In vitro analysis of an atrial shunt in balancing an electrohydraulic total artificial heart

In vitro tests were performed to evaluate the use of an interatrial shunt in balancing a dual energy converter, actively filled, volumetrically coupled, electrohydraulic total artificial heart. The in vitro atrial shunt was comprised of a 8 mm (PTFE) Teflon graft placed between the left and the right atrium. Other features under study were 1) cardiac output (CO) response to preload, 2) CO relationship to mean aortic pressure, and 3) balance of ventricular outputs. The tests were performed by varying the right filling pressure and monitoring ventricular output and inflow/outflow pressures. Effects of changes in afterload were simulated by varying the (AoP) pressure from 80 mmHg to 120 mmHg, and the (PAP) pressure from 15 mmHg to 40 mmHg. The test results indicated a rise in CO from 4 L/min to 9 L/min, with a change in mean right atrial pressure from 0 mmHg to 12 mmHg. No significant difference in CO was found as afterload pressures were varied. The interatrial shunt (IAS) was effective in establishing ventricular balance over a wide range of preload and afterload conditions, and a mean positive flow from left to right was maintained in the atrial shunt, even at conditions simulating an extreme left-right imbalance.