Outcomes of Mechanical Thrombectomy in the Early (&lt;6-hour) and Extended (≥6-hour) Time Window Based Solely on Noncontrast CT and CT Angiography: A Propensity Score–Matched Cohort Study

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FIG 1.
Flow sheet patient selection.
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FIG 2.
A, Mean proportion of favorable functional outcomes (mRS 0–2) per 4-hour interval of time since symptom onset to intervention, including a trendline. The trendline declines with time. B, CT-ASPECTS of all cases plotted across time from symptom onset to intervention. The trendline remains almost stable with time, representing patient selection based on favorable CT-ASPECTS.
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FIG 3.
Standardized mean differences for covariates integrated into propensity score matching. Prematching (unadjusted) standardized mean differences and postmatching (adjusted) standardized mean differences are shown. Standardized mean difference < 0.1 indicates well-matched samples.
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FIG 4.
Unadjusted (unmatched) and adjusted (matched) group comparison for the early 0- to 6-hour time window (indicated by 0) and the extended 6- to 24-hour time window (indicated by 1). Density overlay for age, baseline NIHSS, and ASPECTS and equality of height of proportions for female sex and location demonstrate good comparability after propensity score matching.

Table 1:

Baseline characteristics

	Overall Cohort
	0–6 Hours (n = 205)	6–24 Hours (n = 132)	P Value
Variable
Age (median) (IQR) (yr)	72 (61–80)	75 (60–83)	.418
Female	104 (50.7%)	71 (53.4%)	.584
Baseline NIHSS (median) (IQR)	18 (14–24)	17 (11–22)	.045
Premorbid mRS (median) (IQR)	0 (0–1)	0 (0–1)	.600
Risk factors
Arterial hypertension	157 (76.6%)	106 (80.3%)	.421
Type 2 diabetes	60 (29.3%)	38 (28.8%)	.924
Dyslipidemia	142 (69.3%)	95 (72.0%)	.596
Coronary artery disease	54 (26.3%)	34 (25.8%)	.905
Atrial fibrillation	90 (43.9%)	47 (35.6%)	.130
Chronic kidney disease	47 (22.9%)	37 (28.0%)	.290
Ischemic stroke	30 (14.6%)	15 (11.4%)	.389
Smoking (ever)	115 (56.1%)	70 (53.0%)	.581
Site of occlusion
ICA	41 (20.0%)	34 (25.8%)	.427
M1	127 (62.0%)	78 (59.1%)	.427
M2	37 (18.0%)	20 (15.2%)
CT-ASPECTS (median) (IQR)	9 (8–10)	9 (7–10)	.005
Transfer to CSC	104 (50.7%)	82 (62.1%)	.040
IV-tPA	117 (57.1%)	18 (13.6%)	<.001
Time to intervention (median) (IQR)	204 (158–263)	684 (476–919)	<.001
Primary aspiration	47 (22.9%)	36 (27.3%)	.366
TICI 2b/3 revascularization	193 (94.1%)	120 (90.9%)	.259
sICH	13 (6.3%)	12 (9.1%)	.347
Functional outcome
mRS 0–2	90 (43.9%)	43 (32.6%)	.038
mRS 6	58 (28.3%)	25 (18.9%)	.052

Note:—CSC indicates comprehensive stroke center; sICH, symptomatic intracranial hemorrhage.

Table 2:

Propensity score–matched cohort

	Overall Cohort
	0–6 Hours (n = 112)	6–24 Hours (n = 112)	P Value
Variable
Age (median) (IQR) (yr)	73 (62–81)	75 (59–83)	.759
Female	61 (54.5%)	59 (52.7%)	.773
Baseline NIHSS (median) (IQR)	17 (12–22)	17 (12–22)	.985
Site of occlusion
ICA	25 (22.3%)	26 (23.2%)	.991
M1	67 (59.8%)	67 (59.8%)	.991
M2	20 (17.9%)	19 (17.0%)
CT-ASPECTS (median) (IQR)	9 (8–10)	9 (8–10)	.720
Time to intervention (median) (IQR) (hr)	210 (157–266)	691 (497–907)	<.001
TICI 2b/3 revascularization	106 (94.6%)	104 (92.9%)	.593
sICH	6 (5.4%)	7 (6.2%)	.782
Functional outcome
mRS 0–2	51 (45.5%)	38 (33.9%)	.091
mRS 6	29 (25.9%)	19 (17.0%)	.096