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 μg 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.
- Coronary artery disease
- Endothelial function
- Vascular ultrasonography
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging
- Cardiology and Cardiovascular Medicine