From the Guidelines
To interpret PYYP studies for cardiac amyloidosis, first assess the visual grade of cardiac uptake and calculate the heart-to-contralateral lung (H/CL) ratio, with grades 2-3 and a ratio ≥1.5 supporting ATTR diagnosis in the absence of monoclonal protein, as recommended by the 2022 AHA/ACC/HFSA guideline 1.
Key Considerations for Interpreting PYYP Studies
- Assess the visual grade of cardiac uptake on a scale of 0-3, with grades 2-3 indicating cardiac uptake equal to or greater than ribs, which is consistent with ATTR when combined with absent monoclonal protein 1.
- Calculate the H/CL ratio by drawing regions of interest over the heart and contralateral lung, with a ratio ≥1.5 supporting ATTR diagnosis 1.
- Timing is important, with images obtained at 1 hour post-injection for optimal results 1.
- False positives can occur with recent myocardial infarction, cardiac metastases, or hydroxychloroquine use, so clinical correlation is essential 1.
- Blood pool activity should be assessed, as its presence may indicate AL amyloidosis rather than ATTR 1.
Integration with Other Diagnostic Tools
- PYP findings should be integrated with clinical presentation, echocardiography, cardiac MRI findings, and laboratory tests to exclude AL amyloidosis (including serum free light chains and immunofixation) 1.
- The use of 99m Tc bone-avid compounds for bone scintigraphy allows for noninvasive diagnosis of ATTR-CM, with PYP being used in the United States 1.
- Genetic sequencing of the TTR gene will determine if the patient has a pathological variant (ATTRv) or wild-type (ATTRwt) disease, which is important for guiding treatment decisions and genetic counseling 1.
From the Research
Interpreting PYYP Studies for Cardiac Amyloidosis
To interpret PYYP studies for cardiac amyloidosis, it is essential to understand the different types of cardiac amyloidosis, including transthyretin cardiac amyloidosis (ATTR-CA) and immunoglobulin light chain (AL)-mediated CA (AL-CA) 2.
Key Considerations
- The diagnosis of cardiac amyloidosis is critical, and non-invasive diagnostic techniques, such as bone scintigraphy and cardiac nuclear scintigraphy, can be used to diagnose ATTR-CA 3, 4.
- The treatment options for cardiac amyloidosis depend on the type of amyloidosis and the stage of the disease. For example, the stabilizer tafamidis is the only US Food and Drug Administration (FDA)-approved treatment for ATTR-CA 2, 4.
- The prognosis of cardiac amyloidosis remains poor, and early recognition is crucial to halt the disease process before irreversible changes occur 5.
- Loop diuretics, such as furosemide, torsemide, and bumetanide, are the primary treatment for fluid overload and symptomatic relief of patients with ATTR heart failure 4.
Diagnostic Approaches
- Serum free light chain assay and immunofixation electrophoresis can be used to exclude light chain amyloidosis 4.
- Cardiac nuclear scintigraphy can be used to detect radiotracer uptake in a pattern consistent with amyloidosis 4.
- A diagnostic algorithm can be used to aid in the diagnosis of cardiac amyloidosis, including clinical scenarios and situations to suspect the condition 6.
Treatment Options
- Tafamidis, a protein stabilizer, has been shown to reduce mortality, hospitalizations, and slow the progression of ATTR amyloidosis 4.
- Other treatment options, such as patisiran and inotersen, are being developed and may offer promising results for patients with cardiac amyloidosis 3.
- Advanced interventions, including heart, heart-kidney, and heart-liver transplantation, may be considered for end-stage cardiac amyloidosis 2.