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Ann Thorac Surg 2007;83:115-119
© 2007 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan
b Department of Cardiovascular Surgery, Sakakibara Heart Institute, Tokyo, Japan
c Department of Cardiovascular Surgery, Shin-Tokyo Hospital, Chiba, Japan
Accepted for publication August 3, 2006.
* Address correspondence to Dr Fukui, Department of Cardiovascular Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka City, 545-8585, Japan (Email: tm-fukui{at}gem.hi-ho.ne.jp).
| Abstract |
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METHODS: We retrospectively reviewed the records of 602 consecutive patients (24.8% female) who underwent isolated off-pump coronary artery bypass grafting between April 2001 and July 2004. Mean age was 66.7 ± 9.3 years. Mean Canadian Cardiovascular Society score was 2.5 ± 0.9. Early postoperative angiograms were evaluated during the same period of hospitalization. Midterm outcomes, including overall patient survival, freedom from cardiac death, and freedom from the combined endpoint of cardiac events, were evaluated.
RESULTS: The average number of distal anastomoses per patient was 3.6 ± 1.4. The average operation time was 286.1 ± 72.1 minutes. Long segmental reconstruction of the left anterior descending coronary artery was performed in 218 patients (36.2%). Total arterial grafting was performed in 466 patients (77.4%). Thirty-day mortality was 0.5%. Overall patency rate for all grafts and anastomoses was 97.5% and 97.6%, respectively. Mean follow-up time was 2.9 ± 1.0 years. Cumulative patient survival at 5 years was 87.9% ± 2.4%. Freedom from cardiac death was 97.7% ± 0.6% at 5 years. Freedom from the combined endpoint of cardiac events was 83.8% ± 2.3% at 5 years.
CONCLUSIONS: Early and midterm outcomes after off-pump coronary artery bypass grafting have acceptable mortality and cardiac events rates, with favorable early graft patency rates.
| Introduction |
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| Patients and Methods |
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Complete revascularization was defined as "traditional" completeness in this study. "Traditional" completeness was defined as all diseased arterial systems (stenosis
50%) receiving at least one graft insertion [7]. Total arterial grafting was defined as no usage of saphenous vein graft (SVG) in the procedure.
Perioperative myocardial infarction was defined as a positive result for new Q waves in the electrocardiogram, or a peak level of creatine kinase MB greater than 10% of total creatine kinase. Low-output syndrome was defined as the need for greater than 5 µg · kg1 · min1 of inotropic agent (dopamine or dobutamine). Postoperative stroke was defined as a central neurologic deficit persisting for more than 72 hours, and was confirmed by computed tomography. In patients with preoperative stroke, postoperative stroke was defined as a worsening of neurologic deficit, with new radiologic findings. Postoperative renal insufficiency was defined as a new requirement for dialysis postoperatively. Patients who required blood transfusion in the present study included those who received not only red blood cells, but also platelets and fresh-frozen plasma.
Surgical Methods
Operations were performed by two surgeons with the same strategy decided by one surgeon (T.S.). All arterial grafts were harvested in a skeletonized fashion using an ultrasonic scalpel (Harmonic Scalpel; Ethicon Endosurgery, Cincinnati, OH), and taken down after milrinone solution (50 mg/L) was injected at the distal end. In situ grafts were divided after heparinization (300 IU/kg). Saphenous vein grafts were harvested using an open technique with fine scissors. The indication for performing bypass grafting was significant stenosis (
50% diameter reduction) in all coronary vessels larger than 1 mm in diameter. Composite and sequential grafting with arterial grafts is our preferred technique [8]. Saphenous vein grafts were used in vessels with nonsevere stenosis, and were not used in composite grafts. When an epiaortic echogram demonstrated ascending aortic atherosclerosis, an aortic no-touch technique was used.
A commercially available heart positioner and stabilizer were applied to the heart (Starfish and Octopus; Medtronic, Minneapolis, MN). A deep pericardial stay suture was not used. A bloodless field was obtained using a proximal silicone elastomer snare suture and a carbon dioxide blower. An intraluminal shunt was sometimes used for grafting to the right coronary artery. Each anastomosis was performed with an 8-0 polypropylene running suture using the parachute technique. When sequential grafting was constructed, diamond-shaped side-to-side anastomosis and terminal T-shaped anastomosis (right-angled anastomosis) were our preferred approaches. Terminal anastomosis was performed first, followed by sequential anastomoses toward the proximal portion of the graft. When a composite graft was constructed, an anastomosis between the donor and branched arteries was performed after all distal anastomoses were completed. As required, long segmental reconstruction of diffusely diseased left anterior descending coronary artery using the left internal thoracic artery was performed [9]. Furthermore, we performed long segmental reconstruction with endarterectomy in a left anterior descending coronary artery that had a severely calcified, long hard fibrous, or long soft plaque. We performed endarterectomy using a long arteriotomy in the left anterior descending coronary artery and grafted an onlay patch of the left internal thoracic artery. Technical details of these methods have been described previously [10]. We did not assess graft patency during the operation.
Anticoagulation was started on the first postoperative day. Patients who received SVGs were given low-dose aspirin (100 mg/day) and warfarin (maintained with a target international normalized ratio of 2.0). After 3 months, the administration of warfarin was stopped.
Angiographic Study
Postoperative angiography was performed to assess graft patency only in patients who gave informed consent, and before discharge at 7.5 ± 2.5 days after surgery. When patients were symptomatic during follow-up, diagnostic angiography was performed at that time. If a new lesion of native coronary artery or graft occlusion was found, percutaneous coronary intervention was performed if possible. Angiographic studies were reviewed and evaluated by two cardiologists.
Statistical Analysis
Continuous variables are reported as the mean ± standard deviation. Continuous variables were compared by Students t test. Discrete variables were compared by the
2 test or Fishers exact test. A logistic regression model was used to determine significant predictors of postoperative stroke. Explanatory variables included all variables in Table 1 and intraoperative aortic manipulation. Actuarial survival and event-free survival curves were estimated by the KaplanMeier method. Differences were considered statistically significant at a probability less than 0.05. Statistical analyses were performed using the StatView 5.0 software package (SAS Institute, Cary, NC).
| Results |
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Blood transfusions were undertaken in 35.4% of cases.
Early Outcome
Three patients died within 30 days (0.5%). One patient with multiple risk factors (hypertension, diabetes, hyperlipidemia, obesity, and Canadian Cardiovascular Society score 4) died of stroke 23 days after surgery. One patient who underwent repeat surgical revascularization with OPCAB died of sepsis 12 days after the second operation. One patient with chronic renal failure died of ventricular arrhythmia 12 days after surgery. Postoperative morbidity is shown in Table 3. The incidence of stroke was 1.5%. When the stroke rate was compared between patients with and without aortic manipulation, it was no different (1.4% versus 1.6%; p = 0.82). Furthermore, no factor was found to be a significant predictor of stroke when a logistic regression model was used. The mean intubation time was 10.7 ± 9.4 hours. Mean intensive care unit and postoperative hospital stays were 1.5 ± 1.2 and 13.6 ± 12.0 days, respectively. Postoperative ejection fraction was 0.561 ± 0.091.
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| Comment |
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To achieve complete myocardial revascularization is one of the important goals of CABG, although the definition of completeness differs among studies. Kleisli and colleagues [13] demonstrated that the 5-year survival rate of complete revascularization was superior to that of incomplete revascularization (82.4% versus 52.6%). In their report, the anatomic reasons for incompleteness were small, such as severely diseased, arteries, nondominant right coronary artery, the presence of prior infarcted tissue, significant collateral circulation, and lack of conduit availability. Many studies have revealed that off-pump surgery itself can be one of the reasons for incomplete revascularization [1315]. Sabik and colleagues [15] reported that the mean number of bypass grafts in off-pump patients (2.8 ± 1.0) was significantly smaller than that in on-pump patients (3.5 ± 1.1). Because we have adopted the definition of "traditional" completeness, the number of distal anastomoses per patient (3.6 ± 1.4) in the present study was similar to that in the on-pump patients of Sabik and associates [15], and complete revascularization was achieved in 99.2% of patients. We indicate that complete myocardial revascularization using an off-pump technique can be safely performed, and we believe that complete revascularization, using the traditional definition, will improve long-term cardiac survival. Long-term follow-up is necessary to elucidate the detrimental effects of incomplete revascularization with OPCAB.
The use of arterial grafts has been widely accepted for myocardial revascularization on the basis of the clinical advantage of using the left internal thoracic artery as a bypass conduit [16]. A decreased risk of cardiac death was associated with arterial grafting in a long-term follow-up study [13]. More recently, use of two or three arterial grafts was shown to improve survival and reduce the need for readmission for treatment of heart disease [17]. We prefer using arterial grafts with the OPCAB technique. Thus, total arterial grafting was performed in 77.4% of patients in the present study. Off-pump CABG is a suitable method for patients in whom proximal anastomoses of conduits cannot be performed because of diseased aorta. In these patients, composite and sequential grafting using arterial grafts can be safely performed [8].
The reduced patency of bypass grafts increases the need for repeat revascularization with time. Puskas and coworkers [18] demonstrated that graft patency in OPCAB patients is similar to that in conventional CABG patients at 30 days (99.0% versus 97.7%) and 1 year (93.6% versus 95.8%) after surgery. Our finding that overall early graft patency rate was 97.5% is almost identical to their results. We believe that the same early graft patency rate can be obtained in patients treated with OPCAB as compared with those undergoing conventional CABG. Some investigators have demonstrated a reduced patency rate for SVG in patients undergoing OPCAB [19]. Hypercoagulability may exist after OPCAB, and prophylactic postoperative anticoagulation therapy may be indicated for these patients [20]. More recently, Halkos and colleagues [21] reported that OPCAB patients could safely receive clopidogrel in the early postoperative period without increased risk for mediastinal bleeding. We have routinely used warfarin in addition to low-dose aspirin in patients with SVG. In the present study, the patency rate of SVG was 97.8%, which is similar to that of arterial grafts. Clopidogrel may be more effective than warfarin with low-dose aspirin to reduce graft occlusion rate.
There are still some patients who cannot be treated with OPCAB, such as those with a large heart and impaired left ventricular function or intramyocardial coronary arteries. The rate of performing OPCAB in our isolated CABG patients was 90%. A recent meta-analysis clearly revealed the favorable outcomes of OPCAB [1], and concluded that OPCAB should be considered a safe alternative to conventional CABG with respect to mortality risk. Similar completeness of myocardial revascularization and graft patency can be achieved by OPCAB procedures using modern technology and techniques. Thus, we suggest that OPCAB should be performed whenever possible in patients undergoing isolated CABG.
The limitations of our clinical study are that the number of patients was small and the length of clinical follow-up was relatively short. Postoperative angiographic data and clinical outcome could not be obtained from all patients. Furthermore, this was a retrospective observational study and was not randomized. It is possible that there are subtle selection biases in patients selected for OPCAB. Because there was no control group, we cannot conclude that the midterm outcomes after OPCAB were superior to those of conventional CABG.
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