99mTc Pyrophosphate (PYP) imaging Transthyretin Cardiac Amyloidosis Imaging: A new an application for an old tracer.

2068 Objectives: Historically, 99mTc PYP is a nuclear medicine radiopharmaceutical bone imaging agent. Recently it has been found that 99m Tc PYP can also be used to image for Transthyretin Cardiac Amyloidosis which can cause heart failure and left ventricular wall thickening.There are two subtypes of amyloidosis to consider, light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR) which can be divided further into wild or mutant (hereditary) subtypes. Transthyretin cardiac amyloidosis is a disease which is often misdiagnosed and often found on autopsy. Compared to the traditional invasive biopsy to diagnose ATTR, 99m Tc PYP has the advantage of being a noninvasive procedure to diagnose ATTR cardiac amyloidosis. This study aims to research and educate the nuclear medicine community on the advantages of using 99mTc PYP to diagnosis heart failure by specifically targeting ATTR protein deposits in the myocardium. Methods: A retrospective review of previous literature was used to obtain the background information regarding the use of 99mTc PYP for Transthyretin Cardiac Amyloidosis. In addition, current SNMMI and ASNC protocols were reviewed to gather evidence of imaging parameters and rationale. Results: An article published by the American Heart Association found that 99m Tc PYP has shown to be a useful method with 97% sensitivity and 100% specificity for differentiating AL vs ATTR cardiac amyloidosis. Thehospital protocols that were reviewed gave criteria to grade the amount of uptake in myocardial tissue. The grading scale was taken from the hospital protocol manual and correlates with the study done by the American Heart Association. The qualitative value for interpretation is determined by comparing the uptake in the myocardium, grade 0= no myocardial uptake, grade 1= myocardial uptake less than bone uptake, grade2= myocardial uptake equal to bone uptake, grade 3= myocardial uptake greater than bone uptake. Grade 2 or 3 uptake is considered a positive indication for ATTR. To interpret the image semi-quantitatively, 2 identical regions of interests (ROI) are placed on the anterior view, 1 over the left ventricle and the other on the contralateral side within the lung. Counts are measured within each ROI and a Heart/Contralateral lung ratio > 1.5 is considered positive for ATTR. Conclusions: The use of 99m Tc PYP is an easy noninvasive exam to diagnose cardiac amyloidosis caused by ATTR proteins. 99m Tc PYP has been found to have both high sensitivity and specificity for differentiating between the types of cardiac amyloidosis. Bibilography:1. Dorbala, S., MD (Chair), Bokhari, S., MD, Miller, E., MD, Bullock-Palmer, R., MD, Soman, P., MD, & Thompson, R., MD. (2018). 99mTechnetium-Pyrophosphate Imaging for Transthyretin Cardiac Amyloidosis. Retrieved 3 February 2019, from https://www.asnc.org/Files/Practice Resources/Practice Points/ASNC Practice Point-99mTechnetiumPyrophosphateImaging2016.pdf 2. Gillmore, J. D., Maurer, M. S., Falk, R. H., Merlini, G., Damy, T., Dispenzieri, A., . . . Hawkins, P. N. (2016). Nonbiopsy Diagnosis of Cardiac Transthyretin Amyloidosis. Cicrulation,133(24), 2404-2412. doi:10.1161/circulationaha.116.021612. Retrieved 3 February 2019, from https://www-ncbi-nlm-nih-gov.ezp.slu.edu/pubmed/?term=Nonbiopsy+Diagnosis+of+Cardiac+Transthyretin+Amyloidosis.