Time-dependent improvements in pacing thresholds with lumenless leads placed in the right atrium

Abstract

Background

Traditional pacemaker implantation often poses risks, such as perforation when positioning atrial leads at the right atrial appendage (RAA). Recent advancements in delivery catheters have enabled atrial lead placement in the right atrial septum, potentially mitigating RAA-related complications. However, the performance of lumenless leads in this context remains unclear.

Objective

This study was performed to assess the performance of lumenless leads as atrial leads.

Methods

Forty-four consecutive patients undergoing pacemaker implantation with lumenless atrial leads were enrolled. Lead implantation was performed using a 3830 SelectSecure lead and C315HIS-sheath. Pacing parameters were collected immediately after screwing, 3 and 5 minutes later, at the end of the procedure, and at every 6-month follow-up.

Results

Lead parameters including P-wave, pacing threshold, and impedance significantly improved over time. The threshold levels from 2.00 ± 0.72 V/0.4 msec immediately after screwing to 1.45 ± 0.57 V/0.4 msec at 5 minutes, 0.95 ± 0.38 V/0.4 msec at the end of the procedure, and 0.78 ± 0.39 V/0.4 msec at discharge. Initially, threshold levels were >2.5 V/0.4 msec in 15 cases; however, they decreased to <2 V/0.4 msec by the end of the procedure. At discharge, 13 of the 15 cases showed a threshold decrease to <1 V/0.4 msec. During follow-up, no threshold increase (>1 V), lead revision, or battery depletion was observed.

Conclusion

Lumenless lead placement in the right atrium results in threshold decrease over time. Therefore, allowing a waiting period instead of immediately repositioning the lead may be more effective when thresholds are high after screwing.

Graphical abstract

Key findings.

• ▪The placement of lumenless leads in the right atrium resulted in a decrease in pacing thresholds over time.
• ▪Even when thresholds were high, waiting instead of immediately repositioning the lead could effectively reduce the thresholds.
• ▪During the postoperative and follow-up periods, no increases in thresholds, lead revisions, or battery depletion were observed.

Introduction

During pacemaker implantation, atrial leads are generally positioned at the right atrial appendage (RAA). However, the walls of the RAA are partially thin and pose a risk of perforation. In addition, active fixation leads are reportedly associated with a higher incidence of pericardial effusion and pericardiocentesis than passive fixation leads.¹

Recently, opportunities to implant leads with delivery catheters have increased, particularly in conduction system pacing (CSP). Delivery catheters have been developed primarily for ventricular lead implantation; however, these tools also can be used for atrial lead implantation. Atrial leads implanted in the right atrial septum using delivery catheters can prevent RAA perforation.

Lumenless leads and delivery catheters are often used in CSP² and atrial leads. However, their performance in the right atrium is unclear. Therefore, this study aimed to investigate the performance of lumenless leads as atrial leads in the right atrium.

Methods

Patient selection

Patients who underwent pacemaker implantation with lumenless atrial leads were enrolled from June 2022 to April 2024. The study protocol was approved by the Institutional Review Board of Saku Central Hospital (R202405-01), and all patients provided written informed consent. The research reported in this study adhered to the guidelines of the Declaration of Helsinki (revised in 2013).

Procedure details

Atrial lead implantation was performed using a 3830 SelectSecure lead and a C315HIS-sheath (Medtronic Japan Co., Ltd., Tokyo, Japan). The leads were positioned in the right atrium. Before screwing, we confirmed that the right atrial myocardium could be captured at 2 V/0.4 msec. The threshold, P-wave amplitude, and impedance in a bipolar fashion were measured immediately after screwing, 3 and 5 minutes later, and at the end of the procedure. Even if the initial threshold was high, waiting was recommended for at least 5 minutes. If the threshold tended to decrease and the injury current could be confirmed, lead replacement was not performed. In contrast, the lead was replaced when the threshold was >3 V/0.4 msec and did not decrease in 5 minutes.

Data collection and follow-up

Baseline data, including patient demographic information, echocardiographic data, pacing lead electrograms, pacing parameters, and 12-lead electrocardiogram were collected.

After device implantation, pacing parameters were collected at discharge (days 1–7 postoperation) and at regular follow-ups every 6 months.

Statistical analyses

The pacing parameter values (capture threshold, P-wave amplitude, and impedance) are presented as means and standard deviations. Categorical variables are presented as numbers and percentages. Unpaired t tests were used for comparisons among each group, and groups were compared using Fisher exact test. A 2-sided P < .05 was considered significant. Statistical analyses were performed using EZR version 1.61 (Saitama Medical Center, Jichi Medical University, Saitama, Japan).

Results

Baseline characteristics

A total of 44 patients were analyzed, and their characteristics are listed in Table 1. Mean age was 76.0 ± 8.6 years, and 23 (52.3%) patients were men. Indications for pacemaker implantation were sinus node dysfunction in 13 patients (29.5%), atrioventricular block in 22 (50.0%), cardiac resynchronization therapy in 4 (9.1%), and implantable cardiac defibrillator in 2 (4.5%). The QRS duration was 128.3 ± 29.5 ms, and the ejection fraction of the left ventricle was 54.4% ± 16.7%.

Table 1.

Patient characteristics for the entire population

	All patients (n = 44)
Age, y	76.0 ± 8.6
Men	23 (52.3%)
Hypertension	14 (31.8%)
Diabetes	10 (22.7%)
Prior atrial fibrillation (AF)	12 (27.3%)
post ablation	7 (15.9%)
Coronary artery disease	6 (13.6%)
Nonischemic heart disease	7 (15.9%)
Cardiac surgery history	13 (29.5%)
Pacing indication
Sinus node dysfunction (SND)	13 (29.5%)
Atrioventricular block (AVB)	22 (50.0%)
SND with AVB	3 (6.8%)
CRT	4 (9.1%)
ICD	2 (4.5%)
Baseline electrocardiogram
QRS duration, ms	128.3 ± 29.5
QRS complex normal	19 (43.1%)
RBBB	12 (27.3%)
LBBB	7 (15.9%)
Paced/escape	6 (13.6%)
Baseline echocardiography
LVEDD, mm	45.3 ± 8.2
LVEF, %	54.4 ± 16.7

CRT = cardiac resynchronization therapy; ICD = implantable cardiac defibrillator; LBBB = left bundle branch block; LVEDD = left ventricular end-diastolic dimension; LVEF = left ventricular ejection fraction.

Lead measurements

The number of screwing attempts was 1.9 ± 2.0, with only 1 screwing in 32 cases. Each parameter is summarized in Table 2, and the trends during the procedure and at discharge are depicted in Figure 1, Figure 2, Figure 3.

Table 2.

Lead parameters

	After screw	3 minutes	5 minutes	End of procedure	Discharge
P-wave amplitude, mV	1.51 ± 0.75	1.58 ± 0.97	1.64 ± 1.01	1.72 ± 0.95	2.06 ± 1.32
Capture threshold, V/0.4 ms	2.00 ± 0.72	1.60 ± 0.56	1.45 ± 0.57	0.95 ± 0.38	0.78 ± 0.39
Impedance, ohms	630.6 ± 129.3	613.0 ± 106.6	610.2 ± 112.7	598.6 ± 106.7	553.1 ± 78.6

Figure 1.

R-wave trend during procedure and at discharge. The P-wave amplitude gradually increased and was significantly higher at discharge than immediately after screwing (P = .021).

Figure 2.

Impedance trend during procedure and at discharge. The impedance gradually decreased, and a significant difference was observed in the values after screwing and at discharge (P = .001).

Figure 3.

Threshold trend during procedure and at discharge. The threshold levels significantly improved over time, and a significant difference was observed between the levels after screwing and at discharge (P < .001).

The P-wave amplitude gradually increased while the impedance gradually decreased. Both showed significant differences after screw placement and discharge (Figures 1 and 2). The threshold significantly improved over time, and the extent of improvement was greater than that of the other parameters (Figure 3).

After the initial screwing, the threshold levels were >2.5 V/0.4 msec in 15 cases; however, all cases demonstrated a decrease to <2 V/0.4 msec at the end of the procedure. At discharge, 13 of 15 cases demonstrated a decrease to <1 V/0.4 msec. Notably, 1 case had a higher threshold of 4.625 V/0.4 msec immediately after screwing, which decreased to 1 V/0.4 msec at the end of the procedure, and to 0.75 V/0.4 msec at discharge.

In addition, no cases showed an increase in threshold levels >0.25 V at 3 minutes after screwing compared with that immediately after screwing. Conversely, the threshold levels decreased at 3 minutes in 31 cases and did not rise again ≥0.25 V at 5 minutes after screwing.

Position of the atrial lead

The C315HIS delivery catheter was pre-shaped toward the septum; therefore, most of the atrial leads could be positioned at the atrial septum. A previous study reported that the success rate of lead placement in the true atrial septum with the C315HIS delivery catheter was 22 of 29 cases (75.9%).³ In the current study, thoracic CT was performed postoperatively in 13 cases for the evaluation or follow-up of other conditions such as aortic disease or pulmonary disease. These scans were used to assess the lead position. Nine cases presented with leads placed in the true atrial septum (Figure 4A). The remaining 3 cases had leads at the anterior edge to the septum (Figure 4B), whereas 1 case had a lead placed in the lateral wall. Although detailed positions were not examined in all cases, the leads were believed to have been placed in the atrial septum in approximately 70% of cases.

Figure 4.

Position of the atrial lead. A: True atrial septum; B: anterior edge to the septum.

Complications and follow-up

No acute complications occurred during this procedure. Thirty cases were followed up at 6 months postoperatively, 15 at 12 months, and 6 at 18 months.

During follow-up, the threshold levels increased only slightly (Figure 5), with no increase of >1 V. Lead revision and battery depletion were not observed either. There were no occurrences of cardiac perforation or pericardial effusion. Three notable events occurred, including 1 case of noncardiac death, 1 of atrial lead dislodgement, and 1 of lead extraction for device infection.

Figure 5.

Threshold trend during follow-up. The threshold increased slightly during follow-up, but no significant differences were observed among the groups.

Discussion

In the current study, we observed significant improvements in the parameters of lumenless leads placed in the right atrium over time, more notably in the threshold levels. Lead repositioning is commonly considered when the levels after screw placement are high. However, our findings suggest that with lumenless leads, the threshold levels often decrease over time, advocating for the implementation of a waiting period, rather than immediate lead repositioning.

We hypothesized that the temporal improvement in the threshold may be influenced by the steroid content of the lead tip and amount of myocardium at the lead placement site. Typically, pacemaker lead tips are coated with steroids, with an active fixation lead from Medtronic (Capsurefix Novus) containing a maximum of 1 mg dexamethasone acetate, whereas that from SelectSecure contains only a maximum of 100 μg beclomethasone dipropionate.⁴ Given the relatively small amount of myocardium in the right atrium, inflammation resulting from screwing, particularly with lower steroid levels, such as those associated with the SelectSecure lead, may have a major impact on atrial thresholds compared with that on the ventricular thresholds. Moreover, repeated screwing may lead to the loss of steroids. Recently, CSP has been widely performed, along with a 2-lead technique.5, 6, 7, 8, 9 In the 2-lead technique, 2 SelectSecure leads are used for the CSP; 1 with good lead parameters is adopted for the CSP lead, and the other is replaced at the right atrium. Repeated screwing before placement in the right atrium may lead to loss of steroid at the lead tip. In our study, we observed 9 cases of screwing at the left bundle branch area before that at the right atrium and 3 cases of multiple screwing at the right atrium. The threshold levels in the single screwing group at the right atrium were 2.05 ± 0.80 V/0.4 msec immediately after screwing and decreased to 0.90 ± 0.36 V/0.4 msec at the end of procedure. Conversely, in the multiple screwing group, the threshold levels were 1.84 ± 0.41 V/0.4 msec immediately after screwing and decreased to 1.08 ± 0.37 V/0.4 msec at the end of procedure. No significant difference was observed between the 2 groups, indicating that the number of screwing attempts did not affect the threshold in our study.

Considering a more detailed examination of the time elapsed after screwing, no cases showed threshold levels ≥ 0.25 V, and 31 cases showed threshold decreases at 3 minutes after screwing, and the levels did not increase 5 minutes after screwing. In almost all cases, the threshold levels decreased over time after screwing, but in 6 cases, they remained unchanged 5 minutes after screwing. However, all 6 cases showed a decrease in threshold at the end of the procedure, and there was no observed increase at discharge or during follow-up. In this study, if the threshold remained unchanged at 5 minutes after screwing and was >3 V/0.4 msec, lead repositioning was performed. However, if the threshold levels remained unchanged or increased slightly 5 minutes after screwing, they were considered to have decreased by the end of the procedure or in the long term. In such cases, strategies such as allowing a longer waiting time or refraining from lead repositioning with the expectation of long-term improvements could be considered. However, prolonging the waiting time may extend the procedure time, and the lack of lead replacement could lead to early battery depletion if no improvement in the threshold is achieved in the long term. Extending the waiting time after lead placement is considered beneficial for enhancing lead stability. However, longer waiting times can extend the overall surgery duration, which in turn increases the risk of infection and the burden on the patient. Therefore, it is important to establish an appropriate waiting time. The current study indicated that it is reasonable to decide on lead repositioning after waiting for approximately 5 minutes in clinical practice. Although larger studies are needed, this finding could serve as 1 of the indicators for determining the optimal waiting time.

Regarding lead placement, among the 13 cases evaluated by computed tomography, 3 were placed on the anterior edge of the septum, and 1 was placed on the lateral wall. The anterior edge of the septum is right in front of the ascending aorta, potentially raising the risk of the lead penetrating the aorta and resulting in significant bleeding. Additionally, lead placement on the lateral wall carries the risk of pericardial effusion or cardiac tamponade because of perforation. Fortunately, no such complications were observed during the follow-up period of this study. Careful long-term follow-up is essential.

To mitigate this risk, modifying the lead position to a more posterior and inferior part of the septum should be considered in the future. In this study, the C315HIS sheath provided stable sensing and thresholds during lead placement, but we did not evaluate the usefulness of other sheaths or the effectiveness and safety of alternative placement sites. Future studies should explore the use of different sheaths and techniques to identify safer and more effective lead positions.

Limitations

This study had 3 limitations.

First, the current study had a small sample, was a single-center study, and had a retrospective design.

Second, the lead placement site was presumed to be mostly in the atrial septum; however, because detailed examinations such as CT or MRI were not conducted in all cases, the leads might have been placed in the right atrial appendage or right atrial lateral wall in some cases. The potential impact of the electrical and physiological properties of the placement site on the threshold levels was not evaluated.

Third, the threshold decrease after a 5-minute wait was used as an indicator in this study. However, in a few cases, even if there were no apparent threshold decrease after 5 minutes, the threshold was sufficiently favorable in the long term. By providing a longer waiting time, it may be possible to confirm threshold decrease and potentially reduce the number of lead screwing attempts. However, further studies are needed to confirm this hypothesis.

Conclusions

With lumenless lead placement in the right atrium, the thresholds tended to decrease over time. Therefore, providing a waiting period instead of immediately repositioning the lead may be more effective when the threshold is high immediately after screwing. Reducing the number of screwing attempts can also reduce complications such as perforation.