Many investigators have shown that endothelial dysfunction is related to the pathogenesis of coronary artery disease. Investigators have also shown that both coronary and brachial arteries have flowmediated vasodilation. Unfortunately, studying the coronaries requires an invasive procedure whereas studying the brachial artery is non-invasive. The important clinical question is whether or not flowmediated changes in the brachial artery reflect flowmediated changes in the coronary circulation. If

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... one has to resort to cardiac catheterization to assess flow-mediated changes in coronary artery diameters using various stimuli, the process has very little clinical value. In contrast, if the brachial artery can be used as a surrogate for the coronary artery, the technique can be performed easily, repetitively and in an outpatient setting and with no discomfort to the patient. Theoretically at least, if the brachial artery is representative of the coronary circulation then one might be able to detect early asymptomatic stages of atherosclerosis. Anderson and Colleagues [1] observed a relatively low correlation coefficient between endothelial dependent vasodilations of the brachial and coronary arteries. These investigators used different endothelial stimuli to examine the endothelium-dependent vasodilations. In the coronary artery, acetylcholine was used and in the brachial artery flow-mediated vasodilation was the stimulus. Thus it is possible that the low correlation coefficient was attributed to the use of different stimuli. In contrast Takasi et al. [2] studied 15 patients with suspected coronary artery disease. The stimulus used by these investigators to evaluate endothelial function of the coronary arteries and the brachial artery was an increase in flow. Adenosine triphosphate was injected into the coronary arteries in order to generate coronary artery flow mediated vasodilation. Flowmediated dilation of the brachial artery was accomplished by inflation of a blood pressure cuff to 200 mmHg for 5 min in order to induce hyperaemia. Results of their investigation indicated that changes in blood flow in either the brachial artery by reactive hyperaemic stimulus or the coronary artery by ATP infusion correlated very well. Comparisons were based on percent diameter changes or flow ratios. The high correlation value suggests that flow-mediated dilation in brachial arteries could well serve as an index of dilation of coronary arteries. Thus, although it may be a stretch of the imagination to consider, a good correlation between brachial artery endothelial dysfunction and coronary artery endothelial dysfunction might be useful in predicting future cardiac events in patients with these abnormalities. In this issue Agewall and colleagues [3] performed an experiment in humans on a subject of current clinical interest. The subjects were not patients but rather healthy persons less than age 40. The investigators used high frequency ultrasound to measure blood flow and percentage brachial artery dilation after reactive hyperaemia induced by forearm cuff occlusion. Red wine with and without alcohol was ingested to determine its effect on endothelial function. The results of this experiment are summarized as follows. A single dose of de-alcoholized red wine increased endothelium-dependent vasodilation in response to hyperaemia, while red wine ingestion resulted in vasodilation without affecting the percentage increase in the artery diameter during the flowmediated vasodilation examination. The authors concede that in this study it is not certain whether brachial artery dilation induced by alcohol (red wine) was endothelium-dependent or not. In addition, brachial artery dilation and the increased resting blood flow induced by the alcohol may have concealed the effect of red wine on flow-mediated brachial artery dilation. Nonetheless, the investigators have tweaked my interest in this subject and if we combine their results with those found by Takasi et al. it may be that what is going on in the brachial artery with de-alcoholized wine is going on in the coronary arteries as well. What this means in the long term, of course, is not addressed by this investigation, and the authors are the first to admit that these studies should be confirmed, particularly in patients with coronary heart disease. In addition they strongly recommend studying the long-term effects of red wine consumption on endothelial function. As far as I know, that question has not been addressed anywhere in the literature.