REPOLARISATION ASSAYS

LANGENDORFF WHOLE HEART

ELECTRICAL AND MECHANICAL MEASUREMENTS IN THE LANGENDORFF WHOLE HEART

Figure 1 Electrical and mechanical measurements made on line using the Langendorff heart preparation.

Figure 1 shows records taken from a Langendorff whole heart preparation.(click to enlarge image ).
 

The parameters that can be directly measured include:

  • Developed tension
  • Developed pressure
  • Electrical activity

Derived measurements include:

  • Spontaneous beating rate
  • QT interval
 

Figure 2   Prolongation of QT interval in a whole heart Langendorff preparation.

 
 

Figure 2  shows representative ECG records (average 30 beats) made in the presence (red) and absence (black) of a test compound.  It is clear from the ECG measurements that after 10 minutes exposure to the test compound that there is  prolongation of the QT interval.

 

 
 

Figure 3  Measurements of heart rate variability and arrhythmia using the Langendorff heart preparation.

 
   
 

Figure 3  shows measurement of heart rate variability in the Langendorff whole heart preparation.
Instability in heart rate variability is associate with an increase in the potential for arrhythmias.  The above record shows data taken from a Langendorff heart preparation which displays early after depolarisations, giving rise to an ectopic beat,  which is then followed by increased period of diastole.  Both of which may contribute to an increase in heart rate variability. (click to enlarge image ).

 

 
 

Figure 4  Measurements of heart rate variability and arrhythmia using the Langendorff heart preparation.

 
 

Heart rate variability, shown by the blue trace,  is stable under control conditions showing a low variability.  After perfusion of a test compound the the heart rate variability was increased as clearly seen by the red line.  To express numerically the variation in heart rate  we can calculate the Coefficient of variability (CV): CV = (SD / mean). 
In the above example the coefficient of variability was increased by 34 Ქ by the test compound over control values, P<0.04, n=5. 
A test compound that produces a prolongation in the QT interval and increase the heart rate variability may well be pro-arrhythmic.

 
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