Mechanical thrombectomy for large vessel occlusion
In the last years, clinical trial evidence has expanded the time window for successful endovascular treatment to 24 h. Current research is aimed at expanding patient selection to mild strokes, large ischemic cores and occlusions of smaller, more distal blood vessels. Further, Giles et al. developed understanding of how to manage blood pressure after thrombectomy and even had promising results for a neuroprotective agent in these patients. Thrombectomy has transformed the ischemic stroke treatment due to large-vessel occlusion. Recent research has focused on expanding patient candidacy for endovascular treatment and improving medical management to support better neurologic outcomes 1).
This device includes a microcatheter that is advanced over a microwire, through the positioned guide catheter. The tip of the microcatheter is positioned adjacent to the proximal aspect of the clot. A separator is advanced through the microcatheter that is advanced back and forth through the clot to disrupt it. The proximal end of the microcatheter is connected to an aspiration pump that is turned on to aspirate the clot fragments. Unlike stent retrievers that a ect recanalization within minutes, Penumbra aspiration device takes longer, with median time of 49 min 4).
Its use is confined to the straight arterial segments because of risk of vessel perforation by the separator action.
In addition to above, other techniques to extract thrombus have also been employed with mixed results including, aspiration with a simple syringe attached to a microcatheter, usage of snares, angioplasty at site of thrombus, stenting etc…
Blood Pressure Management
There is an absence of specific evidence or guideline recommendations on blood pressure management for large vessel occlusion stroke patients. Until randomized data are available, the periprocedural blood pressure management of patients undergoing endovascular thrombectomy can be viewed in two phases relative to the achievement of recanalization. In the hyperacute phase, prior to recanalization, hypotension should be avoided to maintain adequate penumbral perfusion. The American Heart Association guidelines should be followed for the upper end of prethrombectomy blood pressure: ≤185/110 mm Hg, unless post-tissue plasminogen activator administration when the goal is <180/105 mm Hg. After successful recanalization (thrombolysis in cerebral infarction [TICI]: 2b-3), we recommend a target of maximum systolic blood pressure of < 160 mm Hg, while the persistently occluded patients (TICI < 2b) may require more permissive goals up to <180/105 mm Hg. Future research should focus on generating randomized data on optimal blood pressure management both before and after endovascular thrombectomy, to optimize patient outcomes for these divergent clinical scenarios 5).
Mechanical thrombectomy is recommended for selected patients 6–16 hours from onset with large vessel occlusion (LVO) in the anterior circulation who meet other DAWN or DEFUSE-3 eligibility criteria (Level I 6)).
Patients with large vessel occlusion and target mismatch on imaging may be thrombectomy candidates in the extended time window. However, the ability of imaging modalities including non-contrast CT Alberta Stroke Program Early Computed Tomographic Scoring (CT ASPECTS), CT angiography collateral score (CTA-CS), diffusion-weighted MRI ASPECTS (DWI ASPECTS), DWI lesion volume, and DWI volume with clinical deficit (DWI + NIHSS), to identify mismatch is unknown.
We defined target mismatch as core infarct (DWI volume) of < 70 mL, mismatch volume (tissue with TMax > 6 s) of ≥ 15 mL, and mismatch ratio of ≥ 1.8. Using experimental dismantling design, ability to identify this profile was determined for each imaging modality independently (phase 1) and then with knowledge from preceding modalities (phase 2). We used a generalized mixed model assuming binary distribution with PROC GLIMMIX/SAS for analysis.
We identified 32 patients with anterior circulation occlusions, presenting > 6 h from symptom onset, with National Institute of Health Stroke Scale of ≥ 6, who had CT and MR before thrombectomy. Sensitivities for identifying target mismatch increased modestly from 88% for NCCT to 91% with the addition of CTA-CS, and up to 100% for all MR-based modalities. Significant gains in specificity were observed from successive tests (29, 19, and 16% increase for DWI ASPECTS, DWI volume, and DWI + NIHSS, respectively).
The combination of NCCT ASPECTS and CTA-CS has high sensitivity for identifying the target mismatch in the extended time window. However, there are gains in specificity with MRI-based imaging, potentially identifying treatment candidates who may have been excluded based on CT imaging alone 7).
Patients with favorable imaging profiles on both modalities had higher odds of receiving endovascular thrombectomy (EVT) and high functional independence rates. Patients with discordant profiles achieved reasonable functional independence rates, but those with an unfavorable CTP had higher adverse outcomes. Trial registration: ClinicalTrials.gov NCT02446587 8).
The benefit of mechanical thrombectomy (MT) in patients with stroke presenting with mild deficits (National Institutes of Health Stroke Scale [NIHSS] score <6) owing to emergency large-vessel occlusion (ELVO) remains uncertain.
To assess the outcomes of patients with mild-deficits ELVO (mELVO) treated with MT vs best medical management (bMM).
Goyal et al. retrospectively pooled patients with mELVO during a 5-year period from 16 centers. A meta-analysis of studies reporting efficacy and safety outcomes with MT or bMM among patients with mELVO was also conducted. Data were analyzed between 2013 and 2017.
They identified studies that enrolled patients with stroke (within 24 hours of symptom onset) with mELVO treated with MT or bMM.
Efficacy outcomes included 3-month favorable functional outcome and 3-month functional independence that were defined as modified Rankin Scale scores of 0 to 1 and 0 to 2, respectively. Safety outcomes included 3-month mortality and symptomatic and asymptomatic intracranial hemorrhage (ICH).
They evaluated a total of 251 patients with mELVO who were treated with MT (n = 138; 65 women; mean age, 65.2 years; median NIHSS score, 4; interquartile range [IQR], 3-5) or bMM (n = 113; 51 women; mean age, 64.8; median NIHSS score, 3; interquartile range [IQR], 2-4). The rate of asymptomatic ICH was lower in bMM (4.6% vs 17.5%; P = .002), while the rate of 3-month FI (after imputation of missing follow-up evaluations) was lower in MT (77.4% vs 88.5%; P = .02). The 2 groups did not differ in any other efficacy or safety outcomes. In multivariable analyses, MT was associated with higher odds of asymptomatic ICH (odds ratio [OR], 11.07; 95% CI, 1.31-93.53; P = .03). In the meta-analysis of 4 studies (843 patients), MT was associated with higher odds of symptomatic ICH in unadjusted analyses (OR, 5.52; 95% CI, 1.91-15.49; P = .002; I2 = 0%). This association did not retain its significance in adjusted analyses including 2 studies (OR, 2.06; 95% CI, 0.49-8.63; P = .32; I2 = 0%). The meta-analysis did not document any other independent associations between treatment groups and safety or efficacy outcomes.
This multicenter study coupled with the meta-analysis suggests similar outcomes of MT and bMM in patients with stroke with mELVO, but no conclusions about treatment effect can be made. The clinical equipoise can further be resolved by a randomized clinical trial 9).
Mechanical thrombectomy utilizing combined manual aspiration with a stent retriever is an effective and safe strategy for endovascular recanalization of large vessel occlusions presenting within the context of acute ischemic stroke (AIS). 11).
However, when difficult anatomy is encountered in which the reperfusion catheter cannot be positioned well, the outcomes can be less than optimal.
A 45-year-old male had a type A aortic dissection that presented with sudden onset neck pain and cold sweating. Aortic valve resuspension, proximal anastomosis of the ascending aortic graft, partial aortic arch graft replacement, and innominate artery reimplantation was performed. After the aortic surgery, left limb weakness was noted in the intensive care unit. Computed tomography angiography of the brain showed right common carotid artery (CCA) occlusion up to the internal carotid artery (ICA). The right CCA was exposed and directly punctured. A thrombus was successfully removed, and a total of 5 stents were deployed to treat the ICA and CCA dissection. Angiography showed a final TICI 3 result, and the patient had excellent clinically recovery.
Acute mechanical thrombectomy through open direct neck puncture due to an acute type A aortic dissection and concurrent CCA dissection and occlusion is an effective and optimal method 12).