KATALYST-AV: A study to evaluate whether the investigational medicine, ataciguat, slows down the progression of the dysfunction of the aortic valve in adults 50+ with calcific aortic valve stenosis

Inclusion Criteria 1. Age \> 50 years 2. Male or female sex 3. Aortic valve area greater than 1.0 cm2 but less than 2.0 cm2 4. Aortic valve calcium levels greater than 300 AU from chest CT 5. Ejection fraction \>50% Exclusion Criteria 1. Orthostatic intolerance or symptomatic hypotension prior to study or during study visits 2. Positive pregnancy test during screening visit 3. Nitrate use or α-antagonist medication use within 24 hours 4. Systolic blood pressure \<110 mm Hg 5. Mean systemic arterial pressure \<75 mm Hg 6. Severe mitral or aortic regurgitation 7. Retinal or optic nerve problems 8. Recent (≤30 days) acute coronary syndrome 9. Oxygen saturation \<90% on room air 10. Congenital valve disease 11. Hepatic dysfunction/elevated liver enzymes 12. Prescription of drugs known to alter NO-sGC-cGMP signaling (sildenafil, nitrates, etc.) 13. Prescription of Warfarin (Coumadin) for chronic anticoagulation 14. Concomitant participation in other trials at Mayo Clinic or elsewhere 15. Use of phenytoin or related compounds for any indication 16. Chronic midazolam treatment for any indication 17. Use of monoamine oxidase inhibitors for any indication 18. Use of anti-diabetic drugs in the sulfonylurea family