Myocardial and cerebral injury after off-pump coronary artery surgery.

Coronary Artery Surgery To the Editor: Van Dijk and colleagues1 are to be congratulated on the contribution of their randomized trial to the on-pump versus off-pump coronary artery bypass surgery debate and, in particular, the discussion of the high proportion of patients undergoing total arterial revascularization. Most of the pertinent points are covered in Dr Yacoub’s balanced accompanying editorial.2 Two methodological flaws may, however, invalidate the authors’ conclusions regarding myocardial and cerebral injury. First, the reduction in creatine kinase (CK)-MB release in the off-pump group compared with the on-pump group is based on measurements taken within the first 20 hours postoperatively. Release of biochemical markers of myocardial injury over this period may reflect turnover of cytosolic pools and increased membrane permeability as a consequence of cardiopulmonary bypass rather than true myocardial necrosis.3 Demonstration of rising CK-MB levels up to 48 hours would have helped to resolve this issue. Second, the observation of a similar stroke rate in both groups is difficult to interpret without knowing precisely what proportion of patients had composite arterial grafts without needing to fashion a “top-end” on the aorta. Atherosclerosis of the ascending aorta is a major risk factor for cerebral macroemboli, and the benefits of avoiding aortic cannulation and cross-clamping are negated by the use of the partial occlusion clamp to construct proximal anastomoses.4 Consequently, we consider the use of a “no touch technique” for the aorta, with use of composite arterial grafts based on internal thoracic arteries, the best method of eliminating the risk of stroke.4 We have previously reported5 similar severity of neuropsychological injury in “low-risk” patients undergoing on-pump and off-pump surgery. In the on-pump group, such injury results from the microembolization of particulate debris, whereas in the off-pump group, this is almost certainly due to a reduction in cardiac output during manipulation of the heart. The major benefits of off-pump surgery are likely to be seen in the elderly who are most susceptible to the damaging effects of cardiopulmonary bypass. Indeed, practice is moving rapidly in this direction.