An atrial hydraulic shunt in a total artificial heart. A balance mechanism for the bronchial shunt.
An implantable TAH must be able to maintain physiologic atrial pressures over a range of left side shunt flows, which in humans can range up to 5% of the total cardiac output (CO). The authors describe the characteristics of an atrial hydraulic shunt in an electrohydraulic TAH. A small (10 cc stroke) chamber placed in line between the left atrial cuff and the inflow valve is shunted to the right hydraulic chamber. High left atrial pressure increases the volume displaced by this chamber; this concurrently reduces the right chamber stroke volume and flow relative to the left side. For left atrial pressures (LAP) between 0 and 15 mmHg, CO increased from approximately 3 to > 9 L/min (Starling-like behavior). This was attainable with bronchial flow settings between 0.2 to 0.7 L/min, satisfying physiologic needs. Left atrial pressure and RAP (right atrial pressure) tracked each other. The mean difference, LAP-RAP, remained within 5 mmHg at low filling pressures and approached 0 mmHg difference at high filling pressures. The results showed that the atrial hydraulic shunt method can adequately compensate for and manage physiologic left-right flow differences.