electronic cigarettes. The anatomy of an e-cig is ostensibly simple: As you suck on the mouthpiece, a tiny battery ignites to heat a liquid nicotine solution until it becomes vapor, which you then inhale. Depending on the type and brand, an e-cigarette can last anywhere from 250 to 400-plus puffs (one real cig lasts for about 10 drags). Some are ready-to-use disposables ($4 and up per cigarette), others are rechargeable ($30 and up), and still others take refillable cartridges (up to $325). Missing from e-cigs are tobacco and the more than 4,000 chemicals, many of them carcinogenic, that you'd get with a typical smoke (think ammonia, arsenic, tar). But the most important ingredient in both versions is nicotine, which can have some nasty long-term effects, says cardiologist Suzanne Steinbaum, D.O., author of Dr. Suzanne Steinbaum's Heart Book. The addictive stimulant constricts blood vessels, increases blood pressure, and restricts blood flow to your hea...