Targeting Pulsatile Load to Increase Exercise Capacity and Quality of Life After Aortic Valve Replacement for Severe Aortic Stenosis (PULSE AS)

Inclusion Criteria: 1. Adults aged 50-90 years of age 2. Diagnosis of severe aortic stenosis prior to aortic valve repair 3. Successful trancatheter aortic valve repair via transfemoral procedural approach or successful surgical aortic valve repair at least three months prior to enrollment 4. Stable medical therapy: no addition/removal/changes in anti-hypertensive medications, or beta-blockers in the preceding 30 days. Exclusion Criteria 1. Supine systolic blood pressure (SBP) \< 100 mmHg OR supine diastolic blood pressure (DBP) \<60 mmHg 2. Poorly controlled hypertension, as defined as SBP \> 160 mmHg OR DBP \> 100 mmHg 3. Pregnancy. Women of childbearing potential will undergo a pregnancy test during the screening visit 4. Atrial fibrillation within the prior 8 weeks before enrollment 5. Inability/unwillingness to exercise 6. Moderate or greater mitral regurgitation or aortic/peri-valvular regurgitation, any degree of mitral stenosis, severe right-sided valvular disease, or presence of a mitral prosthetic valve. 7. Moderate or severe patient prosthesis mismatch, as defined by Effective Orifice Area Index \< 0.85 cm2/m2 8. Hypertrophic, infiltrative, or inflammatory cardiomyopathy 9. Pericardial disease 10. Current angina 11. Acute coronary syndrome or coronary intervention within the past 2 months 12. Primary pulmonary arteriopathy 13. Clinically significant lung disease as defined by: Chronic Obstructive pulmonary disease meeting Stage III or greater GOLD criteria, treatment with oral steroids within the past 6 months for an exacerbation of obstructive lung disease, or the use of daytime supplemental oxygen 14. Ischemia on stress testing without subsequent revascularization (during the screening visit) 15. Treatment with phosphodiesterase inhibitors that cannot be withheld 16. Treatment with organic nitrates 17. Significant liver disease impacting synthetic function or volume control (ALT/AST \> 3x ULN, Albumin \<3.0 g/dL) 18. eGFR \< 30 mL/min/1.73 m2 19. G6PD deficiency. For males of African, Asian or Mediterranean decent, this will be evaluated prior to drug administration. A qualitative test positive for deficiency or a quantitative test with clinically significant G6PD deficiency (\<60% of normal activity) will prompt exclusion from the trial (prior to drug administration). 20. History of methemoglobinemia or methemoglobin level \>5% at baseline visit 21. Serum K\>5.0 mEq/L 22. Severe right ventricular dysfunction. 23. Any medical condition that, in the opinion of the investigator, will interfere with the safe completion of the study.