Inclusion Criteria:  Resident of Southeastern Minnesota (Olmsted, Dodge, Fillmore, Mower, Freeborn, Wabasha, or Steele County) Age ≥ 75 years  Current diagnosis of moderate or severe aortic stenosis by most recent (within 6 months at most) echocardiogram as defined by:  Moderate AS: 1.0 cm2 < aortic valve area (AVA) ≤ 1.5 cm2 Severe AS: AVA ≤ 1.0 cm2  Exclusion Criteria:  Any cardiac surgery or major chest trauma within 4 weeks of PYP scan Myocardial infarction within 4 weeks of PYP scan defined by typical angina, EKG changes and significant change in serial troponins. (Note that chronic troponin elevation is extremely common in cardiac amyloidosis). Prior or current exposure to Plaquenil (Hydroxychloroquine)