**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.**
Mannat Dhillon, University of Calgary, Calgary, Alberta, Canada.

**Main Body of the Abstract**
Background:
Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is an infiltrative process with poor prognosis without treatment. Conduction system disease is prevalent among ATTR-CM patients. ATTR-CM patients are also predisposed to development of tachyarrhythmias such as atrial fibrillation, and less commonly ventricular arrhythmias. This project assessed the progression of conduction system disease and electrophysiological events in ATTR-CM patients, comparing those treated and untreated with tafamidis.
Methods:
We collected baseline and serial longitudinal parameters associated with conduction system dysfunction and tachyarrhythmia in ATTR-CM. Comparison of the occurrence of study endpoints in treated and untreated patients was performed using paired analyses.
Results:
A total of 145 patients with ATTR-CM (126, 87% men, 19 women; mean age at diagnosis 79.1±0.7 years) were identified from 2011 to 2021. Eighty (55%) patients were treated with tafamidis. There were 102 (70%) patients with atrial fibrillation or flutter, and 42 (29%) patients underwent pacemaker or ICD implantation. The median baseline QRS duration increased significantly for both tafamidis-treated and untreated patients at 1-year follow-up compared to baseline. Tafamidis-treated patients had a baseline median QRS duration (Q1-Q3) of 104.0 ms (88.0-128.0 ms), which increased to 122.0 ms (96.0-166.0 ms) at 1-year follow-up (n=45) (p<0.05). Untreated patients exhibited a baseline median QRS duration of 119.0 ms (100.0-144.0 ms), which increased to 130.0 ms (106.0-160.0 ms) at 1-year follow-up (n=30) (p<0.05).
Conclusion:
Tachyarrhythmia and conduction system disease, along with progressive QRS widening in follow-up, are highly prevalent in ATTR-CM, though similar between patients treated and untreated with tafamidis.



Arrhythmia burden and progression in ATTR-CM patients treated and untreated with tafamidis PC131 (#344)

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.