E-cigarettes: harmful or not harmful? Just as traditional nicotine-containing products have long been proven to be harmful, in the case of electronic cigarettes, emerging reports are often completely contradictory. New information on the possible adverse effects of e-cigarettes on the heart has emerged thanks to a study by scientists in Los Angeles. The analyses were carried out on a small group of patients, but allowed a conclusion to be drawn - electronic cigarettes can adversely affect the cardiovascular system.