Note:
Active fixation irritates the myocardium.
This can result in a temporary change in the measured values.
Wait until the measured values have become sufficiently stabilized. In general, this
occurs 5 to 10 minutes after fixation.
Note:
More details regarding electrophysiological measurements can be found in
the technical manual of the measuring device.
Note:
If the device system fails to terminate VT or VF during the DFT test, the
patient gets into a life-threatening condition. Therefore, it is essential to have an
external defibrillator ready during the DFT test.
19
Handling and Implantation
Suitable measuring devices
BIOTRONIK provides measuring devices calibrated to the properties of the active
devices for measuring pacing threshold, defibrillation threshold and intracardiac
potentials.
The input filter characteristics of the measuring device must be as close as possible
to those of the active device, especially when evaluating the intracardiac signal
amplitude.
Please refer to the technical manuals of the respective testing and measuring
devices for further details on performing measurements and tests.
Measuring the threshold
In order to measure the pacing threshold, the pacing rate of the measuring device
should be set slightly higher than the patient's intrinsic rate (if present).
The threshold is the lowest pulse amplitude at which the heart can still be paced.
Measuring intracardiac signal
amplitudes
The heart must not be paced externally while measuring the amplitudes of intrinsic
cardiac events.
Target values
Generally, the lead position is considered acceptable if the pacing threshold does
not exceed the maximum values shown below and if the intracardiac signal
amplitude is not less than the minimum value shown below:
Determinating the
defibrillation threshold
(DFT test)
Use the DFT test to find out which shock energy level and lead configuration can be
used to conduct a safe defibrillation on the patient.
Testing the complete device
system
When the lead is connected to the ICD and the ICD is implanted, you have to perform
a final function test of the device system using the programmer.
Ventricle
Measurement condition
Pacing threshold
Max. 1.0 V
Pulse width: 0.5 ms
Intracardiac signal
Min. 5 mV
