Correction to: Pressure-Corrected Carotid Stiffness and Young’s Modulus: Evaluation in an Outpatient Clinic Setting

In the article “Pressure-Corrected Carotid Stiffness and Young’s Modulus: Evaluation in an Outpatient Clinic Setting” by van der Bruggen M, Spronck B, Bos S, Heusinkveld MHG, Taddei S, Ghiadoni L, Delhaas T, Bruno RM, and Reesink KD (Am J Hypertens 2021; 34(7):737-743. doi: 10.1093/ajh/hpab028), an error was found in equation (S9) in the supplementary data file. This equation is used to calculate the pressure-corrected intima-media thickness. The correct formula reads:

$${\displaystyle \begin{array}{l}{\displaystyle \mathrm{I}\mathrm{M}{\mathrm{T}}_{\mathrm{c}\mathrm{o}\mathrm{r}\mathrm{r}}=\frac{D_{\mathrm{d},\mathrm{c}\mathrm{o}\mathrm{r}\mathrm{r}}-\sqrt{D_{\mathrm{d},\mathrm{c}\mathrm{o}\mathrm{r}\mathrm{r}}^2-4D_{\mathrm{d}}\cdot \mathrm{I}\mathrm{M}\mathrm{T}+4\mathrm{I}\mathrm{M}{\mathrm{T}}^2}}{2}.}\end{array}}$$ (S9)

Consequently, the exact numerical values of pressure-corrected pulse wave velocity, Young’s elastic modulus, and stiffness index β₀ as presented in Tables 2, 3, and 4 in the original article and corresponding values in the Results section in the original article were incorrect. Although the exact numerical values for pressure-corrected measures have slightly changed by using the corrected version of equation (S9), the main findings as presented in the original article remain unchanged. Updated versions of Tables 2, 3, and 4 are printed below. In the Results section, this leads to the following corrected sentences:

Table 2.

Conventional and corrected carotid dimensions and stiffness measures

Parameter	Baseline	Follow-up	∆ (unit/year)
IMT (mm)	0.75 ± 0.15	0.78 ± 0.18	0.01 ± 0.08
IMTcorr (mm)	0.76 ± 0.15	0.78 ± 0.18	0.01 ± 0.08*
D d (mm)	7.24 ± 0.85	7.55 ± 0.87	0.12 ± 0.30**
D d,corr (mm)	7.20 ± 0.87	7.56 ± 0.88	0.13 ± 0.30*
cPWV (m/s)	7.5 ± 1.3	7.7 ± 1.2	0.1 ± 0.6*
cPWVcorr (m/s)	7.1 ± 1.2	7.5 ± 1.2	0.1 ± 0.6*
E (MPa)	0.59 ± 0.23	0.65 ± 0.23	0.02 ± 0.11*
E corr (MPa)	0.53 ± 0.20	0.60 ± 0.22	0.03 ± 0.10**
β0	8.5 ± 2.9	9.3 ± 2.9	0.3 ± 1.3*

Data are presented as mean ± SD, n=124. ∆ denotes (follow-up value – baseline value)/(follow-up time in years). Abbreviations: β₀, pressure-independent stiffness index; cPWV, carotid pulse wave velocity; cPWV_corr, pressure-corrected cPWV; D_d, diastolic diameter; D_d,corr, diameter corresponding to a pressure of 80 mm Hg; E, Young’s modulus; E_corr, pressure-corrected Young’s modulus; IMT, intima-media thickness; IMT_corr, IMT corresponding to a pressure of 80 mm Hg.

Follow-up (2.9 ± 1.0 years) values were tested against baseline values using paired t-tests: *P < 0.05, **P < 0.001.

Table 3.

Final regression models for the associations of ∆cPWV and ∆cPWV_corr, as well as ∆E and ∆E_corr with ∆MAP

	∆cPWV		∆cPWVcorr
	β (95% CI) (m/s/mm Hg)	P value	β (95% CI) (m/s/mm Hg)	P value
Crude	0.023 (0.000; 0.045)	0.047	-0.018 (-0.040; 0.003)	0.091
Model 2	0.028 (0.005; 0.051)	0.017	-0.017 (-0.038; 0.005)	0.123
Model 3	0.027 (0.002; 0.051)	0.032	-0.018 (-0.041; 0.005)	0.121
	∆E		∆E corr
Crude	0.007 (0.003; 0.012)	0.001	-0.001 (-0.005; 0.003)	0.539
Model 2	0.007 (0.003; 0.012)	0.001	-0.001 (-0.005; 0.002)	0.484
Model 3	0.007 (0.003; 0.012)	0.002	-0.002 (-0.006; 0,002)	0.424

Abbreviations: ∆ denotes (follow-up value – baseline value)/(follow-up time in years); β, unstandardized regression coefficient; BMI, body mass index; CI, 95% confidence interval; cPWV, carotid pulse wave velocity; cPWV_corr, pressure-corrected cPWV according to equation (S1); E, Young’s modulus; E_corr, pressure-corrected Young’s modulus according to equation (S6); MAP, mean arterial pressure. For ∆cPWV model 2: crude model + ∆IMT, ∆HR, and use of anti-hypertensive drugs at the first visit. Model 3: model 2 + age, sex, smoking status, BMI, diabetes status, and hypercholesterolemia. For ∆E model 2: crude model + ∆HR and use of anti-hypertensive drugs at the first visit. Model 3: model 2 + age, sex, smoking status, BMI, diabetes status, and hypercholesterolemia. In models 2 and 3 for ∆cPWV the change in intima-media thickness ∆IMT was used. Correspondingly, in the models for ∆cPWV_corr the pressure-corrected ∆IMT_corr was used.

Table 4.

Final regression models for the association of ∆β₀ with ∆MAP

	∆β0
	β (95% CI) (mm Hg-1)	P value
Crude	-0.042 (-0.092; 0.009)	0.103
Model 2	-0.038 (-0.088; 0.012)	0.138
Model 3	-0.041 (-0.095; 0.013)	0.135

Abbreviations: ∆ denotes (follow-up value – baseline value)/(follow-up time in years); β, unstandardized regression coefficient; β₀, pressure-independent stiffness index according to equation (4); BMI, body mass index; CI, 95% confidence interval; MAP, mean arterial pressure. Model 2: crude model + corrected ∆IMT, ∆HR, and use of anti-hypertensive drugs at the first visit. Model 3: model 2 + age, sex, smoking status, BMI, diabetes status, and hypercholesterolemia.

• In the Carotid stiffness subsection, the third sentence should read “For ∆cPWV_corr, there was no significant relation with ∆MAP (β = -0.018, CI: [-0.041; 0.005] m/s/mm Hg, P = 0.121).” The last sentence in this subsection should read “These findings were corroborated by the fact that in model 2, ∆IMT_corr was the only significant determinant of ∆cPWV_corr (β = 1.634, CI: [0.319; 2.950] m/s/mm, P = 0.015) which persisted in model 3 (β = 1.752, CI: [0.391; 3.114] m/s/mm, P = 0.012).”

• In the Carotid Young’s modulus subsection, the first sentence should read “The change in MAP was a significant determinant of ∆E (β = 0.007, CI: [0.003; 0.012] MPa/mm Hg, P = 0.001) but not of ∆E_corr (β = -0.001, CI: [-0.005; 0.003] MPa/mm Hg, P = 0.539).”

• In the Stiffness index β₀ subsection, the last sentence should read “∆IMT was a significant determinant of Δβ₀ in models 2 and 3 (respectively: β = 3.540, CI: [0.449; 6.631] mm^-1, P = 0.025; and β=3.765, CI: [0.562; 6.969] mm^-1, P = 0.022).”