Elena Zapata-Arriaza, MD

Mosimann PJ, Kaesmacher J, Gautschi D, Bellwald S, Panos L, Piechowiak E, et al. Predictors of Unexpected Early Reocclusion After Successful Mechanical Thrombectomy in Acute Ischemic Stroke Patients. Stroke. 2018

Obtaining and maintaining TICI 2b-3 recanalization grade is one of the most important modifiable predictors related to a good functional outcome in stroke patients due to large vessel occlusion.

The authors performed a retrospective analysis obtained prospectively from the institutional Bernese Stroke Registry. All patients with acute ischemic stroke (n=972) treated by mechanical thrombectomy between January 2010 and July 2017 with a Solitaire stent retriever ± distal aspiration catheters were reviewed. The main goal of this paper was to identify the prevalence, clinical impact, and predictors of early reocclusion after initially successful thrombectomies. The originality of the paper is the possibility to know the reocclusion rate after a successful thrombectomy in a real-life prospective cohort. In addition, predictors of reocclusion and the relation with clinical outcomes entail an interesting point to predict some cases of futile recanalization. The authors included in the analysis all the patients with successful recanalization grade (TICI 2b-3 score) and magnetic resonance or computed tomography angiography images available at follow-up within 48 hours (N= 711).

Among the mentioned 711 analyzed patients, 16 (2.3%) presented reocclusion after successful recanalization. Median time to early reocclusion diagnosis was 20 hours, and most reocclusions were related with clinical improvement absence or even secondary worsening after procedure (evaluated by a drop in NIHSS). Repeated thrombectomy for reocclusion was performed in 3/16 patients (18.8%). After multivariable logistic regression analysis, functional dependency before the stroke, site of occlusion, stroke pathogenesis, and admission platelet count were factors significantly associated with early reocclusion within 48 hours. In fact, the best cutoff between early and no reocclusion was a platelet count of ≥220 g/L (Youden index), yielding a sensitivity of 87.5% and specificity of 46.9%.

It is remarkable that 13/16 (81.3%) patients with reocclusion had angiographic irregularities on the last angiographic run, which were not reported or misinterpreted by the neurointerventionalist as material-induced vasospasm. In an occlusion site-matched cohort, admission platelet count (aOR for every g/L increase, 1.01; 95% CI, 1.00–1.03; P=0.042), residual thrombus/vessel wall irregularities after thrombectomy (aOR, 58.94; 95% CI, 4.94–703.16; P=0.001), and other determined pathogenesis according to the TOAST classification were the only significant predictors of early reocclusion identified in a multivariable logistic regression analysis in this subgroup. Finally, patients with early reocclusion compared with those with sustained recanalization had a worse clinical outcome at day 90 (modified Rankin Scale ≤2, 20.0% versus 51.3%; P=0.019), although mortality did not differ (20.0% versus 19.0%; P>0.999), and the 3 patients with early reocclusion in whom thrombectomy was repeated showed no clinical improvement.

Interesting analysis can be obtained from this paper. Regarding clinical aspects, it is relevant to know that the mean time to reocclusion onset is within the first 24 hours after endovascular treatment. Reocclusion could be the underlying cause of the clinical worsening or lack of improvement seen in patients with a good recanalization degree. Although the control of intracranial vascularization is not the usual practice in the first 24 h after treatment, it would be interesting to propose an intracranial angiographic study (by CT or MRI) in those patients with TICI 2b-3 after the procedure and who do not improve or even get worse on the first day after the onset of stroke. It is possible we could find numerous cases of arterial reocclusion, differentiating it from a futile recanalization. Another piece of information to take into account is the clinical consequence of reocclusion and its re-treatment; the N of re-treatment is small (3 of 16 reocclusions) and none with clinical improvement. Given the low prevalence found in the study, it is possible that more extensive cohorts are needed to know the true clinical implication of re-treating a patient with reocclusion. Is it really worth knowing if there is reocclusion, if the possible retreatment may not imply clinical improvement? In a patient who does not show improvement, how is it possible to know reocclusion clinically? This could have occurred half an hour after the end of the procedure or at 10 hours after this, and the time to recanalization affects the functional result.

Regarding the predictors of such reocclusion, the study has identified 4 factors associated with early reocclusion despite an initial mTICI2b/3 result: elevated platelet counts at admission >220 g/L, missed residual thrombus or stenosis on the past angiographic run after thrombectomy, M2 occlusion as the initial occlusion site, and stroke of undetermined cause. A high platelet count at admission could be taken as a risk marker for reocclusion, although considering an early administration of antiplatelet agents, especially in patients treated with intravenous fibrinolysis, present a currently high risk. Likewise, the loading dose of the usual antiplatelets therapy could be very high and risky to guarantee early and rapid antiplatelet therapy in the patient. Regarding residual thrombus or stenosis in angiography, it should make us think if it is necessary to wait a reasonable time after completing the procedure, in order to avoid early reocclusion and remedy if necessary. It is possible that the rest of thrombus is related to the existence of a significant burden of thrombus that requires other techniques for resolution. An example would be to use a continuous aspiration pump with distal aspiration or the combination of this with a stentriever to extract the entire thrombus in patients with a high risk of reocclusion or with a high burden of thrombus. In the case of ESUS, it is possible that its embolic origin generates a new embolism to the same artery rather than a new reocclusion.

In any case, this article is an interesting basis to assess the possibility of reocclusions that can be interpreted as futile recanalizations and to raise risk groups in which to propose a closer follow-up, given its clinical implication. For the time being, more studies are needed to assess the therapeutic management of these cases.