Influence of vessel size, age and body mass index on the flow-mediated dilatation (FMD%) of the brachial artery
Introduction
To current understanding, endothelial dysfunction (ED) is the functional prestep in atherosclerosis [1]. The healthy endothelium secretes powerful vasodilating (e.g. Endothelium Derived Relaxing Factor, EDRF [2]) and vasoconstricting substances (e.g. endothelin-1 [3], [4]). Endothelial function is usually impaired in the presence of cardiovascular risk factors, e.g. hyperlipidemia [5], diabetes mellitus [6], hypertension [7] or smoking [8]. Since ED is a generalised process, the determination of flow-mediated vasodilatation (FMD%) of the brachial artery was found to be a reliable marker for systemic endothelial function [9], [10], [11], [12]. There is evidence, that the non-invasive measurement of FMD% might be also used as a screening test for coronary artery disease (CAD) in patients with clinical suspicion of CAD [11], [13]. Since the measurement of FMD% could thus, become a widely used method in the clinical setting, further studies addressing methodological issues are required. In this context, it is of special interest, whether FMD% is influenced by the anatomical vessel size of the brachial artery, the patient’s age, body mass index or gender. The present study was conducted to elucidate these questions.
Section snippets
Subjects and study protocol
In this prospective study we included 122 patients who were scheduled to our department for coronary angiography. All subjects gave their informed consent to participate in the study. The study was performed according the principles of the declaration of Helsinki and was approved by the local ethics committee. Patients with chronic congestive heart failure, renal insufficiency, chronic hemodialysis, significant valvular heart disease or former coronary angiography were excluded. In addition to
Results
In the 122 patients, lumen diameters (LD) of the brachial artery at rest ranged from 2.48 to 6.33 mm (4.56±0.74 mm).
A positive correlation between body length and lumen diameter was found (r=0.47, P<0.0001, Fig. 1), indicating that taller patients have tend to have larger arteries. Female patients had significantly smaller LD than male patients (3.9±0.1 mm vs. 4.6±0.07 mm, P<0.0001, body length female patients 161±1.0 cm vs. body length male patients 174.8±0.7 cm).
Flow-mediated vasodilatation
Discussion
The most important findings of the present study are: (a) Although an inverse correlation between the lumen diameter of the brachial artery at rest and the extent of FMD% was found, this correlation was less distinct than previously reported; (b) the test-results (FMD%) were found to be rather independent of the patients age or body mass index and (c) a positive correlation between body length and lumen diameter of the brachial artery could be proofed.
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