(Hypertension. 1996;27:816-822.)
© 1996 American Heart Association, Inc.
Articles |
Contributions of Vascular Tone and Structure to Elastic Properties of a Medium-Sized Artery
From Division d'Hypertension (CHUV), and the Biomedical Engineering Laboratory, Swiss Federal Institute of Technology (N.S.), Lausanne, Switzerland.
Correspondence to Daniel Hayoz, Division d'Hypertension, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland.
Abstract Isobaric compliance and distensibility of the radial
artery were recently reported to be normal or slightly increased in
untreated hypertensive patients. However, these findings provide no
information on the intrinsic mechanical properties of the wall
material. To address this question, we determined intima-media wall
thickness, wall-to-lumen ratio, and incremental elastic modulus
in the radial artery of 25 untreated hypertensive patients with blood
pressure of 150±14/103±6 mm Hg (mean±SD) and 25 matched
control
subjects with blood pressure of 118±9/79±6 mm Hg.
High-resolution echo-tracking for assessment of internal
diameter and intima-media wall thickness was combined with
measurements of blood flow velocity by Doppler and blood pressure
by photoplethysmography. In addition, isobaric compliance and
distensibility and incremental elastic modulus were measured at peak
diameter during reactive hyperemia after a 5-minute brachial
occlusion. No significant difference was found between the two groups
for isobaric compliance or distensibility at baseline or during
hyperemia. However, incremental elastic modulus at 100 mm Hg
tended to be lower in hypertensive patients than control subjects
(1.9±1.1 versus 2.5±1.2 mm Hg·104,
P=.1) in resting conditions. Hypertensive patients and
control subjects had similar internal diameters (2.47±0.32 versus
2.41±0.35 µm), but intima-media wall thickness and
wall-to-lumen ratio were significantly increased in
hypertensive patients compared with control subjects (0.268±0.032
versus 0.236±0.025 mm [P
.01] and
0.220±0.038 versus
0.195±0.028 [P.05], respectively). Peak
hyperemic blood flow response (hypertensive patients versus
control subjects: 349% versus 360% increase from baseline) and
reactive hyperemic dilation (7.2% versus 7.9%) were similar
in amplitude and duration in the two groups. These results suggest that
wall thickening is an adaptive process that reduces wall tension in
hypertensive patients while preserving a normal mechanical behavior of
the radial artery. This is most likely accomplished by modification of
the incremental elastic modulus of wall components rather than by a
change in vascular tone.
Key Words: compliance • vasomotion • hypertrophy
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