The isolated heart system (ihs) from emka TECHNOLOGIES is a versatile and powerful solution for pharmacological researchers investigating  hearts following drug challenges.

With an ihs, you can perform Langendorff heart (lh) and working heart (wh) experiments on hearts from mice, rats, guinea-pigs or rabbits.

There are two setups available:

• the working heart setup for isolated heart experiments in either the working heart or Langendorff perfusion mode,
• the Langendorff heart setup for isolated heart experiments in Langendorff mode only

Several parameters can be measured, including left ventricular pressure (lvp), perfusate temperature, perfusate flow rate and ecg. You may also stimulate the heart.

Up to three solutions (two perfusate and one cleaning solution) may be used in the Langendorff heart setup. Only one or two solutions can be used for the  working heart setup.

Setup for isolated heart experiments in Langendorff perfusion mode

In the Langendorff heart perfusion mode, the perfusate is pumped through the aorta towards the heart. It does not enter the left ventricle, but is diverted into the coronary arteries. The Langendorff heart mode permits the study of heart contraction, heart rate and vascular effects.

The system can measure lvp with a fluid-filled balloon connected to a cannula and pressure transducer, or simply using a pressure transducer to directly measure pressure within the left ventricle using a Millar Mikro-tip pressure catheter.

Setup for isolated heart experiments in working heart perfusion mode

In the working heart perfusion mode, the flow of perfusate mimics the flow of blood in situ, the perfusate enters the left atrium via the pulmonary vein, is pumped into the left ventricle, from where it is pumped into the aorta.

As the name implies, this technique allows the heart to perform its physiological pumping action, i.e. it performs pressure/volume work. The working heart technique therefore provides a complete analysis of heart function.

A Millar Mikro-tip pressure catheter can be inserted into the left ventricle to measure lvp directly. 

System components

The system provides experimental conditions to ensure survival of the isolated heart as long as possible: the temperature is kept constant at 37^oC, while oxygen and nutrients are provided by perfusing the heart.

The main components of the IHS are:

• mainframe
• heater/pump
• amplifiers
• pressure/flow regulator
• iox software

The mainframe is the central component containing the heart chamber, heat exchangers, perfusion heads and electrovalves... It is connected to all other components.

The thermostatically controlled heater/pump sends water at a constant temperature to the mainframe (to heart chamber walls and to heat exchangers).

Amplifiers are needed to amplify signals received from transducer(s) and ecg electrodes (if used). The supplied mainframe is equipped with up to four amplification modules. There are two types of amplification modules to amplify:

• signals from strain-gauge transducers, such as the signal from the pressure transducer measuring lvp.
• signals from ecg electrodes.

iox software acquires, analyzes and stores data and also controls hardware.

The pressure/flow regulator integrates perfectly into the IHS. It:

• regulates flow or pressure in the Langendorff configuration
• regulates pressure in the working heart configuration
• allows easy and instant switching between physiological solutions
• allows easy and instant switching between different operating modes (constant flow and constant pressure modes for Langendorff heart ; post-charge mode for working heart).
• amplify ecg signal for Langendorff heart

The last feature is particularly useful in working heart experiments: the heart is prepared in constant flow mode, then, once the cannulas are in place, you can switch to the post-charge mode.
 

Parameters recorded 

left ventricular pressure (lvp)

perfusion temperature
The thermostatically controlled heater/pump maintains the water temperature constant. For more precise control, a temperature sensor may be placed into a port of the perfusion head specially designed for this purpose.

electrocardiogram (ecg)
The ecg is usually obtained by applying contact electrodes to the heart's surface.

pO₂, pCO₂, pH, metabolite chemistry
Probes are available to measure O₂, CO₂, pH or metabolite chemistry in the perfusion liquid or in the used perfusate.
 

Stimulation
Specific stimulating electrodes are available. They are connected to a stimulator mainframe, which is itself controlled by iox.