Abstract
Both a multicenter cohort and a post-approval registry of the Micra™ transcatheter pacemaker (Medtronic, Minneapolis, MN, USA) reported high successful implantation rates (>99%) with long-term stability of electrical performance and long-term safety. Therefore, there has been little discussion on the causes of cases of failure in terms of anatomical findings. We report a case of failure of implantation of the Micra because of a tortuous inferior vena cava (IVC) secondary to severe scoliosis. A retrospective assessment of 3D reconstructed computed tomography imaging could visualize the configuration of the IVC-right atrium junction. A preprocedural anatomical assessment may help to predict the implantability of the transcatheter leadless pacemaker or to image the manipulation of the delivery catheter.
<Learning objective: The Micra™ leadless pacemaker had high successful implantation rates (>99%). There has been little discussion on the causes of cases of failure in terms of anatomical findings. We report a case of failure of implantation of the Micra device because of a tortuous inferior vena cava secondary to severe scoliosis. A preprocedural 3D reconstructed computed tomography may help to predict the procedural difficulty of the Micra implantation or to image a manipulation of the delivery catheter.>
Key words: Leadless pacemaker, Micra, Complication
Introduction
Given the low risk of infection [1], a leadless pacemaker has been developed as an alternative to a conventional transvenous pacemaker with respect to efficacy and safety [2], [3], [4]. Both a multicenter cohort [3] and a post-approval registry [5] of the Micra™ transcatheter pacemaker (Medtronic, Minneapolis, MN, USA) reported high successful implantation rates (>99%) with long-term stability of electrical performance and long-term safety. There has been little discussion on the causes of cases of failure in terms of anatomical findings. We report a case of failed implantation of the Micra device in a patient with tortuous inferior vena cava (IVC) caused by severe scoliosis with a retrospective assessment of 3D reconstructed computed tomography (CT) imaging.
Case report
A 67-year-old man with a history of complete atrioventricular block, severe scoliosis, and long-term (>30 years) hemodialysis presented with signs of local infection, including local erythema, swelling, and warmth at the pocket of his pacemaker. The device was initially implanted on the rectus abdominis muscle with epicardial dual chamber leads for accompanied complete atrioventricular block and surgical aortic valve replacement 20 years prior to presentation. Subsequently, he underwent device replacement three times (Fig. 1). Considering the high risks associated with surgical total epicardial lead extraction, partial lead extraction and generator removal were performed with negative pressure wound therapy in the pocket, and a temporary pacing lead was placed in right ventricle (RV) via the right jugular vein. After 4-week vancomycin therapy, reimplantation of the pacemaker was scheduled. Given his stable hemodynamic status with RV pacing without atrioventricular synchrony, a leadless pacemaker (Micra™ transcatheter pacing system) was chosen as an alternative.
Fig. 1.
A preprocedural abdominal X-ray revealing severe scoliosis (triangle arrow) and an implanted pacemaker with epicardial leads (arrow).
Under mild sedation with midazolam and pentazocine and local anesthesia, vascular access was obtained via the bilateral femoral veins. A 4-polar catheter was inserted into the RV via the left femoral vein for back-up temporal pacing. Angiography of the IVC in the left anterior oblique 40° view demonstrated that the introducer headed toward the posterior wall of the IVC opposite the junction between the right atrium (RA) and the IVC (Fig. 2). We attempted steerable delivery catheter to advance to the RV, however, it was difficult to insert into the RV or to direct to the RV septum despite repositioning of the introducer sheath into the RA. The delivery catheter successfully inserted into the RV only once despite multiple attempts. Nevertheless, device deployment ended in failure because of incomplete device fixation and a high pacing threshold of 2 V. We were obliged to change the leadless pacemaker to a transvenous pacemaker using the left subclavian vein approach. Although a dual chamber pacemaker was a preferable choice to achieve atrioventricular synchrony, the left subclavian vein was not available for insertion of dual leads. A ventricular lead was successfully fixed in the RV mid-septum with a suitable pacing threshold of 1 V, and a generator was implanted into the subfascial layer of greater pectoral muscle. Subsequently, fixed RV pacing maintained hemodynamic stability with no local infectious signs at the pocket. The patient has been in a good clinical condition without pacemaker syndrome or further infections.
Fig. 2.
The angiography of inferior vena cava. Fluoroscopic image of the left anterior oblique (LAO) 40° view revealing that the introducer headed toward the posterior wall of IVC opposite the junction between right atrium and IVC. IVC, inferior vena cava; RA, right atrium; RV, right ventricle.
A retrospective 3D-reconstruction of CT revealed a severe tortuous IVC joined to the RA from left side with a steep angle between the IVC and RV apex (Fig. 3A) and from the posterior side (Fig. 3B) due to scoliosis. The present anatomical finding may have been responsible for failure of the implantation of the leadless pacemaker, resulting from the disturbance of flexible manipulation of the delivery catheter.
Fig. 3.
Three-dimensional reconstructed CT images of cardiovascular configuration. Three-dimensional reconstructed CT images of IVC (blue), RA (green), and RV (red) revealing the severe tortuous IVC joining the RA from left side with a steep angle between IVC and RV apex (dotted line) in the anteroposterior view (A), and from posterior side in left anterior oblique (LAO) and cranial view (B), due to scoliosis. By comparison, a normal IVC-RV apex (dotted line) and a normal IVC-RA attachment are represented in a case with a successful implantation (C, anteroposterior view; D, LAO and cranial view). IVC, inferior vena cava; RA, right atrium; RV, right ventricle.
Discussion
The present case is rare because of his severe tortuous IVC and IVC-RA junction secondary to severe scoliosis. This presented an impediment to successful implantation of the Micra system. In a multicenter cohort and a post-approval registry of the Micra, implant failure occurred in less than 1% [2,5]. In the multicenter-cohort, the details of failed cases were tortuous venous anatomy (n = 1), unsatisfactory pacing performance of high pacing threshold (n = 1), and major complications of cardiac perforation (n = 3), and pericardial effusion (n = 1) [2]. In the post-approval registry [5], there was no detailed description of implantation failure. Real-world data from Switzerland were also in line with the high success rate of 97.8% [6]. The literature includes two cases of failed implantation associated with cardiac tamponade and hemodynamic collapse [6]. Although few failure cases have been published, these publications appear to indicate that the causes of failed implantation can be classified in two groups: 1) procedural factors or operator's limited experience, and 2) patient-related factors including the anatomical abnormalities. First, focusing on technical training or the physician's experience, the paper showed that implant case number was not a determinant of procedural success and there were no differences in safety outcomes by training methods [7]. Second, anatomical abnormalities have been less well-investigated as predictors of implant failure.
On the product description, the Micra steerable delivery catheter has an in-plane distal shaft articulation angle of 120° and a length of 5.8 cm. Our patient had a steep coronal angle between IVC and RV apex (Fig. 3A) and a posterior connection from IVC to RA (Fig. 3B). By comparison, a representative case with successful implantation from our institute had a greater IVC-RV apex angle and a normal IVC-RA attachment (Fig. 3C and D). These anatomical anomalies in our case may interfere with a delivery catheter into the RV and optimal contact with the RV septum. It is worth noting that preprocedural anatomical assessment may help predict the implantability of the transcatheter leadless pacemaker and image a manipulation of the delivery catheter. Further assessment in a larger population should be required to identify the anatomical features that give rise to difficulty of Micra implantation.
Conclusions
We report a case of failed implantation of the Micra device in a patient with tortuous IVC caused by severe scoliosis with a retrospective assessment of 3D reconstructed CT imaging. A preprocedural anatomical assessment could visualize the configuration of the IVC-RA junction and may help to predict the procedural difficulty of the Micra implantation or to image a manipulation of the delivery catheter.
Declaration of Competing Interest
The authors declare that there is no conflict of interest.
Acknowledgments
All authors contributed to the interpretation of the patient's data, the drafting of the manuscript, or revising it critically for important intellectual content.
We would like to thank Editage (www.editage.com) for English language editing.
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