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Year : 2023  |  Volume : 71  |  Issue : 2  |  Page : 204--206

Endovascular Thrombectomy in Acute Ischemic Stroke Due to Large Vessel Occlusion: Current Concepts and Controversies

P Sarat Chandra, Ramesh Doddamani 
 Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India

Correspondence Address:
P Sarat Chandra
Department of Neurosurgery, CN Centre, All India Institute of Medical Sciences, New Delhi - 110 029

How to cite this article:
Chandra P S, Doddamani R. Endovascular Thrombectomy in Acute Ischemic Stroke Due to Large Vessel Occlusion: Current Concepts and Controversies.Neurol India 2023;71:204-206

How to cite this URL:
Chandra P S, Doddamani R. Endovascular Thrombectomy in Acute Ischemic Stroke Due to Large Vessel Occlusion: Current Concepts and Controversies. Neurol India [serial online] 2023 [cited 2023 Sep 24 ];71:204-206
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Full Text

The management of acute ischemic stroke (AIS) has witnessed a sea change over the years. Patients of AIS were managed in the primary stroke centers with intravenous thrombolysis (IVT) as a standard of care in the past decade, irrespective of the type of stroke. However, with the emergence of mechanical thrombectomy (MT) in recent years, especially for the anterior circulation large vessel occlusions (ACLVOs), there has been a paradigm shift in the management of this patient population. The HERMES study, incorporating five randomized controlled trials (RCTs), evaluated individual patient data and has shown superior efficacy of MT compared to IVT in AIS due to ACLVO. The efficacy of MT in appropriately selected patients amounts to 80% recanalization rate compared to 20%–30% using IVT alone.[1] Beyond doubt, MT has now become the new standard of treatment for ACLVO strokes.

 Primary and Comprehensive Stroke Centers

The stroke workflow has synchronously undergone changes to meet the demands of this subgroup of patients. Especially, development of comprehensive stroke centers (CSCs), capable of performing both IVT and MT (round-the-clock emergency services) apart from access to advanced stroke imaging. This does not negate the role of primary stroke centers (by definition, capable of performing IVT without the facility for MT). The limited access to the CSCs for the patient population residing in the remote/nonurban areas prolongs the door to puncture time in candidates eligible for MT. The role of Primary strike centres (PSCs) becomes equally important in this scenario, as timely (<4.5 h) institution of IVT as a bridge till MT is performed. The drip and ship model (IVT in PSCs in all eligible patients followed by shifting to CSCs for MT) or the mothership model (direct transfer to CSCs) is adopted depending upon the geographic location.[2] In a prospective study from Catalonia (Spain), D'Anna et al.[3] compared both the models, seeking answers to the difference in outcomes. The authors found no difference in 90-day functional outcomes, whereas statistically significant increase in the hemorrhagic complications was noted in the drip and ship model. Similarly, the RACECAT trial, a multicenter nonurban population-based RCT, tried to address this issue. This study compared the 90-day disability outcomes between patients of nonurban areas transferred to PSCs followed by CSCs and those transferred directly to the CSCs. This study replicated similar results.[4]

Several interesting aspects may be noted from the above studies. Overall, the mean time from onset to groin puncture in the drip and ship model was 302 min, despite the mean transport time of 48 min. This highlights the robustness of their health policies as well as the understanding of the emergent nature of the disease among the health-care professionals at primary stroke care level. Another interesting fact noted in this study was the door to groin puncture time. Patients received from PSCs had shorter mean time of 53 minutes from arrival to groin puncture compared to those directly presenting to the CSCs (mean time of 138 min). Thereby indicating the excellent tele-networking between the centers, with consequent preparedness well before the patient arrives. This reinforces the need for a collaborated approach to achieve best results.[4]

 Debate of Bridging Thrombolysis Versus Direct MT

Despite the fact that MT has been proven to be the best management in large vessel occlusion (LVO) strokes in suitable patients, the role of IVT cannot be undermined. As noted in the RASECAT trial, patients of AIS with LVO should be shifted to the nearest available stroke center, either PSC or CSC.[4] Patients presenting to PSCs, after evaluation, if eligible for IVT, should be given the benefit followed by transfer to the MT capable center (drip and ship model). However, the dilemma exists when a similar patient arrives directly to the CSCs; whether to proceed with direct MT or to initiate IVT followed by MT called bridging thrombolysis (BT). There is a strong debate regarding the benefits of BT versus direct MT (d-MT) in LVO strokes. The advantages of BT include softening of the clot, partial dissolution, its benefits in distal clots (M2-Middle cerebral artery (MCA), and the first-pass effect during MT. These benefits are achieved at the cost of increased chances of intracranial bleeds and distal embolization of the softened proximal clot. Six noninferiority RCTs studied the efficacy of either treatment strategy in patients presenting to CSCs. Two of these studies demonstrated noninferiority of direct Mechanical Thrombectomy (d-MT) in comparison to the standard BT, while three of them failed to show noninferiority of d-MT so far.[5] The SWIFT DIRECT randomized trial demonstrated enhanced efficacy of BT compared to d-MT, with similar rates of symptomatic parenchymal bleed.

Leyla et al.[6] have similarly compared the role of BT versus d-MT in ACLVO strokes and have published their study in this issue of Neurology India. The authors have reported superior functional outcomes with BT (n = 149) in terms of 90-day modified Rankin Scale (mRS) scores compared to d-MT (n = 210). There was no significant difference noted in the occurrence of intracranial hemorrhage.[6] In the real-world situation, considering that two-thirds of the world's population inhabits in the low- and middle-income countries (LMICs), the role of PSCs is still highly relevant. The longer travel distances due to nonavailability/limited number of CSCs, IVT may still b e the only available option. The recanalization rate following IVT for M2 occlusion is around 70%, while for M1 and terminal internal carotid artery (ICA), it drops drastically to 30% and 10%, respectively.[4]

Indian scenario

Considering new-onset strokes, the stroke burden in India is approximately 130–152/100,000 population per year. This corresponds roughly to 19 million new strokes/year and considering 30% of these to be LVO strokes, it would be just above half a million/year. As per the European Stroke Organization, a minimum of one CSC for every 1 million population (ideal target being seven or eight) is necessary. In India, we just have 0.1 stroke centers for every 1 million population, with 0.2 trained neuroendovascular specialists (currently, less than 1000 trained neurointerventionists exist in the country). They are mainly restricted to major tier 1 cities, with 70% concentrated in the private sector hospitals. These numbers showcase the need to bridge the enormous treatment gaps.[7],[8]

Development of the infrastructure and strengthening the public sector hospitals at the tier 2/3-level cities by enforcing stringent polices might be beneficial. This would be possible through public–private collaboration. The other concern is to increase the trained specialists to tackle this ever-increasing disease number. The clinicians, mainly neurologists and neurosurgeons, are often the first point of contact for patients presenting with stroke. Currently, exclusive neurointervention residency programs do not exist in India. The neuroradiology residency program though has limited exposure, except in high-volume centers. In 2020, the National Board of Examination (NBE)-accredited 2-year program was introduced, which awards the degree of Fellow in National Board (FNB) in neurovascular intervention. The neurosurgeons, neurologists, and radiologists are eligible for pursuing this course at any of the four centers recognized across India. This is a welcome step toward increasing the number of trained neurointerventionists, thereby filling the treating gap. Recruiting more centers in future shall be a step toward addressing the deficient numbers.[9]

The role of dual trained/hybrid neurosurgeons is tremendous at the community level. At present, India has just short of 500 accredited intake positions for neurosurgery training annually, which is likely the highest number worldwide. The numbers are more than the neurology and far more than the neuroradiology programs. Given these numbers and the increasing availability of neurosurgeons even in tier 2/3 cities makes it highly necessary to be trained in neurointervention. The ready availability of cardiac cath labs in these small cities provides the required infrastructure to be able to cater to the stroke patients in a timely manner. Apart from performing MT, a hybrid neurosurgeon is capable of providing a comprehensive care in the event of hemorrhagic transformation/large infarct by performing decompressive surgeries.[10],[11]

Lack of awareness among the general population and general practitioners regarding timely stroke intervention still poses a significant challenge. This leads to delay in reaching the stroke centers, and hence the treatment. Studies in the past from the eastern part of India have shown the onset to door timings was 3 h in the urban setting, while in the rural areas, it was more than 24 h.[7] The study by Rishi and Collegues in this issue of Neurology India titled “Decompressive Hemi Craniectomy in Malignant Middle Cerebral Artery Infarction: Adding Years of Quality Life or Mere Existence? “, highlights the importance of early revascularization. The authors studied the quality of life in patients undergoing decompressive craniectomies for malignant MCA infarcts (n=43). They noted survival advantage and improvement in functional outcomes. However, functional independence and cognitive improvement was not achieved, owing to the loss of cerebral tissue due to ischemia. This study underscores the need for timely institution of revacularization therapy (IVT & MT) might lead to excellent outcomes in patients presenting with AIS.[12] With the extension of the time window from stroke onset to MT (i.e. up to 24 h) as per the American Heart Association/ American Stroke Association/ Acute Ischemic Stroke guidelines, there is scope for improving the onset to door time duration.[13] In a recent study published from a tertiary care center in North India, it was reported that the proportion of stroke patients presenting was comparable to the studies from the west.[14] This indicates changing trends, suggesting growing awareness among the urban population. However, this lacuna still persists in the suburban/rural population and can be dealt with by creation of public awareness through stroke programs. The concept of “Time is Brain” should reach the remote areas, especially the health workers. This can be achieved by strengthening telemedicine services, consolidating and upgrading emergency medical services in the future.

In conclusion, acute ischemic LVO strokes show gratifying results if appropriate and timely intervention in the form of MT with or without BT is instituted.



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