Background: Using a bifurcated Y-graft as the Fontan baffle is hypothesized to streamline and improve flow dynamics through the total cavopulmonary connection (TCPC). This study conducted numerical simulations to evaluate this hypothesis using postoperative data from 5 patients. Methods: Patients were imaged with cardiac magnetic resonance or computed tomography after receiving a bifurcated aorto-iliac Y-graft as their Fontan conduit. Numerical simulations were performed using in vivo flow rates, as well as 2 levels of simulated exercise. Two TCPC models were virtually created for each patient to serve as the basis for hemodynamic comparison. Comparative metrics included connection flow resistance and inferior vena caval flow distribution. Results: Results demonstrate good hemodynamic outcomes for the Y-graft options. The consistency of inferior vena caval flow distribution was improved over TCPC controls, whereas the connection resistances were generally no different from the TCPC values, except for 1 case in which there was a marked improvement under both resting and exercise conditions. Examination of the connection hemodynamics as they relate to surgical Y-graft implementation identified critical strategies and modifications that are needed to potentially realize the theoretical efficiency of such bifurcated connection designs. Conclusions: Five consecutive patients received a Y-graft connection to complete their Fontan procedure with positive hemodynamic results. Refining the surgical technique for implementation should result in further energetic improvements that may help improve long-term outcomes.

Background: This study was undertaken to evaluate an in vitro mitral valve (MV) simulator's ability to mimic the systolic leaflet coaptation, regurgitation, and leaflet mechanics of a healthy ovine model and an ovine model with chronic ischemic mitral regurgitation (IMR). Methods: Mitral valve size and geometry of both healthy ovine animals and those with chronic IMR were used to recreate systolic MV function in vitro. A2-P2 coaptation length, coaptation depth, tenting area, anterior leaflet strain, and MR were compared between the animal groups and valves simulated in the bench-top model. Results: For the control conditions, no differences were observed between the healthy animals and simulator in coaptation length (p = 0.681), coaptation depth (p = 0.559), tenting area (p = 0.199), and anterior leaflet strain in the radial (p = 0.230) and circumferential (p = 0.364) directions. For the chronic IMR conditions, no differences were observed between the models in coaptation length (p = 0.596), coaptation depth (p = 0.621), tenting area (p = 0.879), and anterior leaflet strain in the radial (p = 0.151) and circumferential (p = 0.586) directions. MR was similar between IMR models, with an asymmetrical jet originating from the tethered A3-P3 leaflets. Conclusions: This study is the first to demonstrate the effectiveness of an in vitro simulator to emulate the systolic valvular function and mechanics of a healthy ovine model and one with chronic IMR. The in vitro IMR model provides the capability to recreate intermediary and exacerbated levels of annular and subvalvular distortion for which IMR repairs can be simulated. This system provides a realistic and controllable test platform for the development and evaluation of current and future IMR repairs.

Objective: Forces acting on mitral annular devices in the setting of ischemic mitral regurgitation are currently unknown. The aim of this study was to quantify the cyclic forces that result from mitral annular contraction in a chronic ischemic mitral regurgitation ovine model and compare them with forces measured previously in healthy animals. Methods: A novel force transducer was implanted in the mitral annulus of 6 ovine subjects 8 weeks after an inferior left ventricle infarction that produced progressive, severe chronic ischemic mitral regurgitation. Septal-lateral and transverse forces were measured continuously for cardiac cycles reaching a peak left ventricular pressure of 90, 125, 150, 175, and 200 mm Hg. Cyclic forces and their rate of change during isovolumetric contraction were quantified and compared with those measured in healthy animals. Results: Animals with chronic ischemic mitral regurgitation exhibited a mean mitral regurgitation grade of 2.3 ± 0.5. Ischemic mitral regurgitation was observed to decrease significantly septal-lateral forces at each level of left ventricular pressure (P <.01). Transverse forces were consistently lower in the ischemic mitral regurgitation group despite not reaching statistical significance. The rate of change of these forces during isovolumetric contraction was found to increase significantly with peak left ventricular pressure (P <.005), but did not differ significantly between animal groups. Conclusions: Mitral annular forces were measured for the first time in a chronic ischemic mitral regurgitation animal model. Our findings demonstrated an inferior left ventricular infarct to decrease significantly cyclic septal-lateral forces while modestly lowering those in the transverse. The measurement of these forces and their variation with left ventricular pressure contributes significantly to the development of mitral annular ischemic mitral regurgitation devices.