Evidence of the intravenous tissue plasminogen activator (tPA) efficacy beyond the 4.5hours window is emerging. We aim to study the factors affecting the outcome of delayed thrombolysis in patients of clear onset acute ischemic stroke (AIS).

Data of patients with AIS who received intravenous thrombolytic after 4.5hours were reviewed including: demographics, risk factors, clinical, laboratory, investigational and radiological data, evidence of mismatch, treatment type and onset, National Institutes of Health Stroke Scale (NIHSS) score at baseline, 24hours, 7days after thrombolysis and before discharge, and 3 months follow-up modified Rankin Scale (mRS).

We report 136 patients treated by intravenous tPA between 4.53 and 19.75hours with average duration of 5.7h. The ASPECT score of our patients was≥7. Sixty-four cases showed intracranial arterial occlusion. Perfusion mismatch was detected in 117 (84.6%) patients, while clinical imaging mismatch was detected in 19 (15.4%). Early neurological improvement after 24hours occurred in 114 (83.8%) patients. At 90days, 91 patients (67%) achieved good outcome (mRS 0–2), while 45 (33%) had bad outcome (mRS 3–6). Age, endovascular treatment, NIHSS, AF, and HT were significantly higher in the bad outcome group. Age (P=0.001, OR: 1.099, 95% CI: 1.042–1.160) and baseline NIHSS were predictive of the poor outcome (P=0.002, OR: 1.151, 95% CI: 1.055–1.256). The best cutoff value of age was 72.5 with AUC of 0.76, sensitivity 73.3% and specificity 60.4%. While for NIHSS at admission, the cutoff value of 7 showed the best results with AUC of 0.73, sensitivity 71.1% and specificity 63.7%. Combination of age and admission NIHSS raised the sensitivity and specificity to 84.4% and 63.7%, respectively.

Increased age and admission NIHSS may adversely affect the outcome of delayed thrombolysis and narrow the eligibility criteria. Age and baseline NIHSS based stratification of the patients may provide further evidence as regards the efficacy of the delayed thrombolysis.