Table 2.

Typical false‐positive and false‐negative cases in planar ^99mTc‐PYP scintigraphy for the diagnosis of ATTR‐CM

Planar 99mTc‐PYP scintigraphy results	Potential causes of false results
False positive	Recent history of acute myocardial infarction AL amyloidosis AApoAI, AApoAII, AApoAIV, and Aβ2M Hypertrophic cardiomyopathy Hydroxychloroquine toxicity Cardiac blood pool Intravenous iron injections
False negative	Insufficient amount of amyloid deposits Rib fractures and valvular/annular calcifications Recent myocardial infarction (<4 weeks) Delayed or premature acquisition in 99mTc‐PYP scintigraphy ATTRv‐CM with a low sensitivity in scintigraphy (Ser77Tyr or Phe64Leu mutation) Initial diagnosis of cardiac pools with myocardial deposits

A positive ^99mTc‐PYP scintigraphy result refers to Grade 2 (moderate cardiac uptake equal to rib uptake) or Grade 3 (high cardiac uptake greater than rib uptake), and a negative result refers to Grade 0 (no cardiac uptake) or Grade 1 (mild cardiac uptake less than rib uptake).

^99mTc‐PYP, ^99mtechnetium‐pyrophosphate; Aβ2M, β2‐microglobulin amyloidosis; AApoAI, apolipoprotein AI amyloidosis; AApoAII, apolipoprotein AII amyloidosis; AApoAIV, apolipoprotein A‐IV amyloidosis; AL, light chain; ATTR‐CM, transthyretin amyloid cardiomyopathy; ATTRv‐CM, variant ATTR‐CM.