@granof6
You are right about the little information.
Here is some information, if you don't know it already:

Apolipoprotein A-IV Cardiac Amyloidosis Diagnosed by Mass Spectrometry–Based Proteomic Analysis https://www.sciencedirect.com/science/article/pii/S266608492600505X

Rare Forms of Cardiac Amyloidosis: Diagnostic Clues and Phenotype in Apo AI and AIV Amyloidosis https://pmc.ncbi.nlm.nih.gov/articles/PMC10351905/

(1124) - Amyloid Unmasked: A Rare Case of Apolipoprotein A- IV Cardiac Amyloidosis
https://www.jhltonline.org/article/S1053-2498(24)00784-8/fulltext
I hope it helps.