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 (Delta RI) 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 (Delta RI(SALB)) and endothelium-independent (Delta RI(NTG)) pressure wave reflection. Delta RI(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 Delta RI(SALB) between two visits was -0.2%, with SD of the difference 4.9%. Both Delta RI(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 Delta RI(SALB) and FMD, respectively), whereas Delta RI(NTG) and NTGD were similar in the two groups. Delta RI(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.