(Ivanhoe Newswire) -- Stroke victims who also have abnormal electrical activity in their hearts are at a higher risk of dying within 90 days, compared to those with normal EKGs at the time of emergency treatment, according to a new study.

An EKG records the waves of activity in the heart and its pattern, which is labeled with the letters Q and T. Doctors look for the appropriate intervals between each letter, which shows that the heart's electrical signals are steadily passing through the ventricles. A prolonged QTc interval means it takes too long for the electrical signal to pass.

In this study, researchers also discovered a threshold at which the threat of death is highest: QTc intervals greater than 440 milliseconds in women and 438 milliseconds in men have the worst prognosis.

Researchers said prolonged QTc intervals could be the result of a rare genetic disorder, medications, electrolyte imbalances or congenital heart disease. When researchers studied the medical records of 345 ischemic stroke patients treated at the Mayo Clinic between 2001 and 2004, they found that about 35 percent had a prolonged QTc interval when they arrived at the emergency room.

An estimated 81 percent of all patients were expected to survive the next three months, but only 70.5 percent of the patients with a prolonged QTc interval lived that long compared with 87.1 percent of the patients without a prolonged QTc interval.

SOURCE: Journal of Stroke and Cerebrovascular Diseases, March 20, 2009