Heart Valve Device Testing

Stress artifacts caused by high frequencies testing of heart valve prosthesis have been reported in various versions of ISO 5840 and discussed in standardization committees for years. It is known that Accelerated Wear Testing (AWT) imposes unrealistically severe conditions not seen in normal physiologic conditions. It is common knowledge that the inertial forces on heart valve prosthesis increase significantly when exposed to accelerated wear testing conditions. To avoid unwanted in-vitro test artifacts resulting in premature failure of perfectly sound heart valve prosthesis designs, ViVitro’s AWT System with Dual Control Technology (DCT)™ maintains constant leaflet closing velocities across the entire AWT cycling period. With its proprietary and patented Dual Control Technology (DCT)™, the ViVitro’s AWT System uses two separate position feedback sensors and algorithms to control piston displacement and bypass valve independently to meet differential pressure requirements while preserving initial leaflet closing velocities, and optimizing passing cycles.

A contactless optical gauging machine is used to measure dimensional attributes of the device.

Durability testing is intended to determine the in-vitro lifetime, the anticipated failure modes, and  potential failure consequences (e.g. immediate total loss of  function or gradual degradation of  function).

Dynamic Failure Mode (DFM) testing of heart valve prosthesis is used together with Accelerated Wear Testing (AWT) to provide a thorough assessment of durability. Since AWT is a “test to success” approach meaning samples are intended to survive the test, DFM testing is a “test to failure” approach which is intended to characterize potential durability-related failure modes.

A measurement at which pressure of a device begins to migrate under pulsatile flow conditions.

An assessment of the effects of post-implant dilatation on the leaflets and frame should be conducted if this is an expected use condition to which the (novel) heart valve substitute will be exposed.

Our ex-vivo beating heart simulator is used to test transcatheter devices when realistic anatomy is required.

The thrombogenic and haemolytic potential of the heart valve substitute can be assessed using a combination characterization techniques: digital particle image velocimetry (DPIV), computational fluid dynamics (CFD), and ex-vivo methods (e.g. blood loops).

The goal of the test is to determine, in vitro, for a specific artificial cardiac valve the value of the coefficient K in the Bernoulli equation, ΔP = K (Vd2 – Vp2).

Hydrodynamic Performance Pulsatile Flow Testing – Forward flow and regurgitant performance of the device will be assessed under physiological pulsatile flow conditions. Key indicators of valve performance such as Effective Orifice Area (EOA) and regurgitant fraction (RF) are determined.

Real-time wear testing (RWT) is intended to match physiological loading conditions as closely as possible as to what would be obtained in a real patient. Due to the viscoelastic nature of some materials, Accelerated Wear Testing may actually under test devices, so RWT can be used to identify frequency dependent failure modes.

A measure of the resistance to sewing ring dehiscence. Failure may result from sutures, suture retention failure, fabric tensile strength failure, fabric weave failure, or fabric seam failure.

Before conducting other evaluations, test samples should undergo all the steps a finished device would go through before being implanted in the patient.

Devices can be subjected to various physiological pulsatile flows and pressures.

Hydrodynamic Performance Steady flow testing determines the forward and reverse flow performance characteristics of a valve in a simple and highly controlled manner. While no formal acceptance criteria exists for steady flow testing, it can be useful in confirming results of pulsatile flow testing.

The deflection of the stent lateral struts (post) is measured when subjected to different back-pressures.