Hi there. There is information about magnesium all over the forum right now. Seems to be a hot topic :-). One link is
http://www.medhelp.org/posts/show/353019 and another is a thread that is titled Celeste77 from sugarpea. As is stated in MANY of these posts, Magnesium is not a silver bullet. It seems to work for some people and not for others. In some cases, it may be a placebo effect that is doing the most work, and I will fully admit that may be the case with myself. You see, when these things start to really bother you, you begin to realize that you will try just about anything to make them go away. Magnesium is cheap and it's recommended by many doctors (mine suggested I try...but didn't promise anything) as a possible course of action, so I tried it. It may well not do a thing for me, but since my PVC's are currently a sidebar in my life and not at the forefront, I figure why mess with a good thing? I take 3 tablets of Mg citrate daily (as recommended on the supplement bottle).
I will say one thing that many do not bring up on this forum however. If you are planning to use magnesium and/or potassium supplements be sure to mention this to your doctor. While Mg and K in high levels is excreted from the body in the urine, very high doses CAN be dangerous. So, feeding yourself half a bottle of supplements in order to make your PVC's go away isn't a really good idea. Also, depending on your specific circumstances, and the medicines you are currently taking different levels of the supplement to suit your situation is adviseable. If you don't want to talk to your doctor, ask your pharmacist.
I would also advise that you be careful with the "decaf." Decaffeinated coffee, in MANY cases, contains approximately 40% of the caffeine as regular coffee. And "light" coffee has as much as 75% of the caffeine as regular coffee. Also, chocolate contains a caffeine related molecule that can cause similar cardiac responses, so be careful to avoid chocolate if you are having a particularly rough bout with PVC's.
As for positional PVC's, I have to say that laying on my right side makes them much more noticeable for me. But, when they are being particularly annoying it really doesn't matter how I lay...they bother me.
I understand your frustration though. Sometimes you can live your life on the extremely careful, no caffeine, no chocolate, no fearful encounters, no nothing, and the PVC's are on you like a vengeance. Then there are other times when you can be going along drinking 2 cups of regular coffee a day along with sodas and whatever else and you don't notice them at all. I'm not really sure that Magnesium does anything "real" for me, but since it seems to work I use it. I'm not sure that drinking little to no caffeine really does much, but who wants to tempt fate by dousing my system with revving caffeine drinks?
I know one thing to be absolutely true and necessary. You MUST get a decent amount of sleep every night. If you are run down, tired, or nursing an illness, you WILL have increased PVC's. If you sleep 12 hours today, but only 3 tomorrow, you WILL have a hard time with PVC's. If you are stressed and wakeful throughout the night, your PVC's WILL bother you. I think the number ONE link to increased PVC's in my life is inadequate sleep, and EVERYONE on here has mentioned that sleep plays a MAJOR role in their symptoms. So, get your rest.
Take care.