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The beneficial vortex and best spatial arrangement in total extracardiac cavopulmonary connection
Antonio Amodeo1, Mauro Grigioni, Guido Oppido
1Department of Cardiac Surgery, Bambino Gesù Hospital, and the Laboratory of Biomedical Engineering, Trieste, Italy. antonioamodeo@yahoo.it
Objective:
Total extracardiac cavopulmonary connection is an established procedure, but the best spatial arrangement remains controversial. On the basis of our clinical experience with total extracardiac cavopulmonary connection, we performed quantitative and qualitative flow analysis on total extracardiac cavopulmonary connection models simulating the two most frequent arrangements applied to our patients to determine the most favorable hydrodynamic pattern.
Methods:
We selected two main groups among 110 patients who underwent total extracardiac cavopulmonary connection, those with left-sided inferior vena cava anastomosis (type 1) and those with facing superior and inferior vena cava anastomoses (type 2). Blown-glass total extracardiac cavopulmonary connection phantom models were constructed on the basis of nuclear magnetic resonance and angiographic images. Flow measurements were performed with a Nd:YAG Q-switched laser and a particle imaging velocimetry system. A power dissipation study and a finite-element numeric simulation were also carried out.
Results:
When applying superior and inferior vena caval flow proportions of total systemic venous return of 40% and 60%, respectively, a vortex was visualized in the type 1 phantom that rotated counterclockwise at the junction of the caval streams. This apparent vortex was not a true vortex; rather, it represented a weakly dissipative recirculating zone modulating the flow distribution into the pulmonary arteries. The power dissipation and finite-element numeric stimulation confirmed the beneficial nature of the apparent vortex and a more energy-saving pattern in the type 1 phantom than in the type 2 phantom.
Conclusion:
Total extracardiac cavopulmonary connection with left-sided diversion of the inferior vena caval conduit anastomosis is characterized by a central vortex that regulates the caval flow partitioning and provides a more favorable energy-saving pattern than is seen with the total extracardiac cavopulmonary connection with directly opposed cavopulmonary anastomoses.