Abstract 17363: Cardiac Output and Valve Orientation Affect Blood Flow Patterns Local to Bioprosthetic Pulmonary Valves in Tetralogy of Fallot

Introduction: Tetralogy of Fallot (ToF) typically requires surgical repair of the right ventricular outflow tract (RVOT) and subsequent placement of an artificial pulmonary valve. Bioprosthetic valve longevity is highly variable and there is currently little understanding of what hemodynamic factors may lead to early valve dysfunction. Hypothesis: We hypothesize that cardiac output and valve orientation impact the performance of bioprosthetic valves by affecting blood flow patterns in the RVOT. Methods: We analyzed hemodynamics in a 3D printed ToF anatomy model in a physiological flow loop. A 25mm surgical valve was implanted in the model at two orientations: native and rotated 180 degrees. Full 3D, three-component, phase-averaged velocity fields were obtained over the cardiac cycle using 4D flow MRI at cardiac outputs of 2, 3.5, and 5 L/min. We acquired images of valve leaflet motion at 1500Hz. The 4D flow MRI and high-speed camera experiments were run identically, allowing us to examine the relationship between flow fields and leaflet motion. Results: The full velocity fields from the MRI scans revealed key differences among cases in flow features including location of reverse flow regions, systolic jet shape, and asymmetry local to the valve. At 2 L/min, the forward flow through the jet was more asymmetric compared to the other cases and a strong vortex formed, indicating a region of recirculation. With the rotated valve orientation, the 2 L/min case also produced a unique pattern as flow was washed from the RVOT inner curve back toward the center of the valve (Fig 1). Leaflet behavior during systole varied with cardiac output as well, as higher frequency flutter was observed at 5 L/min and the effective valve orifice area was decreased by 8.5% at 2 L/min compared to 5 L/min. Conclusions: We observed key differences in flow patterns and leaflet motion due to cardiac output and valve orientation that could impact leaflet loading and fatigue and long-term valve function.

P750 Dynamics of tricuspid regurgitation after right ventricular lead implantation

Placement of ICDs, permanent pacemakers, and biventricular devices is performed under fluoroscopic guidance. Implantable device leads can cause tricuspid regurgitation (TR) when they interfere with leaflet motion. In the past, we had the experience of 2 cases with RV lead who had severe TR; one had lead repositioning and the other needed surgery. Aim: Evaluation of TR after right ventricular (RV) permanent lead implantation to check if echocardiographic guidance is needed for adequate lead positioning. Methods: Seventy six patients had trans-thoracic Doppler echocardiographic studies before and after implantation of permanent RV leads. Results: Before RV lead implantation 96% of patients had TR, grade 1 in 57 patients (75%), grade 2 in 12 (16%), grade 3 and 4 in 4 (5%). After RV lead implantation 44 patients with grade 1 TR remained with the same degree (77%) while in 2 (3.5%) TR progressed to grade 2, and in the remainder the TR disappeared. Most of the patients with grade 2 TR before RV lead implantation (75%) remained in grade 2 while 25% the grade decreased to grade 1. In all the patients with grade 3 and 4 TR pre-implantation, the severity of TR decreased by one grade. In 56 patients with non-CRT device implantations, 39 (70%) had grade I TR before procedure and in 28 (72%) of them TR grade did not change and 11(28%) TR grade progressed to grade 2 after implantation. Grade 2 TR before implantation in 8 patients (14%), the TR grade decreased in3 (37.5%) and did not change in the others. In 3 (5.4%) patients with grade 3 and 4 TR before procedure, the TR decreased after procedure. Conclusions: Implantation of permanent RV leads did not worsen TR grade.

Echocardiography and Correction of Mitral Regurgitation: An Unbreakable Link

Background: Degenerative mitral valve (MV) disease causing mitral regurgitation (MR) is the most common organic valve pathology and is classified based on leaflet motion. MV repair is indicated as the preferred technique (Class I indication) when the results are expected to be durable. Therefore, a detailed and systematic evaluation of MV apparatus is pivotal in allowing the proper surgical planning, as well as the screening for trans catheter-based treatment when surgery is not indicated. Aim: The aim of the present review is to describe the crucial role of both Transthoracic Echocardiography (TTE) and Transesophageal Echocardiography (TEE) in the decisional process and the guidance of MV repair procedures. TTE is the main investigation and the first approach used to make diagnosis of MR, to assess the severity and to describe the underlying mechanism, while TEE, especially with 3D echocardiography, has been shown to be useful for clarifying complicated valvular anatomy, assessing the surgical result and detecting complications. The surgical treatment of MR takes advantage of ultrasound evaluation of MV apparatus at any stage of the process, thus making the link between surgery and echocardiography unbreakable throughout the perioperative phase.

Fixed Points and Stability Analysis in the Motion of Human Heart Valve Leaflet

This work was set out to gain further insight into the kinetics of the human heart valve leaflet. The Korakianitis and Shi lumped parameter model was adopted for this study. The fixed points were determined, and then, their stability properties were assessed by evaluating eigenvalues of the Jacobian matrices. Normal physiological parameters for the valve model were simulated; based on which, a local bifurcation diagram was generated. Phase portraits were plotted from simulated responses, and were used to observe the qualitative properties of the valve leaflet motion. The evaluated fixed points were found to be dependent on pressure and flow effects, and independent on friction or damping effect. Observed switching of stability between the two fixed points indicated that the leaflet motion undergoes transcritical bifurcation. Of the two fixed points, one is always either a stable spiral or generative node while the other is a saddle. Numerical simulations were carried out to verify the analytical solutions.