A new test circulatory system for research in cardiovascular engineering.

A new test circulatory system (TCS) has been developed for the in vitro testing of artificial hearts (AH) and for research in cardiovascular engineering, when connected to an AH that mimics the natural heart. The TCS is controlled by five variables whereby the slopes of the systemic and pulmonary venous return curves and the mean circulatory pressure can be fixed. It allows us to observe the mutual influence between TCS and AH characteristics and particularly the blood volume distribution, the pressure distribution, and the flowrates in steady-state conditions and (in the near future) also in dynamic conditions.

Digital system for P-wave detection and synchronization of the artificial heart.

This paper describes the implementation of a microcomputer based P-wave synchronization system for the artificial heart. This system provides for synchronization of the cardiac prosthesis pump with P-wave signals from electrodes implanted in the remnant of the natural atrium. The device carries out the functions of P-wave detection and determines the duration of systole based upon a moving average of the time intervals between successive pulses.

A new automatically controlled electric TAH.

Cardiovascular regulatory mechanisms are implemented by means of a very complex control system involving neural, humoral, and mechanical agents. The state of the art in TAH today reveals that we have passed a stage where we can be satisfied with a 6 or 9 mo survival. Development and implementation of a versatile control theory must be another milestone before a TAH can really serve the prospective patient population requiring such a device.

Comparative study of rigid vs flexible pneumatic artificial blood pumps.

For HR in the range of 70--110 beats/min, and same driving conditions, the pump with rigid housing produced a maximum of 15% greater CO than that with the soft housing, against an arterial pressure of 125/75 mm Hg. All 3 pumps exhibited greater sensitivity in function curves for HR in the range of 90--110 beats/min. The greatest sensitivity point in the function curve, for the rigid housing pump was found to be independent of HR change in the range of 90--110 beats/min.

Peripheral vascular effects of glucagon, acetylocholine and dopamine with an implanted total artificial heart (TAH).

Three vasoactive drugs--glucagon, acetylcholine and dopamine were used in calves with an implanted TAH to study their mere vascular effects. We noticed that glucagon, besides being a potent vasodilator, affected the vascular system gradually rather than instantly. Also, it allowed for the gradual recovery of the system, thus avoiding sudden fluctuations in systemic and pulmonary blood pressures.

Mean systemic pressure and mean pulmonary pressure: their effects on the total artificial heart.

Mean systemic pressure (MSP) and mean pulmonary pressure (MPF), which are mean driving pressures for venous return in the natural heart, were studied in 11 calves in which the natural heart had been replaced with a total artificial heart (TAH). They were measured simply by stopping the artificial heart pumping. Although blood translocation from the arterial to the venous side was not performed, the eventual right and left atrial pressures reached six to eight seconds after stopping the TAH would represent MSP and MPP with reasonable accuracy.