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The effect of a wave phenomenon shown in Fig. 2 is described by a following equation:
where:  - pulse pressure;
where:  - length of a blood vessel section;
where:  - vessel's thickness;
where:  - modular of elasticity;
where:  - diameter increase;
where:  - a lag of the blood flow;
where:  - blood flow velocity;
where:  - pressure wave velocity (mod reduction)
where:  - outside diameter of the vessel.
This pulse phenomenon of a natural blood circulating system (BSC) can be easily detected by anyone "looking for a pulse" which is in fact a wave pressure propagating along a blood vessel actually stretching the wall of that vessel.
Because of physiological requirements, the human body must be supplied with a particular quantity of blood under normal conditions. The quantity of blood per beat (volumetric velocity) is a function of a pressure drop in circulating system. The phenomenon of the peripheral blood pressure pulsation is well known as "phenomenon of the peripheral heart". The physics of this is described by the following wave equation [8 and 9]:
where:  - pulse pressure;
where:  - length of vessel section;
where:  - time of wave propagation;
where:  - flow velocity;
where:  - pressure wave velocity (sound velocity);
where:  - fluid density;
where:  - system impedance.
The wave phenomenon increases cross-sectional area of blood vessels and assists the heart to circulate the "required" volume at a reduced blood pressure.
The simulation of the wave phenomenon by simulating a natural blood pulse shape with a steep front ( but not steeper than the natural one) of the pulse could reduce the blood pressure in the BSC and thereby reduce or even eliminate the danger of
damage to the vessels. In a TAH with simulation of the pulse shape the blood
pressure could be reduced up to 30% for pumping the same amount of blood. This approach can be illustrated by the following calculation :
where:  - pressure drop (systolic minus diastolic pressure);
where:  - hydraulic coefficient of resistance;
where:  - volumetric velocity of blood flow;
where:  - area of vessel inner cross section;
where:  - gravity acceleration
where:  - specific blood density.
For a system without a wave phenomenon ( without pulse shape simulation) p=87.6 g/cm2 =61Hgmm, for a system with the wave phenomenon (with pulse shape simulation), p = 44 g/cm 2 = 33 Hg mm.
According to this analysis and the analysis described in [7], it has been predicted in 1977, long before the first TAH was developed and implanted in a human, that the
pulse shape with a flat front, i.e. with a harmonious shape, will cause a prolongation of systole and necessitate an increase in pressure in order to pump the required volumeof blood. It was rather interesting that the data gathered from the very first TAH had conformed precisely with the above predictions. In the NEJM, Dr. W. C. DeVries et al. [10] fig.3 shows a significant flattening of the front of the pulse and an undesirable demand of an approximate 30% increase in both systolic and diastolic pressure needed to supply the required volume of blood.
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Figure 3. Electrocardiographic (Vs) Rhythm Strips (Above) and
Corresponding Arterial-Pressure Tracings (Below) Obtained Pre-
operativety (Left) and Postoperatively (Right).
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Conclusion.
In light of the above, we suggest that before the conclusion that the aberrant pulse wave is unimportant and non contributory to poor outcomes in patients with TAH, more research should be done. It is now possible to create and implement a
TAH which would be able to simulate not only the "rate of pressure rise and fall" [4] but the actual pulse shape more closely.
The proposed devise will allow the blood pressure needed to adequately perfuse all tissues to remain lower and less damaging to the vessel walls. At the same time it will deliver the "natural" wave effect needed to propagate the blood to the smallest
peripheral vessels thus improving the perfuion of the end- organs. This may indeed proof to be a major step in the development of a viable TAH.
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