Working Heart

Overview:

The first method of perfusing isolated hearts was introduced by Oscar Langendorff, which uses a retrograde perfusion. A second method of perfusing isolated hearts, was developed by Neely et al in the 1960’s. This is known as the ‘working heart’ method. This method allows the heart to pump fluid via the normal left ventricular circulatory pathway as the perfusate enters the heart via the cannulated left atrium, passes through to the left ventricle and is ejected out of the aorta.

Commonly with the working heart method, the atrial pressure (preload) and aortic resistance (afterload) are regulated experimentally as the heart circulates the perfusate solution. The aortic and coronary flows can also be monitored and the resulting cardiac output calculated.

Method:

For adequate perfusion of the heart a suitably sized cannula for insertion into the aorta is provided. Initially the heart is perfused in the Langendorff mode. Then a second cannula is inserted into the pulmonary vein to perfuse the left atrium. After successful cannulation of pulmonary vein, the perfusion is switched to the working heart mode. There are then a number of parameters that can be measured from the working heart preparation.

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 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 to the perfusate line exiting the aorta.

Contractile Force
A simple method that can be used to measure the contractile force of the heart, is to connect the apex of the heart to a force transducer and bridge amp via a pulley system.  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 of a Langendorff preparation can be measured using a bioamplifier and suitable 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, monophasic action potentials can be measured form single cardiac cells.

Temperature
It is important that a stable temperature is maintained in the isolated heart.  The temperature can be measured with a t-type temperature probe and 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 sinoatrial node is crushed or the right atrium excised. Pacing voltage is determined as a set percentage (normally 110-150%) above the voltage required to capture (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 conjuction with the Stimulator panel in LabChart, can be used to control the frequency of the stimulator pulses.

Left Ventricular Pressure/Volume
As the working heart is a closed system, with the perfusate following the normal left sided circuitory, simultaneous left-ventricular pressure and volume measurements can be made using a Millar Pressure Volume catheter and control unit. Further heamodynamic measurements can be made from the resulting Pressure-Volume loops.  More details regarding PV measurements can be found on the Ventricular Pressure-Volume application pages.

Atrial, Aortic and Coronary Flow
By inserting a suitable 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 a suitable oxygen concentration of the perfusate solution. These can be measured if required using a suitable pH electrode and pH amplifier 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:

LabChart
LabChart software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with 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.


 

Using LabChart, the following raw inputs can be made from a Working Heart experiment using the standard equipment:

  • Atrial (Preload) Pressure
  • Aortic (Afterload) Pressure
  • ECG
  • Temperature


The following calculated measurements can be made using LabChart functionality:

  • Heart Rate (cyclic rate of Aortic Pressure)
  • Left Ventricular Systolic & Diastolic Pressure (cyclic Maximum and Minimum of LVP)
  • dV/dT Atrial Pressure (1st derivative Atrial Pressure)
  • dV/dT Aortic Pressure (1st derivative Aortic Pressure)


Additional measurements that can be made with the ultimate working heart systems include:

  • Left Ventricular Pressure and Volume
  • Atrial Flow Rate
  • Aortic Flow Rate
  • Coronary Flow rate (Atrial Flow-Aortic Flow)
  • Cardiac Output
  • pH
  • Oxygen concentration or consumption


LabChart Extensions include:

  • Cardiac Axis LabChart Extension: Automate thecalculation of frontal plane ECGs and vector cardiograms and display ofthe instantaneous cardiac vector.
  • SAECG(signal averaged ECG) LabChart Extension (MAC only): Calculates theaverage cycle of ECG signals and automatically identifies specificationwaveforms and cardiac indices.
  • PeakParameters LabChart Extension: Determines a number of parameters for anindividual peak and is ideal for analyzing cardiac action potentials.


Blood Pressure Module (Windows)
The MLS370/7 Blood Pressure Module for Windows automatically detects, analyzes and reports cardiovascular parameters from arterial or ventricular pressure signals.


The settings dialog allows the user to select ventricular pressure for analysis and the Classifier View allows for easy selection of pressure waveforms for further analyses. Pressure cycles that are contaminated by artifact, have abnormal cycle heights or cycle durations (frequency) can be excluded from analysis using the classifier.

The Analysis View displays pressure cycles as beat-by-beat or as the average of a specified number of cycles. Ventricular parameters such as EDP, Max dP/dt, Min dP/dt, Min and Max Pressure are labeled. These measurements along with other calculated parameters are logged in the Table View for easy exporting.

Features and benefits include:

  • Suitable for analysis of pressure signals from humans as well as large and small animals
  • Pressure signals can be analyzed in real time during acquisition
  • The BP Classifier makes detection and exclusion of atypical waveforms easy
  • Parameters can be displayed as continuous data on separate channels
  • Values are logged to the Table View
  • Averages any number of pressure waveforms


Calculated arterial parameters include:

  • Systolic, Diastolic and Mean Pressure
  • Pulse Pressure
  • Dichrotic Notch Pressure
  • Ejection and Non-ejection duration
  • Cycle Duration
  • Heart Rate


Calculated ventricular parameters include:

  • Maximum Pressure
  • Maximum dP/dt
  • Isovolumic Relaxation
  • Minimum Pressure
  • Minimum dP/dt
  • Mean Pressure
  • End Diastolic Pressure (EDP)
  • Maximum-Minimum Pressure
  • Contractility Index


ECG Analysis Module (Windows)
The MLS360/7 ECG Analysis Module provides a comprehensive set of tools that automatically detects and reports values of ECG recordings. The software can be used with ECG recordings taken from humans and many species of animals from pigs through to mice.

It provides

  • Real-time analysis and data extraction of ECG parameters
  • PQRST amplitudes
    • Time intervals such as RR, PR, JT, QT and QTc
    • Analysis of ECG parameters in real-time or offline
  • Automated detection and averaging of ECG cycles
  • Automated tabulation and data extraction of ECG parameters
  • Automated real-time or offline ECG Plots
    • Graphical QT vs RR, QT vs Time & RR vs Time plots
    • Waterfall plot


Heart Rate Variability (HRV) Module (Windows or Macintosh)
The MLS310 HRV Module provides a comprehensive set of tools for the analysis and display of variation in the interval between heartbeats in human and animal electrocardiogram recordings.

The HRV module provides:

  • Detects and analyzes R waves & RR interval variation in ECG real-time or offline recordings
  • Includes or excludes ectopic beats from analysis
  • Adds R waves or remove short artifacts from analysis
  • Provides data export options
  • Provides automated HRV Analysis Windows
    • Poincaré Plot, Tachogram & Spectrum
    • Period Histogram & Delta NN Histogram

Dose Response Module (Windows)
The MLS390/7 Dose Response Module provides easy analysis of dose response type data (response to stimulation by chemical, electrical or physical agonists) recorded in LabChart from various studies including:

  • Muscle contraction
  • Enzyme activity
  • Hormone secretion
  • Heart rate
  • Blood pressure
  • Membrane potential

This module provides:

  • Real-time or offline analysis
  • 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
 

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:

ADInstruments provides a number of versatile hardware solutions for Working heart experiments. There are both standard and ultimate systems for working heart experiments in a number of species from mice to rabbits. (The systems can be configured for larger animals).

Working Heart Systems


These systems include:


Ultimate Working Heart Systems

These systems include:



 

 

Transgenic rat hearts expressing a human cardiac troponin T deletion reveal diastolic dysfunction and ventricular arrhythmias.
Norbert Frey, Wolfgang M. Franz, Katharina Gloeckner, Michael Degenhardt, Matthias Muller, Oliver Muller, Hartmut Merz, Hugo A. Katus, Cardiovascular Research, 254-264, 2000

Protection of hearts from reperfusion injury by propofol is associated with inhibition of the mitochondrial permeability transition.
Sabzali A. Javadov, Kelvin H.H. Lim, Paul M. Kerr, M.-Saadah Suleiman, Gianni D. Angelini, Andrew P. Halestrap, Cardiovascular Research, 360-369, 2000

Proteolytic N-terminal truncation or cardiac troponin 1 enhances ventricular diastolic function
J C Barbato, Q-Q Huang, M M Hossain, M Bond and J-P Jin, Journal of Biological Chemistry, 6602-6609, 2005

Influence of substrate supply on cardiac efficiency, as measured by pressure-volume analysis in ex vivo mouse hearts
O-J How, E Aasum, S Kunnathu, K L Severson, E S P Myhre and T S Larsen, American Journal of Physiology: Heart and Circulatory Physiology, H2979-H2985, 2005

Citations Database


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.

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