Asian Cardiovasc Thorac Ann 2002;10:322-325
© 2002 Asia Publishing EXchange Pte Ltd
Comparison of Off-Pump Versus Conventional Coronary Revascularization
Erdinç Naseri, MD,
Meral Sevinç, MD1
Department of Cardiovascular Surgery
1 Department of Anesthesiology and Resuscitation Academic Hospital Istanbul, Turkey
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For reprint information contact: Erdinç Naseri, MD Tel: 90 216 341 1821 Fax: 90 216 341 1403 email: enaseri{at}turk.net Department of Cardiovascular Surgery, Academic Hospital, Altunizade, Nuhkuyusu Cad. No. 88, Baglarbasi, Üsküdar, Istanbul 81190, Turkey.
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ABSTRACT
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Between May 1999 and August 2001, 231 patients underwent off-pump coronary bypass, of whom 171 required revascularization of the anterior vessels of the heart. They were compared with a group matched for age, sex, and risk factors undergoing revascularization of the same group of vessels under cardiopulmonary bypass. Mortality was comparable in both groups but the incidence of cerebrovascular accident, respiratory insufficiency, and renal failure was less in the off-pump group. Postoperative drainage and blood transfusion requirements were significantly less in the off-pump group. Intensive care and hospital stay were shorter in the off-pump patients. A considerable number of patients are potential candidates for off-pump coronary bypass, the only contraindication being technical limitations. Follow-up at 6 to 24 months indicates that off-pump coronary bypass can be performed safely with a decrease in morbidity and more rapid return to normal lifestyle.
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INTRODUCTION
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Conventional coronary artery bypass grafting (CABG) has been performed with reproducible success, but complications cause significant morbidity and mortality.1 Some complications may be secondary to cardiopulmonary bypass (CPB) and include neurologic dysfunction and a systemic inflammatory response syndrome ending in vital organ damage.2,3 Although off-pump coronary artery bypass (OPCAB) on a beating heart is an attractive alternative to conventional CABG on CPB, it also has drawbacks. Stabilization instruments are needed for OPCAB, and surgical techniques for the anterior vessels differ from those for the lateral and posterior arteries. Advocates of OPCAB propose that avoidance of CPB can decrease the incidence of dysfunction in all organ systems and facilitate postoperative recovery.4–6 Critics argue that regardless of stabilization devices, the chief unresolved concern regarding OPCAB is the quality of anastomosis and long-term graft patency.7 In view of these controversies, we evaluated our experience in a group of patients undergoing CABG with CPB and a similar group having OPCAB on the anterior coronary arteries, without using special stabilization devices.
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PATIENTS AND METHODS
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A retrospective analysis was conducted on 331 patients who underwent CABG on anterior vessels of the heart at Academic Hospital, Istanbul, between March 1999 and August 2001. Anterior vessels were defined as: the left anterior descending artery and its diagonal, high lateral, or obtuse marginal branches; and the right coronary artery up to the origin of the posterior descending artery. Of 231 patients undergoing OPCAB in that period, 171 (74%) had such anterior targets. In 6 patients (3%), the operation started as OPCAB but because of hemodynamic instability or lack of adequate exposure it was converted to an on-pump procedure; these 6 patients were excluded from the study. Results in the other 165 patients were compared with a group of 160 consecutive patients undergoing CABG on anterior vessels of the heart under CPB from the outset. The on-pump group of patients were treated earlier in the study period to avoid selection or exclusion bias. Both groups were well matched for age, sex, and preoperative risk factors (Table 1
). Congestive heart failure was defined as the need for diuretic therapy or clinical manifestations of heart failure. Left ventricular dysfunction was defined as an ejection fraction < 35%, renal insufficiency was serum creatinine > 20 mg.L-1 in a well-hydrated patient. Postoperative myocardial infarction was ascertained by electrocardiographic criteria and troponin-I levels > 11 ng.mL-1 up to 24 hours after surgery. Respiratory insufficiency was defined as prolonged mechanical ventilation (> 24 hours) postoperatively. Postoperative renal insufficiency was serum creatinine > 20 mg.L-1, an increase in serum creatinine to more than twice the baseline level, or a new requirement for hemodialysis or peritoneal dialysis. Postoperative neurologic events comprised documented cerebrovascular accident, seizure, and delirium.
After induction of anesthesia, internal mammary arteries and saphenous veins were harvested as required. Following partial heparinization (1.5 mg.kg-1), additional heparin was given to maintain an activated clotting time > 300 seconds. For OPCAB, exposure of the left anterior descending artery was acquired using retrocardiac sponges, the right coronary was exposed by passing a 0/0 silk suture around it through the epicardial fat pad at the right atrioventricular groove. A single long sponge passed through the transverse sinus and then posterior to the inferior vena cava was put under traction toward the right inferior corner of the surgical field while performing anastomosis on the high lateral artery. Stabilization was maintained with the aid of a proximal circular suture and a distal semicircular suture of 3/0 monofilament polypropylene. Two epicardial fine-traction sutures allowed manipulation of the anastomosis without handling the coronary arteries. No intracoronary shunts were used. Appropriate pharmacologic intervention was made to maintain the heart rate below 70 beats per minute. For conventional on-pump CABG, standard aortic and 2-stage venous cannulae, and mild to moderate systemic hypothermia were used with tepid blood antegrade cardioplegia to arrest the heart. Blood for cardioplegia was driven from the CPB circuit during the cooling period at 32ºC. Anastomoses were performed on an arrested heart. Only partial aortic clamping was used for the proximal anastomoses.
Follow-up was from 6 to 24 months (complete at 6 months). It included physical examination, an electrocardiogram, and a treadmill exercise test. At 1-year postoperatively, 23 randomly selected asymptomatic patients from the OPCAB group and 25 from the on-pump group underwent angiography.
Data were expressed as mean ± standard deviation. All statistical analyses were performed using Student’s t test for continuous variables and the chi-squared test for categorical variables. In all cases, statistical significance was defined as p < 0.05.
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RESULTS
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There were 2 deaths in each group; operative and postoperative data are summarized in Table 2. Complete myocardial revascularization was achieved in all patients. Left internal mammary artery was the graft of choice for left anterior descending artery revascularization; 7 (4%) patients in the off-pump group and 10 (6%) in the on-pump group did not receive arterial grafts for various reasons. The 7 patients in the off-pump group and 4 in the on-pump group who developed postoperative myocardial infarction were all diabetics with diffuse coronary artery disease. There were no neurologic complications in the off-pump group, but 5 transient ischemic attacks and 3 strokes occurred in the on-pump group. No patient in either group developed deep sternal wound infection.
At the 6-month follow-up, all patients were in New York Heart Association functional class I or II, with no major adverse coronary events. At one year, 23 randomly selected asymptomatic patients from the off-pump group (42 grafts) and 25 (57 grafts) from the on-pump group underwent coronary angiography. Graft patency was 93% in the off-pump group and 91% in the on-pump group (p > 0.1). There were 3 occluded grafts (2 diagonals, 1 right coronary) in OPCAB patients, and 5 (2 right coronary, 1 high lateral, 2 diagonal) in the on-pump group; none required re-intervention.
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DISCUSSION
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A whole-body inflammatory response has been attributed to CPB. It begins with activation of the complement system, coagulation pathways, and the fibrinolytic and kallikrein cascades, promoting the release of humoral factors of the immune system by already activated leukocytes.8 The whole cascade of events results in the release of proteolytic enzymes and oxygen free radicals, resulting in end-organ injury and mortality.3,9 Revascularization of the myocardium directly or indirectly on a beating heart was among the earliest accomplishments of modern cardiac surgery.10 With the invention and refinement of CPB, and because of concerns over long-term patency following grafting on a beating heart, the enthusiasm for off-pump surgery faded until the theoretical disadvantages of CPB prompted renewed interest in this approach.11,12
Potential effects on cerebral function have been paramount in the minds of cardiac surgeons since cardiac operations were first carried out. In the same year that Gibbon13 reported the use of CPB in humans, Fox and colleagues14 described neurologic complications associated with cardiac surgery. Avoidance of aortic cannulation, crossclamping, and low or no perfusion states during CPB could reduce neurologic complications. There was a marked difference between the two cohorts in this study regarding the incidence of postoperative neurologic dysfunction. Perioperative myocardial dysfunction and infarction in CABG patients has also been associated with CPB and aortic crossclamping. Significantly lower troponin-I levels, arrhythmias, balloon pump support, and inotropic requirements were observed in OPCAB patients in a prospective randomized study.4 Our study showed less balloon pump support but no decrease in the incidence of perioperative myocardial infarction in the OPCAB group. There was a surprisingly higher rate of atrial fibrillation in the OPCAB group, which is not in accordance with the literature.
Avoidance of CPB may reduce organ damage elsewhere in the body. Less postoperative renal insufficiency in OPCAB patients was observed in a prospective randomized study that revealed significantly poorer glomerular filtration rates and renal tubular function in the CPB group.4 Pulmonary dysfunction associated with CPB and its triggering action on the whole-body inflammatory response has also been demonstrated by evidence of longer ventilatory support, lower arterial oxygen pressures, and more pulmonary complications.14 Our study showed a significant decrease in the incidence of renal failure and respiratory insufficiency in the OPCAB group.
The only study examining long-term graft patency revealed a lower patency rate and a higher re-intervention rate at 7 years for the off-pump procedure.15 Early angiographic patency of 99% overall and 98.2% for the marginal branches has been reported.7,16 While we await long-term graft patency results, the patency at 1 year was comparable in randomly selected samples of patients from each group. Several retrospective studies showed lower mortality and morbidity after redo operations off-pump than on CPB.17,18 Our experience with redo coronary bypass patients also showed a smoother recovery following off-pump operations. Other benefits of OPCAB in this study were shorter hospital and intensive care stays, as noted by others.19 In addition, our findings agree with previous reports of decreased postoperative drainage and use of blood products.20
This study was different from other studies in that we compared groups with revascularization of the anterior vessels only, so there was no need for special stabilization instruments which bring additional costs and variable success. There was no difference in mortality but significantly less morbidity in the OPCAB group. Although graft patency was comparable in both groups, it was only assessed in a randomly selected subset of asymptomatic patients. With rapidly increasing interest in minimally invasive surgery and the recent explosion of surgical experience and technological advances, beating-heart surgery has evolved into a valuable alternative for coronary revascularization. We contend that a high proportion of patients with ischemic heart disease can benefit from off-pump coronary revascularization. We believe that short-term advantages of this approach have been adequately demonstrated, but prospective randomized trials with extended follow-up are required to evaluate long-term graft patency.
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ABSTRACT
INTRODUCTION
