MRI-based Algorithm for Acute Ischemic Stroke Subtype Classification

Abstract

Background and purpose: In order to improve inter-rater reliability and minimize diagnosis of undetermined etiology for stroke subtype classification, using a stroke registry, we developed and implemented a magnetic resonance imaging (MRI)-based algorithm for acute ischemic stroke subtype classification (MAGIC).

Methods: We enrolled patients who experienced an acute ischemic stroke, were hospitalized in the 14 participating centers within 7 days of onset, and had relevant lesions on MR-diffusion weighted imaging (DWI). MAGIC was designed to reflect recent advances in stroke imaging and thrombolytic therapy. The inter-rater reliability was compared with and without MAGIC to classify the Trial of Org 10172 in Acute Stroke Treatment (TOAST) of each stroke patient. MAGIC was then applied to all stroke patients hospitalized since July 2011, and information about stroke subtypes, other clinical characteristics, and stroke recurrence was collected via a web-based registry database.

Results: The overall intra-class correlation coefficient (ICC) value was 0.43 (95% CI, 0.31-0.57) for MAGIC and 0.28 (95% CI, 0.18-0.42) for TOAST. Large artery atherosclerosis (LAA) was the most common cause of acute ischemic stroke (38.3%), followed by cardioembolism (CE, 22.8%), undetermined cause (UD, 22.2%), and small-vessel occlusion (SVO, 14.6%). One-year stroke recurrence rates were the highest for two or more UDs (11.80%), followed by LAA (7.30%), CE (5.60%), and SVO (2.50%).

Conclusions: Despite several limitations, this study shows that the MAGIC system is feasible and may be helpful to classify stroke subtype in the clinic.

Keywords: Algorithm; Classification; Magnetic resonance imaging; Stroke.

Figure 1

MRI-based algorithm for acute ischemic stroke classification (MAGIC) (A) Step 1: Consideration of other determined etiology of stroke. (B) Step 2: Screening for small vessel occlusion (SVO) using MRI. (C) Step 3: Consideration of relevant artery stenosis or occlusion. (D) Step 4: Consideration of recanalization status of occluded artery after thrombolytic therapy. (E) Step 5: Consideration of follow-up recanalization status of occluded artery without thrombolytic therapy. ★: If one of three examinations (TTE, Holter, and TEE [or MDCT]) was not performed, then the patient was classified as 'undetermined incomplete'. ☆: The follow-up vascular status would be evaluated by MR/CT angiography or transcranial doppler (TCD). If no examinations are performed, then the patient should be classified as 'undetermined incomplete'. LAA, large artery atherosclerosis; SVO, small vessel occlusion; CE, cardioembolism; UD, undetermined cause; UD ≥2, two or more undetermined causes; DWI, diffusion weighted image; Hx, history; ECG, electrocardiography; LAA-LC, large artery atherosclerosis with lacunae; LAA-BR, branch atheromatous disease; W/U, work-up; TTE, transthoracic echocardiography; TEE, transesophageal echocardiography; MDCT, multi-detector row computerized tomography; Ant, Anterior; LAA-NG, large artery atherosclerosis with normal angiography; F/U, follow-up.

Figure 2

Kaplan-Meier survival curves comparing risk of recurrent stroke. Cumulative analysis shows fatal or nonfatal recurrent stroke rates according to stroke subtypes. LAA, large artery atherosclerosis; SVO, small vessel occlusion; CE, cardioembolism; UD, undetermined cause.

Figure 3

Kaplan-Meier survival curves comparing risk of recurrent stroke. Cumulative analysis shows fatal or nonfatal recurrent stroke rates according to special categories of MAGIC. LAA, large artery atherosclerosis; Pure LAA, classically defined LAA; LAA-BR, branch atheromatous disease; LAA-NG, LAA with normal angiography; LAA-LC, LAA with lacunae; SVO, small vessel occlusion.