My heart has done all sorts of stuff, including weird beats, like it stops for a while then starts up again sort of in a spasm. One weird beat problem occurred in front of the cardiologist during a stress test, he said it was a "benign problem" caused by an extra beat in the upper chamber. These problems would go away when I took magnesium/potassium aspartate. These two minerals are extremely important to the heart, so if you get low in them, you can get all sorts of heart issues. Of course all this happened a few years before I got Lyme Disease (or at least before I was diagnosed with it and my symptoms getting a lot worse). These days magnesium/potassium aspartate doesn't make my heart problems go away because they are due to medication side affects mostly (mepron in particular). Have you checked the side affect list of your medications?
BTW, what is a TBI?