Exeter Clinical and Health Research
Standard Operating Procedure:
Carotid artery stiffness assessment (generic)
SOP Number:
NIHRexe/088/GEN
Version Number & Date:
V1 10/05/2016
Effective Date: 10/05/2016
Review Date: 10/11/2016
Superseded Version Number & Date: N/A
(if applicable)
Author:
Name: Kunihiko Aizawa
Position: Clinical Research Facilitator
Signature:
Date: 24/08/2015
Approved by:
Name: Dave Mawson
Position: Laboratory Technical Manager
Signature:
Date: 24/08/2015
Senior Management Agreement:
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Name: Angela Shore
Role: Scientific Director of CRF
Signature:
Date: 10/05/2016
SOP Number: NIHRexe/088/GEN
Effective Date: 10/05/2016
Version: 1.0
I agree that appropriate members of my workforce (as named above) have written
and approved this SOP for use in clinical research.
1. BACKGROUND:
Arterial stiffness, especially in central elastic arteries such as the aorta and the common
carotid artery, is emerging as an important determinant of increased systolic and pulse
pressure. The consequence of increased central artery stiffness is an increased left
ventricular afterload and impaired coronary perfusion, which may contribute to a host of
cardiovascular diseases such as left ventricular hypertrophy, heart failure, myocardial
infarction, stroke and renal failure. Therefore, the assessment of central artery stiffness
provides important haemodynamic information regarding the interaction between the left
ventricle and arterial system.
The non-invasive assessment of aortic stiffness is somewhat difficult due to technical
limitations inherent to blood pressure measurement, although it is desirable because the
aortic pressure is what the left ventricle “sees”. For that reason, carotid artery stiffness
has been used in many studies for a surrogate of central artery stiffness assessment.
2. SCOPE:
This SOP applies generically to clinical trials and research projects, clinical and health
research in Exeter, unless a trial agreement specifically indicates that another
organisations’ SOP should be used.
3. PURPOSE:
The purpose of this technique is to non-invasively assess carotid artery stiffness.
4. DEFINITIONS AND ABBREVIATIONS:
 BP: blood pressure
 DBP: diastolic blood pressure
 ECG: electrocardiogram
 QC: quality control
 SBP: systolic blood pressure
5. ROLES AND RESPONSIBILITIES:
It is the responsibility of staff undertaking clinical research to read and use this SOP
when they are expected to perform the carotid artery stiffness assessment. Investigators
who perform this assessment are detailed in the delegation log within the Site File for
each study.
6. SKILL LEVEL:
One investigator is required to perform this procedure, and this procedure should only
be carried out by personnel who have undergone the appropriate departmental training.
7. EQUIPMENT:

ALOKA SSD-5500

3 ECG leads (from ALOKA) and 3 ECG electrodes

BP monitor (Dinamap or other BP monitor can be used)

SpygmoCor module and its computer
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
Clean linen (linen cupboard Harvey)
There is no personal safety equipment required. In case of emergency, there is an
emergency bell in each laboratory under the desk, the crash trolley is stored in the
corridor opposite to the Starling and Landis rooms, and if an ambulance is required, dial
9999.
8. PROCEDURE:
Preparation required before subject’s arrival
 ensure that the mains cable for ALOKA, and SphygmoCor are plugged in and the
wall socket is switched on
 turn on the ALOKA by pressing the ON button on the right side of the system
 turn on the computer that the SphygmoCor module is connected by pressing the
ON button on the top left
 make sure that the computer and the SphygmoCor module are firmly connected
by a USB cable
Preparation required after subject’s arrival
 make sure that the subject will not need to go to the bathroom during the
assessment
 lay subject down on the examining bed
 put an appropriate-sized BP cuff to the subject’s left arm
 attach 3 ECG electrodes to the torso of the subject; at the top of the sternum (a),
just below the sternum (b), and on the left-hand side just below the rib-cage(c).
 attach the ECG leads to the electrodes: red to a, black to b and green to c.
 allow a 10-min supine rest (the subject needs to keep still thereafter)
 ensure ECG trace, if not, adjust it (PHYSIO → ECG SENS → knob)
 press “PRESET” button and select “CAROTID”
 press “NEW PATIENT” button and enter subject’s information accordingly
 once done, press “ID” button that will take you to the scanning mode
 click “SphygmoCor” icon on the SphygmoCor’s computer screen
 once the software has been loaded up, click “System”, then “Database Manager”
 select the appropriate study name from database and click “Select”, then “OK”
 either 1) enter patient information if new, or 2) select patient from the list on the
left if reassessment
 click “Study”
 tick the box beside “Radial”
 after the supine rest, check brachial BP 3 times with a 1-min interval and record
the mean of last 2 BP’s
Assessment Procedure for Carotid Artery BP by SphygmoCor
 perform assessment before obtaining carotid artery image
 check brachial BP, and enter the SBP and DBP numbers to the SphygmoCor’s
data entry page
 click “Capture Data”
 find the right radial artery by palpation
 place the tonometer gently on the artery without applying excessive pressure
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SOP Number: NIHRexe/088/GEN
Effective Date: 10/05/2016
Version: 1.0
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optimise pressure waveforms (consistent in shape and within a similar pressure
range)
once optimal waveforms have been obtained, keep applanating the artery for
about 20 seconds
click “Space” key on the QWERTY keyboard so that SphygmoCor starts
analyzing
once analyzed, repeat above procedure twice (a BP measurement is required
before capturing data)
all QC indices have to be “green”, if not, discard that data collection and redo the
procedure
3 successful data collections (with satisfactory QC indices) are required
Assessment Procedure for Carotid Artery Image
1.
turn subject’s head toward the left, up to about 45º with neck slightly hyperextended
 ask the subject to breathe calmly and check that he/she is comfortable
 apply generous amount of gel on the transducer
 search the right common carotid artery with a cross-sectional approach first
 start with the frequency of 13 MHz and reduce it to 10 or 7.5 MHz if necessary by
pressing the “IMAGE/FREQ” button and using the knob
 confirm that it is the artery by pressing the transducer a little bit (vessel should not
deform) as well as the using Colour Doppler (press “FLOW” button)
 turn the probe 90º toward the longitudinal direction of the artery with the
transducer’s “dot” facing toward the subject’s head
 centre the artery by using “DEPTH/RANGE” buttons
 optimise image quality (clear and crisp wall/lumen boundaries for both the near
and far walls), and, if needed, use STC sliders to change in the brightness at a
specific depth
 make sure that arterial walls are perpendicular to the skin
 check for pulsatile blood flow and good signal with Doppler and Colour Doppler
 removing a pillow from the patient may be necessary to get a good image
 make sure to keep a little bit of the bulb area in sight (for the purpose of analysis)
 once images have been satisfactory, press “REC3” to save the images (the
button becomes orange and about 9 seconds of images are collected)
 wait until the “REC3” buttons becomes green (do not press the button until it
becomes green)
 Repeat the image saving procedures above twice or more until 3 satisfactory
sequences have been recorded
 once all the procedures have been done, the study is completed and all ECG
electrodes etc can be removed
9. DESIRED OUTCOME:
3 image files (cine-loops stored in Aloka), and 3 SphygmoCor-derived aortic BPs.
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