Cocaine causes the body’s blood vessels to become narrow, constricting the flow of blood. This is a problem. It forces the heart to work harder to pump blood through the body. (If you’ve ever tried squeezing into a tight pair of pants, then you know how hard it is for the heart to pump blood through narrowed blood vessels.)
When the heart works harder, it beats faster. It may work so hard that it temporarily loses its natural rhythm. This is called fibrillation, and it can be very dangerous because it stops the flow of blood through the body.
Many of cocaine’s effects on the heart are actually caused by cocaine’s impact on the brain—the body’s control center.