Prolonged exposure to cigarette smoke has been shown to change the shape of the heart.

In a study of rats by the University of Illinois at Chicago, researchers found changes in the left ventricle, which is the heart’s pumping chamber.

They also found elevated levels of a stress hormone norepinephrine, which is essential to the body’s fight or flight response.

Norepinephrine has a number of physiological changes in the body.

Rats were exposed to cigarette smoke or normal room air for five weeks and the effect on their hearts was examined under a microscope.

According to professor of biobehavioral health science and lead researcher Mariann Piano, cigarette smoke contained more than 4,000 different chemicals, which interacted with the body to be a likely cause heart disease.

Research was published in the European Journal of Heart Failure this month.

The National Cancer Institute estimated more than 438,000 deaths were caused by smoking the US each year and 38,000 were caused by exposure to second hand smoke.