In vitro steady-flow analysis of systemic-to-pulmonary shunt haemodynamics

A modified Blalock-Taussig shunt is a connection created between the system ic and pulmonary arterial circulations to improve pulmonary perfusion in ch ildren with congenital heart diseases. Survival of these patients is critic ally dependent on blood flow distribution between the pulmonary and systemi c circulations which in turn depends upon the flow resistance of the shunt. Previously, we investigated the pressure-flow relationship in rigid shunts with a computational approach, to estimate the pulmonary blood flow rate o n the basis of the in vivo measured pressure drop. The present study aims a t evaluating, in vitro how the anastomotic distensibility and restrictions due to suture presence affect the shunt pressure-flow relationship. Two act ual Gore-Tex((R)) shunts (3 and 4 mm diameters) were sutured to compliant c onduits by a surgeon and tested at different steady How rates (0.25-11 min( -1)) and pulmonary pressures (3-34 mmHg). Corresponding computational model s were also created to investigate the role of the anastomotic restrictions due to sutures. In vitro experiments showed that pulmonary artery pressure affects the pressure-flow relationship of the anastomoses, particularly at the distal site. However, this occurrence scarcely influences the total sh unt pressure drop. Comparisons between in vitro and computational models wi thout anastomotic restrictions show that the latter underestimates the in v itro pressure drops at any flow rate. The addition of the anastomotic restr ictions (31 and 47% of the original area of 3 and 4mm shunts, respectively) to the computational models reduces the gap, especially at high shunt flow rate and high pulmonary pressure. (C) 2000 Elsevier Science Ltd. All right s reserved.