Abstract 2086: The Adjustable Systemic Pulmonary-Artery Shunt Provides Precise 2-Day Control of Pulmonary Blood Flow
Objective: Our laboratory has developed an adjustable systemic-pulmonary artery shunt (AS) to provide improved control of pulmonary blood flow (PBF) after neonatal palliation of single ventricle physiology. The first anticipated human use of the device is temporary implantation during delayed sternal closure (DSC). The objective was to test the device for up to 44 hours, a similar time frame as period of DSC.
Methods: Six piglets 6 –10 kg underwent left thoracotomy and placement of a 3.5 mm polytetrafluoroethylene (PTFE) shunt from the left subclavian artery to the left pulmonary artery (LPA). The assumption was made that flow characteristics of a systemic-pulmonary artery shunt to one lung of a 6 –10 kg animal would be similar to both lungs of a human infant. The LPA was ligated at its origin. An adjustable screw-plunger resistor mechanism was placed on the PTFE graft after both anastomoses had been performed. A flow probe was placed on the LPA distal to the shunt insertion; flow probe data only reflected flow through the AS. The AS was adjusted every 2 hours from fully open to an estimated 60% flow reduction throughout the test period (range 34 – 44 hours). Each cycle of flow reduction was performed in 0.1 mm increments over 18 minutes.
Results: A predictable relationship was found between shunt flow and resistor setting. Little flow reduction occurred until 1 mm of plunger depression was achieved. Flow then decreased according to a third-order equation with increasing shunt constriction. R2 values varied from .981 to .997 among the 6 piglets. The standard deviation of flow among the trials at each resistor setting was 5.4%. There was no trend towards this relationship changing over the 44-hour period. The relationship between shunt setting and flow among the 6 piglets at each point in time was similar.
Conclusion: The AS provided a stable relationship between systemic-pulmonary artery shunt flow and device setting over a 44 hour test period in vivo. These data lend strong evidence that the device would perform successfully in a human infant during the period of DSC. Clinical trials are necessary to determine whether mechanical control of PBF results in improved clinical outcomes.
This research has received full or partial funding support from the American Heart Association, South Central Affiliate (Arkansas, New Mexico, Oklahoma & Texas).