Benefits of off‐pump coronary artery surgery?

As rightly suggested by Heames et al. in the recent review of off-pump coronary artery bypass surgery (Anaesthesia 2002; 57: 676–85), further work is required to clarify certain aspects of the efficacy of off-pump surgery. In particular, the issue of postoperative cognitive function remains unresolved (Singh. Anaesthesia 2002; 57: 1219). However, since the review was published there have been several studies published comparing on- and off-pump technique and we feel these should be brought to your readers' attention. In April 2002, the findings of two major studies were presented. Firstly, Angelini and colleagues published a pooled analysis of the Beating Heart Against Cardioplegic Arrest Studies (BHACAS) 1 and 2 [1]. These two studies were prospective randomised trials with a total of 200 patients undergoing off-pump and 201 on-pump coronary artery surgery between March 1997 and November 1999. Notably, they excluded patients with a history of stroke or transient ischaemic attack (TIA). They demonstrated significant reductions in the incidence of atrial fibrillation, chest infection, inotropic support and red cell transfusion, and the number of patients requiring more than 1 day on the intensive care unit and more than a total of 7 days in hospital in the off-pump group. Only gross neurological events such as TIA or stroke were recorded and there was no difference in the incidence of these between the 2 groups. Second, in a less well-designed, non-randomised study of on- vs. off-pump surgery in 300 patients (150 in each group), there were significant reductions in the time to extubation, intensive care and hospital lengths of stay in those patients undergoing off-pump surgery [2]. However, the initial off-pump patient population had only 1 or 2 grafts performed due to lack of surgical experience with the technique. Again, there was no difference in the incidence of postoperative stroke, but this end-point required radiological confirmation by way of CT scanning. Unfortunately, neither study made any attempt to measure the incidence of cognitive dysfunction. The study of Van Dijk quoted by Dr Singh is probably the best-designed study to date addressing the issue of cognitive dysfunction following coronary artery surgery [3]. A total of 281 patients with a mean age of 61 years were randomised to either on-pump (n = 142) or off-pump (n = 139) surgery. There was a small, but non-significant reduction in the incidence of cognitive dysfunction 3 months after surgery in the off-pump group (21% vs. 29%). This was not evident at 12 months. Again, many patients had only single or double-vessel disease and their anaesthetic management was not standardised. Most interestingly, Zamvar and colleagues recently demonstrated a dramatic reduction in cognitive dysfunction after off-pump surgery [4]. In their randomised comparison of 60 patients undergoing either on- or off-pump surgery, the incidence of cognitive dysfunction was only 27% and 10% in the off-pump group vs. 63% and 40% in the on-pump group at 1 week and 10 weeks, respectively. Anaesthesia was standardised and all patients had triple vessel disease with a similar number of grafts in each group. This study, though well matched for patient characteristics, comprises a small low-risk group for cognitive dysfunction with a mean age of 62 years. Nevertheless, the findings are significant and emphasise the need for a larger trial, which should be designed with a more precisely defined cardiopulmonary bypass management protocol and intra-operative haemodynamic management in the off-pump group. Whilst these findings are encouraging for the advocates of off-pump surgery, it must be remembered that there is a significant incidence of cognitive dysfunction after major non-cardiac surgery. The International Study of Postoperative Cognitive Dysfunction reported an incidence of 25.8% at 1 week after surgery and 9.9% at 3 months after surgery [5]. Clearly, a large and well-designed trial is still needed to see whether off-pump surgery, perhaps by total arterial revascularisation avoiding all aortic manipulation as advocated by Taggart [6], can reduce the incidence of cognitive dysfunction comparable to that seen after non-cardiac surgery.