Temporal heterogeneity of endothelium-dependent and -independent dilatation of brachial artery in patients with coronary artery disease

摘要

Background: Endothelial function is routinely assessed with high frequency ultrasound of the brachial artery. Fixed time points (1' post-occlusion and 3' post-nitrate) are commonly used to assess dynamic changes in brachial artery diameter. The underlying assumption is the lack of variability in temporal response to both endothelium-dependent and -independent stimuli. Objective: To evaluate the temporal course of endothelium-dependent (flow-mediated) and endothelium-independent (nitrate-induced) vasodilation of the brachial artery in patients with coronary artery disease (CAD) using high resolution (10 MHz) ultrasound. Methods: Thirty-seven patients with angiographically assessed CAD were prospectively enrolled in the study. End-diastolic, two-dimensional, long axis ultrasonographic images of the brachial artery were digitally stored on-line every 10 s, from baseline up to 4' during flow-mediated and up to 7' during 300 < mu >g sublingual nitrate-induced vasodilation of the brachial artery. Results: The mean percent endothelium-dependent flow-mediated maximal dilation (FMD) measured at 60 s was lower than the mean peak FMD (4.8 ?4.1 vs. 6.6 ?5.2%; p < 0.01). By 60 s only eight patients (35%) reached their maximum FMD response. The mean time to reach peak FMD was 87 ?33 s. The mean time for the peak nitrate dilation was 291 ?73 s. The peak nitrate-induced percent dilation was higher than that measured at 3 min (12.2 ?6.7 vs. 5.4 ?4.5%; p < 0.001). By 190 s, only four patients (11%) reached their maximum nitrate response. Conclusion: The routinely used measurement time points for evaluation of FMD and endothelium-independent vasodilation may not be adequate to detect the peak responses of individual patients with CAD.