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The Thrombolysis in Cerebral Infarction (TICI) grading system was first described by Higashida in 20031 and later modified.2 More recently a 2C grade (near complete, >90%) has been adopted widely (table 1).3 However, this grading system is based on the assumption that the emergent large vessel occlusion (ELVO) involves the M1 segment (or carotid terminus) and loses relevance when this is not the case. Consider a superior division M2 occlusion, for example. Assuming codominant M2 divisions, from the onset of the procedure the TICI grade would be a 2B: an endpoint indicating successful recanalization in the historical literature. If partial M2 recanalization was achieved it may still be graded as a 2B at the conclusion, rendering it impossible to decipher if progress had been made. An alternative approach would be to grade the M2 occlusion a ‘target vessel TICI’ 0. In this manner, at the procedure conclusion, whether it remained a 0 or if it were recanalized to a 2C or 3 would provide more pertinent and clinically relevant information. This same principle can be applied to any target vessel during thrombectomy. This would include target vessels in the anterior and posterior circulation, as well as those supplying eloquent and non-eloquent territories.
Rapid advancements continue to make this an exciting time in the history of stroke therapy. Research and development efforts continue to expand our device armamentarium for thrombectomy procedures. Evidence from randomized clinical trials continues to elucidate patient cohorts who can benefit from treatment. The time window for treatment has expanded up to 24 hours with the results from DAWN4 and DEFUSE-35 utilizing advanced imaging for triage.6 Data have also shown a potential benefit for patients presenting with larger core infarcts.7 8 Recent level 1A evidence has proven the utility of direct aspiration as another useful technique to treat patients with ELVO.9 10 Most recently, the target vessel that might be considered for possible treatment, and even the very definition of ELVO, has expanded. Subgroup analysis of ASTER data on M2 occlusions11 in the context of observational data from multiple centers around the globe12–23 now begs the question: should paradigms developed for M1 occlusions be applied to the M2 divisions and its branches? Additionally, evidence demonstrating feasibility has been recently published in support of thrombectomy for more distal locations in both the anterior and posterior circulations such as the M3, A2, P2, etc.24–28
As thrombectomy is offered to an increasingly larger patient population involving more distal occlusions, safety and outcomes data must be carefully examined. The move to treating more distal occlusions requires a re-thinking of one of the most important and commonly cited metrics for any published data involving thrombectomy—the TICI grading system.29 TICI is no longer applicable when applied to more distal ELVO. A revision of this important angiographic endpoint will be required to ensure that results from future work will be consistent from one trial to another. A more precise post-thrombectomy angiography grading system would ensure data collection of the highest level.
As devices continue to access more distal vasculature in a safe and expedient fashion, paradigms for ELVO treatment and description will evolve. As procedures involve M2 segments and beyond, it is imperative that thrombectomy results are categorized in a clear and standardized fashion using standardized reporting.30 31 In other words, we recommend assigning a TICI score for the target vessel.
We would like to thank Alyssa Pierce for editing and submitting this manuscript.
Contributors All authors should receive authorship credit based on the material contribution to this article, their revision of this article, and their final approval of this article for submission to this journal.
Competing interests AMS: Penumbra Consulting, Honorarium, Speaker Bureau; Pulsar Vascular Consulting, Honorarium, Speaker Bureau; Microvention Consulting, Honorarium, Speaker Bureau, Research; Stryker Consulting, Honorarium, Speaker Bureau. AST: Codman Consulting, Honorarium, Speaker Bureau, Research Funding; Covidien Consulting, Honorarium, Speaker Bureau; Penumbra Consulting, Honorarium, Speaker Bureau, Research Grants; Microvention Consulting, Honorarium, Speaker Bureau, Research Grants; Blockade – Stock, Consulting, Honorarium, Speaker Bureau; Pulsar Vascular Stock, Consulting, Honorarium, Speaker Bureau, Research; Medtronic Consulting, Honorarium, Speaker Bureau. Minnetronix consulting Penumbra consulting Cerenovus consulting. ASA: Consultant for Johnson and Johnson, Leica, Medtronic, Microvention, Penumbra, Scientia, Siemens, Stryker; Research support from Microvention, Penumbra and Siemens; Shareholder Bendit, Cerebrotech, Endostream, Magneto, Neurogami, Serenity, Synchron and Triad Medical. D Fiorella: Medtronic (Consultant, Proctoring), Cerenovous (Royalties, Consulting), Microvention (Consulting, Research Support), Vascular Simulations (Board Member, Stockholder), Penumbra (Research Support), Siemens (Research Support), Neurogami (Stockholder). D Frei: Medical Advisory Board/Consultant/Speakers Bureau Ceranovus, Genentech, Penumbra, Shape Memory Medical, Stryker; Research support Ceranovus, Medtronic, Microvention, Penumbra, Siemens, Stryker; Stock ownership Penumbra.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement N/A.
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