Abstract
After unsuccessful implantation at the conventional right atrial appendage site, an atrial leadless pacemaker was implanted at the high right atrial septum. Electrical parameters were maintained during 6‐month follow‐up.
Keywords: atrial pacing, device implantation, leadless pacemaker, right atrial appendage, right atrial septum
Leadless atrial pacemakers have been developed to avoid complications related to transvenous atrial leads and are generally implanted at the base of the right atrial appendage (RAA) [1, 2]. Although this site is considered practical in terms of fixation and electrical performance, acceptable pacing parameters cannot always be obtained. In addition, there is no established approach when conventional atrial implantation is unsuccessful.
An 84‐year‐old woman was referred for permanent pacemaker implantation because of symptomatic bradycardia due to complete atrioventricular block. Because the right ventricular cavity was small, advancement of the delivery catheter using the standard technique was difficult. A ventricular leadless pacemaker was therefore implanted using a snare‐assisted technique [3].
Subsequently, implantation of an atrial leadless pacemaker was attempted. Initially, multiple conventional implantation sites around the RAA base were evaluated. Among these sites, the site considered most favorable based on its anatomical position and commanded atrial electrogram (cEGM) morphology was selected for screw fixation (Figure 1). The current‐of‐injury (COI) amplitude was 1.0 mV before fixation and 1.5 mV after fixation. Atrial capture was absent at 6.0 V/0.4 ms both before and after fixation. Despite approximately 15 min of observation after fixation, atrial capture remained absent at 6.0 V/0.4 ms; therefore, the device was repositioned.
FIGURE 1.
Unsuccessful implantation at the conventional right atrial appendage site. (A) Fluoroscopic image demonstrating the positioning and screw fixation of the atrial leadless pacemaker at a conventional right atrial appendage (RAA) site. (B) Commanded atrial electrograms recorded before and after screw fixation. The current‐of‐injury amplitudes were 1.0 mV before fixation and 1.5 mV after fixation. Atrial capture was absent at 6.0 V/0.4 ms both before and after fixation. Despite screw fixation and approximately 15 min of observation, atrial capture remained absent at 6.0 V/0.4 ms.
The device was subsequently repositioned to explore additional atrial sites, with the protective sleeve used during movement between sites. Premapping was performed at each candidate site by pacing at 3.0 V/0.4 ms. Atrial capture was observed at several sites, and representative cEGMs are shown in Figure 2. These sites were assessed without screw fixation; therefore, complete implantation parameters were not obtained.
FIGURE 2.
Commanded atrial electrograms during systematic premapping. Representative commanded atrial electrograms (cEGMs) recorded at atrial sites where capture was observed during premapping at 3.0 V/0.4 ms. These sites were assessed without screw fixation.
At the high right atrial septum, although the cEGM morphology appeared less favorable than that observed at the conventional RAA site, reproducible and consistent atrial capture was obtained. Therefore, screw fixation was performed (Figure 3). Before fixation, the COI amplitude, impedance, pacing threshold, and sensing amplitude were 2.0 mV, 300 Ω, 3.5 V/0.4 ms, and 2.0 mV, respectively. After fixation, these values were 2.0 mV, 260 Ω, 2.25 V/0.4 ms, and 1.3 mV, respectively. Stable fixation was confirmed by a gentle tension test (Video 1).
FIGURE 3.
Final implantation at the high right atrial septum. (A) Fluoroscopic images demonstrating the positioning of the atrial leadless pacemaker at the high right atrial septum. (B) Commanded atrial electrograms recorded before and after screw fixation at the final implantation site. The current‐of‐injury amplitude was 2.0 mV both before and after fixation. The pacing threshold was 3.5 V/0.4 ms before fixation and 2.25 V/0.4 ms after fixation. (C) Cardiac computed tomography and three‐dimensional reconstruction demonstrating the anatomical location of the atrial leadless pacemaker at the high right atrial septum and its relationship to the superior vena cava, right atrial roof, and right atrial appendage region.
VIDEO 1.
Tension test confirming stable fixation at the high right atrial septum. Fluoroscopic recording demonstrating the tension test after screw fixation of the atrial leadless pacemaker at the high right atrial septum. Gentle traction was applied to confirm adequate mechanical engagement and stability of the device before release of the tether. Video content can be viewed at https://onlinelibrary.wiley.com/doi/10.1002/joa3.70486.
On the following day, the pacing threshold improved to 0.5 V/0.25 ms, with a sensing amplitude of 0.9 mV and impedance of 280 Ω. Cardiac computed tomography confirmed the device position at the high right atrial septum (Figure 3). At 6‐month follow‐up, the pacing threshold remained 0.5 V/0.25 ms, with a sensing amplitude of 1.0 mV and impedance of 250 Ω. No procedure‐related or device‐related complications were observed during the 6‐month follow‐up period (Table 1).
TABLE 1.
Electrical parameters of the atrial leadless pacemaker during implantation and follow‐up.
| Site/time point | COI (mV) | Sensing amplitude (mV) | Impedance (Ω) | Pacing threshold |
|---|---|---|---|---|
| RAA site, before fixation | 1.0 | Not recorded | Not recorded | No atrial capture at 6.0 V/0.4 ms |
| RAA site, after fixation | 1.5 | Not recorded | Not recorded | No atrial capture at 6.0 V/0.4 ms |
| High right atrial septum, before fixation | 2.0 | 2.0 | 300 | 3.5 V/0.4 ms |
| High right atrial septum, after fixation | 2.0 | 1.3 | 260 | 2.25 V/0.4 ms |
| Post‐procedure day 1 | — | 0.9 | 280 | 0.5 V/0.25 ms |
| 6‐month follow‐up | — | 1.0 | 250 | 0.5 V/0.25 ms |
Note: The sites shown in Figure 2 were assessed by premapping without screw fixation; therefore, complete implantation parameters were not obtained at these sites.
Abbreviations: COI, current of injury; RAA, right atrial appendage.
At the conventional RAA site, a COI was observed after fixation; however, adequate pacing performance could not be obtained. Importantly, the finding was persistent noncapture at 6.0 V/0.4 ms rather than a high but measurable pacing threshold. Recent data suggest that very high but measurable acute pacing thresholds during atrial leadless pacemaker implantation may substantially improve after device release when an adequate COI is present [4]. However, these observations involved sites at which atrial capture was present, whereas a measurable threshold could not be obtained at the RAA site in the present case. Although the optimal observation period before repositioning in the setting of persistent noncapture has not been established, we elected to reposition the device because reliable atrial capture could not be demonstrated despite fixation and observation.
Non‐RAA atrial implantation has also recently been reported. Ogano et al. described atrial leadless pacemaker implantation in the right anterosuperior region with stable electrical performance [5]. Anatomical studies have suggested that the right atrial septum may be a suboptimal fixation site for atrial leadless pacemakers [1]. Accordingly, this single case should not be interpreted as establishing the high right atrial septum as a preferred alternative to the RAA. In this case, successful implantation was achieved at the high right atrial septum after unsuccessful conventional RAA implantation. Site selection should be based on a comprehensive assessment of atrial capture, electrical parameters, fixation stability, anatomical suitability, and the overall clinical context.
Author Contributions
Morio Ono: conceptualized the case report and led the manuscript drafting. Toshihiko Gokan, Yuya Nakamura, Taku Asano, and Junko Honye: contributed equally to the case report by assisting with data collection, providing critical insights during the intervention, performing diagnostic imaging analysis, and revising the manuscript for intellectual content.
Funding
The authors have nothing to report.
Ethics Statement
This case report did not require formal ethical approval, as it describes a single patient's case without any experimental intervention. All patient data were anonymized in accordance with institutional policies and the Declaration of Helsinki.
Consent
Written informed consent was obtained from the patient for the publication of this case report and the accompanying images.
Conflicts of Interest
The authors declare no conflicts of interest.
Acknowledgments
The authors thank Yugo Ito (Abbott Medical Japan) for providing non‐financial technical assistance with EnSite X image preparation and figure formatting. Abbott Medical Japan had no role in the clinical management, data interpretation, or manuscript content.
Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.