I completely understand that your heart FEELS like it is in bad shape...but I'd be willing to bet that it really is just POTS and other aspects of autonomic dysfunction. Most of the autonomic symptoms come from the heart...whether it be BP related, racing heart rates, slow heart rate, or cardiac vasospasms. These few things that can go wrong WILL have a huge impact on how you feel. Literally, you are lacking in oxygen (as you said) when your BP drops...because not enough blood is getting to your brain. This will make you feel lightheaded, dizzy, and can even make you pass out. it can also cause chest pain (even in the center of your back). The racing heart rate will feel like palpitations gone crazy...as it is not uncommon for those with POTS to have a heart rate over 200 at times. Slow heart rates are just as problematic as fast rates...just in a different way. You may feel run down, without energy, and also lightheaded. And lastly (but NOT least), the cardiac vasospasms feel just like a heart attack...because it literally can cut off blood supply when a large artery clamps shut in a spasm. this can last from a few seconds, up to a minute. It is an unbelievable feeling as the spasms can (and often will) repeat over and over so you feel as if it will never end. The symtpoms can be just like a heart attack with chest pain, left arm pain, neck pain, lightheadedness, sudden sweat, and shortness of breath. The symptoms are brief, but again, they can repeat over and over.

Thankfully, there are medications that can help all of these symptoms/problems (except slow heart rate), and get your heart working in better unison with the rest of your body. Slow heart rates cannot be fixed with medication...only a pace maker (IF they are slow enough to warrant such a device). The tests you will undergo will help determine what is happening.

I'm so glad you are having all these things addressed. Stay positive that they will find out exactly what is going on and fix it for you.