The Radnoti Working Heart System may be used in either Langendorff costant flow or constant pressure modes, recirculating or non-recirculating, and working heart. Because of the large volumes of fluid pumped by the heart, the working heart preparation usually operates in the recirculating mode. The following diagram illustrates working heart recirculating mode. Here it is recommended to create a closed loop by connecting tubing from the compliance loop reservoir back to the oxygenating chamber.
During the re-circulating of perfusate, the heart releases proteins that cause foaming and the formation of embolites. For this reason, it is essential to have an in-line filter to remove contaminants (1 micro m porosity).To remove these proteins and other precipitates that may exist in the solution, this filter is inserted in the pump output line. The filter may then be removed at the end of the experiment and replaced before the next experiment is started. This is an improvement over systems that incorporate the filter as a permanent fixture in the design, necessitating extensive cleaning procedures of the entire apparatus after each use.
Polytetrafluorethylene (PTFE) membranes are unaffected by most organic solvents, concentrated acids and bases, propellants, and cryogenic fluids and may be used for gas/air filtration. It is recommended to use the 140136 Glass Fiber Filters during recirculation mode. These are disposable and can be changed for each experiment. One filter is included with each Working Heart System. However, they may also be purchased in packages of 15 for those using recirculating mode.
Please refer to the attached manual for more information regarding recirculating perfusate circuits for rat Langendorff heart applications.