@slawekb Have you tried taurine? I have personally found it helpful. (https://pmc.ncbi.nlm.nih.gov/articles/PMC2586397/)
Other things to consider (the following are from my notes from the other forum):
Thyroid, aspirin, vitamin K, vitamin C, taurine, hawthorn RPF, Vitamin e, chondroitin sulfate
Studies have shown 580mg of ubiquinol/day increased ejection fraction up to 77%. Here's one study I was able to find quickly: (https://pubmed.ncbi.nlm.nih.gov/19096107/)Ubiquinol worked where equal doses of CoQ10 didn't. Dr. Peat says Vitamins K2 and E work at the CoQ10 site to enhance the effects of CoQ10.
Taurine, Vitamin K2, Magnesium are essential for blood pressure control and vascular health. These three can easily replace hypertension drugs.
T3-T4, Inosine, COQ10, Calcium are safest positive inotropic agents. Meaning that they all strengthen the force of the heartbeat without causing tachycardia.