Pattern and significance of cerebral microemboli during coronary artery bypass grafting

Background Strokes that occur during coronary artery bypass grafting are of ten caused by embolism. Intraoperative transcranial Doppler monitoring can detect cerebral microemboli. The aims of this study were to identify the pa ttern of microembolic phenomena during various stages of coronary artery by pass grafting, to verify whether numbers of high-intensity transient signal s correlated with early neuropsychologic deficits, and to identify, using m agnetic resonance imaging scans, whether radiologic evidence of cerebral in farction correlated with microembolic numbers during the bypass period. Methods. Forty-one consecutive patients undergoing coronary bypass grafting with transcranial Doppler monitoring were enrolled in this study. All had preoperative and postoperative magnetic resonance imaging brain scans. A su bgroup of 32 patients were studied by Comparing microembolic load and early neuropsychological outcomes. Results. Transcranial Doppler monitoring confirmed that most microemboli oc curred during cardiopulmonary bypass. A significant early neuropsychologica l deficit after coronary artery bypass grafting did correspond to the total microembolic load during bypass (p = 0.008). However, patients with cerebr al infarction on magnetic resonance imaging had significantly more microemb olic signal during the preincision phases and not during the bypass period. Conclusions. Microembolic load during bypass is associated with early neuro psychologic deficits. In contrast, patients who show evidence of strokes du ring coronary artery bypass grafting have a higher microembolic load during the preincision phase than those without cerebral infarction. Differing me chanisms may be responsible for these different outcomes. (C) 1998 by The S ociety of Thoracic Surgeons.