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In coronary surgery, protective strategies that offer adequate safety for patients with healthy ventricles may not be adequate for those with severe impairment of ventricular function
In this issue of Heart Antunes and colleagues,1 in reporting excellent outcomes for coronary surgery in patients with advanced left ventricular dysfunction, highlight a source of continued controversy concerning the best way of protecting the heart in these circumstances. What has heightened current interest, and prompted reassessment of existing techniques, is the advent of beating heart surgery2 to add to available strategies for conducting the operation in those whose myocardium has been severely damaged by the effects of coronary disease.
The value of revascularisation in those with impaired left ventricular function is well established.3 However, when non-working “hibernating” myocardium or fibrous tissue has replaced much contractile myocardium, there are reduced reserves for coping with the injury that so often accompanies coronary surgery. Thus, protective strategies that offer adequate safety for patients with healthy ventricles may not be adequate for those with severe impairment of ventricular function, leading to postoperative low output syndrome and high mortality.
Although there may be a perception that surgeons are operating on older and sicker coronary patients than before, data from the National adult cardiac surgical database4 indicate that the proportion of surgical patients in the UK with poor left ventricular function (defined, as in the Antunes paper, as an ejection fraction below 30%) remained fairly constant at about 7% over the period 1993 to 1999 inclusive. Illustrating the problem, however, is the fact that the crude hospital mortality for this group over the period was 9.8%, compared with 1.8% for those with good left ventricular function (ejection fraction over 49%).
MYOCARDIAL INJURY DURING SURGERY
There are many sources of myocardial injury during coronary surgery. Ischaemic injury is a risk …