Narrator: This is Science Today. Six percent of all heart attack patients in the United States have a condition called left bundle-branch block. This occurs when an electrical current can't pass through a small area of damaged heart tissue and ultimately results in very inaccurate ECG readings. Dr. Michael Shlipak, a researcher at the University of California, San Francisco, says these skewed results make it hard to accurately diagnose and treat heart attacks in these patients.

Shlipak: The current standard of care recommended by the American Heart Association is that if the patient with left bundle is suspected of having a heart attack, they should be then treated with either thrombolytic therapy or angioplasty.

Narrator: But this doesn't happen often. Since 1996, many doctors began using a mathematical formula developed for the ECG, which claimed to detect over 70% of left bundle patients having a heart attack. In a recent validation study however, Shlipak's results were far different.

Shlipak: The test only picked up about ten percent. To treat all of them with thrombolytic therapy as recommended by the current standard of care was by far the best option.

Narrator: For Science Today, I'm Larissa Branin.