P.23 Relationship Between Aortic Stiffness, Aortic, and Carotid Impedance with Vascular Aging in Community-Based Healthy People
Authors: Liao Chao-Feng , Chuang Shao-Yuan , Cheng Hao-Min , Chen Chen-Huan 
Published: December 2020

Abstract
Background
Stiffening of the aorta has been associated with microvascular structural brain damage and cognitive dysfunction in cross-sectional and longitudinal studies, probably due to the reduced wave reflection at the interface between carotid and aorta and transmission of excessive flow pulsatility into the brain. The present study investigated whether age-related stiffening of the proximal aorta is disproportionately greater than the carotid arteries and whether the coupling of stiffness between proximal aorta and carotid arteries affects wave reflection at the interface.

Methods
Comprehensive pulsatile hemodynamics evaluation using applanation tonometry, carotid ultrasonography and echocardiography was performed in 1236 apparently healthy community residents (age range 40 to 96 years, average 62.4 ± 10.5 years) who had no history of cardiovascular events and stroke. Aortic (Zc) and carotid (CCI) characteristic impedance were estimated in the time domain. Carotid pulsatility index (PI) was computed from the carotid flow and a carotid reflection coefficient was computed from bilateral carotid impedance and distal aortic impedance.

Results
CFPWV (Standardized Beta = 0.56, p < 0.001), CCI (Beta = 0.46, p < 0.001) and carotid reflection coefficient (Beta = 0.26, p < 0.001) significantly increased with age. In contrast, PI (Beta = −0.06, p = 0.026) significantly decreased with age, and a U-shape association between Zc (Beta = 0.09, p = 0.002) and age was found. Carotid flow PI was significantly related to the aortacarotid reflection coefficient negatively (r = −0.28, p < 0.001).

Conclusions
In this healthy population, stiffening of the proximal aorta was not disproportionately greater than that of the carotid arteries. This might favorably maintain the wave reflection at the carotid-aorta interface so that carotid flow PI did not increase with age.
Table 1
Subjects characteristics (subdivided into groups according to the age)

Age group
40~49
50~59
60~69
≧70
p value for

n = 1236
n = 137
n = 356
n = 445
n = 298
trend

Age (years)
45 (3)
55 (3)
64 (3)
76 (5)
<0.001

Male (male, %)
53 (41.7)
153 (43.7)
207 (47.2)
159 (55.0)
0.002

Height (cm)
162.5 (8.1)
161.5 (8.1)
159.5 (7.5)
158.3 (8.2)
<0.001

Weight (kgw)
64.0 (12.7)
64.7 (10.6)
63.0 (10.4)
62.0 (10.9)
0.004

BMI (kgw/m2)
24.1 (3.6)
24.7 (3.3)
24.7 (3.3)
24.7 (3.4)
0.31

HTN (n, %)
9 (7.1)
76 (21.7)
172 (39.2)
158 (54.7)
<0.001

DM (n, %)
5 (3.9)
32 (9.1)
78 (17.8)
71 (24.6)
<0.001

Hyperlipidiemia (n, %)
6 (4.7)
50 (14.3)
229 (52.2)
144 (49.8)
<0.001

Creatinine (mg/dL)
0.77 (0.45)
0.73 (0.21)
0.79 (0.27)
0.93 (0.57)
<0.001

LDL (mg/dL)
116.5 (34.8)
120.0 (35.9)
117.7 (34.1)
113.3 (35.1)
0.083

Glucose (mg/dL)
94.5 (18.1)
100.4 (21.2)
104.3 (28.2)
105.3 (26.3)
<0.001

Age group
40~49
50~59
60~69
≧70
p value for

n = 1236
n = 137
n = 356
n = 445
n = 298
trend

Smoking (n, %)

0.08

Non-smoker
95 (74.8)
255 (72.9)
341 (77.7)
204 (70.6)

Current-smoker
14 (11.0)
44 (12.6)
38 (8.7)
14 (4.8)

former-smoker
18 (14.2)
51 (14.6)
60 (13.7)
71 (24.6)

MMSE score < 24
0
3 (0.9)
13 (3.0)
31 (10.8)
<0.001

Echocardiography variables

Ea (mmHg/ml)
1.86 (0.44)
1.78 (0.43)
1.70(0.43)
1.70 (0.53)
<0.001

Ees (mmHg/ml)
4.00 (1.06)
4.09 (1.06)
3.67 (1.12)
3.99 (1.73)
0.12

Ea/Ees
0.48 (0.09)
0.45 (0.09)
0.48 (0.12)
0.45 (0.13)
0.87

Stroke volume (ml)
58.5 (12.3)
64.0 (14.2)
69.5 (14.9)
72.5 (17.6)
<0.001

Cardiac index (L/min/m2)
2.4 (0.6)
2.6 (0.6)
2.7 (0.6)
2.9 (0.8)
<0.001

Ef (%)
69.5 (6.2)
70.7 (6.4)
68.8 (7.1)
68.5 (7.9)
0.001

Data were presented as mean(SD). BMI, body mass index; HTN, hypertension; DM, diabetes mellitus; LDL, low density lipoprotein; MMSE, mini-mental state examination; Ea, arterial elastance; Ees, left ventricular end-systolic elastance; LVEDV, left ventricular end-diastolic volume; LVESV: left ventricular end-systolic volume.

Table 2
Hemodynamics parameters (subdivided into groups according to the age)

Age group
40~49
50~59
60~69
≧70
p value for trend

n
n = 137
n = 356
n = 445
n = 298

Central

SBP (mmHg)
107.0 (16.2)
112.5 (13.9)
118.0 (15.5)
121.6 (14.9)
<0.001

DBP (mmHg)
74.3 (12.5)
77.8 (10.2)
78.8 (10.6)
77.5 (9.7)
<0.024

PP (mmHg)
33.6 (7.1)
35.5 (7.4)
40.1 (8.7)
45.3 (9.9)
<0.001

Brachial

SBP (mmHg)
120.2 (17.3)
125.3 (15.1)
131.2 (16.8)
134.6 (16.5)
<0.001

DBP (mmHg)
73.3 (12.5)
76.8 (10.2)
77.5 (10.5)
76.1 (9.7)
0.70

PP (mmHg)
41.2 (9.1)
43.7 (11.7)
48.9 (11.7)
53.4 (12.6)
<0.001

MAP (mmHg)
90.9 (14.3)
95.0 (12.4)
98.4 (13.6)
99.9 (12.5)
<0.001

Heart rate (bpm)
69 (9.7)
69 (10.3)
66 (10.2)
66 (10.3)
<0.001

pf (mmHg)
28.8 (7.1)
28.1 (6.6)
30.2 (6.9)
34.5 (8.7)
<0.001

pb (mmHg)
14.5 (3.1)
15.4 (3.3)
17.7 (3.8)
19.5 (4.4)
<0.001

CFPWV (m/s)
9.4 (1.9)
10.8 (2.4)
12.4 (3.1)
15.2 (4.4)
<0.001

Aortic flow-pressure

Zc (dyne·s/cm5)
102.3 (32.2)
89.6 (31.6)
90.8 (38.4)
104.7 (50.7)
0.027

SVR (dyne·s/cm5)
1782.0 (551.4)
1685.2 (435.7)
1683.7 (441.9)
1664.0 (543.7)
0.06

Mean flow (ml/s)
63.4 (16.6)
69.6 (19.7)
70.7 (17.4)
73.7 (20.6)
<0.001

normalized Zc
0.06 (0.02)
0.05 (0.02)
0.05 (0.02)
0.06 (0.02)
<0.001

Carotid flow-pressure

CCI (dyne·s/cm5)
2060.2 (520.5)
2198.2 (708.0)
3183.0 (1030.9)
3328.3 (1154.5)
<0.001

CVR (dyne·s/cm5)
9421.3 (2472.4)
9860.9 (2049.4)
11879.2 (2612.3)
12347.4 (3022.2)
<0.001

Mean flow (ml/s)
13.2 (2.5)
13.1 (2.3)
11.2 (2.2)
10.9 (2.2)
<0.001

normalized CCI
0.22 (0.05)
0.23 (0.06)
0.27 (0.08)
0.27 (0.08)
<0.001

Data were presented as mean(SD). SBP, systolic blood pressure; DBP, diastolic blood pressure; P P, pulse pressure; MAP, mean arterial pressure; pf, forward pressure; pb, backward pressure; CFPWV, carotid-femoral pulse velocity; Zc, aortic characteristics impedance; SVR, systemic vascular resistance; CCI, carotid characteristics impedance; CVR, carotid vascular resistance.