Cerebral augmentation index derived from external counterpulsation predicts ischemic stroke outcome: A prospective observational study

Background and Purpose: External counterpulsation (ECP) noninvasively augments cerebral blood flow in patients with ischemic stroke. We investigated whether the cerebral augmentation index (CAI), measured by transcranial Doppler (TCD) during ECP, could predict the functional outcome of ischemic stroke. Methods: Patients with unilateral ischemic stroke in the anterior circulation territory were enrolled within 7 days of symptom onset. Mean flow velocities in both middle cerebral arteries (MCA) were monitored by TCD before, during and immediately after ECP. CAI was defined as the percentage increase in MCA mean flow velocity during ECP relative to baseline. TCD data from the ipsilateral and contralateral sides of the cerebral infarct were analyzed and compared between patients with good outcomes (modified Rankin Scale (mRS) 0-2) and those with poor outcomes (mRS 3-6) at 3 months post-stroke. Results: Among 200 recruited patients (mean age, 64.5 ± 8.9 years; 86.5 % men), functional outcomes were good in 148 (74.0 %) and poor in 52 (26.0 %). Admission NIH Stroke Scale, history of ischemic heart disease, and CAI on both the ipsilateral and contralateral sides differed significantly between the two groups (all P < 0.05). In multivariate analysis, NIH Stroke Scale (OR, 1.677 [95 % CI, 1.363-2.064]; P < 0.001), ipsilateral CAI (OR, 1.282 [95 % CI, 1.148-1.646]; P = 0.012), and contralateral CAI (OR, 1.104 [95 % CI, 1.002-1.234]; P = 0.038) independently predicted poor functional outcomes. Conclusion: CAI, a cerebral hemodynamic index measured over the MCA on either the ipsilateral or contralateral side of an acute cerebral infarct, may predict unfavorable stroke outcomes.