Arterial stiffness measurement
AS was evaluated, according to the guidelines, using the gold standard
carotid-femoral pulse wave velocity by the Sphygmocor (SphygmoCor
Cardiovascular Management System software version 1.3; AtCor Medical
Pty. Ltd., Sydney Australia). Participants were studied in the morning
in the supine position after resting for 5–10 minutes in a quiet and
temperature-controlled room. According to the instructions of the
device, SphygmoCor XCEL PWA uses a standard brachial cuff to measure
brachial systolic and diastolic pressures, and capture a brachial
waveform. The brachial waveform is then analyzed by SphygmoCor to
provide a central aortic waveform. Central BP measurements such as
central aortic systolic BP, central pulse pressure, and an augmentation
index were also reported. To conduct a carotid-femoral PWV measurement,
a cuff placed around the femoral artery of the patient to capture the
femoral waveform, and a tonometer was used to capture the carotid
waveform. The distance in millimeters from the patient’s carotid artery
to their sternal notch (Carotid to Sternal Notch) and also the distance
from their sternal notch to the top edge of the femoral cuff (Sternal
Notch to Cuff) is measured, and the velocity automatically determined by
dividing the distance by the pulse transit time. After 10 seconds of
simultaneous valid carotid tonometer signal, The SphygmoCor software
derives the ascending aortic pressure wave, substantially equivalent to
the pressure wave measured by an invasive catheter. From the aortic
pressure wave, the number of valuable cardiovascular measurements is
determined, including central aortic systolic pressure, aortic
augmentation index and central pulse pressure. The PWV was calculated
using the distance and mean time difference between the two recorded
points.
The central augmented pressure calculated as the difference between the
maximum systolic peak on the aortic pulse wave and the inflection point.
The latter is defined as the merging point for the incident and
reflected wave. The cAIx indicates as the augmented pressure divided by
pulse pressure (PP) ×100.