In 2015, a series of randomized trials led to the
widespread acceptance of mechanical thrombectomy (MT) as a treatment for
patients with acute ischemic stroke. Particularly, MT for large vessel
occlusion (LVO) under specific pre-treatment conditions is now
considered the standard of care (1).(That standard of care is still a complete failure, not 100% recovery! The operative word there is 'care'; NOT RESULTS OR RECOVERY!)
Meanwhile, clinical investigations have shifted their
focus toward expanding treatment indications by exploring the
effectiveness of MT in cases with longer treatment time windows, lower
pre-treatment ASPECT scores, distal branch occlusions, and posterior
circulations. LVO associated with intracranial atherosclerotic disease
(ICAD) is one of the actively discussed conditions. Reports indicate
that ICAD accounts for 6% (2) to 29.6% (3)
of ischemic strokes, with varying prevalence among ethnic backgrounds,
being more common in Asian, African-American, and Hispanic populations.
The challenges in treating ICAD-related LVO are 2-fold.
Firstly, diagnosing ICAD based on the initial imaging is often
technically impossible due to the lack of contrast filling in the target
lesion. As a result, interventionalists need to make a decision once
partial recanalization of the target lesion is achieved although
differentiating between ICAD-related occlusion and occlusion caused by
hard clot or arterial dissection can also be challenging. Secondly,
ICAD-related occlusions are known to be associated with a higher rate of
post-treatment re-occlusion (4).
Therefore, the selection of rescue therapies such as Percutaneous
Transluminal Angioplasty (PTA), PTA with stenting (PTAS), and/or
antiplatelet therapy (Glycoprotein IIB/IIIA inhibitor) plays a crucial
role in maximizing treatment efficacy while minimizing post-procedure
complications such as symptomatic intracerebral hemorrhage (sICH).
Numerous non-controlled studies have been conducted to
address these issues; however, the optimal timing to shift from MT to
PTA/PTAS during the procedure remains unclear. The number of
thrombectomy attempts made can provide more convincing evidence of
unsuccessful reperfusion/underlying ICAD, but it also raises concerns
about intimal damage due to endothelial denudation, vessel perforations
or stretching/torsions.
In this Research Topic of Frontiers of Neurology, Deng et al.
conducted a retrospective subgroup analysis of the Angel-ACT registry
to evaluate the efficacy and safety of PTAS for ICAD-related acute LVO.
Of the 1,793 patients enrolled in the Angel-ACT group, 475 patients who
met the inclusion criteria were included in the study. The patients were
divided into three groups based on treatment methods: (1) Early Rescue
Therapy Group: Patients underwent PTA/PTAS after one or no MT attempt,
(2) No Rescue Therapy Group: Patients treated only with MT, and (3) Late
Rescue Therapy Group: Patients underwent PTA/PTAS after two or more MT
attempts.
After propensity score matching, the Early Rescue
Therapy group showed better functional outcomes (mRS 0–1) at 90 days
compared to the No Rescue Therapy group [adjusted odds ratio (aOR),
0.55, p = 0.01] or Late Rescue Therapy group (aOR 0.39, p = 0.01). There was no difference in the risk of symptomatic intracranial hemorrhage between the groups.
The authors concluded that once ICAD-related LVO is
suspected, early decision-making to perform rescue therapy improves the
efficacy of treatment without increasing the risk of post-procedural
complications. The relatively poor clinical outcome in the Late Rescue
Therapy group, which underwent MT attempts of twice or greater before
transitioning to PTA/PTAS, was accounted for by (1) the lower
reperfusion rate that can lead to prolonged procedure time and (2) more
intimal damage causing vasospasm and intraluminal thrombosis.
This article provides a valuable contribution to the
field of neuro-interventional practice by addressing another predicament
that interventionalists have to face from time to time. The study
provided another evidence that early decision making of shifting the
procedure from simple MT to the rescue therapy improves the treatment
outcomes of patient with ICAD-related-LVO.
The results above is also consistent with a recently
performed large-scale study, the SAINT (Stenting and Angioplasty in
Neurothrombectomy) study, which is a multicenter retrospective study
evaluating the efficacy of rescue intracranial stenting for failed
thrombectomy (2).
In our Research Topic, there is another article that delves into the same subject. Authored by Cai et al., the article is titled “Rescue
intracranial stenting for acute ischemic stroke after mechanical
thrombectomy failure: a systematic review, meta-analysis, and trial
sequential analysis.” The authors conducted a meta-analysis and
trial sequential analysis of 15 clinical studies (1,595 patients)
evaluating the efficacy and safety of rescue stenting for the failed MT.
Compared to non-stenting approaches, rescue stenting was associated
with better modified Rankin Scale (mRS) scores (0–2), a lower 90-day
mortality rate, without increasing the risk of symptomatic intracranial
hemorrhage. The trial sequential analysis also confirmed sufficient
sample size and statistical power of the meta-analysis concerning mRS
scores. Authors concluded that the study supported the use of rescue
stenting as an effective and safe treatment for patients with acute
ischemic stroke after a failed MT.
As we witness the growing body of positive clinical data
regarding the effectiveness of rescue therapy for IACD-related-LVO, it
is logical to consider a randomized clinical trial (RCT) as the
subsequent phase to gain more clarity on the treatment's clinical
advantages. Nevertheless, it is important to exercise caution due to the
historical track record of PTA/PTAS for “symptomatic ICAD”, which has
been discouraging (5, 6).
Recently, another RCT, the CASSIS trial, also failed to show the
benefit of PTAS for the treatment of symptomatic severe ICAD (7).
Needless to say the “ICAD-related-LVO” and “symptomatic ICAD” are
totally different condition. Nevertheless, the occurrence of
post-treatment stroke events or deaths within a 1-year timeframe, which
range from 8.5 to 19.7% (5, 8),
cannot be ignored, and it emphasizes the urgent requirement for new
technological advancements or peri-procedural therapies to enhance the
safety of the procedure.
The overall efficacy of rescue therapy for failed
thrombectomy cases has been improving over the past several years,
partially due to the improvement of the peri-procedural antiplatelet
therapy. For instance, an increasing number of studies have reported the
benefits of utilizing intra-arterial (IA) injection of short-acting
IIb/IIIa inhibitors, such as Tirofiban, as a rescue treatment for failed
thrombectomy (9).
Furthermore, post treatment protocols of antiplatelet therapy have been
changing. Interventionalists are now screening patients more frequently
using CYP2C19 genetic testing or platelet aggregometry to rule out
potential clopidogrel non-responders and proactively using the
new-generation antiplatelet agents, such as ticagrelor or prasugrel,
which are fast-acting agents with more consistent efficacy compared to
the first-generation thienopyridine, clopidogrel. Given that the
majority of RCTs in the past were designed to use clopidogrel for
post-dual antiplatelet therapy, there is hope that future RCTs may be
expected to have better efficacy and safety in the treated arm.
Currently, there are ongoing developments for the ICAD
treatment with the introduction of new-generation endovascular stents
specifically designed for this condition, including drug-eluting stent
systems. Encouraging results have emerged from several clinical studies
conducted in China (10).
On the other hand, the lack of an appropriate animal model that
accurately simulates ICAD poses challenges in conducting preclinical
evaluations for these innovative devices. Therefore, there is a pressing
need to establish ICAD animal models that effectively replicate
post-treatment thromboembolism and in-stent stenosis. By doing so, we
can expedite the progress of new device development aimed at treating
patients with treatment resistant LVO.