Positron emission tomography (PET) is being used in new research to detect harmful changes in coronary blood vessels. Recent studies on the PET possibilities were presented at the Society of Nuclear Medicine's 55th Annual Meeting. The use of PET may be a boon to individuals with no prior history or symptoms of heart disease. At least 50 percent of all deaths due to cardiac vessel disease are with previously asymptomatic patients.

The PET use is hoped to detect disease early and prolong life. According to Thomas Schindler, M.D., chief of nuclear cardiology at the University Hospitals of Geneva in Geneva, Switzerland, "Assessment of standard coronary risk factors such as arterial hypertension, smoking, hypercholesterolemia or diabetes appears to be limited in defining an individual's future cardiac risk."

Early stages of atherosclerosis can be detected by different cardiovascular imaging techniques, Dr. Schindler went on to explain. For example, intravascular ultrasound may identify abnormal thickening of the subintimal space (below the inner layer of blood vessels) of the carotid artery as an early sign of developing arterial disease; electron-beam or multi-detector computed tomography (MDCT) may identify calcification of the heart vessels and now PET may detect functional abnormalities of the coronary arteries by unmasking mild reductions in the blood flow supply to the heart during stress testing.
All of these imaging techniques been shown to identify the initiation and development of atherosclerotic disease of the heart vessels and future cardiovascular events such as myocardial infarction, sudden cardiac death, heart failure or the need for revascularization procedures for the heart.

"These measures to detect clinically silent heart vessel disease may be more useful in defining the future cardiac risk in individuals than conventional coronary risk factor assessment and could thereby better reinforce the preventive therapy for improving the long-term cardiovascular outcome," said Dr. Schindler. The difficulty in diagnosis is that it is still unknown which markers of heart vessel disease is first to manifest.

In the study of 68 asymptomatic individuals with type 2 diabetes (adult onset diabetes), researchers were able to determine the concurrent prevalence of the thickening in arterials walls (carotid-intima media thickness, IMT), coronary artery calcification (CAC) and functional abnormalities of the coronary circulation (coronary vascular dysfunction). The patients all had coronary vascular dysfunction as determined by PET scans, and showed a 56 percent increase in the prevalence of abnormal carotid IMT; 66 percent also had evidence of CAC.

The significant finding in the results was that when PET revealed coronary vascular dysfunction as a functional precursor of coronary artery disease, these findings were not always accompanied by abnormal increases in the carotid IMT or CAC, leading the researchers to believe that the dysfunction may precede these abnormalities of the arterial wall.

"PET assessment of functional abnormalities of the coronary circulation, therefore, may allow the earliest identification of developing heart vessel disease. This could lead to an optimized identification of the very early stage of the development of coronary artery disease, allowing physicians to initiate and/or reinforce preventive medical therapy strategies in order to improve the long-term cardiovascular outcome in these individuals at risk for heart disease," said Dr. Schindler.

More information available at: http://www.snm.org/index.cfm?PageID=7674&RPID=7665

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