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Tuesday 23 October 2007

Assessment of endothelial function: comparison of the pulse wave response to beta-adrenoceptor stimulation with flow mediated dilatation.

By: Rambaran C, Jiang B, Ritter JM, Shah A, Kalra L, Chowienczyk PJ.

Br J Clin Pharmacol 2007 Oct;(): [Epub ahead of print]

Aims To assess the reproducibility of the digital pulse wave response to beta(2)-adrenoreceptor stimulation and to determine if an attenuated response to beta(2)-adrenoceptor stimulation is associated with impaired flow mediated dilatation (FMD). Methods Subjects (n = 20) with endothelial dysfunction (ED), were compared with healthy control subjects (n = 20). Change in reflection index (DeltaRI) of the digital volume pulse in response to salbutamol (SALB, 5 microg min(-1) i.v) and to nitroglycerin (NTG, 5 microg min(-1) i.v) was used to assess endothelium-dependent (DeltaRI(SALB)) and endothelium-independent (DeltaRI(NTG)) pressure wave reflection. DeltaRI(SALB) was assessed on two occasions to examine reproducibility. High resolution ultrasound of the brachial artery was used to measure FMD and also dilation to NTG (NTGD). Results The mean difference in DeltaRI(SALB) between two visits was -0.2%, with SD of the difference 4.9%. Both DeltaRI(SALB) and FMD were impaired in subjects with ED compared with values in control subjects (5.0 +/- 0.7 vs. 11.3 +/- 1.2%, mean values +/- SEM, P < 0.01 and 4.2 +/- 0.6 vs. 7.5 +/- 0.8%, P < 0.02 for DeltaRI(SALB) and FMD, respectively), whereas DeltaRI(NTG) and NTGD were similar in the two groups. DeltaRI(SALB) was correlated with FMD (r = 0.44, P < 0.01) and had 88% sensitivity and 79% specificity to detect abnormal (FMD < 4%). Conclusions The pulse wave response to a beta(2)-adrenoceptor agonist correlates with FMD and has high sensitivity and specificity in detecting abnormal endothelial function as defined by FMD. However, FMD is the preferred test to detect effects of interventions on endothelial function.

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