The contrast dye used during certain heart imaging studies can harm the kidneys in the days following the procedure, particularly in older patients. A chemical called acetylcysteine has long been used to protect the vital organs, but now a new study has shown that it is not nearly as effective at protecting the kidneys as once believed.

Doctors use contrast dye to visualize various blood vessels in the body, particularly the ones in the heart during procedures like arteriograms and angiographs. In patients who are at higher risk, like the elderly or those who have had earlier kidney problems, heart troubles, or diabetes, the contrast dye can cause problems in kidney function.

The current study set out to determine how effective acetylcysteine really is. Over 2,300 patients undergoing heart x-rays with contrast dye were studied — along with their procedures, half of the patients were given the chemical acetylcysteine and half were given placebo.

The researchers were surprised to find that 13% of the patients in the acetylcysteine group and 13% of patients in the placebo group experienced kidney damage. The drug appeared to offer no protection.

If the drug offers no protective benefits over placebo, what’s the next step? Study author Otavio Berwanger notes in the American Heart Association press release that "[a] lot of research needs to be done. We have different types of contrast and the newer types claim to be less toxic to the kidney. But we don’t know which new one to choose. We need to use contrast, so we need to give patients the best and the safest." Developing a safer contrast dye or a more powerful protective drug will certainly be the next race.

Though it’s often necessary to weigh the costs against the benefits for any procedure, in this case, as Berwanger puts it, "it’s not good enough to fix the heart if it harms the kidneys." If you are planning on undergoing one of these procedures, please talk to your doctor about any safety concerns you may have.

The study was carried out by researchers at Research Institute at the Hospital do Coração in Sao Paulo, Brazil and presented at the American Heart Association’s Scientific Sessions 2010.