Imaging Cardiac Amyloidosis: A Pilot Study Using F-18 Florbetapir and C-11 PiB Positron Emission Tomography

• Mean Myocardial Radiotracer Uptake [ Time Frame: This study will take about 4 hours to complete. This study entails measurement of mean myocardial radiotracer dose on the images obtained on the day of the study.No follow-up is planned. ] [ Designated as safety issue: No ]

  This is a pilot feasibility study using the newly approved radiotracer F-18 florbetapir and C-11 PiB. Mean myocardial uptake will be estimated in the subjects on the images obtained Mean liver to heart ratio will be estimated. No follow-up images are planned.

  The myocardial F-18 Florbetapir images will be processed and viewed in the standard cardiac imaging planes. Visual assessment of relative myocardial uptake of F-18 Florbetapir will be performed and scored using a 0-3 scale (0=normal, 1= mild uptake, 2= moderate uptake, 3=significant uptake). Myocardial uptake of F-18 Florbetapir will be quantified using a software on the Hermes system (image viewing station). Also, specific uptake values of the radiotracer in the myocardium will be computed.

  
  

F-18 florbetapir has been studied in multiple clinical trials to image beta-amyloid deposition in the brain of subjects with Alzheimers' disease. Florbetapir F-18 has been well tolerated in studies of more than 2000 human subjects. Biodistribution studies in humans revealed predominantly hepatobiliary excretion. The tracer clears rapidly from the blood pool in about 20 minutes. This radiotracer has been recently approved for clinical imaging of brain amyloid in subjects with suspected Alzheimers disease. The investigators propose to test this FDA approved radiotracer for an off label indication in a pilot study to evaluate its potential utility, if any, to image cardiac amyloidosis. Preliminary studies using C-11 labeled PiB (Pittsburgh B compound, another agent used to image beta-amyloid in the brain of patients with Alzheimer's disease) show that this tracer can be taken up by cardiac amyloidosis.

Amyloid related heart disease is associated with LV wall thickening due to infiltration; however, this myocardial wall thickening is not definitively distinguishable from left ventricular myocyte hypertrophy from increased afterload to the heart from hypertension or aortic stenosis. Typically myocardial or other tissue biopsy with typical echo features of amyloidosis is required for confirmation of amyloidosis. This pilot study is designed to understand whether cardiac amyloid burden can be measured using a specific radiotracer targeted against amyloid protein (F-18 Florbetapir). F-18 Florbetapir is structurally similar to C-11 PIB and hence likely that it will also bind to cardiac amyloid. At this point it is unknown of F-18 Florbetapir will bind to either AL or TTR amyloid protein or to both of them or to neither of them. The investigators would like to study 5 patients with AL and 5 patients with TTR amyloidosis to understand these differences if any. The investigators also seek to understand if the signal to noise ratio of the circulating amyloid protein in the blood pool (AL amyloid disease) allows for good differentiation of myocardial amyloid uptake.

The purpose of the proposed research study is to examine in detail, using quantitative PET, myocardial F-18 Florbetapir uptake in cardiac amyloidosis in order to better understand mechanisms of heart damage in this disease.