I found this excellent comment from a anonymous commentator on Wisegeek (click here to see the actual discussion)today that explained so very clearly what may be causing my heart beat troubles, and how it relates to the vagus nerve. It also has a very good discussion on anxiety in relationship to this condition, as well. I'll copy and paste here....
Whoever you are, anon329693, thank you for caring enough about others suffering from this condition to post.
It's worth noting that there is a condition called POTS (postural orthostatic tachycardia) and this is also related to the vagus nerve and can account for a lot of symptoms on here. I know this because I have it, as well as getting heart pauses and extra beats. It works like this: the vagus nerve, if malfunctioning, drives the blood pressure low and sends signals to the heart to compensate for this, so the heart gets faster and faster until the blood pressure catches up. This can cause a whole load of symptoms, like dizziness, fainting, getting lightheaded, vomiting, headache and heart palpitations, but the good thing is it is not dangerous.
If the worst were to happen, your heart will simply stop because it's run out of ideas, but here is the catch: as soon as you lie down or collapse, it restarts and will every time. Your blood pressure will return and you're back to normal. This is a newly diagnosed condition and is thought to be related to the vagus nerve.
This is where the rest comes in with back pain, chest pain, pain in your arms, etc. It is quite simply anxiety! This is a crippler. Anxiety can mimic a heart attack quite easily. It causes sickness, heavy breathing and muscle tension. It also affects the digestive system, because when this happens, the fight or flight response occurs and your body will send everything it has to your heart, brain and other vital organs to keep you alive! I know this because I have had it for a year with a 10 out of 10 for severity and am only now just learning how to deal with it. The body can quite easily handle anxiety and it will not kill you, but it can ruin your life if you let it. The thought of death consumes you and your train of thought will get worse and worse, which makes the anxiety worse because it feeds off it
Please, if you have these symptoms in any way and you have been checked out treated or just told you are O.K., then you must find the strength to pick yourself up and keep going. Do not stop. You might be scared and fearful of death, but if you are going to die, there is nothing you can do about it and sitting at home dwelling on it won't make a difference. You must fight, continue your life and keep going.
Anxiety is you. It's your thoughts that drive it. Once you stop fearing death, you can continue your life. What I mean by that is it doesn't matter what you are doing. Nothing is going to happen to you. Continuing your life is the answer. If you work, then carry on. If the worst is going to happen, it will, and it doesn't matter if you're in bed too scared to move or out running a marathon. Your body decides when it's time, not you. But you can help yourself by walking and looking after yourself. As long as you do your bit, the body will do its bit.
The vagus nerve is a fascinating thing and controls most things we so heavily depend on, but we can help ourselves. We need to just take care of ourselves and trust the professionals. Like my doc always says when I see him, “Well you're still here alive. Now do you believe me?” That is something to always remember: You're still here reading this and you will have a long life!