Door-to-Needle Delays in Minor Stroke: A Causal Inference Approach

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Background and Purpose—

Thrombolysis rates among minor stroke (MS) patients are increasing because of increased recognition of disability in this group and guideline changes regarding treatment indications. We examined the association of delays in door-to-needle (DTN) time with stroke severity.


We performed a retrospective analysis of all stroke patients who received intravenous tissue-type plasminogen activator in our emergency department between July 1, 2011, and February 29, 2016. Baseline characteristics and DTN were compared between MS (National Institutes of Health Stroke Scale score ≤5) and nonminor strokes (National Institutes of Health Stroke Scale score >5). We applied causal inference methodology to estimate the magnitude and mechanisms of the causal effect of stroke severity on DTN.


Of 315 patients, 133 patients (42.2%) had National Institutes of Health Stroke Scale score ≤5. Median DTN was longer in MS than nonminor strokes (58 versus 53 minutes; P=0.01); fewer MS patients had DTN ≤45 minutes (19.5% versus 32.4%; P=0.01). MS patients were less likely to use emergency medical services (EMS; 62.6% versus 89.6%, P<0.01) and to receive EMS prenotification (43.9% versus 72.4%; P<0.01). Causal analyses estimated MS increased average DTN by 6 minutes, partly through mode of arrival. EMS prenotification decreased average DTN by 10 minutes in MS patients.


MS had longer DTN times, an effect partly explained by patterns of EMS prenotification. Interventions to improve EMS recognition of MS may accelerate care.

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