Working Heart
Overview:
Isolated mammalian heart studies have been in use for over a century in one form or another (for a review, see Zimmer 1998), mostly involving the Langendorff technique (for an appraisal, see Skrzypiec-Spring et al 2007) which involves retrograde perfusion of the coronary arteries via the ascending aorta. However, one immediate disadvantage of the Langendorff technique is the inability to vary the amount of external cardiac work during perfusion. This is because the heart effectively pumps into a low resistance open circuit system which was not designed to model circulatory effects on heart performance, such as the influence of preload and afterload on cardiac work. To overcome this limitation the Working Heart apparatus was developed by Neely and Morgan in the 1960s (Neely et al, 1967), who were at the time interested in determining the relationship between oxygen consumption and external work performed by the heart.
The working heart model has the following key features:
- A closed-loop circuit is established between the left atrium and left ventricle
- Preload and afterload can be altered
- Heart performs external work during each cycle
- Aortic pressure curve can be calibrated against circuit resistance
- Coronary flow is proportional the size of the dicrotic notch
- Pressure-volume studies can be performed ex vivo
The nature of the Working Heart model makes it amenable to many different types of studies. Some examples are: metabolic and free radical analysis, ischemia-reperfusion models, effects of hormones and novel drugs, energy homeostasis, transgenic models and genetic therapy, and toxicology.
References
Zimmer, H.-Gerd. (1998). The Isolated Perfused Heart and Its Pioneers. News in physiological sciences, 13(4), 203-210.
Skrzypiec-Spring, M., Grotthus, B., Szelag, A., & Schulz, R. (2007). Isolated heart perfusion according to Langendorff---still viable in the new millennium. Journal of pharmacological and toxicological methods, 55(2), 113-26
Neely, J. R., Liebermeister, H., Battersby, E. J., & Morgan, H. E. (1967). Effect of pressure development on oxygen consumption by isolated rat heart. The American journal of physiology, 212(4), 804-14
Method:
For isolated working heart preparations, a suitably sized cannula is inserted into the aorta and initially the heart is perfused in Langendorff mode i.e. retrogradely down the aorta to remove blood and to allow recovery from anoxia during excision and initiation of perfusion (see Langendorff Heart application page). During this time, a second cannula is inserted into the pulmonary vein to perfuse the left atrium. After successful cannulation of the pulmonary vein, working heart mode begins by initiating flow into the left atrium from the atrial bubble trap. The fluid passes into the left ventricle, and ventricular contraction forces perfusate into a pressure chamber attached to the aortic cannula. This chamber is partly filled with air to provide some elasticity to an otherwise rigid fluid system. Pressure development in this chamber forces the perfusate out through tubing into an aortic bubble trap above the heart. Overflow from the aortic bubble trap is returned inside the long central oxygenating chamber.
The perfusate is typically a modified Krebs-Henseleit bicarbonate buffer equilibrated with a 95% O2-5% CO2 mixture. It is preferable to perfuse at or near the normal body temperature of the species under study. Since mammalian hearts are used, this would usually involve a perfusate temperature of 37.0 to 37.5°C (unless hypothermia is being investigated).
ADInstruments provides several Working Heart systems which include a PowerLab, Radnoti Working Heart Apparatus, Bridge Amps, Animal Bio Amp, Physiological Pressure Transducers, T-type Pod and T-type Thermocouple Probe.
Parameters of interest that can be obtained with ADInstruments Working Heart models include:
Left Atrial (Preload) Pressure
The left atrial or preload pressure can be monitored in the working heart set-up by attaching a Physiological Pressure Transducer (connected to a Bridge Amp) to the perfusate line entering the left atrium.
Aortic (Afterload) Pressure
The Aortic or afterload pressure can be monitored in the working heart set-up by attaching a Physiological Pressure Transducer (connected to a Bridge Amp) to the perfusate line exiting the aorta.
Contractile Force
The apex of the heart can be connected to a Force Transducer and Bridge Amp via a pulley system to measure the contractile force of the heart. Tension is applied to the thread attaching the heart to the transducer and changes in contractile force can be monitored.
Electrical Activity
The cardiac electrical activity can be measured using a Bio Amp and suitable Spring Clip Electrodes. Typically, one electrode is connected to the apex of the heart and one to the atria. The ground electrode can be connected to the aortic cannula. Alternatively, with a suitable electrode, action potentials can be measured form single cardiac cells.
Temperature
It is critical to maintain good and uniform temperature control. It is strongly recommended to have permanent temperature sensing probes at various parts of the circuit. The temperature can be measured with a T-Type Temperature Probe and T-Type Pod. The probe can be inserted into the perfusate flow or into the heart.
Pacing
The heart may be paced using an external Stimulator with a stimulus that exceeds the natural cardiac pacemaker rate, after the sino-atrial node is crushed or the right atrium excised. Pacing voltage is determined as a set percentage (normally 110-150%) above the voltage required to pace the heart and usually should not have to exceed 3-5V with a duration of 0.1 to 1 msec. The PowerLab data acquisition system has an analog output in conjunction with the Stimulator panel in LabChart and can be used to control the frequency of the stimulator pulses.
Left Ventricular Pressure/Volume
As the working heart is a closed system, simultaneous left-ventricular pressure and volume measurements can be made using a Mikro-Tip Pressure-Volume Catheter and control unit. Further heamodynamic measurements can be made from the resulting pressure-volume loops (see Ventricular Pressure-Volume application pages).
Atrial, Aortic and Coronary Flow
By inserting a suitable Tubing Flow Probe into the perfusate lines going into the left atrium and out of the aorta, the atrial and aortic flow rates can be determined. By subtracting the aortic flow from the atrial inflow, you can calculate the resultant coronary flow. Alternatively, the coronary flow can be determined by collecting the coronary effluent over a known time period.
pH & O2 Concentration
It is important to maintain the correct pH and oxygen saturation of the perfusate. These can be measured if required using a suitable pH Electrode and pH Amp and a suitable dip-type or flow-through Oxygen Electrode. To measure the oxygen consumption, O2 electrodes can be placed in the inflow and in the effluent and the difference in concentration calculated.
Software:
The LabChart Advantage:
(May require additional Modules and Extension)
- Online calculation of cardiac parameters: e.g. heart rate, left ventricular pressure, developed pressure, stroke work, contractility (ESPVR, MaxPower) and many more
- Fast data extraction, analysis and export (e.g. csv. or txt.) to other applications using Timed Add to Data Pad and Multiple Add to Data Pad
- LabChart software can be used to control pacing stimulation frequency and timing of pulse trains using an external stimulator
- The PV Loop Module allows for complete analysis of pressure-volume data for investigation of cardiac pump performance
- The Blood Pressure Module allows for the calculation of ventricular haemodynamics online or offline
- The Dose Response Module allows for the calculation of dose response type data from LabChart recordings, automatically or manually, offline or online.
- The Peak Analysis Module provides automatic detection and analysis of multiple, but not overlapping, signal waveforms from recordings, online or offline. Ideal for analyzing cardiac action potentials.
LabChart
LabChart software (for Windows and Macintosh) together with a PowerLab data acquisition system offers up to 32 channels of real-time data acquisition, data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Additional acquisition and analysis functionality is provided with the use of specialized LabChart Extensions and LabChart Modules. LabChart Modules are available as part of LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.
PV Loop Module
The PV Loop Module (Windows) records and analyses pressure and volume data for each cardiac cycle. This is ideal for investigating basic functional pump properties of the heart.
Module benefits:
- Graphing of successive pressure-volume loops (P-V loops)
- Select or exclude individual loops from analysis
- Calculates and displays end-systolic-P-V relationship (ESPVR) and end-diastolic-P-V relationship (EDPVR)
- Haemodynamics parameters of interest, such as stroke work, cardiac output, contractility and many more, are available within the Haemodynamics table
- Simple calibration of pressure and volume to their physical units
Blood Pressure Module
The Blood Pressure Module (Windows) automatically detects, analyzes and reports cardiovascular parameters from ventricular pressure signals.
Module benefits:
- The BP Classifier makes detection and exclusion of atypical pressure waveforms easy
- Parameters can be displayed as continuous data on separate channels
- Automated calculation of commonly used haemodynamics parameters, including: ventricular (systolic and diastolic) pressure, dicrotic-notch pressure, pressure cycle duration, heart rate, developed pressure, isovolumetric relaxation
Dose Response Module
The Dose Response Module (Windows) provides easy analysis of dose response experiments to a variety of measured variables, such as: muscle contraction, enzyme activity, heart rate, blood pressure, and membrane potential.
Module benefits:
- Automated or manual modes of analysis
- Fast analysis of raw data to dose response parameters
- Fast comment detection and conversion to dose response markers
- Easy options for calculating different response parameters
- Instant single or multiple dose response curves (Hill-curves) generation
- Instant calculation of EC50 and Hill slopes
- Export options to other software applications for further analysis
Peak Analysis Module
The Peak Analysis Module (Windows) provides automatic detection and analysis of multiple, but not overlapping, signal peaks in acquired waveforms. This is ideal for investigating the morphology of pressure and volume waveforms.
Module benefits:
- Fast parameter extraction and analysis from single or multiple peaks
- Automatic peak detection of an entire channel or a selection within a channel
- Detection of positive or negative peaks
- Provides several analysis presets suitable for many different types of waveforms, including cardiac action potential
- Easy exporting of width, area of the peak and time to peak parameters into other applications for further analysis
GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.
Hardware:
PowerLab Data Acquisition Systems
The PowerLab is a high-performance data acquisition unit capable of recording at speeds of up to 400,000 samples per second continuously to disk (aggregate). PowerLab units are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other third-party companies. In addition to standard single-ended BNC inputs, 4 differential Pod ports are also available for direct connection of Pod signal conditioners and appropriate transducers. Research PowerLab units include:
- PL3504 PowerLab 4/35 - 4 Channels
- PL3508 PowerLab 8/35 – 8 Channels
- PL3516 PowerLab 16/35 – 16 Channels
Research Systems
Working Heart Systems
These systems include the Working Heart Apparatus (includes a Thermal Circulator Pump and Peristaltic Pump) and:
- PL3508 PowerLab 8/35 (with LabChart software)
- MLS260 LabChart Pro software
- FE221 Bridge Amp (2)
- MLT844 Physiological Pressure Transducer (2)
- ML312 T-type Pod
- MLT1401 T-type Implantable Thermocouple Probe
- FE136 Animal Bio Amp
- MLA1210 Spring Clip Electrodes (Set of 3)
Ultimate Working Heart Systems
- PL3516B56-V Working Heart Ultimate System for Mice
- PL3516B51/S-V Working Heart Ultimate System for Rats
These systems include the Working Heart Apparatus (includes a Thermal Circulator Pump and Peristaltic Pump) and:
- PL3516 PowerLab 16/35 (with LabChart software)
- MLS260 LabChart Pro software
- FE224 Quad Bridge Amp
- MLT844 Physiological Pressure Transducer (2)
- SPR-671 Pressure Catheter (1.4F, Single, Straight, 15cm, Ny) (2)
- ML312 T-type Pod
- MLT1401 T-type Implantable Thermocouple Probe
- FE136 Animal Bio Amp
- MLA1214 Spring Clip Electrodes (Set of 3)
- FE180 Stimulus Isolator
- ML165 pH Amplifier
- MI-405 Miniature Glass Electrode for pH
- MI-409 Miniature Reference Electrode
- MLT1120 Micro-Oxygen Electrode
- MLT1122 Analog Adapter (for Micro-Oxygen Electrode)
- T402-TT Two Channel Tubing Flowmeter
- ME1PXN PXN-Series Inline Flowprobe - 1.2 mm (2)
- MLA260/L Stimulator Cable (4 mm shrouded to Alligator clip, 2 m)
- MLAC16 BNC Extension Cable Kit
- MLAC17 Front-End Extension Cable Kit
- SP2881 Transducer Brackets (2)
- AEC-10D Catheter Interface Cable (Low Profile to DIN 8, 10ft)
- SP0169 Teflon Insulated Platinum Wire (3 m)
- 170403 Latex Balloon (size 3 for rats, 10 pk)
- 170423 Flexible Teflon Balloon Catheter (for sizes 3 & 4)
Excessive thyroxine enhances susceptibility to apoptosis and decreases contractility of cardiomyocytes
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Type 1 diabetic cardiomyopathy in the Akita (Ins2WT/C96Y) mouse model is characterized by lipotoxicity and diastolic dysfunction with preserved systolic function
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GD, Kassiri Z, American Journal of Physiology: Heart and Circulatory Physiology, H2096–H2108, 2009
Impaired ATP turnover and ADP supply depress cardiac mitochondrial respiration and elevate superoxide in nonfailing spontaneously hypertensive rat hearts
Hickey AJ, Chai CC, Choong SY, de Freitas Costa S, Skea GL,
Phillips AR, Cooper GJ., American Journal of Physiology: Cell Physiology, C766–C774, 2009
The material on this page is provided in good faith and believed accurate at the time of writing. No responsibility will be taken, or liability accepted, for damages arising from the use of information herein. Readers are urged to check with respective manufacturers the accuracy of all product related information.
