Japanese PET study reveals patients at risk of atherosclerosis

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Japanese researchers were able to detect the beginnings of atherosclerosis before the disease became clinically evident thanks to a combination of positron emission tomography, the medical isotope 15O-water and cold pressor tests. The results were released Monday at the Society of Nuclear Medicine’s (SNM) 53rd Annual Meeting in San Diego.

This revelation will allow physicians to advise high-risk patients—who show no cardiovascular symptoms—to make lifestyle changes modifications or to undergo medical treatment, said Masanao Naya, a physician at Hokkaido University Graduate School of Medicine in Sapporo, Japan. He is the co-author of “Determinants of Coronary Endothelial Dysfunction in Hypertensive Patients.” In addition, researchers determined that elevated levels of interleukin-6—one of the inflammatory chemicals produced by endothelial cells and that has been associated with an increased risk of heart disease—is “a major determinant” of coronary endothelial dysfunction, especially in individuals with high blood pressure.

Coronary endothelial dysfunction—which occurs when blood vessels aren’t flexible enough to expand in response to increased blood flow—is the central feature of atherosclerosis. Coronary endothelial dysfunction precedes cardiovascular events and is reversible, making its early detection important, said Naya. “We can select high-risk patients with endothelial dysfunction using blood sample analysis at an early stage of atherosclerosis, then start medical treatment or lifestyle modification.” More than 71 million Americans have one or more forms of cardiovascular disease, the single leading cause of death in this country.

Coronary endothelial function is impaired at an early stage of atherosclerosis in hypertensive patients; however, the “magnitude” of dysfunction differs among individuals, said Naya. “We can assess the endothelial dysfunction in the human heart noninvasively using PET and evaluate factors that can determine endothelial dysfunction,” he added.In their study, researchers examined 27 untreated patients with high blood pressure. Myocardial blood flow was measured both at rest and during stimulation induced by a cold pressor test by using PET with 15O-water. The patient’s feet were immersed in icy water for 4 minutes, and a person’s risk for hypertension or high blood pressure was evaluated by observing blood pressure response.

Additional research needs to be done, said Naya. “We have been enrolling more patients and evaluating the relevance to the prognosis and the effect of medical treatments or life modification,” he noted.

Abstract: M. Naya, T. Tsukamoto, S. Fujii, H. Tsutsui, cardiovascular medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan; and M. Inubushi, K. Morita, C. Kato, N. Tamaki, nuclear medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan, “Determinants of Coronary Endothelial Dysfunction in Hypertensive Patients,” SNM’s 53rd Annual Meeting, June 3–7, 2006, Scientific Paper 2.