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)