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EXPLANATION OF PARAMETERS/INDICES (PWA AND PWM ONLY)
The SphygmoCor PWA & PWM report screens and printed reports consist of key patient details at the
top of the screen. The raw peripheral waveform and the derived aortic waveform are displayed in full. At
the centre of the screen and print-outs are the averaged-recorded peripheral waveform (left) and the
averaged (derived) aortic waveform (right).
The bottom of the screen and print-out displays the derived central haemodynamic parameters. The
following parameters apply to each averaged waveform:
Displayed Parameter Summary:
CALCULATED PARAMETERS
ABBREVIATION
UNITS
Heart Rate
HR
Beats/min
Period
TF
msec
Ejection Duration
ED
msec
Peripheral Systolic and Diastolic Pressure
Sp, Dp
mmHg
Aortic Systolic and Diastolic Pressure
Sp, Dp
mmHg
Mean Pressure- Peripheral and Aortic
Mp
mmHg
Pulse Pressure - Peripheral and Aortic
Pp
mmHg
Time to 1st peak- Aortic
T1
msec
Time to 2nd peak- Aortic
T2
msec
Time to Reflection
Tr
msec
Augmented Pressure
Ap
mmHg
Pressure at T1
P1
mmHg
Pressure at T2
P2
mmHg
Augmentation Index – (Ap/P, P2/ P1)
AI
%
Primary Wave Pressure at T1
P1 H
mmHg
Buckberg Sub-Endocardial Viability Ratio (Ad/As)
SEVR
%
Mean Pressure in (Systole, Diastole)
Mp (S,P)
mmHg
End Systolic Pressure
ESP
mmHg
Central Aortic Indices:
In its analysis of the derived aortic pressure waveform, the SphygmoCor System extracts from the
averaged waveform five time-relative points (described below) and from these points further parameters
relating to the heart and arterial system are determined (see graph below).
The basic features of an arterial pulse are shown below. After the foot of the pulse (T0), indicating the
onset of ejection, the pressure wave rises to an initial peak where it forms a shoulder (T1). This is the
peak of the primary LV ejection pressure. It then proceeds to a second shoulder (T2) which is the
peak of the arterial reflection wave. Usually this constitutes the peak pressure in the elderly. The end
of ejection (ED) is point of closure of the aortic valve and time of End of Systole.
These timing points are the basis of the waveform analysis.
Features of the Arterial Pulse
Aortic
Radial
P2
Sp
ESp
P1
PP
7.8
MP
Dp
T0
Page 77
T1
T2
ED
Period
TF