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a Cerebrovascular Neurology, Johns Hopkins Hospital, Johns Hopkins Bayview Medical Center, Baltimore, MD 21287
b Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Hospital, 600 N Wolfe St, Tower 711, Baltimore, MD 21287
(Email: chogue2{at}jhmi.edu).
Filsoufi and colleagues [1] report the results of a retrospective study involving 2985 patients undergoing coronary artery bypass graft (CABG) procedures evaluating for the incidence, timing, and topography of perioperative stroke. Stroke was diagnosed in 1.6% of patients, of which 52% were "early" strokes, or those occurring within 24 hours of the operation. The reported frequency and temporal presentation of stroke in this series is similar to other reports and national benchmarking data [2, 3]. Moreover, the patient outcomes and risk factors identified based on multivariable logistic regression analysis, including female sex, were independently associated with risk for stroke and are similar to prior reports [2, 3].
Of interest are the findings from brain imaging studies that were obtained in 92% of patients with clinical stroke. The imaging pattern was consistent with large embolic stroke in 76% of patients, a watershed pattern indicative of cerebral hypoperfusion was found in 15% of patients, and a mixed brain embolic/hypoperfusion pattern was present in 9% of strokes. Of interest was that brain imaging confirmed cerebral infarction in only 75% of patients with a clinically documented stroke. This suggests that in the latter patients, brain injury occurred in areas not easily imaged with the methods used in this study (ie, brain stem or white matter) or that the size of the brain infarction was small yet involved vital brain areas. The findings that more than three-quarters of strokes were embolic in origin is higher than other series (about 50%) [2, 4].
This study by Filsoufi and colleagues [1] relied primarily on computed tomography (CT) scanning, with only 3 subjects having undergone magnetic resonance imaging (MRI). It is clear that CT has decreased sensitivity as well as lower interrater reliability compared with MRI. We found in patients with clinical stroke after cardiac surgery that bilateral watershed strokes, in particular, were noted on 22% of CT scans but 48% of MRI scans [5]. Scanning with MRI is safe in most postoperative patients after pacing wires are removed and is not adequately used, given the additional information provided by this technology.
The results by Filsoufi and colleagues [1] do underscore the increasingly recognized role of preexisting cerebral vascular disease in the pathophysiology of perioperative stroke. In many series involving brain imaging before and after cardiac operations, cerebral infarction is found in as many as 50% of patients before the procedure [6]. Using single photon emission CT imaging, Moraca and colleagues [7] found that 75% of patients demonstrated abnormal regional cerebral perfusion before CABG procedures and that these findings were associated with older age, current tobacco use, diabetes mellitus, and risk for postoperative stroke.
It is now well documented that the presence of a prior brain infarction increases the risk for subsequent perioperative neurologic complications and long-term decrements in cognition [6]. Of importance is that many prior brain infarctions are clinically asymptomatic. Thus, clinicians will not be alerted to the presence of prior clinically "asymptomatic" stroke by history and physical examination. Filsoufi and colleagues [1] propose that preoperative brain imaging might be considered in high-risk patients as a means to identify patients at high risk for perioperative stroke.
We have previously surmised that prior cerebral vascular disease might be identified before the operation by using screening psychometric testing [8]. Such information might be useful for further considering the risk vs benefits of cardiac surgery or as a means for focusing neuroprotective strategies during surgery [9]. Regardless, such a strategy requires further investigations to examine its efficacy for improving health and economic outcomes for an increasingly aged cardiac surgical population.
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