Weed DOES cause your heart to beat 20bpm above normal, and sometimes double that. You may feel chest pains because of lack of oxygen, or the constriction of blood vessels around your heart (a non-fatal temporary condition; elderly people call it angina). If you look at it from a beneficial point of view, your heart is simply doing exactly what it does during a heavy workout... So if you want to look at it in a purely abstract view, this can actually strengthen your heart, putting you less at risk for coronary problems in the future.
There, I said it. Weed is good for the heart!
