Cardiac amyloid scintigraphy

A report skeleton for 99mTc-PYP, DPD or HMDP scintigraphy in suspected transthyretin cardiac amyloidosis. It uses the visual grades, SPECT requirement and interpretation categories of the multisociety consensus and its 2021 addendum, and includes the mandatory statement on testing for monoclonal protein.

Based on: ASNC/AHA/ASE/EANM/HFSA/ISA/SCMR/SNMMI multimodality imaging consensus in cardiac amyloidosis, Part 1 (Dorbala 2019) and addendum (Dorbala 2021); non-biopsy diagnosis of ATTR (Gillmore 2016)

BONE-TRACER CARDIAC SCINTIGRAPHY (SUSPECTED ATTR CARDIAC AMYLOIDOSIS)

CLINICAL INDICATION:
  [Heart failure with increased wall thickness / echo or CMR features of amyloid / carpal tunnel or spinal stenosis history / known TTR variant / other]
  Monoclonal protein testing: serum free light chains [ ]; serum immunofixation [ ]; urine immunofixation [ ] / not yet available

TECHNIQUE:
  Radiopharmaceutical: [99mTc-PYP / 99mTc-DPD / 99mTc-HMDP] [ ] MBq IV
  Planar imaging: [1 h (PYP only, optional) / 2 h / 3 h]; [anterior / anterior and lateral chest]
  SPECT [/CT] of the chest at [ ] h
  H/CL ratio (PYP): [not measured / measured at [1 / 3] h]

COMPARISON:
  [Prior scintigraphy / echocardiography / CMR / none]

FINDINGS:
  Myocardial uptake on SPECT: [none / diffuse / focal or regional (segments)]; blood-pool activity: [none / present]
  Visual grade (myocardium compared with rib, applied only when SPECT confirms myocardial uptake):
    Grade 0: no myocardial uptake and normal bone uptake
    Grade 1: myocardial uptake less than rib uptake
    Grade 2: myocardial uptake equal to rib uptake
    Grade 3: myocardial uptake greater than rib uptake with mild/absent rib uptake
  Grade: [ ]
  H/CL ratio: [ ] at [1 / 3] h (supportive only; ≥1.5 at 1 h or ≥1.3 at 3 h with myocardial uptake confirmed on SPECT)
  Extracardiac findings: [rib fracture / valvular or annular calcification / soft-tissue uptake / other]

IMPRESSION:
  1. [Not suggestive / Equivocal / Strongly suggestive] for ATTR cardiac amyloidosis
     Not suggestive: grade 0
     Equivocal: diffuse grade 1 uptake, or uncertainty between grade 1 and grade 2
     Strongly suggestive: diffuse grade 2 or grade 3 uptake
  2. This interpretation applies only after exclusion of a systemic plasma cell dyscrasia. Evaluation for AL amyloidosis by serum free light chains and serum and urine immunofixation is recommended in all patients.
  3. [If strongly suggestive and no monoclonal protein: consistent with ATTR cardiac amyloidosis; TTR genetic counselling and testing recommended / if a monoclonal protein is present: tissue diagnosis required]

Before you sign

• SPECT is required in every study. Planar-only imaging at 1 h is not recommended. If there is no myocardial uptake on SPECT, the grade is 0, whatever the planar appearance.
• Separate myocardial uptake from blood pool on SPECT. If excess blood-pool activity is seen, image PYP at 3 h.
• Do not diagnose ATTR on the H/CL ratio alone. It supports the visual grade only when SPECT confirms myocardial uptake.
• Grade 2 or 3 uptake occurs in more than 20% of patients with AL amyloidosis (ASNC practice points), so the scan is interpreted only with serum free light chains and serum and urine immunofixation.
• Gillmore 2016: grade 2 or 3 uptake without a detectable monoclonal protein gave 100% specificity and positive predictive value for ATTR cardiac amyloidosis (95% CI of PPV 98.0–100). This allows a non-biopsy diagnosis.
• False positives include AL and other rarer amyloid types, recent myocardial infarction (under 4 weeks), hydroxychloroquine cardiotoxicity, pericarditis, blood pool, rib fractures and valvular calcification. False negatives include very mild disease and some TTR variants, such as p.Phe84Leu and p.Ser97Tyr (legacy names Phe64Leu and Ser77Tyr).
• Regional rather than diffuse uptake suggests another cause, such as infarction. Once ATTR is confirmed, recommend genetic counselling and TTR testing.

Sources

1. Dorbala S, Ando Y, Bokhari S, et al. ASNC/AHA/ASE/EANM/HFSA/ISA/SCMR/SNMMI expert consensus recommendations for multimodality imaging in cardiac amyloidosis: Part 1 of 2—evidence base and standardized methods of imaging. J Nucl Cardiol. 2019;26:2065–123.
2. Dorbala S, Ando Y, Bokhari S, et al. Addendum to ASNC/AHA/ASE/EANM/HFSA/ISA/SCMR/SNMMI expert consensus recommendations for multimodality imaging in cardiac amyloidosis: Part 1 of 2—evidence base and standardized methods of imaging. J Nucl Cardiol. 2021;28:1769–74.
3. Gillmore JD, Maurer MS, Falk RH, et al. Nonbiopsy diagnosis of cardiac transthyretin amyloidosis. Circulation. 2016;133:2404–12.
4. Garcia-Pavia P, Rapezzi C, Adler Y, et al. Diagnosis and treatment of cardiac amyloidosis: a position statement of the ESC Working Group on Myocardial and Pericardial Diseases. Eur Heart J. 2021;42:1554–68.