IN-VITRO AND IN-VIVO EVALUATION OF A LEFT-RIGHT BALANCING CAPACITY OFAN INTERATRIAL SHUNT IN AN ELECTROHYDRAULIC TOTAL ARTIFICIAL-HEART SYSTEM

The authors evaluated the basic performance of an interatrial shunt (I AS) made by punching a hole in the atrial septum, in accommodating the left-right imbalance in our electrohydraulic total artificial heart ( EHTAH) system. In an in vitro study conducted in a closed mock circuit connected with the EHTAH, the interatrial pressure gradient changed i n compliance with the amount of bronchial flow and the size of the IAS . The IAS of 4.4 mm diameter or larger maintained the interatrial pres sure gradient within physiologically permissible limits when the amoun t of bronchial flow was 5% of cardiac output or less. A left-to-right one-way valve made of a piece of pericardium, a possible option in thi s IAS method, successfully prevented right-to-left reverse shunt flow through the IAS. In a chronic in vivo study using a calf implanted wit h the EHTAH for 10 days, a 4.5 mm IAS without the one-way valve demons trated satisfactory dynamic left-right balancing capacity with a stabl e interatrial pressure gradient of 4 +/- 1 mmHg over a wide range of a trial pressures. No thrombus was found in or around the IAS at autopsy . The authors conclude that the IAS is a simple and promising means of left-right balancing in the EHTAH system.