Blood flow through right atrial-pulmonary artery (RA-PA) conduits was investigated. Experiments were designed to evaluate the pumping function of the right atrium, effects of the atrial versus ventricular pacing site, the necessity of a valve within the conduit, and the effect of positive-pressure ventilation on conduit flow. Twenty foxhounds were subjected to silicone patch closure of 90 percent of the tricuspid valve orifices to create stenosis. Ten dogs successfully underwent RA-PA shunting with a conduit with paralled limbs, one containing a prosthetic valve. The proximal main pulmonary artery was ligated to ensure total diversion of blood via the conduit. Valved and nonvalved conduit flow was significantly correlated with right atrial pressure (RAP): r = 0.95, p less than 0.05; r = 0.98, p less than 0.01, respectively. There was no significant effect of increasing heart rate (p = 0.19), atrial versus ventricular rhythm (p = 0.28), or the presence of a valve (p = 0.63). Increasing tidal volume resulted in increasing tidal conduit flow (expiration-inspiration) (r = 1.0, p less than 0.01), but mean flow was unaffected. Therefore, RAP is the most important factor influencing conduit flow. The absence of a valve, ventricular rhythm, and tachycardia did not significantly alter flow in this acute experimental model.
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