EVT Considerations

1. General & ASPECTS Definition for "Large Core"

A **large core ischemic infarct** is typically defined in clinical practice and trials by:

*   An **ASPECTS (Alberta Stroke Program Early Computed Tomography Score) of ≤5**.

*   A **cerebral infarct volume of >50 to 70 mL**.

2. Core Characteristics (Infarct Core)

On Computed Tomography Perfusion (CTP) imaging, the established **infarct core** (non-viable tissue) is precisely defined by:

*   A reduction in **regional cerebral blood flow (rCBF) to <30%** compared to normal brain tissue (often represented as `rCBF <30%` or `CBF <30%` on perfusion maps).

3. Perfusion Characteristics (Penumbra & Mismatch)

The hypoperfused but salvageable brain tissue surrounding the core (the **ischemic penumbra**) is defined by:

*   A delay on the **time-to-maximum of the tissue residue function (Tmax) map of >6.0 seconds** (Tmax >6.0s).

*   The **perfusion mismatch** represents the volume difference (or ratio) between this total hypoperfused area (Tmax >6.0s) and the established infarct core (rCBF <30%).

Based on the 2026 guidelines and the clinical trials evaluating large core (referred to as "large corridors") strokes, the benefit of Endovascular Therapy (EVT) versus best medical management varies depending on the ASPECTS score, the treatment time window, and the patient's baseline functional status:

1. No Significant Difference in the TESLA Trial (ASPECTS 2 to 5)

While most large core trials (such as SELECT2, ANGEL-ASPECT, TENSION, and LASTE) demonstrated a clear benefit for EVT over medical management

, the TESLA trial stood out as an exception.

ASPECTS 2 to 5: The TESLA trial evaluated patients with an ASPECTS of 2 to 5 within a 24-hour window and found no significant difference in clinical outcomes between patients who underwent EVT and those who received best medical management alone

2. Time Window Constraints for ASPECTS 0–2 (Very Large Core)

The guidelines differentiate recommendations based on how early the patient presents:

Late Window (6 to 24 hours): There is no established recommendation or benefit shown for EVT in patients presenting in the late window with an ASPECTS of 0 to 2. The Class 1 recommendation for EVT in the 6–24 hour window is strictly reserved for patients with an ASPECTS of 3 to 5

Early Window (0 to 6 hours): For patients with ASPECTS 0 to 2, EVT is still supported in the early window as a Class 2a (moderate) recommendation rather than Class 1

. (Note: The LASTE trial, which showed benefit for EVT, included a majority of patients with ASPECTS ≤2).

3. Prestroke Disability (mRS ≥ 2)

The baseline functional level of the patient is a major determinant of whether EVT offers a proven benefit over medical management:

mRS ≥ 2: Across all time windows (0–6 hours and 6–24 hours) and all large core ASPECTS levels (0–2 and 3–5), patients with a prestroke modified Rankin Scale (mRS) score of ≥2 (indicating pre-existing disability) have insufficient data to determine (IDD) any benefit of EVT over medical management

Please follow this Link to Access the 6-24H ACT-Fast Screening Protocol

Active Research Studies - Inclusion/Exclusion Criteria - Point of Care Reference Material:

• Research Studies Page

When patients are repatriated, at times we may want to fax completed notes, beyond the written consultation note. For this purpose, the following ED Fax numbers can be utilized to fax the report:

Hospital ED / FAX #

North York General / 416-756-6793

Mackenzie Health / 905-883-2138

Toronto Western / 414-603-5288

Scarborough and Rouge- General Site / 416-431-8164

Scarborough and Rouge-Centenary Site / 416-281-7455

ICU Fellow #s - direct

ICU CONSULT RESIDENT - 88111

Emerg/Float/Rapid 88121

CRCU blue 88197

CRCU green 88118

CVICU 88114

B5ICU 88112 (AM) Overnight 88114 (4PM-7AM M-F, and W/E) - During COVID-19, 88112 for B5ICU and B4ICU Level 2

Rapid Response 7887 - Rapid RN direct access Line