There are two primary reasons for an addendum. The first is that the document reviewer list is being updated to include Dr. Richard Cheng and Dr. Roy John, who have critically reviewed the document, but were inadvertently not listed as reviewers. In addition, since the publication of this document and introduction of approved therapies for transthyretin cardiac amyloidosis (ATTR-CA), the clinical use of bone tracer cardiac scintigraphy has been extended to populations with lower prevalence of ATTR-CA. Numerous observations have raised concerns about (1) incorrect diagnosis of ATTR-CA based on 99mTc-pyrophosphate (PYP) planar imaging and heart-to-contralateral lung (H/CL) ratio without confirmation of diffuse myocardial uptake on SPECT imaging at some sites; (2) excess blood pool activity on the 1-hour planar and SPECT images being interpreted as positive scans; and (3) missed diagnosis of light chain (AL) amyloidosis, as serum-free light chain studies and serum and urine immunofixation electrophoresis studies may not be recommended in the 99mT¢-PY P/-3,3-diphosphono- 1,2-propanodicarboxylic acid/hydroxymethylene diphosphonate (99mTc-PYP/DPD/HMDP) report. Incorrect diagnosis leads to inappropriate therapy and worse patient outcomes. SPECT and planar imaging performed at 3 hour maximize specificity. 1 Sperry B.W. Burgett E. Bybee K.A. McGhie A.I. O’ Keefe J.H. Saeed I.M. et al. Technetium pyrophosphate nuclear scintigraphy for cardiac amyloidosis: Imaging at I vs 3 hours and planar vs SPECT/CT. , 2 Masri A. Bukhari S. Ahmad S. Nieves R. Eisele Y.S. Follansbee W. et al. Efficient 1-hour Technetium-99m pyrophosphate imaging protocol for the diagnosis of Transthyretin Cardiac Amyloidosis. , 3 Castano A. Haq M. Narotsky D.L. Goldsmith J. Weinberg R.L. Morgenstern R. et al. Multicenter study of planar Technetium 99m pyrophosphate cardiac imaging: Predicting survival for patients With ATTR Cardiac Amyloidosis. Additionally, technical parameters have been updated.