That bit about the fast heartbeat wasn't total bullshit. I sometimes get a noticeably faster heartbeat when i toke, and I've always read that this is a normal effect of smokin' the ganj.

http://www.maps.org/mmj/abrams2.shtml

Plasma drug levels and heart rate peak within 15 minutes of an inhaled dose and rapidly decline. Oral THC increases heart rate to a lesser extent than smoked marijuana with a peak occurring two to three hours after ingestion (Chait 1992). Heart rate remained elevated four hours after ingestion.
http://www.erowid.org/plants/cannabi..._effects.shtml

racing heart
http://en.wikipedia.org/wiki/Health_...ogical_effects
Some of the effects of marijuana use include increased heart rate
Do you have some source that claims otherwise? I would like to read it.