Introduction

Temporary transvenous cardiac pacing is a very effective treatment of severe bradyarrhythmia causing hemodynamic instability. In recent years, with the improvement of the reliability of pacing systems and the increase of clinical experience, temporary transvenous pacemakers are increasingly used in the treatment of acute and critical cardiovascular diseases in children, such as fulminant myocarditis, congenital heart block, and malignant arrhythmia [1, 2]. In the past, the vast majority of temporary pacing in children was implanted under fluoroscopic guidance, which required a long preparation and anesthesia time and was not conducive to the rescue of critical patients [3, 4]. How to choose the appropriate guidance method and implantation path in children maybe a serious challenge.

In the adult field, a large number of studies have demonstrated the efficacy and safety of ultrasound-assisted bedside temporary pacing [5,6,7], but there is still lack of relevant studies in the pediatric field [3, 4, 8]. This study aims to evaluate the effectiveness and safety of the two types of temporary pacing by observing and comparing the treatment process and complications of bedside ultrasound-guided and fluoroscopy-guided cardiac pacing in children, so as to provide a reference to choose the appropriate temporary pacing method for children.

Material and Methods

Patient Selection

Children with bradyarrhythmia admitted to Hunan Provincial Children’s Hospital from January 2017 to June 2023 were selected. The indications for temporary pacing implantation are as follows: 1. bradycardia due to various causes, with symptoms of cardiac insufficiency or hemodynamic instability and 2. electrocardiogram (ECG) shows sinus node insufficiency, slow-fast syndrome, high-grade atrioventricular block (AVB), or cardiac arrest. Exclusion Criteria included 1. coagulation dysfunction and 2. infective endocarditis. This study protocol was approved by the Ethics Committee of the hospital (HCHLL-2024–259). All patients’ family members signed informed consent.

Clinical Data Collection

Clinical data were collected, including gender, age, weight, time of admission and discharge, and underlying clinical diseases. Clinical manifestations include onset, basal heart rate at admission, circulatory manifestations during the course of the disease, and onset of Adams–Stokes syndrome. Results of clinical ancillary tests such as electrocardiogram, echocardiography, and myocardial markers. Treatment conditions such as ventilator use and circulatory assistance, drug use, timing of installation and removal of temporary pacemakers, time from pacing decision to successful implantation, guidance methods used, complications related to implantation, and post-implantation follow-up.

Patient Grouping

All children underwent initial cardiac function assessment and ECG in the intensive care unit and a pediatric cardiologist completed the preoperative evaluation of temporary pacing implantation if indicated. Two pediatric cardiologists (with interventional qualifications) should select cardiac pacing guidance methods according to the child’s condition and the doctor’s implantation experience. According to the selected implant guidance method, it was divided into bedside ultrasound guidance group (ultrasound group) and fluoroscopy guidance group (fluoroscopy group).

Temporary Pacing Placement Method

Bedside ultrasound-guided temporary pacing implantation process: In the intensive care unit, the need for intravenous anesthetics or respiratory and circulatory support depends on the child’s age, state of consciousness, and circulation state. A pediatric cardiologist uses a vascular ultrasound probe to show a cross-section of the vein and guide the needle into the vessel. After the puncture is completed, a pacing electrode is inserted into the blood vessel. The sonographer or another cardiologist uses an ultrasound probe to direct electrodes through the vena cava into the right atrium and across the tricuspid valve into the apex or septum of the right ventricle in the inferior view of the xiphoid process. The cardiologist selects right jugular vein, subclavian vein, or femoral vein for venous access and proficiency in puncture. See Fig. 1 for details.

Fig. 1
figure 1

The process of ultrasound-guided temporary pacing implantation. a ultrasound-guided jugular vein puncture (red arrow: needle pathway); b the electrode tip is advanced in the right atrium through superior vena cava; c the lead pathway to the right ventricular apex is monitored under ultrasound guidance (red arrow: electrode tip). CA carotid artery, JV jugular vein, RA right atrial, RV right ventricular

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Fluoroscopy-guided temporary pacing implantation process: In the cardiac catheterization room, the anesthesiologist evaluates and selects the appropriate anesthesia (intravenous aspiration combined with general anesthesia or local anesthesia). The pediatric cardiologist completes the vascular puncture and places the pacing electrode at the apex or septum of the right ventricle under fluoroscopic guidance. If conventional puncture is difficult, vascular ultrasound-guided puncture can also be used.

Connect the pacing electrode and the temporary extracorporeal pulse generator, set the output pacing current of 3 ~ 5 mA according to the age and condition of the child, the perception sensitivity is 2 ~ 3 mV, the pacing heart rate is (70 ~ 110) times/min, and the pacing catheter and sterile dressing are fixed when the ECG monitor shows a normal pacing signal. Postoperatively, a chest X-ray was taken to observe the position of the pacing lead and a 12-lead electrocardiogram was recorded. If ECG shows no pacing signal or intermittent pacing, electrode displacement is considered, and electrode positioning is adjusted under ultrasound or fluoroscopy until the pacing ventricles are stabilized. Use the Medtronic 5348 single-chamber temporary pacemaker or the Livetec Pace T10 temporary pacemaker with the Abbott 5F bipolar temporary pacing electrode catheter.

Statistical Analysis

Continuous variables are expressed as mean ± SD or median (interquartile range) and categorical variables are expressed as frequency (%). Continuous variables were compared using the Mann–Whitney U test. Categorical variables were compared using the Fisher exact probability method, where p < 0.05 represents a statistically significant difference. Statistical analysis was performed using SPSS for Windows version 23.

Results

A total of 30 children were enrolled, including 18 males and 12 females, with a median age of 5.5 (2.9, 10.0) years, a median weight of 18.7 (12.7, 32.7) kg, and the smallest weight was only 1.58 kg. There were 17 cases of bedside ultrasound guided (ultrasound group) and 13 cases of fluoroscopy guided (fluoroscopy group). There were no statistically significant differences in age, weight, gender and clinical manifestations between the ultrasound group and the fluoroscopy group (P > 0.05). The general conditions and clinical characteristics of the two groups are shown in Table 1.

Table 1 The general conditions and clinical characteristics of the two groups of children
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Among the primary diseases, there were 13 cases of fulminant myocarditis, with a median age of 9 (4.6, 10.8) years and a median weight of 27.5 (18.2, 40.0) kg, and 10 cases of congenital high AVB, with a median age of 2.7 (1.7, 8.7) years and a median weight of 12.4 (8.4, 21.2) kg. There were significant differences in age (P = 0.011) and weight (P = 0.035) between the two groups. See Table 3 for details.

Among them, the proportion of congenital high AVB in the fluoroscopy group was significantly higher than that in the ultrasound group, and the difference was statistically significant (p = 0.007). However, postoperative high-grade AVB (2/30 cases), channelopathy (3/30 cases), and cardiomyopathy (2/30 cases) were all in the ultrasound group, and none of the cases were in the fluoroscopy group, but the difference was not statistically significant due to the small number of cases (P > 0.05).

In clinical treatment, 17 children were treated with respiratory support, 2 with extracorporeal membrane oxygenation (ECMO), and 3 died. Among them, the ECMO and death cases were in the ultrasound group. However, there was no statistically significant difference between the two groups (P > 0.05). Among the children supported by ECMO, one had channelopathy with malignant arrhythmias and one had fulminant myocarditis with shock and then died of multiple organ failure. Among the other two deaths, one was cardiomyopathy with cardiac arrest and died after prolonged hypoxia and the other was a neonatal with congenital high AVB combined with necrotizing enteritis and died after sepsis.

In the follow-up treatment, 10 cases were treated with permanent pacemakers, 8 cases in the fluoroscopy group and 2 cases in the ultrasound group, and the difference between the two groups was statistically significant (P = 0.007). See Table 1 for details.

The implantation process was successful in all 30 children. From the time of pacing decision to implantation, the median time of ultrasound group was 56 (30, 60) min and that of fluoroscopy group was 154 (78, 180) min, with a statistically significant difference (P < 0.001). The median time of preoperative preparation was 25 (12, 34) min in the ultrasound group and 103 (52,140) min in the fluoroscopy group, with a statistically significant difference (P < 0.001). In duration of the procedure, the median time was 22 (18, 31) min in the ultrasound group and 31 (26, 39) min in the fluoroscopy group, with a statistically significant difference (P = 0.012). The median pacing threshold was 1.0 (1.0, 2.0) mV, the median time of duration of temporary pacing was 90 (68, 128) hours, and there was no significant difference between the two groups (P > 0.05). See Table 2 for details.

Table 2 Comparison of the safety and efficacy of the two methods of implantation
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A total of 5 cases developed complications, including 1 electrode displacement in the ultrasound group and 2 electrode displacement, 1 myocardial perforation, and 1 puncture site infection in the fluoroscopy group. The 5-month-old (5.5 kg) patient with congenital high-grade AVB had myocardial perforation after electrode displacement and electrode position adjustment under fluoroscopy. After the electrode was removed in time under surgical thoracotomy, no cardiac tamponade occurred. There was no statistically significant difference between the two groups (P > 0.05). See Table 2 for details.

There was no significant difference in the time of indication-to-pace (P = 0.062) and duration of temporary pacing (P = 0.756) between the two groups of fulminant myocarditis and congenital high-grade AVB. See Table 3 for details.

Table 3 Comparison of characteristics and procedure of children with fulminant myocarditis and congenital high-grade atrioventricular block
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Discussion

Temporary transvenous cardiac pacing is a very effective treatment of severe bradyarrhythmia causing hemodynamic instability. In the past, transfemoral vein route implantation was usually used for temporary pacing in children, which was a simple procedure, a well-established method, and had a low complication rate [3]. However, due to the long preparation to enter the fluoroscopy operation room, it is not conducive to the rescue of critical patients and may increase the dangerous situations [8]. Fluoroscopy-guided venipuncture remains challenging in low-weight children and those with poor vascular condition, which may increase the risk of vascular injury, hemopneumothorax, and cardiac tamponade [9]. So, it is very important to choose the appropriate guidance method and implantation path in children to improve the success rate of implantation, shorten the operation time, and reduce the occurrence of complications.

This is the first study comparing the standard temporary pacemaker approach (fluoroscopy-guided temporary pacemaker) with ultrasound-guided temporary pacemaker in children. In the adult field, a large number of studies have demonstrated the efficacy and safety of ultrasound-assisted and bedside temporary pacing [4,5,6]. In an observational study of 203 adults with emergency temporary pacing, the femoral vein was chosen for fluoroscopy-guided temporary pacing, and the right jugular vein was the major access for ultrasound guided [10]. This is mainly due to the fact that ultrasound-assisted access to the jugular vein can improve the success rate of puncture, reduce the complication of bleeding, and make it easier for entering the right ventricle. In this study, the temporary pacing implantation was successful in both ultrasound group and fluoroscopy group, and there was no statistical difference between the two groups in the pacing threshold and electrode duration time. For the time of pacing decision to implantation, the ultrasound group was significantly shorter than the fluoroscopy group (median time 56 vs 154 min, P < 0.001). The main reason is that the preoperative preparation time of the fluoroscopy group is longer than that of the ultrasound group (median time 103 vs 25 min, P < 0.001), including the preparation and waiting of the catheterization laboratory, the evaluation of the anesthesiologist, and the time of transport. The ultrasound group was completed at the bedside, and the ICU physicians directly completed the sedation, which saved time. In addition, the duration of the procedure in fluoroscopy group was slightly longer than that of the ultrasound group (median time 31 vs 22 min, P = 0.012), which may be due to the more complex operation process in the catheterization laboratory, and the difficulty of puncture in some children.

The overall complication rate of transvenous temporary pacing was low, with cardiac tamponade (0.6%), pneumothorax (0.9%), and vascular complications (2.4%) found in a large retrospective analysis of adults [11]. In our study, the overall complication rate was 16.6% (5/30), and there was no statistically significant difference between the two groups. The main reasons for the higher complications in this study than in adults are that the difficulty of temporary pacing operation in children is greater than that in adults, and the compliance of children after electrode implantation is poor, which can cause electrode displacement after operation. There was only one case of electrode displacement in the ultrasound group without serious complications, while in the fluoroscopy group, there was one case of myocardial perforation, one case of puncture site infection, and two cases of electrode displacement. The clinical diagnosis of the patient with perforation was congenital high-grade AVB with enlarged heart. The 5-month-old (5.5 kg) patient had myocardial perforation after electrode displacement and electrode position adjustment under fluoroscopy. The cause of myocardial perforation may be that its dense layer myocardium was thin, which caused electrodes to be embedded in the myocardium and myocardial perforation. The use of cardiac ultrasound guidance or the use of soft balloon floatation electrodes may avoid the risk of myocardial perforation. Harris et al. [12] suggested that myocardial perforation is a serious complication in children with temporary pacing, and the use of ultrasound can be very helpful in detecting and managing complications in a timely, especially in children with low body weight. Pinneri et al. [13] found that the risk of electrode displacement and cardiac perforation was lower in the right jugular vein implantation under ultrasound guidance than in the fluoroscopic transfemoral vein implantation group, suggesting that ultrasound assistance can reduce the occurrence of complications. Sjaus et al. [14] found that the relationship between the position of the electrode lead and the cardiac structure can be seen in real time using the image of the subxiphoid ultrasound section, and complications such as cardiac tamponade can be detected early. Even during cardiopulmonary resuscitation (CPR), children with acute cardiomyopathy can be implanted with temporary pacing [15].

In this study, congenital high-grade atrioventricular block (AVB) accounted for a higher proportion in the fluoroscopy group than in the ultrasound group, which may be due to the fact that children with congenital high-grade AVB usually have milder symptoms and require a permanent pacemaker under fluoroscopy. Although the age and weight of children with congenital high AVB were significantly smaller than those of children with fulminant myocarditis, there was no significant difference in the time of indication to pace (P = 0.062). This may be due to the small sample size of this study and the fact that there was no significant difference in the implantation guidance between the two groups (P = 0.09). Indirectly, the implantation guidance method is the main influencing factor that determines time consumption and has little to do with the primary disease. Other critical cases such as channelopathy, cardiomyopathy, or postoperative AVB were all in the ultrasound group, indicating that clinicians have realized the advantages of bedside ultrasound guided. For children requiring extracorporeal membrane lung support, it is difficult for the patient to move after catheterization, and femoral and jugular vessels are commonly used vascular access, so bedside ultrasound-guided trans-subclavian vein temporary pacing is the best choice for heart rate support.

The puncture site recommended by the Chinese expert consensus of bedside temporary pacing is the right jugular vein, which is easy to learn, has a high success rate, and is easy to enter the right ventricle [5]. The left subclavian vein is often reserved for permanent pacemaker implantation, and the right subclavian vein is an option. For transfemoral venous puncture, it is easy to compress and stop bleeding, but it is not conducive to lower limb movement, and some children need sedation. In this study, different puncture sites were selected in both groups. But due to the small sample size, there was no statistically significant difference in the selection and success rate of puncture at different sites between the two groups. However, in our practical work, it is difficult for infants and young children to puncture through the jugular vein or subclavian vein, while ultrasound guidance can guide deep venous puncture in real time, reduce the occurrence of vascular complications, and improve the success rate. The smallest patient with transvenous temporary pacing in this study was a 29-week preterm infant weighing 1.58 kg, who was successfully punctured into the right internal jugular vein under ultrasound guidance and electrodes were successfully inserted, demonstrating that it can be successfully performed in children with low body weight.

Study limitations

This is a single-center, nonrandomized observational study with a quite small population. Moreover, allowing the physicians the choice of their favorite technique could affect the final results. To limit this selection bias, we recorded and compared all the clinical characteristics that could differ between the two groups. In future, it is expected that multi-center large-sample controlled studies will provide more data support for the selection of treatment techniques for acute and critical cases related to bradyarrhythmia in children.

Conclusion

For children with bradyarrhythmia and hemodynamic instability, bedside ultrasound-guided temporary pacing technology can effectively shorten the operation time and reduce the occurrence of complications compared with traditional fluoroscopic temporary pacing and has become a better choice for children’s emergency and critical care treatment. The right jugular vein is preferred for intravenous implantation.