Tolga D. Dittrich, MD
Endovascular thrombectomy (EVT) is an essential part of acute therapy for ischemic stroke due to large vessel occlusion. As early clinical improvement after successful reperfusion therapy is a reliable predictor of long-term independence, the absence of such clinical progress can discourage the treating stroke team. But does this necessarily mean that the long-term prognosis in such patients is unfavorable? This is one of the questions addressed by Talavera et al. in their paper.
A total of 628 patients with proximal occlusions of the anterior circulation, all of whom received successful EVT (i.e., mTICI 3), were included in the study. After EVT, 142 (22.6%) showed no early neurological improvement. However, 32 (22.5%) still had a favorable long-term outcome. In contrast, 323 (66.5%) of a total of 486 patients with early neurological improvement demonstrated a favorable long-term outcome. Baseline predictors of delayed neurological improvement were male sex (OR 6.4 [95% CI, 2.1-22.3] p=.002), lower baseline NIHSS score (OR 1.4 [95% CI, 1.2-1.5]. p=<.001) and treatment with rtPA (OR 9.1, [95% CI, 2.7-30.9], p=<.001).
The key message of this paper is short and to the point: An initial lack of clinical improvement — despite timely and complete recanalization — may nevertheless be associated with a favorable functional outcome in the long-term. Notably, nearly one in four patients showed a delayed neurological improvement with long-term functional independence. Interestingly, bridging IV thrombolysis was associated with delayed clinical improvement in this study. This could suggest that IV thrombolysis, because of its after-effect following EVT, contributes to improvement in microcirculation due to lysis of residual distal microthrombi not visible in angiograms.
The study has its limitations. In this selected population, it seems likely that there may be other unfavorable accompanying circumstances (such as electrolyte fluctuations or infections) that contributed to the high proportion of patients with a lack of early neurological improvement. The retrospective study design also leaves some uncertainties regarding factors that influence long-term functional outcomes, such as the final infarct volumes on follow-up imaging or the proportion of patients with post-stroke neurological rehabilitation.
Nevertheless, the results of Talavera and colleagues followed by more extensive, prospective studies to clarify the exact mechanisms and clinical influencing factors that lead to delayed neurological improvement after EVT is an interesting area to explore.
