Ann Thorac Surg 2008;86:452. doi:10.1016/j.athoracsur.2008.05.053
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Invited Commentary
Thomas G. Gleason, MD
Division of Cardiothoracic Surgery, University of Pittsburgh School of Medicine, 200 Lothrop St, UPMC-Presbyterian C-718, Pittsburgh, PA 15213
(Email: gleasontg{at}upmc.edu).
Morita and colleagues [1] have presented a brief report on their use of transcranial Doppler ultrasound (TCD) to evaluate blood flow in the left middle cerebral artery (MCA) upon compression of the left carotid artery to help correlate adequate neurocerebral protection during aortic arch reconstructions. Specifically, they sought to determine the safety of left carotid arterial flow interruption during aortic arch reconstruction with selective antegrade cerebral perfusion delivered to the right axillary artery.
In 14% of the patients studied with TCD, the left MCA could not be visualized. Left carotid compression reduced flow in the left MCA by an average of 56%. Left MCA flow completely disappeared in 22% of the patients. Half of these patients were greater than 80 years of age. Fifteen of 21 patients studied with TCD had preoperative magnetic resonance angiography of the brain to evaluate patency and robustness of the Circle of Willis, graded as having good, fair, or poor collaterals. Among patients with good collaterals (ie, an intact anterior and posterior communicating artery, there was adequate flow reserve with the left carotid compression, as measured by TCD). Interestingly, one patient with at least one patent communicating artery demonstrated no flow in the left MCA with carotid compression, suggesting that preoperative MRA may be useful in predicting safety of transient carotid occlusion, only if it confirms patency of both an anterior and posterior communicating artery. Despite the fact that previous reports have suggested that the risk of significant malperfusion during selective antegrade cerebral perfusion through a right axillary arterial cannulation during open arch reconstruction may be only 14% to 16%, the authors of this current report demonstrate that at least 22% have no flow in the left MCA with this approach, and 39% have flow reduced by 60% or more.
Based on this relatively limited study, TCD clearly has clinical utility in helping to direct a perfusion strategy during open arch reconstruction. On the other hand, MRA as a tool to predict the physiologic consequence of the interruption of unilateral carotid blood flow based on patency of the communicating arteries of the Circle of Willis seems useful only if it demonstrates wide patency of the entire Circle of Willis which, at least based on this study, may be present in only one third of the patients. Perhaps the most relevant conclusion that can be posed from the report is that selective antegrade cerebral perfusion to the right side, particularly at moderate hypothermia, places more significant risk of malperfusion to the left hemisphere in a larger percentage of patients than has been clinically appreciated in the past. This raises significant concern about the safety of such unilateral perfusion approaches without confirmation of adequate flow reserve to the territories in greatest jeopardy. Intraoperative use of TCD should be considered when using selective antegrade cerebral perfusion strategies at moderate hypothermia.
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- Morita S, Yasaka M, Yasumori K, et al. Transcranial Doppler study to assess intracranial arterial communication before aortic arch operation Ann Thorac Surg 2008;86:448-452.[Abstract/Free Full Text]
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