Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of alpha-1 receptors in humans.

BACKGROUND: Carotid artery (CCA) dilation occurs in healthy subjects during cold pressor test (CPT), whilst the magnitude of dilation relates to cardiovascular risk. To further explore this phenomena and mechanism, we examined carotid artery responses to different sympathetic tests, with and without α1-receptor blockade, and assessed similarity to these responses between carotid and coronary arteries. METHODS: In randomised order, 10 healthy participants (25{plus minus}3yrs) underwent sympathetic stimulation using CPT (3-minutes left hand immersion in ice-slush) and lower-body negative pressure (LBNP). Before and during sympathetic tests, CCA diameter and velocity (Doppler ultrasound) and left anterior descending (LAD) coronary artery velocity (echocardiography) were recorded across 3-min. Measures were repeated 90-min following selective α1-receptor blockade via oral Prazosin (0.05mg-per-kg bodyweight). RESULTS: CPT significantly increased CCA diameter, LAD maximal velocity and velocity-time integral area-under-the-curve (all P<0.05). In contrast, LBNP resulted in a decrease in CCA diameter, LAD maximal velocity and velocity time integral (VTI, all P<0.05). Following α1-receptor blockade, CCA and LAD velocity responses to CPT were diminished. In contrast, during LBNP (-30mmHg), α1-receptor blockade did not alter CCA or LAD responses. Finally, changes in CCA diameter and LAD VTI-responses to sympathetic stimulation were positively correlated (r=0.66, P<0.01). CONCLUSION: We found distinct carotid artery responses to different tests of sympathetic stimulation, where α1-receptors partly contribute to CPT-induced responses. Finally, we found agreement between carotid and coronary artery responses. These data indicate similarity between carotid and coronary responses to sympathetic tests and the role of α1-receptors that is dependent on the nature of the sympathetic challenge

Adherence to guidelines strongly improves reproducibility of brachial artery flow-mediated dilation.

BACKGROUND: Brachial artery FMD is widely used as a non-invasive measure of endothelial function. Adherence to expert guidelines is believed to be of vital importance to obtain reproducible measurements. We conducted a systematic review of studies reporting on the reproducibility of the FMD in order to determine the relation between adherence to current expert guidelines for FMD measurement and its reproducibility. METHODS: Medline-database was searched through July 2015 and 458 records were screened for FMD reproducibility studies reporting the mean difference and variance of repeated FMD measurements. An adherence score was assigned to each of the included studies based on reported adherence to published guidelines on the assessment of brachial artery FMD. A Typical Error Estimate (TEE) of the FMD was calculated for each included study. The relation between the FMD TEE and the adherence score was investigated by means of Pearson correlation coefficients and multiple linear regression analysis. RESULTS: Twenty-seven studies involving 48 study groups and 1537 subjects were included in the analyses. The adherence score ranged from 2.4 to 9.2 (out of a maximum of 10) and was strongly and inversely correlated with FMD TEE (adjusted R(2) = 0.36, P < 0.01). Use of automated edge-detection software, continuous diameter measurement, true peak diameter for %FMD calculation, a stereostatic probe holder, and higher age emerged as factors associated with a lower FMD TEE. CONCLUSIONS: These data demonstrate that adherence to current expert consensus guidelines and applying contemporary techniques for measuring brachial artery FMD decreases its measurement error