Experimental Setup to Evaluate the Performance of Percutaneous Pulmonary Valved Stent in Different Outflow Tract Morphologies

Abstract

Percutaneous pulmonary valve implantation is a potential treatment for right ventricular outflow tract (RVOT) dysfunction. However, RVOT implantation site varies among subjects and the success of the procedure depends on RVOT morphology selection. The aim of this study was to use in vitro testing to establish percutaneous valve competency in different previously defined RVOT morphologies. Five simplified RVOT geometries (stenotic, enlarged, straight, convergent, and divergent) were manufactured by silicone dipping. A mock bench was developed to test the percutaneous valve in the five different RVOTs. The bench consists of a volumetric pulsatile pump and of a hydraulic afterload. The pump is made of a piston driven by a low inertia programmable motor. The hydraulic afterload mimics the pulmonary input impedance and its design is based on a three element model of the pulmonary circulation. The mock bench can replicate different physiological and pathological hemodynamic conditions of the pulmonary circulation. The mock bench is here used to test the five RVOTs under physiological-like conditions: stroke volume range 40-70 mL, frequency range 60-80 bpm. The valved stent was implanted into the five different RVOT geometries. Pressures upstream and downstream of the valved stent were monitored. Flow rates were measured with and without the valved stent in the five mock RVOTs, and regurgitant fraction compared between the different valved stent RVOTs. The percutaneous valved stent drastically reduced regurgitant flow if compared with the RVOT without the valve. RVOT geometry did not significantly influence the flow rate curves. Mean regurgitant fractions varied from 5% in the stenotic RVOT to 7.3% in the straight RVOT, highlighting the influence of the RVOT geometry on valve competency. The mock bench presented in this study showed the ability to investigate the influence of RVOT geometry on the competence of valved stent used for percutaneous pulmonary valve treatment.

In Vitro Study of Aortic Valves Treated with Neo-Chordae Grafts: Hydrodynamics and Tensile Force Measurements

“…10,13,14 In brief, the mock loop consisted of a computer-controlled hydraulic piston pump, a test section for ARFU samples housing, and an adjustable dynamic afterload for the simulation of the systemic hydraulic input impedance. The sample housing section was adaptable to samples of different sizes, and its design allowed surgeons to simulate surgery in conditions similar to those of the operating room, including the adjustment of the surgery parameters, namely the NC length.…”

Cardiovascular Modeling

“…A rapid prototyped model is thus useful as a test section within a mock circulatory loop. Test sections in fact can be either simplified morphologies (Bowles et al 1991;Vismara et al 2009) or patient-specific phantoms (Biglino et al 2011a;de Zélicourt et al 2005;Kitajima et al 2008). They can also be either rigid (de Zélicourt et al 2005;Ensley et al 1999) or compliant (Biglino et al 2011b;Kolyva et al 2010;Segers et al 1998) depending on the purpose of the experiment.…”

Rapid prototyping compliant arterial phantoms for in-vitro studies and device testing

“…Data gathered in a mock system can also serve as validation for computational studies [2]. These experimental setups can include anatomical phantoms attached to resistive and compliant elements according to a Windkessel type model [1], and in this setting phantoms can be either an idealised test section [3,4] or patient-specific models [5-7]. Traditionally, rigid models have been manufactured using resins [7,8] or glass [9].…”

“…While these are useful for visualisation studies, such as particle image velocimetry (PIV), they do not replicate the compliant nature of the vasculature and the associated Windkessel effect. Manufacturing flexible models, nonetheless, can be challenging, and methods such as dipping [3,10] or dripping [11] can be cumbersome, often with inadequate results. Different materials have been used for flexible vascular models, including silicone [2,11,12], polyurethane [13] and latex [14].…”