Using the ViVitro Pulse Duplicator for Right Heart Testing
This FAQ discusses configuration considerations when adapting the ViVitro Pulse Duplicator Model Left Heart flow loop to enable right heart testing.
The ViVitro Pulse Duplicator is composed of the clear acrylic Model Left Heart, SuperPump, Flow Measuring System, and ViViTest data acquisition system. This flexible piece of testing equipment simulates physiological pulsatile flow in the heart using customizable waveform control, peripheral resistance, and compliance while allowing clear device visibility as well as pressure and flow measurement and user-friendly data collection.
Initially the system was designed to mimic conditions of the left side of a heart with the intent of testing prosthetic heart valves. However, since its inception, the ViVitro Pulse Duplicator has also been customized to perform hydrodynamic testing on a variety of novel cardiovascular devices. One common custom use of the Pulse Duplicator system is for Right Heart applications.
Six areas to consider when configuring the standard ViVitro Labs Pulse Duplicator for Right Heart testing:
- Peripheral Resistance: The pressures in the Right Heart are significantly lower than those in the Left Heart. As shown in Figure 1, in order to reach the lower pressures of right heart conditions, it may be necessary to replace the Peripheral Resistance Controller from the flow loop with a simple pinch valve.
Figure 1. Standard Peripheral Resistance Controller (left) Pinch valve for resistance control of right heart conditions (right).
- Heat Exchanger: Similar to the Peripheral Resistance, the heat exchanger may require a substitution to obtain the necessary right heart pressures. Shown in Figure 2, ViVitro Labs offers a low pressure drop heat exchanger which, while being less efficient, allows the Pulse Duplicator to achieve right heart conditions
Figure 2. Standard heat exchanger (A) with higher efficiency and pressure drop. Low pressure drop heat exchanger (B) with lower efficiency and pressure drop.
- Compliance: The system compliance will affect the shape of the pressure waveform, including the spread of systolic and diastolic pressures. As with the left heart, for some conditions it may be necessary to adjust compliance volumes to reach the desired pressure waveforms. See Figure 3 and the Pulse Duplicator User Manual for more details on system compliance.
Figure 3. Compliance options for pressure waveform control. The aortic root (taller) and Windkessel (shorter) compliance tanks along with other options (not shown) may be necessary.
- Static Head: The static pressure created by fluid in the atrium will have a large effect on the systemic pressures in the system if right heart conditions are being targeted. It may be necessary to control this height to obtain consistent results. As shown in Figure 4, a line in the atrium chamber may be useful. For hypotensive conditions this fluid should be dropped as low as possible.
Figure 4. Controlling fluid level in the atrium chamber to control static pressure.
- Right Ventricle Outflow Tract (RVOT): Since the glass aorta for the standard ViVitro Labs Pulse Duplicator may not simulate the desired anatomy of the RVOT, the Aortic Conduit Mount (ACM) may be an effective alternative. Essentially, the ACM can be used to mount custom ventricle outflow tracts desired to emulate test site physiology. See Figure 5 below.
Figure 5. Model silicone aortic root mounted in the ACM accessory for the ViVitro Labs Pulse Duplicator.
- ViViTest Software: Currently, ViViTest software (for use with the Pulse Duplicator) utilizes specific terminology for Left Heart applications, mainly in reference to valve sites (aortic and mitral). This software is still effective for Right Heart testing, as all the pressure and flow measurement locations and subsequent calculations are still relevant. Just keep in mind that references to the aortic and mitral valves apply to the pulmonic and tricuspid valves, respectively. For a screenshot of the ViViTest user interface, see Figure 6 below.
Figure 6. ViViTest software user interface.
TIP: Using the ViVitro Labs Pulse Duplicator for Right Heart & Full Heart Simulation
A common question that arises regarding custom use of the Pulse Duplicator system is whether it can be used for Right Heart and Full Heart applications. This PDF by Marshal Kilduff will address this question by noting configurations to the Model Left Heart flow loop to enable right heart testing, as well as how to connect two Pulse Duplicators to allow full heart testing.
10 ways ViVitro Pulse Duplicator and HiCycle compare to equipment built in-house
People often ask, “Why buy a ViVitro Pulse Duplicator or HiCycle when I could build something myself? How do they compare to equipment built in-house ?” My initial reaction is always similar to that of Dominik Obrist: “It’s more complicated than you think.” Dominik speaks from experience.
“Complicated” is actually short hand for “takes time, requires expertise, and ends up costing more.” Here is my top 10 list of reasons why you should outsource the purchase of Pulse Duplicator and Durability testing equipment instead of doing it yourself:
- Ease of Use – First of all ViVitro Pulse Duplicator or HiCycle equipment will hands down be more user friendly and easier to use than any in-house system. This is especially important if you are trying to get fast, repeatable, and consistent results from technicians or students. Simplicity is an inherent design criteria from the device mounting, to the data acquisition system, and software.
- Reliability – When you need results in a hurry you can depend on our equipment. Our Pulse Duplicator and HiCycle products work day in day out in countries around the world and have a proven track record of reliability. If in the unlikely event you manage to damage the equipment, see my next point…
- Repairs- When ViVitro Pulse Duplicator or HiCycle equipment breaks you can immediately call on extra resources to get the issue resolved right away. For example, we inventory parts that can be easily dropped in if anything fails. Will a homemade Pulse Duplicator or Durability Tester system give you that peace of mind? Download our Maintenance Brochure
- Reputation – When you report results from a ViVitro Pulse Duplicator or HiCycle system, regulators, reviewers and academics around the world know exactly what that means and how it was measured. If you do the same with your own system you will likely receive a plethora of questions trying to understand how your measurements were conducted. Check out our citations page for a sampling of publications that use our equipment.
- Qualification – Many users struggle to validate that their in-house equipment is working properly. With ViVitro you can call in expertise to make sure your installed system is working to spec. Download our Qualification Brochure
- Training – If you have user turnover (be it employee or student), you can call in experts or access online information to get their replacements up and running right away. We invest in a variety of user manuals and training materials which in-house systems will not have. Download our Training Brochure
- Cost – Researchers sometimes believe that a simple home built Pulse Duplicator or Durability Tester system could be made for less. First, factor in the time someone will spend developing their own test equipment instead of focusing on advancing their device. Combine that with the one-off machining costs for a “prototype”, and add overhead costs (which are often neglected) like documentation, user manuals etc. ViVitro Pulse Duplicator and HiCycle equipment quickly become a very cost effective way to accelerate your development.
- Flexibility – If your needs change, ViVitro Pulse Duplicator and HiCycle equipment have a variety of accessories to grow with your development. Our platform of testers makes it easy to transition your device from pulsatile testing to durability testing and back. The look and feel of ViVitro Pulse Duplicator and HiCycle equipment and software is consistent from product to product. Once you know how to use one, it is intuitive to work another. If you grow and need more capacity it can be order by phone or email.
- Consistency – If you ever require independent results from an ISO 17025 accredited test lab, you can come back to ViVitro to evaluate your device with no surprises due to equipment differences.
- Looks- As an engineer, my opinions on esthetics are somewhat suspect, but ViVitro systems look professional and impressive to visitors and investors. Home built systems often place no emphasis on appearance and deliver limited visual credibility.
Lab Manager, MSc.
ViVitro Labs Inc
What spare parts should I have on hand for my Pulse Duplicator?
We recommend this list of parts be stocked by a lab using the ViVitro Pulse Duplicator.
|| Ventricle Membrane (modified for your configuration)
|| HDPE Piston Seal
|| O-Ring Dash 152
|| O-Ring Dash 246”
|| O-Ring Dash 034
|| O-Ring Dash 128
||O-Ring Dash 006
|| Hose Barb ½”
||O-Ring Dash 236
|| O-Ring Dash 235
|| O-Ring Dash 232
|| Single Luer Connector
|| Pressure Transducer Stopcock
Can I use blood analogue or blood in the Pulse Duplicator?
Yes, both may be used in the ViVitro pulse duplicator.