Someone with a predisposition to heart attack SHOULD be concerned about using ANY stimulant, but that doesn't mean that EVERYONE should have that same concern anymore than someone who doesn't have a peanut allergy needs to avoid peanut butter.
As far as the nicotine in second-hand vapor, a
1993 study on nicotine in vegetables showed that it would take 9 HOURS of exposure to minimal secondary smoke to be exposed to the same amount of nicotine you would get in just 1/4 cup of eggplant. Even if secondary vapor has the same levels as secondary smoke, it's obviously not a lot or we would be told eggplant is a health hazard. So, unless someone also avoids eggplant and other vegetable with nicotine, concern with the amount of nicotine they are exposed to with vapor in a typically ventilated room is an irrational fear.
Smoking-related heart disease is not attributed solely to nicotine. In fact, the nicotine is considered one of the lowest factors. If nicotine use itself was such a high risk for heart disease then Sweden would have a much higher incidence of heart disease due to rampant smoke-free snus use. As the ANTZ like to point out, snus and smoke-free tobacco has "more nicotine" than cigarettes. So snus users would likely have a much higher rate of heart attack and CVD, but that is
not the case.
Nicotine can temporarily put stress on the heart via increased heart rate & blood pressure, so that is bad if you already have a pre-existing condition or you'll increase risk of triggering a heart attack. People with such conditions should also avoid caffeine - another stimulant that can affect the heart. But there is very little evidence that nicotine can CAUSE heart disease in otherwise healthy people. There are just too few studies on always smoke-free nicotine users (plenty on smokers, ex-smokers and dual users, but then you cannot exclude other factors due to components in smoke.) But what little research we do have on never-smoker snus users shows that the high nicotine content does not increase risk of heart disease or heart attack.