Biomedical Engineering Reference
In-Depth Information
If necessary, lubricate the lead connector sparingly using
sterile water to make its insertion easier. After tightening the
screws, insert the new device to the implantation pocket. If
the device is coated, rotate the uncoated opening off the
muscle and toward the skin to restrict the possibility of
muscle stimulation. In the case of unipolar pacing, the
device case must be in electrical contact with the tissue
under the skin. Otherwise, pacing must not be delivered to
the patient. Before suturing the pocket, interrogate the device
by means of the programmer to verify the telemetric com-
munication. If the correct pacing and/or sensing do not work,
disconnect the lead from the device and check the connector
and leads visually. Inappropriate signals might indicate mis-
alignment of the lead. In such a case it is necessary to correct
the lead's position.
If any unexpected complications occur, the leads must be
solved first. Several procedures were developed to loosen
stuck leads successfully, including:
Loosening stuck setscrews,
Fig. 12.8
Views of wrench rotation to free stuck setscrews [84] (©
2012 Boston Scientific Corporation or its affiliates. All rights reserved.
Used with permission of Boston Scienti fi c Corporation)
appropriate direction to retract the screw. This movement
looks like the so-called precession motion.
When the setscrew is loosened, continue its retraction by
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rotating as necessary.
The torque wrench that is used for this procedure must not
be sterilized and used again because its calibration cannot be
ensured.
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Lubricating the lead-device interface, and
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Exposing the lead's connector by cutting off the header
[ 84 ] .
These procedures can be used so that the lead does not
have to be replaced. The lead may be damaged during any
replacement of the device. As with every other intervention,
comply with standard procedures and ensure continuous
pacing of patients who are dependent on pacing during any
process in which the system of heart rhythm control is being
removed. At the same time, it is recommended that the integ-
rity of the leads be tested to ensure that the permanent leads
are still suitable for use.
12.4.2 Lubrication of Lead-Device Interface
If the screws are completely tightened and the lead cannot be
removed, it might be stuck because it is clogged by body
fluids or a silicone binding substance. In such cases, the ter-
minals might be released by lubrication of the lead-device
interface using a sterile heparinized physiological solution.
Fill a 1-ml syringe with a needle with heparinized physi-
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ological solution.
Gently insert the needle into the device header parallel
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with the lead between the body of the stuck lead and the
seals of the header up to the outermost connector block.
The needle must be visible through the header material.
Inject the heparinized physiological solution to the block
12.4.1 Loosening Stuck Setscrews
From time to time, the setscrews might be stuck in the tight-
ened position, which ensures that the leads cannot be retracted
from the header. The following procedure enables straight-
ening of the screw mechanism and loosening of the stuck
screws by means of a torque wrench.
Gently insert the bidirectional hexagonal torque wrench
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of connectors until it starts spilling out from the setscrew
cap on the same side of the header.
Take hold of the lead as close to the connector as possible
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and pull it out using a gentle force.
During this procedure, the lead's insulation might be
damaged, which will cause an immediate or gradual penetra-
tion of fluid. After this procedure is used, we recommend
planning suitable subsequent checks apart from the careful
visual check and thorough testing of electric functions by
means of the new device.
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into the hexagonal opening in the setscrew through the
central pothole in the seal plug. Using a torque wrench
different than a hexagonal one might lead to the rounding
of the hexagonal opening in the screw.
In accordance with the direction of the torque wrench
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rotation, find out whether the screw is stuck in the tight-
ened position.
Align the screw mechanism so that the stuck screw might
12.4.3 Exposing the Lead Connector by Cutting
Off the Header
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be loosened. Incline the torque wrench from the upright
position to the side, approximately 20°-30° from the ver-
tical axis of the central screw (see Fig.
12.8
). The wrench
bit is bent slightly by the inclination of the hexagonal
wrench at this angle. Start rotating the wrench in the
If the methods described above fail, there is the possibility of
preserving the leads at the price of the destruction of the
implanted device. There is a method that allows a back part
