WEDNESDAY, June 22 (HealthDay News) -- Heart damage caused by heavy cocaine use can occur without producing any symptoms, according to a new study.

Researchers assessed the heart health of 30 long-term cocaine users, average age 37, who entered a drug rehabilitation program 48 hours after they last used cocaine. They had been using cocaine for an average of 12 years and consumed about 5.5 grams of cocaine per day.

Snorting was the most common way of using cocaine, but 10 said they injected intravenously and two said they smoked it (crack cocaine).

More than half of the those addicted to cocaine also used other substances -- such as heroin and alcohol -- and one in five was infected with either hepatitis C or HIV.

Heart function was normal in all the daily cocaine users, but 12 had localized abnormalities, 83 percent had structural damage, and 47 percent had swelling (edema) in the lower left ventricle. Edema was associated with greater cocaine consumption.

The researchers also found that 73 percent of the addicts had heart tissue scarring (fibrosis), possibly caused by a silent heart attack or toxic damage.

Edema is an indicator of recent damage and is reversible, but fibrosis is not, the researchers said.

The study appears online June 21 in the journal Heart.

In about one in five cocaine addicts, autopsy studies reveal myocarditis, inflammation of the heart muscle, according to a journal news release. And, among people younger than 45, one-quarter of non-fatal heart attacks are linked with cocaine, the authors said in a journal news release.

More information

The U.S. Office of National Drug Control Policy has more about cocaine.