Short QT-intervals may be the hereditary cause of arrhythmias and sudden cardiac deaths in certain families, according to research done by a cardiologist at Saint Louis University School of Medicine (USA).

Preben Bjerregaard, MD, director of the electrophysiology and pacemaker service at the university hospital, first evaluated a 17-year-old girl who had developed atrial fibrillation while undergoing surgery for gallstones. The patient’s heart rhythm was normal following electroconversion, but the doctor noted she had an extremely short QT-interval on electrocardiography.

Evaluation of her mother and brother revealed they also had a short QT-interval; family history showed that the mother had a history of episodes of rapid, irregular rhythm and that the maternal grandfather had atrial fibrillation late in life. Because the father’s electrocardiogram was normal and there was nothing notable in his family history, Bjerregaard hypothesized that the trait had been inherited through the maternal grandfather and mother.

All 3 affected family members, mother, daughter, and son, have had implantation of a defibrillator to avoid the possibility of ventricular arrhythmia. "This is an electrical phenomenon of the heart and it's a treatable condition," Bjerregaard said. "Once diagnosed, defibrillators can be implanted to stabilize erratic rhythms, but it first has to be diagnosed."

In 2000, Bjerregaard first published his findings about the affected family in Cardiology, a Swiss journal. At the 2003 meeting of the American College of Cardiology, he heard from colleagues in Germany and Italy who noted similar short QT-intervals in 2 different families. In 1 of those families, 6 people had died suddenly.

"I knew then that we were dealing with something even more serious than noted in any previous medical literature and that we had probably found a new hereditary risk factor for sudden cardiac death," Bjerregaard said.

"A long QT-interval is often the culprit behind the sensational cases of athletes dying from sudden cardiac death who may have exhibited no prior symptoms," added Dr. Bjerregaard. "We've known for years that a long QT-interval is a hereditary condition and is dangerous, but the short QT-interval also appears to be hereditary and often exhibits no symptoms as well. Physicians and patients should be alert to this potentially life-threatening condition and begin to look for both the long and short QT-interval abnormality in any electrocardiogram."