The aim of this study is to investigate the clinical events of the patients with acute cerebral large vessel occlusion or stenosis and atrial fibrillation, treated by apixaban within 14 days after onset. This is the observational study that patients will be made the registration at the timing of both retrospective period and prospective period.

Four novel oral anticoagulants (NOACs) have been released to the market ahead of any county in the world. However, no information is available on the clinical results of NOACS and their secondary preventive effects in Japanese population.

Medical care for acute-phase stroke is constantly advancing. Specifically, in addition to thrombolytic activator tissue plasminogen activator (t-PA), advancement of endovascular thrombectomy has made it possible to treat patients who would not have been saved otherwise. In Japan, cerebrovascular accident had been the third leading cause of death, but now has dropped to the forth thanks to wide use of various treatments. Nevertheless, patients often suffer from severe sequelae after stroke, even if they survive. In other words, major challenge in the treatment of stroke is not only to save the patients but also to improve the long-term prognosis.

In large-scale study, NOAC showed an equal to or greater efficacy in preventing recurrence of stroke compared with warfarin and significantly reduced the incidence of bleeding complications. Furthermore, Aristotle trial comparing apixaban vs. warfarin demonstrated that apixaban provided a significant prevention of stroke recurrence as well as significant reduction of bleeding complications and deaths.

Heparin and warfarin had been used as the mainstream agents for the prevention of recurrence after hyperacute phase treatment.However, Aristotle trial showed that there was a significant difference in thromboembolic events between apixaban treatment (1.27 %/year) and warfarin (1.60%/year) (RR 0.79, p<0.01). Also, major bleeding events were less frequent in the patients with apixaban treatment (2.13 %/year) compared to those with warfarin (3.09%/year) (RR 0.69, p<0.001). This study is conducted on the basis of expectation that the use of apixaban in place of traditional warfarin therapy further improve prognosis and reduce bleeding complications in Japanese patients with acute occlusion of major cerebral artery. Additionally, the study will analyze the correlation of the use of apixaban with the prognosis and the incidence of bleeding/ischemic events in patients with intracranial artery stenosis greater than 50% and with atrial fibrillation

Inclusion Criteria:

1. Patients 20 years and older with acute stroke and treated with oral apixaban within 14 days after onset.
2. Patients who are hospitalized in a period from Oct 1, 2014 to Feb 28, 2018
3. Patients with acute cerebral large vessel occlusion or stenosis (> 50%)
4. Patients with non-valvular atrial fibrillation
5. Patients who are not confirmed ICH by MRI or CT within 24 hours after r-tPA infusion.

Exclusion Criteria:

1. Patients who are considered to be ineligible for the study participation by the investigator.
2. Patients who are pregnant or potentially pregnant.
3. Patients who have a history of hypersensitivity to apixaban
4. Patients with hepatic disease having coagulation disorder and clinically important bleeding risk
5. Patients with renal failure (creatinine clearance < 15 mL/min) 6）Patients with Active pathological bleeding including intracranial bleeding of any type

Any adult patient with acute stroke who treated with apixaban.