Hemodynamics
of
Large Arteries
91
Multi-sensor catheter has been used for simultaneous recordings of
pressure and flow waveforms at several sites along the pulse propagation
path. This allows extraction of pulse transmission information, and in
the interpretation of hemodynamic alterations in diseased conditions.
Simultaneous recording of pressure and flow velocity waveforms in
man can be achieved in the clinical setting with catheter tip pressure and
velocity sensors. In general, pressure and flow waveforms are similar at
corresponding anatomic sites among many mammalian species (Li,
1996).
0.5
sec
...........
...............
0
Pulmonary
A
Pulmonary
A
flow
..............
I"
Aortic
m
E
Pressure
kPdmmHg
I.8
I
Aortic
flow
$[
0
2
Fig.
4.2.2:
Simultaneously recorded pressure and flow waveforms in the pulmonary aorta
(top tracings) and in the ascending aorta (bottom tracings). Notice the pressure and flow
waveforms
are
more similar in the more compliant pulmonary arterial system.
At the onset of systole, left ventricular pressure (LVP or
Py)
develops
rapidly during the cardiac isometric contraction period.
When
LVP
exceeds the aortic pressure (AoP or Pa), ventricular ejection begins. The
ventricular outflow is large and rapid at the onset of ejection, becomes
more gradual and then declines towards end-systole.
At aortic valve
closure, there is backflow, followed by small oscillations.
In diastole,
the aortic flow reaches zero. The diastolic aortic pressure decays
precipitously towards end-diastole. In the windkessel approximation,
this decay follows a mono-exponential pattern. In actuality, there are
