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.