Transcranial Doppler in acute stroke management – A “real-time” bed-side guide to reperfusion and collateral flow

Abstract

Introduction

Assessment of cerebral hemodynamics with transcranial Doppler (TCD) can provide real-time, bed-side assessment of important prognostic variables in acute stroke such as the status of collateral flow and vessel recanalization status. In acute middle cerebral artery (MCA) occlusion, anterior cerebral artery (ACA) flow diversion (FD) is correlated with leptomeningeal collateral flow and may be a clinically useful prognostic indicator. Continuous TCD monitoring of MCA recanalization may also provide useful prognostic information including changes in flow pattern and the occurrence of microembolic signals (MES). We present studies examining associations between ACA FD, MCA recanalization and MES patterns on the characteristics of ischemia and infarction in acute MCA stroke.

Methods

Patients studied were consecutive sub-6 h from onset internal carotid artery (ICA) territory ischemic stroke cases. A subset of these cases with MCA occlusion were studied with 2 h of continuous MCA monitoring. All patients underwent baseline multimodal computed tomographic (CT) scanning, baseline diagnostic TCD, and 24 h post stroke magnetic resonance (MR) imaging. All MCA occlusion patients studied with continuous monitoring were treated with intravenous thrombolysis. ACA flow diversion was defined as ipsilateral mean velocity of 30% or greater than the contralateral artery. Recanalization status was assessed using the Thrombolysis In Brain ischemic (TIBI) grading system and MES counted “off-line” by experienced observers. Leptomeningeal collateralisation (LMC) was graded on CT angiography. Infarct core and penumbral volumes were defined using CT perfusion thresholds. Infarct volume, reperfusion, and vessel status were measured at 24 h using MR techniques. In patients undergoing recanalization monitoring, comparison was made between those with and without major reperfusion. Multivariable regression analysis was performed to assess for any associations between ACA flow diversion, TIBI grades and MES on infarction controlling for other important clinical variables.

Results

Flow diversion: 53 patients qualified for FD analysis. ACA FD was associated with good collateral flow on CT angiography (p < 0.001) and was an independent predictor of admission infarct core volume (p < 0.001), and 24 h infarct volume (p < 0.001). The likelihood of a favourable outcome (modified Rankin score 0–2) was higher (Odds ratio = 27.5, p < 0.001) in those with flow diversion.

Recanalization monitoring: 27 patients with MCA occlusion treated with intravenous thrombolysis were included in the analysis of recanalization patterns (16 cases with major reperfusion, 11 cases of non-reperfusion). Major TIBI grade improvement (Δ ≥ 3 grades overall) was associated with major reperfusion (p = 0.04) excellent 90 day clinical outcome (p = 0.03), improvement in clinical outcome at 24 h (p = 0.049) and attenuated infarct growth (p = 0.06). MES did not associate with reperfusion status or outcome variables.

Conclusions

ACA FD is independently associated with the smaller infarction volumes and more favourable 90 day clinical outcome. Flow diversion may provide enhanced perfusion of ischemic tissue, offering some protection against infarct expansion and “buying-time” for effective reperfusion and tissue salvage.

Major TIBI grade improvement associates with major reperfusion, favourable 24 h and 90 day clinical outcomes along with a trend to smaller infarct volumes in patients treated with intravenous thrombolysis.

Acute bedside transcranial Doppler assessment of ACA FD and recanalization aids prognostication and therapeutic decision making in acute stroke.