Impaired Myocardial Oxygenation Response During Stress in Patients With Severe Aortic Stenosis: Insights From Oxygenation-sensitive Cardiovascular Magnetic Resonance by Mahmod, M, Francis, J, Pal, N, Lewis, A, Sairia, D, De Silva, R, Petrou, M, Sayeed, R, Westaby, S, Ashrafian, H, Neubauer, S, Karamitsos, T