Diastolic dysfunction is indeed a major issue with congestive heart failure…the ventricle, inter-ventricular septum etc thicken…causes are multi-factorial, (for example cardiac amyloid, wall motion issues with obstructed coronary arteries, infarctsetc) but the end result is that the muscle becomes less compliant. Left ventricular filing on diastole is dependent on a compliant muscle…in a young healthy heart it springs open very quickly encouraging a maximal volume fill.

I would have to look further into the pathophysiology with each cause before I could conclude Leronlimab would help…probably a subset but I am doubtful with cardiac amyloid…that protein build-up crowds out the myocytes and the amyloid protein itself would have to be cleared.

Here is a good abstract for more high level:
https://pubmed.ncbi.nlm.nih.gov/12025467/