This is a research study using the Keystone Heart Embolic Deflection Device and involving patients with aortic stenosis (a disease of the aortic valve), to be treated with Transcatheter Aortic Valve Replacement (TAVR).

The TAVR procedure consists in replacing the diseased aortic valve by a new artificial valve. The new valve is put into place using a long, thin tube called a catheter that is inserted into a small incision (cut) in the patient's groin and threaded through his/her arteries up to the heart.

This is a research study using the Keystone Heart Embolic Deflection Device and involving patients with aortic stenosis (a disease of the aortic valve), to be treated with Transcatheter Aortic Valve Replacement (TAVR).

The TAVR procedure consists in replacing the diseased aortic valve by a new artificial valve. The new valve is put into place using a long, thin tube called a catheter that is inserted into a small incision (cut) in the patient's groin and threaded through his/her arteries up to the heart.

During the TAVR procedure, there is a risk that an abnormal particle (called embolism) could break off from inside the arteries and travel to the brain. The embolism could be made of clumps of blood (clots), air, part of your body tissue, or part of a medical device. If the embolism is carried through the blood to the brain, it could cause a stroke or other neurological (brain) problems. A stroke happens when blood flow to a part of the brain is blocked, causing brain cells to die.

The Keystone Heart Embolic Deflection Device has been developed to prevent an embolism from going to the brain and causing a stroke or other brain damage. The device is a wire mesh filter that covers the vessels that carry blood to brain, deflecting any any blood clots or other materials away from the patient's brain and towards the lower body, where they are less likely to cause harm.

Inclusion Criteria:

1. The patient must be ≥18 years of age.
2. Patient meets indications for TAVR procedure.
3. The patient is willing to comply with protocol-specified follow-up evaluations.
4. The patient, or legally authorized representative, has been informed of the nature of the study, agrees to its provisions and has provided written informed consent, approved by the appropriate Medical Ethics Committee or Institutional Review Board.

Exclusion Criteria:

1. Patients undergoing TAVR via the trans-axillary, subclavian, or direct aortic route
2. Pregnant or nursing subjects and those who plan pregnancy in the period up to 1 year following index procedure. Female subjects of child-bearing potential must have a negative pregnancy test done within 7 days prior to index procedure per site standard test.
3. Patients with known diagnosis of acute myocardial infarction (AMI) within 72 hours preceding the index procedure (according to definition) or AMI >72 hours preceding the index procedure, in whom creatine kinase and creatine kinase have not returned to within normal limits at the time of procedure.
4. Patients who are currently experiencing clinical symptoms consistent with new onset AMI, such as nitrate-unresponsive prolonged chest pain.
5. Patients with impaired renal function (estimated Glomerular Filtration Rate [estimated Glomerular Filtration Rate] <30, calculated from serum creatinine by the Cockcroft-Gault formula)
6. Patients with a platelet count of <100.000 cells/mm³ or > 700.000 cells/mm³ or a white blood cell < 3000 cells/mm³ within 7 days prior to index procedure.
7. Patients with a history of bleeding diathesis or coagulopathy or patients in whom anti-platelet and/or anticoagulant therapy is contraindicated, or who will refuse transfusion.
8. Patients who have received any organ transplant or are on a waiting list for any organ transplant.
9. Patients with known other medical illness or known history of substance abuse that may cause non-compliance with the protocol, confound the data interpretation or is associated with a life expectancy of less than one year.
10. Patients with known hypersensitivity or contraindication to aspirin, heparin/bivalirudin, clopidogrel/ticlopidine, nitinol, stainless steel alloy, and/or contrast sensitivity that cannot be adequately pre-medicated.
11. Patients with a history of a stroke or transient ischemic attack (TIA) within the prior 6 months.
12. Patients with an active peptic ulcer or history of upper gastrointestinal (GI) bleeding within the prior 6 months.
13. Patients presenting with cardiogenic shock.
14. Patients with severe peripheral arterial disease that precludes 9 French sheath vascular access.
15. Patients with documented friable or mobile atherosclerotic plaque in the aortic arch.
16. Patients with contraindication to cerebral MRI.
17. Patients who have a planned treatment with any other investigational device or procedure during the study period

all baseline characteristics were provided for study participants