ARRS 2022 Abstracts

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E1855. Sensitivity and Specificity of Using CMR in Diagnosing ATTR Cardiac Amyloidosis
Authors
  1. Kapil Chandora; Morehouse School of Medicine
  2. Kalyani Ballur; Medical College of Georgia
  3. Stuart Cavalieri; VA Hospital
  4. Darko Pucar; Yale School of Medicine
  5. Jayanth Keshavamurthy; Augusta University Medical Center
Background
Cardiac amyloidosis is an infiltrative cardiomyopathy that causes heart failure with preserved ejection fraction and is due to the deposition of amyloid fibrils. There are two major subtypes: cardiac amyloid light-chain (AL) and transthyretin-related (ATTR) amyloidosis. The gold standard for showing deposits of amyloid fibrils remains to be endomyocardial biopsy with immunohistochemical staining. Imaging techniques for diagnosis include cardiac MRI with global transmural or diffuse subendocardial late gadolinium enhancement (sensitivity of 90–95% and specificity of 80–85%), nuclear imaging with tracer 99m Tc-PYP (sensitivity of 97% and specificity of 100%), and nuclear imaging with tracer 99mTc-PYP (use of PYP score ratio of myocardial to ventricular cavity mean counts with sensitivity of 84.6% and specificity of 94.5%).

Educational Goals / Teaching Points
By the end of this exhibit, the participant should understand the benefits and limitations of various cardiac MRI techniques, understand use of the Perugini grading scale for differentiation between AL and ATTR cardiac amyloidosis, and the predictive value of Tc-DPD scintigraphy.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
A 70-year-old man’s cardiac MRI findings were positive for infiltrative cardiomyopathy. The 99mTc nuclear medicine scan was strongly positive for ATTR cardiomyopathy. The semi-quantitative Perugini grading scale was 3.0. ROI ratio was 1.9 (> 1.5 is positive). Another 70-year-old man’s cardiac MRI findings were negative for cardiac amyloidosis. The 99mTc-Pyrophosphate scan showed that the semi-quantitative Perugini grading scale was 3.0. ROI ratio was 1.7. The Perugini scale is assigned as follows: 0 = no cardiac uptake and normal bone uptake; 1 = mild cardiac uptake that is less than bone uptake; 2 = moderate cardiac uptake with attenuated bone uptake; 3 = strong cardiac uptake with mild/absent bone uptake. A Perugini grade of 2 or 3 has high diagnostic sensitivity (91%) and specificity (87%) for ATTR amyloidosis. A quantitative grade helps differentiate ATTR from AL with almost 100% specificity. Histology is not needed for an ATTR amyloidosis diagnosis if these criteria are met: heart failure with echocardiography or cardiac MRI suggestive of amyloidosis, grade 2 or 3 on Perugini scale, and absence of monoclonal protein. Some limitations of the scale are that it has poor prognostic and amyloid burden information.

Conclusion
Diagnosis of ATTR cardiomyopathy is delayed sometimes due to its rarity and diverse presentations, poor sensitivity and specificity of echocardiography, and the need for histological confirmation of biopsy. the gold standard for diagnosis is endomyocardial biopsy, but it is associated with risk of myocardial perforation and tamponade and a specialist needs to perform and examine the biopsy, further delaying diagnosis. With the high specificity and sensitivity of nuclear imaging in identifying ATTR amyloidosis and the Perugini scale in identifying ATTR amyloidosis, a diagnosis can be made for ATTR amyloidosis, sparing the need and risk for endomyocardial biopsy and prompting quicker management.