**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Yousuf Razvi, National Amyloidosis Centre, University College London, Royal Free Hospital Campus

**Main Body of the Abstract**
Background:
Transthyretin amyloid cardiomyopathy (ATTR-CM) is an increasingly recognised cause of heart failure. 99mTc-DPD scintigraphy, due to its exquisite sensitivity for ATTR-CM forms a critical part of the accepted diagnostic algorithm. Therefore, there is substantial interest in utilising Tc-DPD scintigraphy to track treatment response. We conducted a multimodality study assessing utility of 99mTc-DPD in tracking treatment response in ATTR-CM.
Methods:
We identified ATTR-CM patients at the UK National Amyloidosis Centre retrospectively who were receiving disease modifying therapy and had pre and post-treatment 99mTc-DPD/SPECT-CT. Myocardial percentage injected dose (PID), a proposed marker of amyloid burden, was measured as previously described. Patients were split into three tertiles according to absolute change in PID at follow-up relative to baseline.  At time of Tc-DPD scintigraphy, patients underwent assessment with echocardiography and blood biomarkers.  A subset of patients had cardiac magnetic resonance (CMR) imaging available.
Results:
Sixty-six patients (median age 66 years) ATTR-CM patients receiving treatment (43 patisiran, 14 inotersen, 10 tafamidis) with serial 99mTc-DPD scans were identified. No statistically significant correlation between the change in PID at follow up and a wide range of echocardiographic, biochemical and CMR parameters was identified. Discordance between a reduction in PID and clinical, imaging and biochemical parameters was common. (Figure 1). Furthermore, no statistically significant correlation (assessed with Spearman's and Pearson's correlation coefficients) was detected PID change and other parameters.
Conclusion:
Our study suggests that a reduction in 99mTc-DPD uptake at follow up is not correlated with a wide range of established biomarkers of treatment response in ATTR-CM.



The limitations of 99mtc-dpd scintigraphy in tracking treatment response in transthyretin amyloid cardiomyopathy (ATTR-CM) OB5 (#405)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.