Analysis of Short‐term Reproducibility of Arterial Vasoreactivity by Pulse‐wave Analysis After Pharmacological Challenge

Abstract

1. Pulse-wave analysis (PWA) is an established method to assess arterial wave reflections and arterial vasoreactivity in humans. A high short-term reproducibility of baseline augmentation index (AIx) has been reported. However, the short-term reproducibility of AIx changes following pharmacological challenge with either inhaled salbutamol (endothelium-dependent vasodilatation) or sublingual glyceryl trinitrate (GTN; endothelium-independent vasodilatation), using appropriate statistical methods, is largely unknown. 2. Baseline AIx and GTN- and salbutamol-mediated changes in AIx (all corrected for a heart rate of 75 b.p.m.) were measured on two separate occasions, 1 h apart, in 22 healthy controls (mean (+/-SD) age 52.0 +/- 13.4 years) and 11 elderly patients with chronic heart failure (CHF; 73.1 +/- 8.7 years). Reproducibility was assessed by measuring intraclass correlation coefficients (ICC), coefficients of variation (CV) and Bland-Altman plots. 3. Baseline AIx showed good short-term reproducibility with high ICC in both the control and CHF groups (0.90 and 0.87, respectively). In contrast, in the control and CHF groups, the ICC of GTN- (0.58 and 0.17, respectively) and salbutamol-mediated (0.18 and 0.04, respectively) changes in AIx were substantially low. The CV was relatively low for baseline AIx in control and CHF groups (25.0 and 22.5%, respectively), but not for GTN- (22.3 and 59.8%, respectively) or salbutamol-mediated (45.1 and 184.0%, respectively) changes in AIx. Bland-Altman analysis revealed poor reproducibility, with limits of agreement beyond either +15% or -15% for changes in AIx after GTN and salbutamol for both control and CHF groups. The changes in blood pressure and heart rate following pharmacological challenge were similar between the two measurements. 4. The poor reproducibility of changes in AIx following pharmacological challenge questions the use of this method in acute studies.

The impact of exercise on derived measures of central pressure and augmentation index obtained from the SphygmoCor device

“…Our observation that measures of pressure and stiffness differ depending on whether the limb from which they are derived was involved in an exercise stimulus suggest that exercise alters the characteristics of conduit arteries in ways that may compromise the integrity of the GTF. This finding is consistent with a study at rest using applanation tonometry, which found that GTF-derived values became unreliable and had poor reproducibility in response to pharmacologically induced vasodilation using glyceryl trinitrate (9). Despite glyceryl trinitrate having central hemodynamic effects, which we designed our study to avoid, the data of Paul et al (9) nonetheless support our finding that the GTF may be compromised under conditions of altered peripheral function or tone.…”

Assessments of Arterial Stiffness and Endothelial Function Using Pulse Wave Analysis

“…Any valid technique utilised for the measurement of physiological variables must be reproducible [82]. A high intra- and interobserver reproducibility of baseline AIx has been observed in healthy controls and patients with cardiovascular disease and renal dysfunction [7, 38, 82–94].…”

“…A high intra- and interobserver reproducibility of baseline AIx has been observed in healthy controls and patients with cardiovascular disease and renal dysfunction [7, 38, 82–94]. Good reproducibility of baseline time to reflection ( T r), an alternative index to AIx, has been reported in several studies [88, 91, 94].…”

Should the Augmentation Index be Normalized to Heart Rate?

“…The Intraclass Correlation Coefficient (ICC) values for repeated measurements obtained at hourly or weekly intervals have been reported to be 0.72-0.90 for the AIx 2, 13, 14) , which compares favorably with the values (ICC: 0.92-0.97) reported for the carotid-femoral pulse wave velocity [15][16][17] . Unfortunately, few trials have reported the reproducibility of HR-corrected Aix values 2,18,19) ; only one study, as far as we are aware, reported both AIx and AIx@75 2)…”