Off-pump coronary artery bypass grafting

2.1 Indications and current treatments

2.1.1 Coronary artery disease (CAD) refers to the hardening and narrowing of the coronary arteries as a result of atherosclerosis. It can cause angina, myocardial infarction and heart failure. One treatment option is CABG, most often performed 'on pump', maintaining the circulation and oxygenation of the blood extracorporeally using a cardiopulmonary bypass machine, while the heart is arrested (not beating).

2.2 Outline of the procedure

2.2.1 Off-pump CABG aims to avoid the potential hazards of cardiopulmonary bypass, mainly in relation to the risk of stroke. With the patient under general anaesthesia, after a thoracotomy, the heart is displaced and snares are placed around target coronary arteries to occlude them while bypass grafts are sutured in place. An immobilising device is used to minimise movement of the beating heart while the anastomoses are performed. Donor vessel harvesting is performed in the standard way.

2.3 Efficacy

2.3.1 Some studies reported outcomes that could be interpreted as relating either to efficacy or to safety, depending on their timing, which was not documented. Outcomes with uncertain timing of occurrence have been considered as efficacy outcomes. It is assumed that these occurred after the immediate postoperative period because they were reported with long-term follow-up data.

2.3.2 A meta-analysis of 5537 patients reported no significant difference in mortality rate between off-pump and on-pump CABG (relative risk 0.98, 95% CI 0.66 to 1.44) (follow-up not stated). A non-randomised controlled study of 3014 patients treated by off-pump or on-pump CABG reported major adverse events (death, stroke or myocardial infarction) in 11% (72/637) and 15% (367/2377) of patients respectively at 1-year follow-up (p = 0.012). A randomised controlled trial (RCT) of 2203 patients treated by off-pump or on-pump CABG reported death, myocardial infarction or revascularisation between 1-month and 1-year follow-up in 10% (105/1104) and 7% (78/1099) of patients respectively (p = 0.04).

2.3.3 A UK national register report of 86,047 patients treated since 1999 reported that 1-year survival for patients treated in the period 2004 to 2008 was 97% for off-pump CABG and 96% for on-pump CABG. By 5-year follow-up (for patients who had reached that time point), survival was 89% for off-pump CABG and 89% for on-pump CABG (significance and absolute figures not stated).

2.3.4 The meta-analysis of 5537 patients and a meta-analysis of 297,000 patients reported no significant difference between off-pump and on-pump CABG in relative risk of revascularisation: 1.35 (95% CI 0.83 to 2.18) and 1.35 (95% CI 0.76 to 2.39) respectively (follow-up not stated).

2.3.5 The non-randomised controlled study of 3014 patients reported graft failure (≥ 75% stenosis) in 45% (181/402) of patients in the off-pump group and in 46% (697/1518) of patients in the on-pump group at 12 to 18 months follow-up (p = 0.75). An RCT of 2203 patients treated by off-pump or on-pump CABG reported that fewer grafts were inserted than were planned pre-operatively in 18% of patients in the off-pump group and 11% in the on-pump group (p < 0.001) (absolute figures not stated).

2.3.6 In a case series of 312 patients, off-pump CABG was converted to on-pump CABG in 4% (12/312) of patients.

2.3.7 The Specialist Advisers listed key efficacy outcomes as requirement for additional revascularisation, symptom relief and length of stay.

2.4 Safety

2.4.1 A meta-analysis of 297,000 patients reported that 30-day mortality was significantly lower following off-pump rather than on-pump CABG (pooled odds ratio 0.72, 95% CI 0.66 to 0.78) (p < 0.00001). The RCT of 2203 patients reported no significant difference in 30-day mortality between the off-pump group and the on-pump group (2% [18/1104] and 1% [13/1099] respectively, p = 0.47).

2.4.2 Stroke occurred significantly less frequently following off-pump CABG than on-pump CABG in the meta analysis of 297,000 patients (pooled odds ratio 0.62, 95% CI 0.55 to 0.69) (p < 0.00001) (follow-up not stated).

2.4.3 The Specialist Advisers listed theoretical adverse events as infection, bleeding and renal dysfunction. They commented that inaccurate suturing may lead to graft failure.

2.5 Other comments

2.5.1 This review of existing guidance was precipitated by recent evidence of higher graft occlusion rates in the longer term after off-pump CABG compared with on-pump surgery (see the RCT of 2203 patients). The Committee considered this evidence carefully in the context of other evidence on large numbers of patients for whom off-pump CABG had shown advantages without additional safety concerns.

2.5.2 The Committee was advised that off-pump CABG may have a particular role in the management of patients with gross calcification of the ascending aorta and those with low ejection fractions.