Off-pump coronary artery bypass surgery The beginning of the end?

In the past decade, the idea of lessening the invasive aspect of coronary surgery led to the development of new techniques based on two approaches, the reduction of the incision (mini-invasive direct coronary artery bypass, MIDCAB) or the abandon of the cardiopulmonary bypass (off-pump coronary artery bypass, OPCAB). Nevertheless, these techniques remain subject to controversies and the decline of MIDCAB seems evident. Based on a review, the analysis of the OPCAB technique and results seem to be of interest, and the conclusions are not very optimistic. Arguments to promote OPCAB are based on the suppression of the deleterious effects of CPB, and a significant reduction in the costs and the perioperative morbidity and mortality. The systemic inflammatory response that occurs after coronary artery surgery has been analyzed in a randomized study [1], either after CPB or in beating heart surgery: the authors concluded that the increase in acute phase reactants was the same in both patient groups, and that an inflammatory response following coronary artery bypass grafting (CABG) was predominantly caused by the surgical procedure, rather than by the use of CPB or not. Moreover, a randomized study [2] suggested that the deterioration in pulmonary gas exchange associated with CABG is due to factors other than the use of CPB. More convincing was a randomized study on the neuropsychological outcome after CABG [3]: cognitive impairment seemed to be strongly associated with CPB and the occurrence of perioperative micro-emboli; the off-pump technique appears promising in order to eliminate the source of these neuropsychological impairments following CABG operation. Comparison between the costs of both procedures relies on one randomized study [4]. Regarding the material costs per patient needed to perform a routine operation, the OPCAB technique allowed an economy of $300/patient; but if a single use device had been used in each procedure, as is now the case, the over-cost would have been about $100/patient. The other economical aspects, such as bed occupancy, postoperative complications, and transfusion requirements were favourable to OPCAB surgery. However, it is noteworthy that the length of hospital stay is aleatory and that reduction in postoperative transfusion is mainly related to the perioperative control of haemostasis. Both morbidity and mortality seem to be lower when CPB is avoided; this observation must be considered with caution because there is no randomized study regarding this point. The majority of the comparative studies included an important bias in patient selection. Cartier [5], who recommended OPCAB for multiple vessels disease, observed a comparable postoperative course versus CPB. Arom [6] noticed a significant, reduced morbidity in the OPCAB group, but comparable mortality in both techniques. The reason for this difference remains questionable; one should consider that in routine coronary surgery, the mortality rate is closely related to the morbidity rate. In this series, OPCAB surgery introduces a new bias that can either be a limited revascularization (with a mean of one anastomosis less than in CPB patients) or the high rate of early redo for graft occlusions (up to 14 times more); these data may explain the relative over-mortality observed in the OPCAB group and are of importance when it comes to the reliability of the coronary grafting. In this series, the 1-year rates of recurrent angina and angioplasty were 24 and 10% after OPCAB vs. 9 and 2% after the CPB procedure, respectively. Thus, if arguments to promote OPCAB are not really convincing, these observations regarding the survival and functional outcome of patients are worrying. It is easy to consider that the extended indications of OPCAB may compromise the clinical results and that OPCAB surgery must be reserved to selected patients, such as high risk candidates, in order to improve the surgical results. Locker [7] suggested that OPCAP is associated with a reduced early mortality in patients with acute myocardial infarct, but finally with the same 2-year cumulative mortality, at the cost of an impairment of functional results and freedom from coronary re-operation (Table 1) . Sternik [8] analyzed the outcome of OPCAB patients in cases of severe left ventricular dysfunction; the survival at 2 years was improved in comparison with CPB, but only 2 years postoperatively, functional degradation and the re-operation rate were higher in the OPCAB group (Table 1). In both studies, such disappointing results can be related to a primary incomplete revascularization, the impact of which on the long-term results is well-known. In a comparative study at 7 years, Gundry [9] concluded that limited revascularization of the beating heart provided long-term results comparable with full revascularization with CBP (2.4 vs. 3.2 grafts/patient), but at the cost of a three-fold increase in re-interventions. Nevertheless, this study did not take into account the use of myocardial stabilizers which were introduced later. CABG off-pump versus on-pump in high risk patients In a meta-analysis, Stanbridge [10] compared the results of MIDCAB (3300 patients) and OPCAB (3060 patients) techniques; if early anastomotic dysfunction was lower in OPCAB with a stabilizer than in MIDCAB without a stabilizer (Table 2) , it was up to three times higher than in a conventional approach. Early angiographic controls after MIDCAB and OPCAB, according to a meta-analysisa Critical analysis of OPCAB surgery is motivated by the diversity of the technical approaches: different stabilizers with different paddles, the use of intra-coronary shunt with potential endothelium damage, controversial methods of vessel occlusion, and the use of blowers with irreversible endothelium desiccation changes [10]. The lack of a standardized technique is indirect evidence of an unsuitable technical approach. A severe selection of the OPCAP patients could probably lead to better results, such as avoiding sequential grafting, calcified arteries, diffuse and distal coronary lesions, congestive heart failure, ventricular dilation or multivessel disease (more than three or four anastomoses); thus, such a severe selection is irreconcilable with most of the coronary patients nowadays referred to surgery, or at least contradictory to the systematic use of OPCAB as recommended by several authors [4–6]. Finally, OPCAB surgery presents two major limiting factors, incomplete myocardial revascularization and early anastomotic dysfunction, severely compromising this technique as soon as frequent re-operations are needed, and the functional results are uncertain, from the first postoperative years. Despite the enthusiasm of pioneers in this field, objective analysis leads to scepticism. Now it is time to carry out randomized studies; to be convinced, we await them.