Pulse wave analysis of β2-agonist-mediated response in hypertension

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University of Manchester (2003) J Physiol 552P, P37

Communications: Pulse wave analysis of β2-agonist-mediated response in hypertension

Curtis Rambaran, Elizabeth Iveson, Philip J. Chowienczyk, James M. Ritter, Ajay M. Shah, Terrence Forrester and Lalit Kalra

Cardiovascular Research Group, Guy's, King's and St Thomas' School of Medicine, King's College London and Tropical Medicine Research Institute, University of the West Indies, Kingston, Mona, Jamaica

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β2-Adrenoreceptors activate the L-arginine-nitric oxide pathway in human vasculature and may play an important role in the regulation of vascular function (Dawes et al. 1997; Chowienczyk et al. 1999).

We examined effects of systemic administration of the selective β2-agonist albuterol on the contour of the digital volume pulse (DVP) waveform in subjects with essential hypertension and normotensive controls. The digital volume pulse is highly sensitive to changes in pressure wave reflection and arterial distensibility. Nitroglycerine was used as a comparator vasodilator. The digital volume pulse was recorded in 22 subjects with essential hypertension and 19 normotensive controls (systolic blood pressure: 147 ± 21 vs. 118 ± 9 mmHg, mean ± S.D., P < 0.001; diastolic blood pressure: 92 ± 12 vs. 73 ± 7 mmHg, P < 0.001) at baseline and during intravenous infusion of albuterol (5 µg min-1) and nitroglycerin (5 µg min-1). Baseline DVP measurements and responses to drugs were compared by Student’s paired t test or analysis of variance for repeated measures using SPSS. All tests were two tailed and P < 0.05 was considered significant. The study was approved by King’s College Hospital Research Ethics Committee.

Albuterol had no significant effect on blood pressure but induced characteristic changes in pulse contour consistent with a decrease in pressure wave reflection and increase in large artery distensibility. These changes were blunted in hypertensive subjects compared with controls (change in reflection index: 4.1 ± 1.2 vs. 10.4 ± 2.0 %, means ± S.E.M., P < 0.02; change in peak-to-peak time: 23.6 ± 5.0 vs. 48.7 ± 7.3 ms, P < 0.02). By contrast changes induced by nitroglycerine were similar in both groups (Fig. 1).

Selective blunting of the pulse wave response to albuterol in subjects with essential hypertension compared with normotensive controls implicates an altered β2-adrenoceptor pathway in arteries responsible for wave reflection in these hypertensive subjects. Further investigation will be needed to establish how generalisable this will be.

We thank the Wellcome Trust for their support.

Figure 1. Characteristics of the digital volume pulse. Mean change from baseline in reflection index (DRI) and peak to peak time (DPPT) of the digital volume pulse in response to intravenous infusion of albuterol (ALB 5 µg min-1) and nitroglycerine (NTG, 5 µg min-1) in normotensive (n = 19) and hypertensive subjects (n = 22).
Click to enlarge

Figure 1. Characteristics of the digital volume pulse. Mean change from baseline in reflection index (DRI) and peak to peak time (DPPT) of the digital volume pulse in response to intravenous infusion of albuterol (ALB 5 &micro;g min-1) and nitroglycerine (NTG, 5 &micro;g min-1) in normotensive (n = 19) and hypertensive subjects (n = 22).

Where applicable, experiments conform with Society ethical requirements.

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