The administration of rtPA before mechanical thrombectomy in acute ischemic stroke patients is associated with a significant reduction of the retrieved clot area but it does not influence revascularization outcome

Abstract

Both intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) are evidence-based treatments for acute ischemic stroke (AIS) in selected cases. Recanalization may occur following IVT without the necessity of further interventions or requiring a subsequent MT procedure. IVT prior to MT (bridging-therapy) may be associated with benefits or hazards. We studied the retrieved clot area and degree of recanalization in patients undergoing MT or bridging-therapy for whom it was possible to collect thrombus material. We collected mechanically extracted thrombi from 550 AIS patients from four International stroke centers. Patients were grouped according to the administration (or not) of IVT before thrombectomy and the mechanical thrombectomy approach used. We assessed the number of passes for clot removal and the mTICI (modified Treatment In Cerebral Ischemia) score to define revascularization outcome. Gross photos of each clot were taken and the clot area was measured with ImageJ software. The non-parametric Kruskal–Wallis test was used for statistical analysis. 255 patients (46.4%) were treated with bridging-therapy while 295 (53.6%) underwent MT alone. By analysing retrieved clot area, we found that clots from patients treated with bridging-therapy were significantly smaller compared to those from patients that underwent MT alone (H1 = 10.155 p = 0.001*). There was no difference between bridging-therapy and MT alone in terms of number of passes or final mTICI score. Bridging-therapy was associated with significantly smaller retrieved clot area compared to MT alone but it did not influence revascularization outcome.

Does prior administration of rtPA influence acute ischemic stroke clot composition? Findings from the analysis of clots retrieved with mechanical thrombectomy from the RESTORE registry

“…Although it could be very informative, there is very little published about the influence of IVT on the characteristics of the retrieved clot, such as its general composition and structural organization. Our recent study comparing the size of extracted thrombi showed that bridging-therapy clots were significantly smaller than MT-only clots [16], a finding that is reproduced in the present larger study.…”

“…There are several studies in the literature comparing final recanalization rate and other clinical outcomes for patients treated with bridging-therapy or MT alone, although there is not yet a clear consensus of opinion [11][12][13][14][15][16]. Nevertheless, bridging-therapy, i.e.…”

“…1b). Median RBCs composition was 45 % for bridging-therapy and 44 % for MTalone clots (H1 = 0.018, P = 0.895); median FIB composition was 30 [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]% for bridging-therapy and 29 % for MT alone (H1 = 0.552, P = 0.458); median PTL composition was 16 % for bridging-therapy and 17 [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]% for MT alone (H1 = 0.014, P = 0.905). Further analysis was then performed combining size and histological composition (Fig.…”

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“…The composition of the clot signifi cantly infl uences the outcome for patients treated with both rtPA and mechanical thrombectomy devices. For example, there is evidence that clots that are red blood cell rich with loose fi brin strands respond best to tPA, which effectively reduces the size of those clots, while other clots are tPA resistant, and need to be removed by mechanical thrombectomy (Rossi et al, 2020). Other recent work in our lab has found that clot composition varies with stroke aetiology (Fig.…”

Histological evaluation of acute ischemic stroke thrombi may indicate the occurrence of vessel wall injury during mechanical thrombectomy

“…We also found that IV rtPA administration correlated with a lower rate of VWI. A recent study demonstrated that thrombolysis significantly reduced the clot size, 22 which may help to retrieve the clot without damaging the occluded vessel. Furthermore, a recent three-dimensional scanning electron microscopy analysis of AIS emboli showed that rt-PA treatment resulted in thinning of fibrin fibers and disruption of fibrin network which may explain the reduced clot size.…”