Pulmonary outcomes of off-pump vs on-pump coronary artery bypass surgery in a randomized trial

STUDY OBJECTIVES: Comparison of pulmonary outcomes after off-pump coronary artery bypass (OPCAB) vs on-pump coronary artery grafting with cardiopulmonary bypass (CABG/CPB).Study design: We examined preoperative and postoperative respiratory compliance, fluid balance, hemodynamics, arterial blood gases, chest radiographs, spirometry, pulmonary complications, and time to extubation in a prospective trial of 200 patients randomized to OPCAB vs CABG/CPB performed by one surgeon. RESULTS: One CABG/CPB patient and two OPCAB patients required mitral valve repair or replacement and were withdrawn. After three crossovers from CABG/CBP to OPCAB and one crossover from OPCAB to CABG, 97 CABG/CPB patients and 100 OPCAB patients remained. There were no significant preoperative demographic differences between groups. Postoperative compliance was reduced more after OPCAB than after CABG/CPB (- 15.4 +/- 10.7 mL/cm H(2)O vs - 11.2 +/- 10.1 mL/cm H(2)O [mean +/- SD]; p = 0.007), associated with rotation of the heart into the right chest to perform posterolateral bypasses (p < 0.001) and the concomitant increased fluid requirements necessary to maintain hemodynamic stability during rotation of the heart. In addition to higher intraoperative fluid intake (4,541 +/- 1,311 mL vs 3,585 +/- 1,033 mL, p < 0.0001), OPCAB patients had higher intraoperative fluid balance (3,903 +/- 1,315 mL vs 1,772 +/- 1,373 mL, p < 0.0001), and higher postoperative pulmonary arterial diastolic pressure (15.0 +/- 5.5 mm Hg vs 11.8 +/- 5.2 mm Hg, p < 0.0001) and central venous pressure (10.4 +/- 4.5 mm Hg vs 8.4 +/- 4.7 mm Hg, p < 0.0001). Despite lower compliance, immediate postoperative Pao(2) on fraction of inspired oxygen of 1.0 (275 +/- 97 torr vs 221 +/- 92 torr, p = 0.001) was higher after OPCAB and extubation was earlier (p = 0.001). Postoperative chest radiographs, spirometry, mortality, reintubation, or readmission for pulmonary complications were not different between groups. CONCLUSIONS: Compared to CABG/CPB, OPCAB was associated with a greater reduction in postoperative respiratory compliance associated with increased fluid administration and rotation of the heart into the right chest to perform posterolateral grafts. OPCAB yielded better gas exchange and earlier extubation but no difference in chest radiographs, spirometry, or rates of death, pneumonia, pleural effusion, or pulmonary edema.     

Mid-term outcomes of off-pump versus on-pump coronary artery bypass graft surgery

OBJECTIVE:

To evaluate survival and readmissions to hospital for cardiac events or coronary revascularization (REVASC) in patients having off-pump (OPCAB) versus conventional on-pump (CCAB) coronary artery bypass graft surgery (CABG).

METHODS:

Of 11,368 consecutive patients undergoing isolated CABG between 1996 and 2002, 514 had OPCAB surgery. Using propensity scores, 503 CCAB patients were randomly matched to 503 OPCAB patients.

RESULTS:

There were no clinical or statistical differences between the two groups for any prognostic variable. However, OPCAB patients received significantly fewer distal anastomoses than the CCAB group (2.6±1.0 versus 3.1±1.0; P<0.001). There was no difference in operative mortality (OPCAB 1.0%, CCAB 1.4%; P=0.6), but the OPCAB group had significantly fewer operative strokes (0.2% versus 1.8%; P=0.01). Follow-up was 99.7% complete at 2.2±1.2 years (range 0 to 6 years). Twice as many OPCAB patients (n=24) required REVASC compared with the CCAB (n=11) group. The following five-year actuarial outcomes are presented for CCAB and OPCAB, respectively: survival: 77±6%, 76±8%, P=0.8; freedom from REVASC: 95±3%, 92±2%, P=0.02; and cardiac event-free survival: 76±5%, 62±8%; P=0.05. Cox regression revealed that OPCAB was a significant independent predictor of poorer freedom from REVASC (RR 2.2, 95% CI 1.0 to 4.6; P=0.04) and cardiac event-free survival (RR 1.6, 95%CI 1.1 to 2.2; P=0.02).

CONCLUSIONS:

The use of OPCAB remains controversial. These results, from this early experience, suggest that despite improved hospital outcomes, the lesser degree of REVASC raises concerns about the need for repeat revascularization in the OPCAB group.     

Technology insight: randomized trials of off-pump versus on-pump coronary artery bypass surgery

Coronary artery bypass grafting has proven a remarkably effective treatment for occlusive coronary artery disease, with demonstrable impact on both symptoms and survival. As conducted traditionally, cardiopulmonary bypass is required, and a global myocardial ischemic insult imposed with aortic occlusion under the protection of cardioplegic arrest. Despite the remarkable success of this approach, concerns over the systemic effects of bypass, including neurologic sequelae as well as ischemic myocardial injury, have stimulated development of techniques and technology to perform coronary bypass 'off-pump'. This technique obviates the need for the bypass machine and imposes only brief regional ischemia during construction of each individual anastomosis. Despite enthusiastic support by a devoted cohort of surgeons, and a host of nonrandomized retrospective studies demonstrating an apparent benefit to the off-pump technique, the technique has not been universally adopted. How can there be such controversy over what appears to be a superior approach? In part, many surgeons are concerned that the greater technical difficulty of the technique will impact long-term results adversely. There is also uncertainty with regard to the actual advantage of off-pump coronary artery bypass over the tried-and-true methods. Surgeons recognize that the results of any surgical series are particularly subject to the influence of subtle selection biases. Accordingly, prospective randomized studies add particular value to the debate. It is the aim of this review to examine the evidence for off-pump coronary artery bypass critically, from a surgeon's perspective, with particular emphasis on knowledge derived from a representative selection of published prospective randomized studies.     

The Canadian off-pump coronary artery bypass graft registry: a one-year prospective comparison with on-pump coronary artery bypass grafting

BACKGROUND: The authors sought to examine in-hospital and one-year outcomes of off-pump coronary artery bypass grafting (CABG) and to determine the subgroups of patients most likely to benefit from the off-pump procedure in a regular surgical practice. METHODS: From March 2001 to December 2002, 1657 consecutive patients were treated with off-pump CABG and 1693 consecutive patients were treated with on-pump CABG. Propensity score modelling was performed to control for treatment and selection bias. A propensity-matched analysis was performed to identify factors associated with survival benefit from the off-pump procedure. RESULTS: The mortality was similar postoperatively and at one year after surgery. The rate of stroke was decreased in the off-pump group postoperatively (OR=0.49, 95% CI 0.23 to 1.06) and significantly at one year after surgery (OR=0.49, 95% CI 0.27 to 0.90). A significant reduction in acute renal dialysis and a significant increase in myocardial infarction rates were seen in off-pump patients during the initial hospitalization but these differences disappeared during the follow-up period. The number of grafts completed was significantly lower in off-pump CABG than in on-pump CABG (2.62+/-1.00 versus 3.36+/-0.92, respectively; P<0.001). Hospital length of stay and the percentage of patients who required mechanical ventilation were significantly lower in the off-pump group than in the on-pump group. At one year after surgery, the adjusted rate of coronary angiogram and revascularization was similar between the two groups, and the adjusted rate of self-reported angina and memory status was significantly better in the off-pump CABG group. Almost all subgroups of patients had a neutral effect or a survival benefit with the off-pump technique. CONCLUSIONS: The results from a Canada-wide multicentre registry showed the safety and effectiveness of off-pump CABG in most subgroups of patients in a regular surgical practice.     

The relation between surgeon volume and outcome following off-pump vs on-pump coronary artery bypass graft surgery

STUDY OBJECTIVE: Off-pump coronary artery bypass graft (CABG) surgery has been recently reintroduced into clinical practice. In light of the relatively low level of experience of most cardiac surgeons with off-pump CABG surgery, and the exceptional technical challenge of working on a "beating heart," off-pump CABG surgery presents a unique opportunity to explore the effect of surgeon case volume on surgical outcome after controlling for the effects of patient case mix and hospital volume. DESIGN: A retrospective cohort study analyzing the association between surgeon volume and in-hospital mortality rate for off-pump and on-pump CABG surgery using random-effects logistic regression modeling. SETTING AND PATIENTS: The analyses were based on the New York State clinical CABG surgery registry. The study sample consisted of 36,930 patients undergoing isolated CABG surgery between 1998 and 1999 that was performed by 181 surgeons at 33 hospitals. INTERVENTIONS: None. RESULTS: There is no association between the number of CABG procedures performed off-pump by an individual surgeon and in-hospital mortality rates (p = 0.93) after controlling for hospital CABG surgery volume and patient-level risk factors. There is also no association between the off-pump CABG surgery mortality rate and the total number of both off-pump and on-pump CABG surgery cases (p = 0.78). In the on-pump CABG surgery cohort, surgeons performing a high volume of CABG procedures had significantly lower risk-adjusted mortality rates among their patients compared to those performing a very low volume, a low-volume, and a medium volume of CABG procedures (p < 0.006). CONCLUSION: For off-pump CABG surgery, surgeons performing a high volume of procedures do not have better mortality outcomes than those performing a low volume of procedures. However, higher surgeon case volumes are associated with lower mortality rates for on-pump CABG surgery. The absence of a volume-outcome association for off-pump CABG surgery is especially surprising in light of the more technically demanding nature of off-pump CABG surgery compared to on-pump CABG surgery.     

Cost-effectiveness of on-pump and off-pump bypass surgery

We read with great interest the comprehensive review by Murphyet al.¹ This review of the published literature criticallyexamines the potential     

Revascularization options for ischemic cardiomyopathy: on-pump and off-pump coronary artery bypass surgery

Patients with ischemic cardiomyopathy and markedly reduced left ventricular (LV) function should be evaluated for coronary artery bypass surgery (CABG) before other surgical options are considered. The success of surgery depends on the presence of viable myocardium and target coronary arteries of acceptable quality. Long-term survival in this setting may be comparable to that with cardiac transplantation. Off-pump CABG can be safely and reproducibly performed in patients with diminished LV function. Off-pump beating heart surgery may provide additional benefits to these patients by reducing some of the complications that are associated with cardiopulmonary bypass.     

Association between early and three month cognitive outcome after off-pump and on-pump coronary bypass surgery

Objective: To describe the association between cognitive outcome in the first postoperative week and that at three months after both off-pump and on-pump coronary bypass surgery, and to make a direct comparison of early cognitive outcome after off-pump versus on-pump surgery.

Design: Randomised trial with an additional prediction study within the two randomised groups.

Setting: Three centres for heart surgery in the Netherlands.

Patients: 281 patients, mean age 61 years.

Interventions: Participants were randomly assigned to off-pump or on-pump coronary bypass surgery.

Main outcome measures: Cognitive outcome, assessed by psychologists who administered neuropsychological tests one day before and four days and three months after surgery. A logistic regression model was used to study the predictive association between early cognitive outcome, together with eight clinical variables, and cognitive outcome after three months.

Results: Cognitive outcome in the first week after surgery was determined for 219 patients and was a predictor of cognitive decline after three months. This association was stronger in on-pump patients (odds ratio (OR) 5.24, p < 0.01) than in off-pump patients (OR 1.80, p = 0.23). Early decline was present in 54 patients (49%) after off-pump surgery and 61 patients (57%) after on-pump surgery (OR 0.73, p = 0.25).

Conclusions: In patients undergoing first time coronary bypass surgery, early cognitive decline predicts cognitive outcome after three months. Early cognitive decline is not significantly influenced by the use of cardiopulmonary bypass.