\[68Ga\]CBP8 is a novel gallium-68 labeled positron emission tomography (PET) probe that selectively binds collagen type I, which constitutes the majority of fibrotic tissue. In pre-clinical mouse models, \[68Ga\]CBP8 had the sensitivity to detect pulmonary fibrosis even at early stages and specificity for collagen uptake with low non-specific uptake in background tissues and organs. In preliminary studies in humans with idiopathic pulmonary fibrosis, patients tolerated \[68Ga\]CBP8 without adverse effects, and there was a strong correspondence between high collagen tracer signal and fibrotic lung regions established by chest computed tomography (CT) scan. \[68Ga\]CBP8 may be a valuable tool to detect and quantify collagen in the heart. The investigators propose to test \[68Ga\]CBP8 in a pilot study to image myocardial fibrosis in patients with cardiac amyloidosis.
Cardiac amyloidosis is characterized by myocardial interstitial infiltration by misfolded amyloid fibrils. Infiltration leads to increased myocardial stiffness and heart failure. In patients with cardiac amyloidosis, myocardial stiffness may also be caused by extracellular collagen deposition in the myocardium. Collagen deposition (i.e. myocardial fibrosis) results in adverse cardiac remodeling through similar mechanisms as amyloidosis and may potentiate heart failure in patients with cardiac amyloidosis. Myocardial fibrosis can be mitigated or prevented. In addition, therapies directed against amyloid fibrils also have differential response rates in cardiac amyloidosis patients with or without coexistent fibrosis. Magnetic resonance imaging (MRI) is an established method of measuring extracellular volume (ECV), a reliable way of quantifying myocardial fibrosis in conditions where the primary reason for ECV expansion is myocardial fibrosis. ECV may not be an optimal surrogate of myocardial fibrosis in patients with cardiac amyloidosis, where ECV is already quite expanded due to myocardial amyloid infiltration. Thus, a means of accurate, non-invasive quantitation of myocardial fibrosis has the potential to significantly improve cardiac amyloidosis care.
This pilot study is designed to understand whether myocardial fibrosis can be measured using a collagen 1 targeted radiotracer (\[68Ga\]CBP8). The investigators would like to study 15 patients with light-chain (AL) cardiac amyloidosis and 15 patients with transthyretin (ATTR) cardiac amyloidosis to understand differences in radiotracer uptake, if any. The investigators will also enroll 15 patients with recent myocardial infarction and 15 patients with hypertrophic cardiomyopathy as positive controls for fibrosis and will enroll 5 individuals without cardiovascular disease as negative controls.
The aim of this proposed research study is, using simultaneous PET/MRI imaging, to determine whether \[68Ga\]CBP8 uptake will accurately identify and quantify myocardial fibrosis in patients with cardiac amyloidosis, recent myocardial infarction, and hypertrophic cardiomyopathy. The aim of this study is also to correlate \[68Ga\]CBP8 PET uptake with standard MRI measures in patients with cardiac amyloidosis.
