It is a medication doctors often prescribe, but it could pose a risk for deadly heart problems. Vanderbilt Medical Center researchers have been studying the antibiotic azithromycin. You may know it as a Z-pack. Researchers say patients with heart issues may want to stay away.Azithromycin can be a life-saver for a person suffering from bronchitis, but new research suggests the widely used antibiotic may increase the risk of death."In this case it was a pretty marked finding," says Vanderbilt researcher Dr. Wayne Ray.A new article in Thursday's New England Journal of Medicine was authored by Vanderbilt researchers. The team studied 14 years of health records and found that Tennessee Medicaid patients taking azithromycin, instead of other antibiotics, were at a greater risk for sudden heart failure. "And if you don't have immediate medical attention, you die," says Dr. Ray.The study found that patients taking azithromycin had a two and a half time greater risk of death than those taking another antibiotic, like amoxicillin.