thats another reason why vaporisers are good, smoke has the effect, as check minus said, of reducing oxygen supply to the organs, yer heart beating faster when youve been smoking is compleatly normal, and providing u dont do it to often, not very dangerous, its the smoke that reduces the oxygen supply, so if you vaporize even though yer heart will still beat faster, yer organs will be able to get a decent amount of oxygen. but the real trick to avoiding getting paranoid about yer heart rate when stoned is to not think about it!