Biomedical Engineering Reference
In-Depth Information
Local Turbulence of a Blood-Flow “Jet.”
The factor causing local tur-
bulence of blood flow is described in the following. When the blood vessel in
the heart ventricle wall is strongly compressed by contraction of the cardiac
muscle, the coronary blood flow decreases. Therefore, the coronary blood flow
mainly flows during cardiac muscle diastole, which is different from other ar-
teries. Also, the left ventricle wall is thicker than that of the right ventricle:
therefore, the left coronary artery blood flow is accelerated at diastole, and it
reaches the maximum blood flow from almost zero. When stenosis occurs, the
fluid is accelerated at diastole, and it is immediately decelerated afterwards.
Transmission of the Jet Vibration to the Chest Wall.
There have
been several cases in the past in which the stenotic murmur of the coronary
artery could be detected in a clinical demonstration [83-86]. The murmur
generally cannot be detected, as it is very minute and is attenuated in in-
verse proportion to involution of a frequency from a source of vibration. It
is considered as a cause that the murmur has been buried in other biological
vibrations with the attenuation. The vibration of coronary artery stenosis,
which is very minute, intermingles with the displacement vibration of the
surface are amplifier processing, signal processing are carried out by using
the high-resoluble
In what follows, the measuring principle is described. The vibration signal,
which is a mechanical and physical signal, arises in the body.
On the vibration signal, there are heart sounds that derives from swit-
ching of the heart valve (the sound generated as the atrioventricular valve
between the atrium and the heart ventricle closes), heart sounds generated
as an arterial valve between a blood vessel and the heart ventricle closes,
extra heart sounds, valve abnormal sounds, and a murmur that derives from
coronary artery disease. The vibration signal travels to the body surface, cau-
sing biotissue to vibrate. The mechanical vibration transmitted to the chest
wall becomes a displacement signal. At the body surface, the heart sound
and cardiac murmur that are detected by a stethoscope as vibration of the
surface are caught and are recorded by a phonocardiograph, which produces
a displacement signal.
The turbulent flow murmur vibration based on stenosis, diastole coronary
artery and other sources is buried in the overall noise because the amplitude
is very weak, compared with the usual heart sound and murmur, and the
frequency band of the vibration shifts into the high-frequency area. There is
also the displacement signal on the chest wall. Generally, in the record using
the phonocardiograph, the stenotic vibration is buried in the basic line, and
it cannot be detected and distinguished as a stenotic murmur because the
vibration is very minute.
