**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.**
Joshua Bomsztyk
National Amyloidosis Centre
Royal Free Hospital
London, UK

**Main Body of the Abstract**
The identification of amyloid fibril type is fundamental to determining treatment plans in patients with amyloidosis. Aside from those with ATTR amyloidosis who fulfil non biopsy criteria1, the gold standard is a histological diagnosis ideally of the affected organ2. In this study we analysed 874 endomyocardial biopsies by Congo red staining, immunohistochemistry and/or proteomic analysis performed at the UK NAC and describe the baseline characteristics for each amyloid subtype.
The fibril type identified was ATTR in 478 patients (54.7%), AL 218 (25.0%), No amyloid 145 (16.6%) and Other 33 (3.8%). Of the Other category; ApoA4 16 (48.5%), Unspecified 9 (27.2%), AA 3 (9%), ApoA1 2 (6%), ANP 2 (6%), AFib 1 (3%). 12 (1.4%) patients had ≥2 types identified.
Table 1 highlights the baseline characteristics for each subtype. Of the patients with AL amyloidosis, 39 (17.9%) had a Kappa isotype and 177 (81.2%) a Lambda isotype, 2 were not evaluable. Only 21/218 (10.7%) of those with AL amyloidosis had a normal baseline sFLC ratio. In contrast 194/511 (38.0%) with non-AL amyloidosis had an abnormal sFLC ratio.
Those with AL amyloidosis vs. ATTR had a substantially higher median NT-ProBNP (5555 pg/ml vs. 2860.5 pg/ml, p<0.001) and cardiac Troponin T (84 ng/L vs. 60ng/l, p<0.001) with a lower mean LV wall thickness (15mm vs. 17mm, p<0.001) respectively.
Endomyocardial biopsy remains an important diagnostic modality for accurate identification of the fibril type, identification of rare and mixed amyloid sub-types, and exclusion of cardiac amyloidosis in the context of suggestive imaging.



A UK experience of 874 endomyocardial biopsies for the diagnosis of amyloidosis PA104 (#513)

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.