Biomedical Engineering Reference
In-Depth Information
PSP
Pacing
impulse
amplitude
Pacing impulse
amplitude decreasing
Frequently
follow-ups
3 m.
BOL
ERN
ERT
EOL
Fig. 2.3
Longevity phases [32] (© 2012 Boston Scientific Corporation or its affiliates. All rights reserved. Used with permission of Boston
Scienti fi c Corporation)
such a battery is always about 3 V, which is given by the
electrochemical potentials of lithium and iodine. The capac-
ity, which depends on the type of battery, ranges from 0.8 to
1.8 Ah or more. The current consumption is approximately
10
Table 2.1
Usual magnet output pacing rates [16, 18 ]
Beginning
of Life (per min)
Elective replacement
time (per min)
Manufacturer
Biotronik
90
80
Boston Scienti fi c
100
85
A; for example, for a particular type of pacemaker, cur-
rent consumption amounts to 13.3
m
ELA
96
80
m
A during pacing and
Medtronic
85
65
10.3
A during inhibition [16]. The life span of a device
depends on the pacing mode used and the number of electric
stimuli; the lifespan of defibrillators especially depends on
the number of shocks delivered or charging cycles. After dis-
charging the battery, a new device must be implanted. The
leads usually remain until they are damaged.
Pacemaker battery status can be evaluated either by means
of a telemetric connection using a programmer or by the out-
put paced rate when a magnet is positioned over the pace-
maker. A window on the programmer showing the battery
status might display a date of the last battery test, previous
and recent indicators of the battery's status, the recent output
of the pacemaker when a magnet is used, as well as esti-
mated service time remaining based on the measurements
indicating the rest of the battery capacity. A valid technical
standard [17] requires an AIMD containing a source of
energy must provide a warning signal on depletion of the
energy source in advance. Time period of the warning under
normal usage of the device must be at least as long as the
recommended time period between the clinical ambulatory
follow-ups. The manufacturer designates when an exchange
of the device is recommended. The standard [ 17 ] de fi nes the
following stages of service life (Fig.
2.3
) according to the
remaining electric capacity of batteries:
Beginning of service (beginning of life) - the implantable
m
St. Jude Medical
98.6
86.3
Vitatron
100
86
Of the terms and abbreviations above, the standards use
the first ones listed. However, in practice, those in parenthe-
ses are used more often. Some manufacturers might also use
an identifier called
elective replacement near
(ERN). After
this point, it is recommended that patient follow-up be per-
formed more often.
Approximately 3 months after elective replacement time,
when the battery is being gradually discharged, the device
reaches the stadium called the end of life (EOL). When the
EOL stadium is reached, some arrangements dealing with max-
imal reduction of the power consumption are made automati-
cally. The mode of dual-chambered pacemakers changes to a
single-chamber mode (DDD and VDD changes to VVI) and
the lower rate limit decreases. With further gradual discharging
of the battery during the EOL state, the pacemaker reduces the
amplitude of electric output. When the EOL is reached, the
telemetry does not have to be guaranteed any longer.
If a magnet with the appropriate features is positioned
over the implanted pacemaker (it is not applied for
defibrillators) and if this function has not been changed by
programming, the mode of pacing changes from the pro-
grammed mode to an asynchronous mode (D00, V00, or
A00), and the paced rate (frequency) is set according to the
manufacturer's requirements (Table
2.1
). That way, it is pos-
sible to check the battery status of the implanted pacemaker
if a programmer is not available.
•
device is authorized by the manufacturer for the first time
as capable of launching.
Recommended replacement time (elective replacement
•
time; elective replacement indicator) - indicator of the
energy source reaches a specific value that had been
appointed in advance by the manufacturer of the implant-
able device for its recommended exchange. This point is
the beginning of the prolonged service period.
Prolonged Service Period- the time period after the point of
2.4
X-Ray Identi fi er
•
the recommended replacement time when the implantable
device continues to operate as specified by the manufacturer.
End of Service (end of life [EOL]) - the prolonged ser-
According to the standards [17], in case of unexpected change
in performance, an implantable device must be identifiable
by a noninvasive procedure that does not require the use of
tools that are usually unavailable at hospitals. Specific devices
(e.g., a programmer) are considered unacceptable. Therefore,
•
vice period has expired and another pacing function is
not specified nor can be expected.
