Assessment of endothelial function using peripheral waveform analysis
A clinical application
Christopher S. Hayward, MD* ,*,
Mustafa Kraidly, MD,
Carolyn M. Webb, PhD and
Peter Collins, MD
* St. Vincent’s Hospital, Sydney, Australia
National Heart and Lung Institute, Royal Brompton Hospital, London, United Kingdom
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Figure 1 An example of the effect of Salbutamol and glyceryl trinitrate (GTN) on the radial waveform in a single individual. It can be seen that the second systolic peak, obvious at baseline, is diminished by Salbutamol and almost completely abolished following GTN. The changes in the wave-shape are quantified using the augmentation index (AIx), calculated as the ratio of the pulse pressure at the second systolic peak to that at the first systolic peak. BP = blood pressure.
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Figure 2 (A, B) Salbutamol, given after saline, was associated with a significant decrease in augmentation index (AIx) compared to baseline (AIx; –11.8 ± 3.7%, p < 0.05). When given after N- -nitro-monomethyl-L-arginine (L-NMMA) there was no significant change in AIx (–2.0 ± 3.1%). The GTN was associated with a similar significant decrease in AIx after saline (–35.1 ± 3.3%) and L-NMMA (–36.5 ± 3.3%), p < 0.001 by analysis of variance (ANOVA). (C, D) There was no significant effect of either Salbutamol alone or L-NMMA on mean blood pressure (BP). The GTN was associated with a slight decrease in BP in both cases. (E, F) Salbutamol was associated with a significant increase in heart rate, which was blocked after L-NMMA infusion, p < 0.05 by ANOVA.
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Figure 3 There was no relationship between the increase in heart rate (HR) seen after Salbutamol with the increase in augmentation index (AIx) seen in the same subjects (r = 0.11, p = 0.75).
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Figure 4 (Top) There was good agreement between the Salbutamol-induced responses on two separate visits (r = 0.80, p < 0.01). (Bottom) As shown by the Bland-Altman analysis, there was good reproducibility and no systematic error according to magnitude of Salbutamol-induced change in augmentation index (AIx).
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Figure 5 Comparison of Salbutamol and glyceryl trinitrate (GTN)-induced changes in augmentation index (AIx) in coronary artery disease patients (CAD) with control subjects. A significantly greater decrease occurred in AIx in control subjects compared to CAD patients following Salbutamol (–2.4 ± 1.9%; controls: –13.2 ± 2.3%, p < 0.002). This difference was not significant following GTN (–27.4 ± 4.2 vs. –38.9 ± 4.4%, p = 0.07).
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