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C-PiB PET in AL Cardiac Amyloidosis
Study Questions:
Does degree of 11C-Pittsburgh Compound B (11C-PiB) on positron emission tomography (PET) correlate with light chain amyloid (AL) deposit burden on immunohistochemistry and clinical prognosis?
Methods:
All patients with AL cardiac amyloidosis diagnosed either with endomyocardial biopsy or left ventricular wall thickness >12 mm without other cause were attempted to be recruited. They underwent 11C-PiB PET imaging. Uptake was quantified as the standardized uptake value in the myocardium and as a ratio with the descending thoracic aorta. Fourteen controls were also recruited for 11C-PiB PET. Biopsy specimens were stained for amyloid P immunohistochemistry and the percentage positive area was quantified. Tissue samples were also analyzed by autoradiography with 11C-PiB. Clinical follow-up was completed for a composite of death from any cause, heart transplantation, or unexpected hospitalization for acute heart failure based on chart review, patient interview, and phone calls.
Results:
Forty-one patients completed the study protocol. Of these, 38 underwent endomyocardial biopsy and the remaining three had diagnosis based on extracardiac amyloidosis and unexplained left ventricular hypertrophy. The degree of 11C-PiB uptake on PET imaging correlated with extent of amyloid deposit on immunohistochemistry (R2 = 0.34, p < 0.001). Importantly, over a median follow-up of 1.2 years (interquartile range, 0.25–3.3), the degree of 11C-PiB PET uptake correlated with the composite major adverse cardiac event outcome (hazard ratio, 1.2; p < 0.0001). Most events were death (n = 21), although two patients underwent heart transplantation and one was admitted for heart failure.
Conclusions:
11C-PiB PET imaging correlates with disease burden in AL cardiac amyloidosis and is associated with prognosis.
Perspective:
Given improving therapeutics for both TTR and AL cardiac amyloidosis, noninvasive diagnosis and disease monitoring are of growing interest. Although 11C-PiB is not widely used due to the need for an onsite cyclotron, several 18F-labelled agents with similar properties are Food and Drug Administration approved and in use for neuro-amyloid imaging. Further studies are required to validate the use of those agents in cardiac amyloidosis and to evaluate the extent to which these may be used to guide therapeutic decisions.
Clinical Topics: Cardiac Surgery, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Aortic Surgery, Cardiac Surgery and Heart Failure, Acute Heart Failure, Heart Transplant, Interventions and Imaging, Computed Tomography, Nuclear Imaging
Keywords: Amyloidosis, Aorta, Thoracic, Autoradiography, Biopsy, Cyclotrons, Diagnostic Imaging, Heart Failure, Heart Transplantation, Hypertrophy, Left Ventricular, Immunohistochemistry, Myocardium, Plaque, Amyloid, Positron-Emission Tomography
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