A new pulse duplicator with a passive fill ventricle for analysis of cardiac dynamics

A new pulse duplicator was designed for evaluation of the performance of ventricular assist devices through pressure-volume (P-V) diagrams of the native heart. A linear drive system in combination with a pusher-plate mechanism was designed as a drive system to implement the passive fill mechanism during diastole of the mock ventricle. The compliances of the native heart during both diastole and systole were simulated by placing a ventricle sack made of soft latex rubber in a sealed chamber and by varying the air-to-fluid volume ratio inside the chamber. The ratio of the capacities of the systemic venous and pulmonary circuits was adjusted to properly reflect the effects of volume shift between them. As the air-to-fluid volume ratio was varied from 1:12.3 to 1:1.58, the contractility of the ventricle expressed by E (max) varied from 1.75 to 0.56 mmHg/ml with the mean V (0) of 4.58 ml closely mimicking those of native hearts (p < 0.05). Because the E (max) value of the normal human heart ranges from 1.3 to 1.6, with a value below 1.0 indicating heart failure, the mock ventricle is applicable in simulating the dynamics of the normal heart and the sick heart. The P-V diagram changes seen with rotary blood pump assistance revealed changes similar to those reported by other workers. The effects of the ventricular assist device, either pulsatile or continuous flow, on cardiac dynamics can be easily simulated with this system to derive design criteria for clinical circulatory assist devices.