Physical Effects of Nicotine on the Heart Rate

Roses fend off predators with thorns, but tobacco plants protect their huge leaves with a more lethal, yet invisible, defense -- nicotine. Naturally occurring in tobacco, the chemical nicotine rapidly hijacks the nervous systems of insects and animals that would dare munch on it. For years nicotine was used to manufacture insecticides, but this was eventually discontinued, as it has the power to also harm animals, including people. Among the myriad effects of nicotine on humans, one readily observed and measured by the layman is its effect on heart rate.

Nicotine has inescapable and immediate effects on the heart. (Image: lola1960/iStock/Getty Images)

Powerful Plant Chemicals

Nicotine is one of the plant-based chemicals known as alkaloids. Other familiar alkaloids include morphine, strychnine, opium and caffeine. Most affect the nervous system of humans and are habit forming and potentially poisonous. Nicotine is readily absorbed through the skin, mucus membranes, gastrointestinal tract and lungs. Nicotine elicits the “fight or flight” response in people by setting off the sympathetic nervous system. The heart revs up for action, accelerating its rate. Other parts of the nervous system are activated as well. Overall, the effects of nicotine in humans are complex.

Raising Many Pulses

The most common effect of nicotine on heart rate is the increase experienced by tobacco and nicotine users. Nicotine increases the heart rate whether it enters the bloodstream from tobacco smoke, a nicotine patch, nicotine gum, nasal spray or snuff. A 2013 article in the "Journal of Clinical and Diagnostic Research" shared research results comparing the electrocardiograms of smokers and nonsmokers. Although the smokers had not smoked for at least 2 hours, their heart rate was significantly higher than that of the nonsmokers. According to MedlinePlus, nicotine increases the heart rate on average 10 to 20 beats per minute.

Effects on the Fetal Heart Rate

A normal heart rate has a regular rhythm or beat. The rate varies with changes in the body's need for oxygen-rich blood. Heart rate variability can be adversely affected by nicotine. For example, a 2005 research article in the "Journal of Pediatric Psychology" reported a study of maternal smoking on the heart rate variability of fetuses. Ultrasounds of pregnant smokers and nonsmokers in their last trimester were performed, and the variability of fetal heart rates were compared. The fetuses whose mothers smoked had lower heart rate variability, which is considered an unhealthy result.

Less Common Effects

Paradoxically, high nicotine levels can lower the heart rate and provoke arrhythmias. This was seen in intentional and unintentional poisonings with nicotine. In 1992, the Centers for Disease Control and Prevention documented a case in which 2 tobacco harvesters required intensive care hospital treatment for a low heart rate because their skin had absorbed high levels of nicotine as they picked wet tobacco. In 2003, a grocery store worker adulterated ground beef with nicotine-laden insecticide; at least 1 poisoned customer experienced an abnormal heart rhythm as a result. While these episodes are rare, they illustrate just how potent the effects of nicotine can be.

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