Experimental Flow Field Assessment – Echo Doppler – Bernoulli’s Equation Verification

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).

Test Procedure

Heart valves samples (or cardiac repair devices) undergoing testing are mounted in the active test position (aortic/mitral) of the Pulse Duplicator and a companion valve is mounted in the opposite test position (aortic/mitral). The test loop is filled with a blood analog solution. The valves are then subjected to a pulsatile flow that is intended to simulate physiologic conditions. The valve samples are installed in aortic position into ViVitro pulse duplicator using specific (PIV) valve test chamber, the test condition is tuned and, flow and pressures are recorded. Pressures and differential pressure are averaged over 10 consecutive cycles.

The echo probe is positioned aligned to the valve axis, 12-15cm downstream the valve. Continuous wave Doppler is used to measure the maximum velocity (Vd) downstream the valve. Pulsed-wave Doppler is used to measure the maximum velocity (Vp) upstream the valve.
As in Bernoulli formula:
ΔP = K (Vd2 – Vp2)
where:
K is a constant
ΔP is the pressure gradient
Vd is the distal velocity measured by continuous wave Doppler
Vp is the proximal velocity measured by pulsed Doppler

Then, the values of ΔP as measured by pressure transducers are plotted against (Vd2 – Vp2) as measured by Doppler for the different test conditions, and the value of the coefficient K is calculated by linear regression.

Equipment

• Calibrated manometer (measurement uncertainty ±1mmHg) or calibrated pressure measuring system (measurement uncertainty ±2mmHg)
• Calibrated thermometer (measurement uncertainty ±0.5°C)
• ViVitro Pulse Duplicator E(Pulse Duplicator + Superpump + Superpump controller)
• Data Acquisition system including ViViTest Software
• Heat bath
• Syringe with graduations of 1mL
• Companion valve (ViVitro spring valve)
• Flow Meter and Flow probes
• 3 ViVitro Pressure transducers
• AmPack (ViVitro Amplifiers)
• ViVitro analog I/O module
• Clinical echocardiograhy system

Measured Parameters

• Valve pressure gradient
• Flow rate
• Maximum downstream velocity
• Maximum upstream velocity

Scope

• Artificial heart valves prosthesis
• Any valvular prosthesis
• Any cardiac repair device
• Surgical, transapical, TAVI, TMVR and any transcatheter valve
• Biological, Polyemeric, mechanical valves, sof or rigid

Service Levels

• Standard Service
• Full Service

Related Tests

• Experimental Flow Field Assessment – Digital Particle Image Velocimetry (DPIV)
• Steady Flow Testing – Hydrodynamic Performance
• Pulsatile Flow Testing – Hydrodynamic Performance
• Accelerated Wear Testing (AWT)

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