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Within Subject Variability and Duration of Brachial Artery Dilation in Response to GTN
Author(s) -
McPhee Iain,
Levac Brendan,
Pyke Kyra
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.lb605
Subject(s) - brachial artery , medicine , clinical trial , nitric oxide , dilation (metric space) , endothelium , cardiology , anesthesia , blood pressure , mathematics , combinatorics
Glyceryl trinitrate (GTN) elicits an endothelium independent dilation by supplying exogenous nitric oxide to vascular smooth muscle. GTN tests are often used in conjunction with flow mediated dilation (FMD) testing to isolate impaired FMD to an endothelium dependent mechanism. The purpose of this investigation was to assess trial to trial variability in GTN induced dilation. A secondary purpose was to evaluate the duration of diameter elevation post GTN administration. A 400‐µg GTN dose was administered sublingually to 17 healthy male subjects (23±3 years) at two time points, trial 1‐ 0min, and trial 2‐ 160min. Pre GTN baseline (1min) and post GTN (10min continuously) artery diameters were measured via ultrasound. Diameter was also measured for 1min at 40min, 80min, and 140min post trial 1 GTN administration. The response to GTN was determined as the percent change from the pre GTN baseline diameter to the peak 30 second average diameter post GTN administration. The within subject trial to trial coefficient of variation (CV) (SD/Mean*100) was calculated from the percent change from baseline for each subject after GTN trial 1 and 2. Data are mean ±SD. Percent change in diameter was not different between trials (21.4± 5.7% vs. 22.4± 5.9%, p =0.153). Within subject trial to trial CV for the GTN response was 7.9± 6.7%. Brachial artery diameter remained elevated from the trial 1 baseline at 40min ( p <0.001), and 80min ( p <0.001), but not 140min (p=0.513) post GTN administration. These results suggest that there is a fairly low within subject variability in the response to GTN between trials, and that the dilatory response to GTN may have persisted for at least 80 min post GTN administration. The potential for prolonged dilation in response to GTN must be considered when planning assessments pre/post acute interventions. NSERC, CFI