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|Title: ||Evidence of left ventricular wall movement actively decelerting aortic|
|Authors: ||Page, Chloe May|
|Advisors: ||Khir, A|
|Keywords: ||Wave intensity analysis|
Forward expansion wave
|Publication Date: ||2009|
|Publisher: ||Brunel University Brunel Institute for Bioengineering PhD Theses|
|Abstract: ||Efficient function of the left ventricle (LV) is achieved by coherent behaviour of its
circumferential and longitudinal myocardial components. Little was known about the
direct association between the long and minor axis velocities and the overall
haemodynamics generated by ventricular systolic function such as aortic waves.
The forward running expansion wave (FEW) during late systole contains important
information about the condition of the LV and its interaction with the arterial system.
The aim of this thesis was to underpin the mechanics and timing of the LV wall
velocities, which are associated with the deceleration of flow. Both invasive and noninvasive
data have been analysed in canines and humans and the following conclusions
can be drawn.
LV long axis peak shortening velocity lags consistently behind the minor axis,
representing a degree of normal asynchrony. The FEW is seen to have a slow onset
before a rapid increase in energy. The slow onset corresponds with the time that the
long axis reaches its peak velocity of shortening. After both axes reach their respective
maximum shortening velocity they continue to contract, although at a slow steady
velocity until late ejection when there is a sudden simultaneous change of shortening
velocity of both axes. This time corresponds with peak aortic pressure and the rapid
increase in energy of the FEW. The time that the minor axis reaches its maximum
velocity of shortening interestingly coincides with the arrival of the reflected wave at
the LV during mid-systole. During canine aortic manipulation through the introduction
of total occlusions along the aorta, the sequence of events observed in control
conditions remains unchanged.
In humans both LV wall movement and carotid wave intensity can be measured
successfully using non-invasive methods. The FEW is generated when the last long
axis segment begins to slow. The minor axis begins to slow before this time and
corresponds to the time of peak aortic flow.|
|Description: ||This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.|
|Appears in Collections:||Brunel Institute for Bioengineering (BIB)|
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