Endothelium-Independent Dilation In Adolescents

Abstract

Vascular function in the brachial artery is assessed with endothelium-dependent dilation (EDD) by reactive hyperemia and endothelium-independent dilation (EID) after sublingual nitroglycerin (NTG) administration. Peak brachial artery dilation post-NTG administration occurs between 3 and 5-min in adults. The time to peak dilation response post-NTG in adolescents is unknown. PURPOSE: To identify the time to peak dilation response to a single dose of sublingual NTG in adolescents. METHODS: EID was measured in 198 healthy (113 males, 85 females) adolescents, age 6-18 years (mean age 13.9 ± 0.2 yrs) via high-resolution ultrasound imaging of the brachial artery. A single dose of 0.3 mg NTG was administered and beat-by-beat ultrasound images were recorded over a 5-min period. The peak diameter following NTG administration was reported relative to baseline as a percentage increase. Tanner stage was determined by trained pediatricians. RESULTS: Mean time to peak EID was 4-min, 28-sec following NTG administration, with no significant difference between genders. There was a significant (p<0.001) difference between brachial EID post-NTG at the 3 vs. 4-min, 4 vs. 5-min, and 3 vs. 5-min time points. Time to peak EID (268.2 ± 2.6 vs. 266.2 ± 3.1 sec, p=0.6), as well as peak EID (24.8 ± 0.5 vs. 25.3 ± 0.6 %, p=0.6) and Tanner stage (3.7 ± 0.1 vs. 4.3 ± 0.1, p=0.3) were not significantly different after accounting for baseline diameter. CONCLUSION: Peak arterial dilation in response to NTG administration occurs between 4 and 5-min in adolescents. The results of this study demonstrate the importance of measuring EID up to 5-min post-NTG administration, as measuring up to only 3-min will likely underestimate artery dilation capacity in adolescents.