Prego, if you using too much caffeine stop it!
You can use 50/50 coffee or better yet decaf even though the decaf contains caffeine too. If you are a cola addict that will cause tachycardias too.
Some people don't realise that caffeine can cause BP to rise, tachycardia, nervousness etc.
As for the PVC's I wouldn't even worry about 4 in a 24 hour period. If you have them constantly , in groups, bigeminies and trigeminies, if they wake you up in the middle of the night, if they last for hours, then we'll talk. Also if you are using alergy or cold remedies check with your doctor because these will cause ectopies too (PAC's, PVC's, Supraventricular Tach).