A Blind-adjudication Multi-center Phase II Randomized Clinical Trial of Continuous Low-dose Intravenous Heparin Therapy in Coiled Low-grade Aneurysmal Subarachnoid Hemorrhage Patients With Significant Hemorrhage Burden

• Age ≥ 18 and ≤ 70 years

• Historical modified Rankin Scale Score 0-1

• Aneurysmal subarachnoid hemorrhage caused by a ruptured saccular aneurysm confirmed by catheter angiography that is repaired by endovascular coil embolization. Initiation of the coil embolization procedure should occur within 48 hours from the time of the aneurysm rupture (ictus). In patients where the exact time of the ictus is uncertain, a reasonable estimate of the time of ictus may be assigned. This reasonable time estimate should be considered likely accurate to within hours of the true unknown time.

• Quality of aneurysm embolization is interpreted to be Raymond-Roy Score of 1 (Complete) or 2 (Residual Neck) indicating that the aneurysm is adequately secured. A tiny amount of contrast in the body of the aneurysm is acceptable as long as the physician considers the aneurysm secured and to NOT represent a Raymond-Roy Score of 3 (Residual Aneurysm).

• WFNS grade 1 or 2 as assessed after repair of the aneurysm during screening but prior to randomization. A patient who presents with a WFNS greater than 2 who then improves with resuscitation, ventriculostomy, or time is acceptable.

• The pre-repair, admission head CT demonstrates an aSAH bleed pattern of thick and diffuse or thick and focal hemorrhage within the subarachnoid basal cisterns measuring ≥ 4 mm in the short axis and ≥ 20 mm in the long axis which is consistent with a modified Fisher grade 3 or 4. Intraventricular hemorrhage is acceptable. Enrollable patients must NOT have a parenchymal hemorrhage greater than 10 cc. Please refer to diagram below for examples. The hemorrhage location should be substantially within the supratentorial space and not isolated to the infratentorial space.

• The location of the aneurysm should be the anterior circulation, posterior communicating, OR a basilar terminus (apex). Angiographic location of the aneurysm should be confirmed by catheter digital subtraction angiography (DSA) usually obtained during the coil embolization procedure. Patients with PICA or other posterior circulation aneurysms as the cause of the SAH should not be included because they typically cause primarily infratentorial bleed patterns.

• Ability to screen the patient and obtain a head CT 2-12 hours after the completion of the coiling procedure and the ability to initiate the study drug 12 ± 8 hours after the completion of aneurysm coiling procedure.

• After recovering from anesthesia following the aneurysm coiling procedure, the patient must remain a WFNS SAH grade ≤ 2 without evidence of a significant new focal neurological deficit including monoparesis / monoplegia, hemiparesis / hemiplegia, or receptive, expressive or global aphasia. New minor cranial nerve defect without any other new findings is permissible. If an NIHSS score was obtained prior to the aneurysm coiling procedure, a post-coiling (pre-enrollment) NIHSS score must not have increased by ≥ 4 points and GCS score must not be decreased by ≥ 2 points. The clinician at the local site should use their best clinical judgment as to whether a significant neurological decline has occurred due to the procedure.

⁃ Patient is willing and able to return for study follow-up visits.

⁃ Patient or their Legally Authorized Representative (LAR) has provided written informed consent.