Biomedical Engineering Reference
In-Depth Information
Subsequently introduce the lead through the guiding sheath
into the coronary venous system. The lead might also be
introduced into the guiding sheath without the guide wire,
and this wire can be used later. Some LV leads might be
introduced by the stylet that changes the shape and flexibility
of the appropriate preformed distal end of the lead. Some
introducer systems contain another internal catheter that is
introduced from the external guiding sheath. This catheter
serves for mapping of the most suitable coronary vein for
implantation of the lead.
After the lead is positioned in the required place, the tip of
the guide wire is partially retracted to the pacing lead so that
it does not overhang the lead tip. When the lead is positioned
correctly, the guide wire is removed. Then, remove the
finishing wire from the package and insert it into the lead
according to the manufacturer's instructions. Both the lead
and finishing wire are kept at the position required for
implantation and, at the same time and in accordance with
the type of sheath, the guiding sheath is removed by cutting
or drawing over. If preformed leads are used, do not advance
the finishing wire at a full stretch but leave it drawn out
lightly when the guiding sheath is being removed. When the
preformed lead end is applied that way, it ensures higher sta-
bility. After the guiding sheath is removed, check again to
ensure the distal end of the lead did not change position. The
proximal end of the lead is kept close to the venous entry
site. The finishing wire is disconnected from the connector
by rotation and retraction and then is removed from the lead.
Using fluoroscopy, check again to ensure the lead did not
move. The finishing wire must not be stuck in the lead. If the
finishing wire cannot be retracted from the lead, remove the
fi nishing wire and the lead as one unit [ 56, 57 ] .
Fig. 12.6 Using a suture sleeve with a percutaneous implant [49]
(© 2012 Boston Scientific Corporation or its affiliates. All rights
reserved. Used with permission of Boston Scienti fi c Corporation)
tissue (Fig. 12.6 ). Use the grooves to ligate the suture sleeve
to the lead and secure the sleeve and lead to the fascia. Then
check again to ensure the lead does not slip in either
direction.
12.2
Evaluating Electrical Performance
of Pacing Leads
Before attaching the lead to the device, perform a test of
lead's electrical parameters. Check these parameters roughly
before fixing the lead and again after fixing and suturing the
lead. For the measurements, pacing system analyzers (PSA)
are used. Connect the lead connectors to a PSA recommended
by manufacturer. The connector pin of the bipolar leads
forms the cathode (−). The pin must be connected to the neg-
ative conductor of the PSA's patient cable. The ring of the
lead connector forms the anode (+). Connect it to the positive
conductor of the patient's cable. The sensed signals can
also be measured by an electrocardiographic recorder or an
oscilloscope. Depending on the possibilities of the device,
several pacing configurations might be measured at the left
ventricular leads.
Electric performance is evaluated by monitoring the data
described in the following sections.
12.1.7 Securing the Lead at the Venous
Entry Site
After the lead is positioned satisfactorily and fixed in the
endocardium, secure the lead to the vein using the suture
sleeve provided. Securing the lead will provide permanent
hemostasis and lead stabilization. The suture sleeve tie-down
technique can vary with the technique used to insert the lead.
For the venous cutdown method, slide the suture sleeve
into the vein past the distal preformed groove. Ligate the
vein around the suture sleeve to obtain hemostasis. Use the
proximal preformed groove to secure the suture sleeve to the
lead. By means of the same groove, secure the suture sleeve
and the lead to the adjacent fascia. After the lead is secured,
check to ensure that the lead does not slip in either direction
(Fig. 12.6 ).
For the subclavian venipuncture method, peel back the
introducer sheath and slide the suture sleeve deep into the
12.2.1 Amplitude of Intracardial Signal Sensing
Sufficient amplitude of the intrinsic intracardial electric sig-
nals (P wave in the right atrium, R wave in the ventricles, or
both) expressed in millivolts is necessary for permanent
sensing of the implantable device by the input sensing
amplifier. No pacing is required during this measurement.
The purpose is to assure that the intrinsic intracardial signal
is of adequate amplitude where it is being detected by the
device and to inhibit pacing. Furthermore, the integrity of the
sensing circuit must be assured. It deals with the integrity of
the lead and the lead-to-tissue touch. The intrinsic implant-
able devices might measure baseline-to-peak amplitude
 
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