Conditions such as abdominal obesity, high blood pressure, abnormal cholesterol levels and high blood sugar are problematic enough for people all on their own. But when patients have three of these disorders at the same time, they have what is called the "metabolic syndrome" - an increasingly prevalent disorder affecting up to 40 percent of the adult population in the United States - frequently leading to diabetes and accelerated heart disease.
Now, researchers at Cedars-Sinai Medical Center have found that patients with metabolic syndrome and a moderate level of calcium in the coronary arteries had a greater chance of having blockage of those arteries, as detected on a stress imaging test. The findings, reported in the June issue of Diabetes Care, show that analyzing a patient's metabolic profile in relation to their coronary calcium levels will help physicians identify patients who need stress testing so that effective treatment measures can be taken.
"Metabolic syndrome is very similar to diabetes in accelerating heart disease," said Daniel Berman, M.D., the director of Cardiac Imaging at Cedars-Sinai Medical Center and senior author of the study. "Importantly, our findings reveal that patients with the metabolic syndrome who had only moderate amounts of calcium in their coronary arteries had a significantly greater chance of having ischemia - too little blood flow to the heart - during a stress test."
Coronary calcium indicates the presence of atherosclerosis - plaque build-up in the arteries surrounding the heart. The amount of coronary calcium in the arteries, called a calcium score, is measured by using computed tomography (CT) scanning to obtain cross-sectional pictures of the heart and surrounding arteries. Even when patients have no symptoms, their coronary calcium score directly correlates with their long-term risk of cardiac events, such as a heart attack, or sudden death. Calcium scores of zero are the best scores; scores between one and 100 are considered mild and correlate with a low risk for any cardiac event over the ensuing five years. Patients with moderate calcium scores of 100 to 400 are at increased or intermediate risk for cardiac events, and patients with extensive coronary calcium (score over 400) are at even higher risk.
"Although coronary calcium scores provide an excellent measure of plaque build-up in the arteries, the presence of calcium doesn't mean that we will see evidence of ischemia or artery blockage when a patient does a stress test," Berman said. "In most patients, the calcium buildup causes the artery to expand outward, without blocking the vessel, and does not cause ischemia. This occurrence is associated with a low likelihood of a cardiac event over the next few years - but a relatively high long-term risk. Regardless, the calcium scan correctly identifies these patients as needing aggressive medical treatment to reduce their risk for a cardiac event, but they don't need to be considered for angioplasty or bypass surgery."
Still, some patients with coronary calcium have arteries that are partially blocked, restricting blood flow to the heart muscle during stress. The most widely used approach to detect blocked coronary arteries is stress imaging, during which patients exercise on a treadmill or, if they can't, are given medication that causes the heart's arteries to dilate. Once the patient reaches "peak" stress, a small amount of radioactive imaging agent is given that concentrates in the heart according to blood flow, emitting signals that are captured by a special type of camera. The cardiac images show the parts of the heart which do not get enough blood flow during stress and is very effective in predicting short-term risk of a cardiac event and determining whether it is necessary to consider angioplasty or surgery at that time.