MURRAY With advanced CT imaging, signs of coronary artery disease can be detected very early, before clogged arteries create symptoms. But once you find it, do you treat it aggressively or wait?
The field of medicine, big on guidelines, simply doesn't know.
Cardiologists, radiologists and others at Intermountain Medical Center and LDS Hospital have launched a study to answer those questions, using 64-slice CT technology to screen people with diabetes a known risk factor for heart disease for the earliest signs of the disease. When it's found, patients will be treated to try to head off heart attacks, strokes and death.
Principal investigator Dr. J. Brent Muhlestein, director of cardiac research at IMC, says the goal is to see if early detection and treatment prolongs life and improves its quality.
On Wednesday, they announced the two-year, 1,100-patient study that will weigh the benefits and risks of early screening and treatment. Men over 50 and women over 55 with diabetes but no known heart disease will be randomly assigned to CT screening or not. Intermountain Healthcare will absorb the cost of the CT.
Gary Steadman, a retired aerospace engineer from Tooele, was one of the first study participants. At 72, he had no clue he had heart disease. But within days of the CT, he underwent triple bypass surgery. He recently returned from a trip to Israel, planned before he enrolled in the study. He believes the trip, which included a lot of walking and activity, could have ended tragically had he not been screened and his disease handled.
In fact, many of the 150 study participants already screened have been diagnosed with asymptomatic heart disease and treated, Muhlestein said.
"By the time there are symptoms, the disease is advanced. We know with a CT we can image a heart in a way never possible before," said Dr. Christopher McGann, cardiologist at LDS Hospital. "It's a powerful tool to detect coronary artery disease at an early stage. Now we need to decide if picking it up early can change outcomes."
He said if this study proves the value, it's likely research will move on to assess populations that do not have diabetes.
Participants assigned to the screening arm of the study are injected with a radioactive dye. The scanner takes X-ray images as the dye races toward the heart. With the CT, the radiologist can, in just seconds, produce 64 cross-sections of the heart, each about one-fourth of the size of the head of a pin. A computer program reassembles those sections to create a 3D image of the heart, revealing any plaque-clogged arteries. It also can differentiate between calcified, more stable plaque and that which is soft and more apt to rupture.
Coronary artery disease is the leading cause of death in the United States. About one-fourth of those who die never knew they had heart disease, because they had no symptoms, Muhlestein said. For half of those with heart disease, a heart attack is the first sign. Diabetics are among those less likely to having warning signs because of disease-induced nerve damage.
CT already has been proven in its ability to provide a "coronary calcium score," said Dr. Todd Lovelace, cardiac and thoracic radiologist. It also could be valuable not only in detecting heart disease, but also in spotting lack of it so that people don't need to go on to more invasive studies, he said.
As for the radiation risks, obtaining a calcium score exposes one to about 3-5 milli Sieverts of radiation, while a full scan is about 20. Catheterization is only about 6-7 mSV, but poses other risks."So far, these levels of radiation are not proven to be detrimental," said Dr. Jeffrey Anderson, associate chief of cardiology at IMC, "but it's always a concern." That's one reason it's important to determine the benefits of early screening, he said.