Relationship between the degree of recanalization and functional outcome in acute ischemic stroke is mediated by penumbra salvage volume

What we really need to know is how to actually save that penumbra, this doesn't help one bit. Just maybe you want researchers to solve how to stop the 5 causes of the neuronal cascade of death in the first week.

Relationship between the degree of recanalization and functional outcome in acute ischemic stroke is mediated by penumbra salvage volume

 

• Gabriel Broocks,
• Hashim Jafarov,
• Rosalie McDonough,
• Friederike Austein,
• Lukas Meyer,
• Matthias Bechstein,
• Noel van Horn,
• Marie Teresa Nawka,
• Gerhard Schön,
• Jens Fiehler,
• Helge Kniep &
• Uta Hanning 

Journal of Neurology (2021)Cite this article

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Abstract

Background

The presence of metabolically viable brain tissue that may be salvageable with rapid cerebral blood flow restoration is the fundament rationale for reperfusion therapy in patients with large vessel occlusion stroke. The effect of endovascular treatment (EVT) on functional outcome largely depends on the degree of recanalization. However, the relationship of recanalization degree and penumbra salvage has not yet been investigated. We hypothesized that penumbra salvage volume mediates the effect of thrombectomy on functional outcome.

Methods

99 acute anterior circulation stroke patients who received multimodal CT and underwent thrombectomy with resulting partial to complete reperfusion (modified thrombolysis in cerebral infarction scale (mTICI) ≥ 2a) were retrospectively analyzed. Penumbra volume was quantified on CT perfusion and penumbra salvage volume (PSV) was calculated as difference of penumbra and net infarct growth from admission to follow-up imaging.

Results

In patients with complete reperfusion (mTICI ≥ 2c), the median PSV was significantly higher than the median PSV in patients with partial or incomplete (mTICI 2a–2b) reperfusion (median 224 mL, IQR: 168–303 versus 158 mL, IQR: 129–225; p < 0.01). A higher degree of recanalization was associated with increased PSV (+ 63 mL per grade, 95% CI: 17–110; p < 0.01). Higher PSV was also associated with improved functional outcome (OR/mRS shift: 0.89; 95% CI: 0.85–0.95, p < 0.0001).

Conclusions

PSV may be an important mediator between functional outcome and recanalization degree in EVT patients and could serve as a more accurate instrument to compare treatment effects than infarct volumes.

Introduction

Mechanical thrombectomy (MT) in acute ischemic stroke substantially improves functional outcome in patients with large vessel occlusion [18, 34]. Yet, the time-sensitive selection of patients who will most likely benefit from MT is a critical factor in clinical practice. Neuroimaging may be used to guide endovascular treatment, and may serve as a prognostic biomarker [1, 2, 35]. Past MT landmark trials including patients 0–6 h from symptom onset applied different brain imaging criteria for treatment selection, for instance using computed tomography (CT) perfusion to estimate ischemic core volume (i.e. volume that is thought to represent irreversible tissue injury), compared to the total volume of hypoperfused brain tissue [1, 22, 28]. Accordingly, the presence of ischemic penumbra (metabolically viable brain tissue that may be salvageable with rapid cerebral blood flow restoration) is the fundamental rationale for reperfusion therapy [11]. However, the effect of endovascular treatment on functional outcome highly depends on the degree of recanalization as exemplified in previous studies [15, 20, 21]. Recently, a meta-analysis found an incremental association between the degree of recanalization and clinical outcome [21]. Currently, the American Heart Association (AHA) guidelines recommend a score of ≥ 2b on the modified Thrombolysis in Cerebral Infarction (mTICI) scale as the angiographic goal of MT [29, 30]. However, a wide range of outcome is still evident even in cases of successful reperfusion, indicating that outcome is completely mediated by further baseline and procedural covariates [9, 21].

Currently, it remains uncertain how the volume of penumbra salvage (PSV) mediates the effect of thrombectomy on functional outcome. Moreover, the relationship of penumbra salvage and the degree of recanalization has not yet been investigated.

We hypothesized twofold: First, a higher degree of recanalization is incrementally associated with higher PSV. Second, we hypothesized that PSV is directly linked to functional outcome.