The one concern that physicians might have concerns the effects of nicotine. Nicotine is a vasoconstrictor, which means that it makes your arteries more narrow.
I am not saying that nicotine is not a vasoconstrictor but this issue might be a little bit overstated.
Following is a Kate51 quote:
When a person is vaping nicotine, of course a very high dose would cause BP to rise, but on the opposite side of that is the fact that vapers are absorbing only 10th the nicotine and none of the other chemicals listed commonly in cigarette ingredients. So to say nicotine can cause cardiovascular harm, that would be an extreme that is not really substantiated by plasma testing in moderate nicotine users, of which I have done numerous, showing my plasma cotinine level at 100-200 ng/l, using 12mg/ml juice @ 1.5-2ml per day...about the same reading as passive 2nd hand exposure. Significantly, no CO2, no tar, no carcinogenic or toxicity at these levels.