Effect of Vessel Size on the Flow Efficiency of the Total Cavopulmonary Connection: In Vitro Studies

Abstract

The total cavopulmonary connection (TCPC) creates a passive system of blood flow into the pulmonary circulation. We hypothesize that the efficiency differences found in models with superior vena cava-inferior vena cava (SVC-IVC) offsets is dependent on vessel size, with flow efficiency improving with larger size vessels. Two sets of in vitro TCPC models (TCPC-3 and TCPC-15) were constructed corresponding to average vessel diameters of 3- and 15-year-old patients. The model with full SVC-IVC offset was the most efficient in TCPC-3 models. There was no significant difference between geometric arrangements in TCPC-15 models; however, the average efficiencies were significantly higher. Among the models representing vessel sizes of the younger age group, the model with the full-diameter SVC-IVC offset was the most efficient. The models representing vessel sizes of the older age group showed marked improvement in efficiencies throughout without obvious differences between various geometric arrangements. This suggests that geometric considerations in TCPC surgical techniques may be of lower than expected significance over the life span of a patient. More important, after balancing the effects of improved flow efficiency with larger vessels against the effects of chronic volume overload, the trend of performing the Fontan surgery on increasingly younger patients may need to be reconsidered after further studies.

Time-resolved three-dimensional magnetic resonance velocity mapping of cardiovascular flow paths in volunteers and patients with Fontan circulation

“…Compared with previous studies based on flow analysis in selected analysis planes [9][10][11], in vitro models [13,21], or numerical simulations [15,22], 3D connectivity mapping allowed unobstructed tracing of postoperative 3D-flow channels in vivo.…”

“…A number of investigators found preferential distributions of blood flow to either the left or the right lung depending on TCPC connection geometry [8][9][10][11][12]. Further, in vitro analysis using vascular models [13] and numerical simulations of blood flow [14] aimed at optimising operative strategies and validating MR haemodynamics [15]. However, all earlier reports relied on the acquisition of flow patterns at a limited number of locations or simplified assumptions (in vitro analysis, numerical simulations).…”

Computational fluid dynamic study of flow optimization in realistic models of the total cavopulmonary connections

“…Resistance to blood flow in a low energy system depends critically on the geometry, where connections with abrupt bends, junctions, and expansions all result in frictional and recirculatory power losses. Therefore, much work has been focused on achieving the energetically optimal Fontan geometry that minimizes venous hypertension, yet still provides satisfactory pulmonary perfusion [11][12][13][14].…”

Computational simulations of the total cavo-pulmonary connection: insights in optimizing numerical solutions

“…one set of vessel sizes, flow rate, etc.) Studies are underway to investigate the effect of various flow rates, vessel sizes [67], compliant walls [33], and complex vessel shapes. This study presents a qualitative comparison between numerical and previous in vitro methods.…”