User manual
ECG signal with additional ECG electrodes. Also the time interval of the R-R waves in the
ECG signal is evaluated. In the fix-rate mode (bradycardia, asystole, tachycardia), it is
possible to set up fixed repetitive frequency of stimulation pulses on the stimulator (usually
30-180 stimuli/min), independently from the heart’s activity.
The size of the stimulation pulse’s energy varying from tenths to single units of joules
can be set up by means of the maximum size of current passing through the patient (0-200
mA). The size of the stimulation pulse’s voltage usually varies between tens to hundreds of
volts. The length of the pulse and the shape of the pulse depend on the apparatus’ type and
manufacturer. The length of the pulse not exceeding 5 ms is called „Short-Pulse Duration“,
the pulse has a typical shape of a stimulation pulse with exponential decrease of the current,
just like in case of implantable cardiostimulators. The length of the pulse not exceeding 20 ms
with variable size of the current is called „Short-Pulse Duration, Current Drop Off (short
duration of the pulse with current decrease by 15-20 % of the current maximum). The shape
of the pulse is similar to the DMT defibrillation pulse. The length of the pulse not exceeding
40 ms with constant size of the current is called “Long-Pulse Duration, Constant Current”.
The pulse’s course is rectangular and the size of the current in this pulse is half compared to
the previous two pulses.
Antitachycardiastimulation
Just like some external defibrillators, also the implantable defibrillators are capable of
heart stimulation. This stimulation, which may precede defibrillation, is called antitachycardia
stimulation (ATP - Antitachycardia pacing). ATP is used to interrupt tachycardia (cardiac
arrhythmia, increased heart rhythm exceeding 90 beats/min) of the heart muscles. ATP’s
effectiveness was clinically confirmed in ventricular tachycardia not exceeding 240 beats/min.
The energy of the ATP stimulation pulse is several digit numbers lower than in the
defibrillation pulse. The energy of the ATP pulse reaches maximum values of tenths to single
units of millijoules (mJ). The shape and the parameters of the ATP stimulation pulse are very
close to the cardiostimulator’s stimulation pulse. The voltage of the ATP pulse’s entering
edge varies between -5 V and -7.5 V; the pulse’s width varies between 0.05 ms and 2 ms.
ATP is based on an application of a dose of stimulation pulses. The first pulse of this
dose is applied before the beginning of the cardiac contraction. The delay between the last
sensed cardiac contraction and the first stimulation impulse of the ATP dose is called the
coupling interval (CI). The coupling interval may be fixed, and then its length is firmly set in
milliseconds, or it may be adaptive, and then its length is calculated in % of the length of the
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