How is ACE inhibitor use in HF?

HF causes increased RAAS system due to diminished renal perfusion pressure increasing renin and sympathetic activation increasing renin. So HF causes increased angiotensin and aldosterone increasing preload and afterload also promoting cardiac and vascular remodeling. ACE inhibitors decrease vascular resistance increasing CO, reduce symptathetic activation, improve O2 supply/demand ratio, prevent remodeling thus improving HF