Can cannabis smoke block arteries?

No: I have never seen a single paper that shows cannabis effect atherosclerosis in any way.

Calgarycmmc.com/athe: Answer is no but...Smoking marijuana can speed up the pulse and raise blood pressure (followed by a sudden fall upon standing or walking), roth notes. "these effects lower the exercise threshold for chest pain [angina], and are an independent risk factor for heart attack and stroke, " he writes. Inhaling marijuana smoke can also impair oxygen delivery . Prague med rep 2009; 110(1):5-12.

Not good srticle: The article quoted is theoretical article with no data that i could find. There is no evidence I have found to show smoking pot increases risk of heart attack. This however is unrelated to question asked.

Vasoconsrtiction: Mj can cause vasoconstriction or narrowing of vessels, but this is during intoxication, not necessarily permanently. However, if the arteries are already blocked, this could lead to problems. Best not to smoke at all unless you're terminally ill.