Introduction.

         The significant number of the Total Artificial Heart (TAH) implemented in humans and the high rate of morbidity and failures during short and median time periods in surviving patients, makes necessary the discussion of the role the hemodynamics and wave phenomenon play in these failures.
         The clinical reports indicate that up to 70% of complications are caused by the damage to peripheral vessels and organs.
         According to [1, Table 2.2] among them are:

                  Renal failure - 18%
                  Respiratory failure - 13%
                  Thromboembolic complications - 13%
                  Infections -21%

         It is necessary to note that most of these complications are caused by an insufficient blood circulation in the peripheral small vessels.
         To analyze and investigate the possibility that the deviation of the artificial shape the pulse from the natural one may be a causative factor in these failures, we have to take a short excursion into the history of the problem and physical background of the wave phenomenon in the blood circulating system.

The Wave Phenomenon.

         It is well known, that a degradation of the steep front of the pulse wave and the deviation of the shape of the pulse from the normal, such as in aortic stenosis among other diseases that contribute to decreased arterial supply, cause life threatening complications including lung and kidney failure [2].
         Despite of these facts the National Heart, Lung and Blood Institute (NHLBI) Requests For Proposal (RFP) [3,4] state that "the pulsatile pumps need not mimic 'normal' ...pulse or arterial pressure waveforms"... There is no known scientific justification for such "unnatural" approach to the development of the TAHs. The scientific practice and common sense requests that the developer of the artificial organs has to prove, that the deviation from the natural feature will not harm patients. This has neither been required of nor done by the researchers of the TAH till this day.
         In 1992 a patent was granted on a new TAH [5] which among other innovations, claims means and methods to simulate a natural shape of pulse. It does not mean that the proposed pump, activated by electromagnets directly, will eliminate most or even some complications in the TAH recipients. However, it at least will give an opportunity to investigate the problem and finally , either prove or disprove the NHLBI's claim of the unimportance of the pulse form.

Proposed Hemodynamics and Discussion.

         Let us now look at the principles of physics, hydromechanics and hemodynamics that are involved in the analysis of the pulse wave form.

         The normal pressure wave form is shown in Fig. 1 [6].

Fig I—Normal pressure waveforms from the car- diac chambers and great vessels. Upper, right heart pressures. lower, left heart pressures (see text for explanations). AF, atrial filling; El, ejection; IC, isovolumclric contraction; IR, isovolumetric relaxation; LA. left atrium; LV, left ventricle; PA, pulmonary artery; PCW. pulmonary capillary wedge; PD. protodiaslole; RF. rapid filling; SF, slow fifting; RA, right atrium; RV, right ventricle.