Background It is known that respiration modulates cavopulmonary flows, but there is little data comparing mean flows under breath holding and free breathing conditions to isolate the respiratory effects, as well as effects of exercise on the respiratory modulation. Methods Real time phase contrast magnetic resonance combined with a novel method to track respiration on the same image acquisition was used to investigate respiratory effects on Fontan caval and aortic flows under breath holding, free breathing and exercise conditions. Respiratory phasicity indices based on beat-averaged flow was employed to quantify the respiratory effect. Results Flow during inspiration was significantly higher than expiration under the free breathing and exercise conditions for both inferior vena cava (inspiration/expiration: 1.6±0.5 and 1.8±0.5, respectively) and superior vena cava (inspiration/expiration: 1.9±0.6 and 2.6±2.0, respectively). Changes from rest to exercise in the respiratory phasicity index for these vessels further showed the impact of respiration. Total systemic venous flow showed no significant statistical difference between the breath holding and free breathing conditions. In addition, no significant difference was found between the descending aorta and inferior vena cava mean flows under either resting or exercise conditions. Conclusions This study demonstrated that inferior vena cava and superior vena cava flow time variance is dominated by respiratory effects, which can be detected by the respiratory phasicity index. However, the minimal respiration influence on net flow validates the routine use of breath holding techniques to measure mean flows in Fontan patients. Moreover, the mean flows in the inferior vena cava and descending aorta are interchangeable.

A direct numerical simulation investigation of the synthetic jet frequency effects on separation control of low-Re flow past an airfoil Phys. Fluids 27, 055101 (2015) A two-dimensional numerical study is performed to investigate the relation between the direction of a deflected wake and the vortex pairing mechanisms. The deflection angle can be correlated with two effective phase velocities defined to represent the trends of symmetry breaking and symmetry holding, respectively. The deflection angle increases with the strength of the vortex pairs, which is associated with the heaving amplitude, frequency, and the free stream Reynolds number. Furthermore, not only the influence of Strouhal number but also those of the two heaving motion componentsamplitude and frequency -are studied individually under different Reynolds numbers. The study shows that the deflection angle consistently increases with the difference between the symmetry-breaking phase velocity and symmetry-holding phase velocity. C 2012 American Institute of Physics. [http://dx

The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical decision-making process. In its current state, surgical planning offers an accurate hemodynamic assessment of the pre-operative condition, provides anatomical constraints for potential surgical options, and produces decent post-operative predictions if boundary conditions are similar enough between the pre-operative and post-operative states. Moving forward, validation with post-operative data is a necessary step in order to assess the accuracy of surgical planning and determine which methodological improvements are needed. Future efforts to automate the surgical planning process will reduce the individual expertise needed and encourage use in the clinic by clinicians. As post-operative physiologic predictions improve, Fontan surgical planning will become an more effective tool to accurately model patient-specific hemodynamics.