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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
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Figure 2
Prolongation of QT
interval in a whole heart Langendorff preparation.
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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.
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Figure 3
Measurements of heart
rate variability and arrhythmia using the Langendorff heart preparation.
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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 ).
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Figure 4
Measurements of heart
rate variability and arrhythmia using the Langendorff heart preparation.
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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 ± 12% 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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