Intravenous thrombolysis with a recombinant tissue plasminogen activator (rt-PA) is the first-line treatment of acute ischemic stroke. However, successful recanalization is relatively low and the underlying processes are not completely understood. The goal was to provide insights into clinically important factors potentially limiting rt-PA efficacy such as clot size, rt-PA concentration, clot age and also rt-PA in combination with heparin anticoagulant. We established a static in vitro thrombolytic model based on red blood cell (RBC) dominant clots prepared using spontaneous clotting from the blood of healthy donors. Thrombolysis was determined by clot mass loss and by RBC release. The rt-PA became increasingly less efficient for clots larger than 50 μl at a clinically relevant concentration of 1.3 mg/l. A tenfold decrease or increase in concentration induced only a 2-fold decrease or increase in clot degradation. Clot age did not affect rt-PA-induced thrombolysis but 2-hours-old clots were degraded more readily due to higher activity of spontaneous thrombolysis, as compared to 5-hours-old clots. Finally, heparin (50 and 100 IU/ml) did not influence the rt-PA-induced thrombolysis. Our study provided in vitro evidence for a clot size threshold: clots larger than 50 μl are hard to degrade by rt-PA. Increasing rt-PA concentration provided limited thrombolytic efficacy improvement, whereas heparin addition had no effect. However, the higher susceptibility of younger clots to thrombolysis may prompt a shortened time from the onset of stroke to rt-PA treatment.

• MeSH
• Stroke drug therapy   MeSH
• Erythrocytes drug effects   metabolism   MeSH
• Fibrinolytic Agents therapeutic use   MeSH
• Blood Coagulation drug effects   MeSH
• Heparin * therapeutic use   MeSH
• Ischemic Stroke * drug therapy   MeSH
• Humans MeSH
• Recombinant Proteins * therapeutic use   MeSH
• Tissue Plasminogen Activator * therapeutic use   MeSH
• Thrombolytic Therapy * methods   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Fibrinolytic Agents MeSH
• Heparin * MeSH
• Recombinant Proteins * MeSH
• Tissue Plasminogen Activator * MeSH

Background The benefit of intravenous thrombolysis is time dependent. It remains unclear, however, whether dramatic shortening of door-to-needle time (DNT) among different types of hospitals nationwide does not compromise safety and still improves outcome. Methods and Results Multifaceted intervention to shorten DNT was introduced at a national level, and prospectively collected data from a registry between 2004 and 2019 were analyzed. Generalized estimating equation was used to identify the association between DNT and outcomes independently from prespecified baseline variables. The primary outcome was modified Rankin score 0 to 1 at 3 months, and secondary outcomes were parenchymal hemorrhage/intracerebral hemorrhage (ICH), any ICH, and death. Of 31 316 patients treated with intravenous thrombolysis alone, 18 861 (60%) had available data: age 70±13 years, National Institutes of Health Stroke Scale at baseline (median, 8; interquartile range, 5-14), and 45% men. DNT groups 0 to 20 minutes, 21 to 40 minutes, 41 to 60 minutes, and >60 minutes had 3536 (19%), 5333 (28%), 4856 (26%), and 5136 (27%) patients. National median DNT dropped from 74 minutes in 2004 to 22 minutes in 2019. Shorter DNT had proportional benefit: it increased the odds of achieving modified Rankin score 0 to 1 and decreased the odds of parenchymal hemorrhage/ICH, any ICH, and mortality. Patients with DNT ≤20 minutes, 21 to 40 minutes, and 41 to 60 minutes as compared with DNT >60 minutes had adjusted odds ratios for modified Rankin score 0 to 1 of the following: 1.30 (95% CI, 1.12-1.51), 1.33 (95% CI, 1.15-1.54), and 1.15 (95% CI, 1.02-1.29), and for parenchymal hemorrhage/ICH: 0.57 (95% CI, 0.45-0.71), 0.76 (95% CI, 0.61-0.94), 0.83 (95% CI, 0.70-0.99), respectively. Conclusions Ultrashort initiation of thrombolysis is feasible, improves outcome, and makes treatments safer because of fewer intracerebral hemorrhages. Stroke management should be optimized to initiate thrombolysis as soon as possible optimally within 20 minutes from arrival to a hospital.

• Keywords
• acute ischemic stroke, door‐to‐needle time, intravenous thrombolysis, stroke logistics,
• MeSH
• Cerebral Hemorrhage complications   MeSH
• Stroke * therapy   MeSH
• Fibrinolytic Agents adverse effects   MeSH
• Administration, Intravenous MeSH
• Brain Ischemia * complications   MeSH
• Middle Aged MeSH
• Humans MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Tissue Plasminogen Activator MeSH
• Thrombolytic Therapy adverse effects   methods   MeSH
• Treatment Outcome MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• Fibrinolytic Agents MeSH
• Tissue Plasminogen Activator MeSH