The Adjustable Systemic-Pulmonary Artery Shunt Provides Precise Control of Flow In Vivo

Abstract

The ratio of pulmonary:systemic blood flow (Qp:Qs) remains problematic after single ventricle reconstruction. The adjustable systemic-pulmonary artery shunt (AS) was created as a solution for this problem. Prototype ASs were created using a screw-plunger mechanism as a variable resistor. A stepper motor controls plunger displacement. Six adult dogs underwent placement of a 4-mm AS in the femoral position to test its ability to control flow. Shunts were placed as arteriovenous fistulae to simulate the continuous flow of systemic-pulmonary AS. The 3.5-mm control shunts (CS) were placed on the contralateral side. The stepper motor was rotated from fully open to 3.4 mm of plunger depression for six complete cycles. Flow in the fully open AS was 687.9 +/- 28.7 cc/min* vs. 578.7 +/- 26.8 cc/min in the CS (flow +/- standard error, *p < 0.005 vs. CS). Standard deviation of flow was similar between the AS and CS, implying hysteresis in resistor function did not contribute to flow variability. Peak torque requirement to turn the resistor was 2.4 mNm. The AS offers excellent control of flow in vivo. Control of Qp:Qs may lead to improved outcomes for single ventricle reconstructions.