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22 June 2010

Cardiac Imaging Breakthrough Helps Determine Diminished Blood Flow to the Heart

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Research presented at the Society of Nuclear Medicine's 57th Annual Meeting is challenging the typical paradigm used to determine whether heart patients will benefit from invasive procedures like stent-placement or open-heart surgery.

Current medical practice favors treating patients with coronary atherosclerosis (or hardening of the artery walls due to plaque build-up) with such procedures if a coronary artery is shown to be blocked by 70 percent or more in order to reduce symptoms and potentially prevent heart attack. However, a group of cardiac investigators are now finding that in addition to the degree of blockage, composition of the plaque causing the blockage also has significant impact on coronary artery blood flow. This may help 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."

Shmilovich and colleagues used two imaging procedures: coronary CT angiography (CCTA) -- which reveals the composition of 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. The investigators found that clinicians can more accurately determine a patient's risk of having reduced blood flow to the heart muscle by identifying three plaque characteristics: 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. Either individually or combined, the presence of these characteristics in diseased arteries can predict diminished blood flow to the heart muscle, which could lead to symptoms, including heart attack.

