Biomedical Engineering Reference
In-Depth Information
Fig. 10.2
Successful antitachycardia pacing (burst)
Fig. 10.3
Antitachycardia pacing therapy schemes [82] (© 2012 Boston Scientific Corporation or its affiliates. All rights reserved. Used with
permission of Boston Scienti fi c Corporation)
10.3.2 Shock
An ATP is a sequence of precisely timed pacing pulses
aiming to interrupt the reentry loop; the pulses are applied at
a rate higher than a patient's tachycardia heart rate (Fig.
10.3
).
It is characteristic of the burst ATP that all pacing intervals in
a burst are constant. In contrast, in the case of the ramp ATP,
the interval of consecutive pacing pulses in a burst gradually
decreases over time. When applying individual pacing pulses
following a burst, the respective interval is shortened by a
programmed shortening parameter value until the last pacing
pulse in a burst or the minimum interval value is reached.
The scan ATP is a sequence of pacing pulses, where the ATP
burst coupling interval decreases systematically. Ramp and
scan ATPs can be combined in certain ICDs.
An ICD applies shocks synchronously or asynchronously in
response to a sensed ventricular event. A shock has several
programmable and nonprogrammable parameters. The pro-
grammable parameters include energy, polarity, a shock vec-
tor, and, in certain ICDs, specific defibrillation waveform
parameters, as mentioned below.
Shock energy is programmable to values determined by
program application, from 0.1 J to the device maximum.
Time required for charging capacitors to a programmed level
depends on the programmed energy, battery status, and the
time elapsed since the previous shock or the last capacitor
