Low Pulsatility Index on Transcranial Doppler Predicts Symptomatic Large-Vessel Vasospasm After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND: Elevated mean cerebral blood flow velocity (mCBFV) on transcranial Doppler predicts vasospasm of the large intracranial arteries after aneurysmal subarachnoid hemorrhage (aSAH). The pulsatility index (PI) is a measure of distal vascular resistance, which may be low when there is compensatory distal vasodilatation following hypoperfusion caused by large-vessel vasospasm. OBJECTIVE: To study the predictive value of low PI for symptomatic large-vessel vasospasm (SLVVS) after aSAH. METHODS: Medical records of patients admitted with aSAH between January 2007 and April 2009 were reviewed. Transcranial color-coded duplex (TCCD) sonography was performed daily between days 2 and 14. Patients with unexplained acute neurological decline underwent catheter- or computed tomography-angiography. The lowest recorded PI and the highest mCBFV on TCCD were correlated to the occurrence of SLVVS, angiographic vasospasm, and delayed cerebral infraction in multivariate analysis by use of logistic regression. Functional outcome was assessed at first follow-up. RESULTS: Eighty-one patients met inclusion criteria. Mean lowest PI was 0.71 + 0.19. Median highest mCBFV was 135 cm/s (interquartile range 99-194 cm/s). SLVVS was seen in 21 of 81 (26%) patients, whereas 27 of 55 (49%) patients with repeat angiography had moderate or severe angiographic vasospasm. Following multivariate analysis, only the lowest PI was an independent predictor of SLVVS (P = .03, odds ratio 0.04, 95% confidence interval 0.001-0.54), whereas only the highest mCBFV was an independent predictor of angiographic vasospasm (P = .02, odds ratio 1.01, 95% confidence interval 1.002-1.02). SLVVS was independently associated with functional outcome at follow-up. CONCLUSION: Low PI on TCCD is an independent predictor of SLVVS after aSAH, whereas mCBFV is a better predictor of angiographic vasospasm.