Discussion
To our knowledge, this is the first case of an Aveir LP retrieval where
the docking button was difficult to access due to its inappropriate
position in the RV. Ultimately, the Aveir LP was successfully retrieved
with a standard retrieval catheter by releasing the wedged docking
button using a loop wire technique.
Sato et al. reported that the RV cavity is not smooth and numerous
trabeculations develop in the RV according to the endoscopic images of
the RV1). On CT in this case, the helix of the Aveir
LP appeared to be attached to the RV endocardial surface, including the
tissue between or even on the trabeculated regions. The lack of firm
burrowing of the helix into the deeper RV endocardial tissue may have
caused the elevated threshold of the Aveir LP because the electrode was
located in the center of the helix. In addition, the unstable fixation
of the helix could have resulted in the progressive slippage of the
Aveir LP. To avoid such an inappropriate placement of the helix, it is
important to ensure that the RV septum is clearly contrasted by the
contrast agent over the protective sleeve with the helix in the LAO view
and to screw the helix perpendicular to the RV septum with appropriate
tension.
Minami et al. reported the feasibility and safety of the retrieval of
long-term implanted Nanostim LPs after a mean duration of 4
years2). They evaluated the movement of the LP docking
button during the cardiac cycle under fluoroscopic imaging and defined a
swinging angle of more than 15° as a considerable SM. Nanostim LPs
implanted on the RV mid-septum adhere to the sub-valvular area, which
contributes to the disappearance of the SM. LPs with significant SM
located in the RV septal apex have been retrieved successfully at a
higher rate than LPs without SM. Based on this report, the evaluation of
the Aveir LP position in the RV on the chest x-ray or CT and the
presence or absence of the SM of the Aveir LP on fluoroscopic imaging
may be helpful in determining whether the Aveir LP can be retrieved or
not. In the present case, the fluoroscopic imaging 4 months after the
implantation showed the disappearance of the significant SM. Considering
the post-implantation period, we estimated that the disappearance of the
SM was mainly due to the inappropriate fixation position of the docking
button on the inferior wall of the RV and not to the adherence to the
surrounding tissue. Reddy et al. reported the Nanostim LP removal
outcomes as having a high removal success rate3). In
one case, a variable electrode catheter was used to change the direction
of the docking button, allowing the docking of a retrieval catheter and
the successful retrieval. We first attempted to capture the docking
button of the Aveir LP with a retrieval catheter, but as shown by the
intraoperative RV angiography, the docking button was fixed to the
inferior wall of the RV and could not be captured. As a next step, we
tried to release the docking button using a deflectable electrode
catheter as reported by Reddy et al.3) However, the
mobility of the electrode catheter was limited and we were not able to
release the docking button. After that, we used the loop wire technique
with the incorporation of a pigtail catheter and
RadifocusTM guidewire through the right internal
jugular vein. Maisch et al. demonstrated the utility of the loop wire
technique for pacemaker lead extractions4). That
technique continues to be widely employed in pacemaker lead removal
procedures. In our case, the RadifocusTM guidewire and
pigtail catheter were initially passed through the inferior wall of the
RV. Then, we used the snare through the right femoral vein to grasp the
pigtail catheter via the RadifocusTM guidewire as a
loop snare technique. Finally, we were able to release the docking
button and retrieve the Aveir LP with a retrieval catheter with
relatively slight traction. Our method could facilitate removals in
cases with an Aveir LP when removal with a retrieval catheter is
difficult due to an inappropriate position of the docking button.
Further experience is warranted to evaluate the feasibility and safety
of our method in cases where the Aveir LP has been implanted for longer
than 6 months.