Utility of Neuromonitoring in Hypothermic Circulatory Arrest Cases for Early Detection of Stroke – Listening through the Noise

Abstract Objective – Stroke remains a potentially devastating complication of aortic arch intervention. The value of neurophysiologic intraoperative monitoring (NIOM) in the early identification of stroke is unclear. We evaluated the utility of NIOM for early stroke detection in aortic arch surgery. Methods – Over 8 years at our institution, 365 patients underwent aortic arch surgery with hypothermic circulatory arrest, and 224 cases utilized NIOM. One patient was excluded for intraoperative death. In the remaining cohort, we reviewed the incidence, timing, and location of strokes, and the incidence and nature of NIOM alerts. Results – Hemiarch was performed in 153 cases and total arch replacement in 71. Stroke occurred in 6.3% of all cases (14/223), 15.5% of total arches (11/71), and 2.0% of hemiarches (3/153). There were 33 NIOM alerts (14.8%), and nine patients had both alerts and stroke. Of these, NIOM deficits plausibly correlated with imaging findings in 7 cases (78%). Of the 5 stroke patients without NIOM alerts, two developed neurologic symptoms three days or more post-operatively, and infarcts in 3 patients did not result in sensory or motor deficits. Excluding two patients with late stroke, the sensitivity of NIOM for stroke detection is 75%, specificity 88.5%, positive predictive value 27.3%, and negative predictive value 97.4%. Conclusions – Despite a low positive predictive value requiring a high level of discrimination when interpreting abnormal findings, NIOM has high sensitivity and specificity for the early stroke detection. Furthermore, its high negative predictive valve is reassuring for low risk of stroke in the absence of alerts.