Flow-mediated vasodilation predicts the presence and extent of coronary artery disease assessed by stress thallium imaging Wen-Chih Wu, MD, a Satish C. Sharma, MD, FACC, a Gaurav Choudhary, MD, a Linda Coulter, RN, a Elizabeth Coccio, RN, b and Charles B. Eaton, MD, FAHA b Background. Endothelial function can be measured by flow-mediated vasodilation (FMD) of the brachial artery and has been associated with cardiac risk factors (RF) and angiographically defined coronary artery disease (CAD). Stress single photon emission computed tomography (SPECT) imaging is commonly used to study patients with CAD. We sought to study the relationship between endothelial dysfunction by FMD and stress thallium SPECT to detect CAD. Methods and Results. Fifty-five consecutive patients with chest pain syndrome referred for stress SPECT and eleven healthy control subjects had FMD measured on the brachial artery by standard techniques. The main outcome was the percent of brachial artery diameter dilation from baseline and the number of perfusion defects by SPECT. In subjects with no RF, those with RF but no defects, and those with defects, the mean FMD was 18.88%  2.31%, 7.85%  1.66%, and 5.91%  1.07%, respectively (P < .05). A significant correlation was found between the number of thallium defects and degree of FMD impairment (r 0.40, P < .01). An FMD cutoff value of less than 7.5% had a 72.5% sensitivity and 73.1% specificity in predicting the presence of any thallium defects. After RF adjustment, FMD remained as the strongest predictor of scintigraphic CAD (odds ratio, 10.96; 95% confidence interval, 2.82-57.31). Conclusion. FMD independently predicts the presence and extent of scintigraphic CAD. (J Nucl Cardiol 2005;12:538-44.) Key Words: Endothelial dysfunction • single photon emission computed tomography • coronary artery disease • flow-mediated vasodilation See related article, p. 518 Recent advances in vascular biology have addressed the crucial role of endothelium in the pathogenesis of atherosclerotic vasculopathy. 1,2 Endothelial function has been associated with coronary risk factors (RF), and its impairment is considered an early predictor of future atheromatous plaque formation. 1-3 Endothelial function can be assessed by flow-mediated vasodilation (FMD) in the brachial artery. 4 Transient ischemia in the forearm leads to a local increase in flow. This increase in flow causes the release of nitric oxide from the endothelium. Nitric oxide, in turn, leads to dilation of the brachial artery. FMD involves the measurement of this change in brachial artery diameter by use of 2-dimensional ultra- sound. 4 FMD has the potential to be applied clinically in the assessment of patients with suspected coronary artery dis- ease (CAD). Patients with angiographically proven CAD have coronary endothelial dysfunction, 5-8 and FMD has been shown to directly correlate with the endothelial vaso- reactivity of the coronary vessels. 5,6 However, studies relating endothelial impairment in the brachial artery to the presence and extent of CAD have yielded controversial results. 7,8 In addition, these studies have used coronary angiography as the method by which to detect and quantify CAD. 5-8 This is in contrast to current clinical practice, where the majority of patients presenting for cardiovascular evaluation do not undergo coronary an- giogram. Moreover, coronary angiography does not ac- count for coronary vasomotor response, and only less than half of patients with angiographically proven sig- nificant disease progress to the development of cardiac events. 9,10 Stress thallium imaging is frequently used in the assessment of patients with suspected CAD and provides independent information about the prognosis in addition From the Division of Cardiology, Providence VA Medical Center, a and Center for Primary Care and Prevention, Memorial Hospital of Rhode Island, Brown Medical School, Providence, RI. b Received for publication Dec 16, 2004; final revision accepted April 11, 2005. Reprint requests: Satish C. Sharma, MD, FACC, 830 Chalkstone Ave, Providence, RI 02908; Satish.SharmaMD@med.va.gov. 1071-3581/$30.00 Copyright © 2005 by the American Society of Nuclear Cardiology. doi:10.1016/j.nuclcard.2005.04.017 538