• ^99mTc-PYP/^99mTc-DPD/^99mTc-HMDP* is to be considered for their avidity for cardiac amyloid deposits³
• The recommended time between injection of ^99mTc-PYP/^99mTc-DPD/^99mTc-HMDP* and scan is 2 to 3 hours³; 1-hour planar-only imaging is not recommended³
• Both planar and SPECT imaging should be reviewed and interpreted using visual and quantitative approaches, irrespective of the timing of acquisition³

• Evaluate planar and SPECT images to confirm any diffuse radiotracer uptake in the myocardium
• Differentiate myocardial radiotracer uptake from residual blood pool activity, focal myocardial infarct, and overlapping bone (e.g. from rib hotspots due to fractures) on SPECT images
• If excess blood pool activity is noted, recommend repeating SPECT imaging at 3 hours

If myocardial tracer uptake is visually present on the SPECT image, then proceed to step 2; Semiquantitative visual grading.

Radiograph showing ^99mTc-PYP/^99mTc-DPD/^99mTc-HMDP* uptake. ​​​​​

Adapted from Dorbala et al. J Nucl Cardiol. 2019.

If no myocardial tracer uptake is present on SPECT, then visual grade is 0

Radiograph showing ^99mTc-PYP/^99mTc-DPD/^99mTc-HMDP* uptake.

Adapted from Dorbala et al. J Nucl Cardiol. 2019.

• Semiquantitative visual grade comparison of myocardial and bone (rib) uptakes at 3 hours³
• Examination of planar and SPECT images for tracer uptake in the myocardium relative to the ribs and grading using the following scale

Radiograph showing ^99mTc-PYP/^99mTc-DPD/^99mTc-HMDP* uptake.
Adapted from Dorbala et al. J Nucl Cardiol. 2019.

Interpretation of the visual scoring method in relation to the bone (rib) uptake at 3 hours³ is as follows:

• Strongly suggestive of ATTR-CM: Visual grade of ≥2 on planar and SPECT images with concurrent testing³ to rule out AL
• Not suggestive or equivocal of ATTR-CM: Visual grade³ <2

When cardiac amyloidosis is suspected, Grade 2 or 3 myocardial uptake with concurrent testing to rule out AL is diagnostic of ATTR-CM.^3,‡,§

• If the visual grade is 2 or 3, then the diagnosis is confirmed, and the H/CL ratio assessment is not necessary
• If discordant or the visual grade is equivocal, then the H/CL ratio may be helpful to classify equivocal visual grade 1 versus 2 as positive or negative

• An H/CL ratio of ≥1.5 at 1 hour can accurately identify ATTR-CM if myocardial ^99mTc-PYP* uptake is visually confirmed on SPECT imaging and systemic AL amyloidosis is excluded
• An H/CL ratio of ≥1.3 at 3 hours can identify ATTR cardiac amyloidosis

      Quantification of cardiac ^99mTc-PYP* uptake using the H/CL ratio⁴ 

Radiograph showing quantification of cardiac ^99mTc-PYP* uptake using H/CL ratio.