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Cardiac Imaging Accurately Determines Diminished Blood Flow To The Heart

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Cardiac Imaging: At the Society of Nuclear Medicine's 57th Annual Meeting, a research was presented challenging theSNM typical paradigm used to determine whether heart patients will benefit from invasive procedures like stent-placement or open-heart surgery. More than 81 million people in the US (or more than one in three) have some form of cardiovascular disease, according to 2010 data from the American Heart Association. Major modifiable risk factors for heart disease include high blood-cholesterol levels, hypertension, diabetes, smoking and sedentary lifestyle.

Medical practice currently prefers treating patients with coronary atherosclerosis, with such procedures if a coronary artery is shown to be blocked by 70 % or more in order to reduce symptoms and potentially prevent heart attack. Despite that, a group of cardiac investigators found that not only does the degree of blockage have significant impact on coronary artery blood flow, but also the composition of the plaque causing the blockage also has significant impact on coronary artery blood flow. This may be a start to explain why two people with similarly blocked coronary arteries can experience vastly different symptoms. "If we can determine certain characteristics of the coronary artery plaque, we can predict whether a patient's symptoms are due to limitation of blood flow to the heart," said Haim Shmilovich, M.D., principal author of the study and a cardiac CT/MRI fellow-cardiologist at the Cedars-Sinai Medical Center, Los Angeles, Calif. "With further studies, our findings may change treatment planning for patients with severe but stable coronary artery disease by helping us determine which patients could be treated just as effectively with medications and lifestyle changes, thereby avoiding unnecessary invasive angioplasty and bypass surgery."

There are two imaging procedures, coronary CT angiography (CCTA) - which reveals the composition ofCCTA coronary artery plaque and the degree of blockage it causes - and myocardial perfusion imaging (MPI) - which measures relative blood flow to different regions of the heart, according to Shmilovich and colleagues. They found that identifying three plaque characteristics can determine a patient's risk of having reduced blood flow to the heart muscle more accurately. These characteristics are: the presence of a fatty core, signs of spotty calcifications and enlargement of the arterial wall from "positive remodeling," which means the body has responded to arterial damage by altering the structure of the artery. The presence of these characteristics, either individually or combined, in diseased arteries can predict diminished blood flow to the heart muscle, which could lead to symptoms, including heart attack. Their study involved 34 patients without known coronary artery disease. They underwent CCTA and MPI imaging to determine the presence of adverse plaque characteristics (APCs) and blood flow. Their results showed that all patients had severe (70 to 89 %) blockage in the beginning or middle section of a major coronary artery on CCTA, and when imaged with MPI, slightly more than 38% of all patients had significant ischemia. In the arteries with plaques that showed a fatty core, significant ischemia of the heart muscle portion nourished by the affected artery occurred at a much higher and statistically significant frequency (80 %) than those without a fatty core (21%). Finding multiple APCs in a plaque was also associated with higher degrees of significant ischemia.

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