary artery bypass grafting? Ann. Thorac. Surg., May 1, 2004; 77(5): 1567 - 1574. [Abstract] [Full Text] [PDF]
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T. Athanasiou, S. Al-Ruzzeh, P. Kumar, M.-C. Crossman, M. Amrani, J. R. Pepper, R. Del Stanbridge, R. Casula, and B. Glenville Off-pump myocardial revascularization is associated with less incidence of stroke in elderly patients Ann. Thorac. Surg., February 1, 2004; 77(2): 745 - 753. [Abstract] [Full Text] [PDF]
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