Angiography‐guided mid/high septal implantation of ventricular leads in patients with congenital heart disease

Abstract Background Conduction system pacing prevents pacing‐induced cardiomyopathy, but it can be challenging to perform in patients with congenital heart disease (CHD), and mid/high septal lead implantation is an alternative. This study aimed to assess intraprocedural angiography's utility as a guide for mid/high‐septal lead implantation in CHD patients. Methods The study subjects were CHD patients with Class I/IIa indications for permanent pacemaker implantation. To guide septal lead implantation, we performed an intraprocedural right ventricular angiogram in anteroposterior, 40° left anterior oblique, and 30° right anterior oblique. The primary endpoint was the lead tip in the mid/high septum on computed tomography (CT). The secondary endpoints were complications and systemic ventricular function on follow‐up. Results From January 2008 to December 2018, we enrolled 27 patients (mean age: 30 ± 20 years; M:F 17:10) with CHD (unoperated: 20, operated: 7). The mean paced QRS duration was 131.7 ± 5.8 ms, and CT done in 22/27 patients confirmed the lead tip in the mid‐septum in 16, high septum in 5, and apical septum in 1 patient. There were no procedural complications, and during a mean follow‐up of 58 ± 35.2 months, there was no significant change in the systemic ventricular ejection fraction (56.4 ± 8.3% vs 53.9 + 5.9%, P = .08). Two patients with Eisenmenger syndrome died because of refractory heart failure. Conclusions Intraprocedural angiography is safe and useful to guide mid/high‐septal lead implantation in CHD patients. Mid/high septal lead position preserves systemic ventricular function in patients with CHD during medium‐term follow‐up.


| INTRODUC TI ON
Atrioventricular block (AVB) and sick sinus syndrome (SSS) can occur in uncorrected congenital heart disease (CHD) or after surgical correction of certain CHDs. 1 CHD patients requiring pacing therapy often have epicardial leads implanted. Unfortunately, steroid-eluting epicardial pacing leads tend to fail more often and earlier compared to transvenous pacing leads. 2 Transvenous pacing is increasingly preferred in CHD patients because it does not need thoracotomy. It is possible to deploy the active fixation at any desired location with good long-term stability and performance. However, patients with It may be challenging if not impossible to perform conduction system pacing in patients with CHD. 8 Hence, in patients with CHD, the preferred lead position has shifted to the high-or mid-septal area of the sub-pulmonary ventricle. 2,9 Fluoroscopy, traditionally used for transvenous lead placement, cannot identify the cardiac chambers' complicated anatomical relationship in patients with CHD. Thus, developing a procedure that can delineate the anatomy of the ventricular septum during permanent pacemaker implantation (PPI) is crucial. The present study describes the utility of intraprocedural angiography to guide mid/high-septal lead implantation as validated by computed tomography (CT) during transvenous PPI in patients with CHD.

| Patient selection
We prospectively enrolled patients with uncorrected or surgically corrected CHD with symptomatic bradyarrhythmia and Class I/ IIa indication for transvenous permanent pacing. 10 All procedures were carried out at the Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bengaluru, India. The institutional ethics committee approved the study. Detailed written informed consent was obtained from all patients or from the parents if patients were <18 years of age. We explained the rationale for the procedure, the risks involved, and the novelty of the approach in the patient's local language before enrollment. Exclusion criteria were systemic/arterial ventricle ejection fraction (EF) of <40%, contrast allergy, pregnancy, and renal dysfunction.
We collected a thorough clinical history from each participant, including details of previous surgical procedures (if any), physical examination, blood chemistry, renal function tests, 12-lead electrocardiogram, and 24-hour Holter or extended external loop recording if necessary. An experienced pediatric cardiologist performed a transthoracic echocardiogram to describe the underlying anatomy, relationship of the various chambers and the great vessels, presence or absence of intracardiac shunts, and systemic ventricular function.
A pre-procedural review of the surgical notes was carried out in patients with previous surgical intracardiac repair to correct CHD.

| Endpoints
The primary endpoint was successful implantation of the ventricular lead in the mid/high septal position with no periprocedural complications. The secondary endpoint was preserved systemic ventricular function over medium-term follow-up, absence of complications such as heart failure, lead-related issues, and death related to the procedure.

| Implantation technique
Implantation procedures were carried out either under conscious sedation, or general anesthesia, after 6 hours of fasting and intravenous hydration with normal saline at 1 mL/kg/min. Venous access was obtained through a single or two separate punctures of the extrathoracic axillary vein for single-or dual-chamber pacemaker implantation. Angiography was carried out using the femoral approach for a single-chamber pacemaker or through the access for the atrial lead for dual-chamber pacemaker implantation. A 7-F peel away introducer (PLI) was used to implant the pacing leads, and a 6/5-F angiographic sheath (AVANTIR+; Cordis Corporation) with a sidearm was used to introduce an angled 6/5-F pigtail catheter for angiography. An active-fixation pacing lead (Medtronic 4076; Medtronic Inc.) along with a stylet was introduced into the right heart through the PLI along with a 6/5-F pigtail/balloon floatation angiographic catheter positioned in the right atrium or right ventricle depending on the anatomy. Angiography was performed using 30-40 mL (or 1 mL/kg) of non-ionic contrast agent (Iohexol) using a flow injector at a flow rate of 12-15 mL/s and a maximum pressure of 1000 psi.

| Statistical analysis
Continuous variables are expressed as mean ± SD, and categorical data are expressed as numbers or percentages. Continuous data were analyzed using the paired t test while comparing the parameters within the same group and unpaired Student's t test for comparing the parameters between the groups. Fisher's exact test was used to evaluate dichotomous variables. A P < .05 was considered statistically significant. All statistical analyses were performed using SPSS software version 22 (SPSS, Inc.).

| Study population
Between January 2008 and December 2018, we recruited 27 patients with CHD for angiography-guided lead placement (unoperated: 20, operated: 7). The characteristics of the study population are shown in Table 1 (unoperated) and Table 2 (operated). The total cohort's mean age was 30 ± 20 years, with 63% men (man:woman, and patients with complete AV block had no measurable R waves and were completely pacing dependent. The mean follow-up duration was 58 ± 35.2 months. There were two deaths in patients with Eisenmenger syndrome not related to the procedure. There was no significant change in the EF 56.7 ± 7.2% vs 54.8 ± 4.8% (P = .10), heart failure, lead-related complications, or deaths related to the procedure.   syndrome died because of intractable heart failure, one 8 months and another 13 months after the procedure.

| Operated patients (n = 7)
The characteristics of operated patients are presented in Table 2.
Operated patients were significantly younger than unoperated pa-  We performed CT examination in 4/7 patients as three patients refused CT scans. The lead tip was in the mid-septum in three (75%) and high-septum in one (25%

| D ISCUSS I ON
The present study is the first to investigate angiography-guided patients from 10 centers with a success rate of 86%. 23 However, selective pacing was only possible in three of 13 patients even after 3D electroanatomical mapping, and the paced QRS showed incomplete or complete left bundle branch block in all patients. 23 In the multicenter study in CHD patients, prolonged fluoroscopy was noted with a median fluoroscopy time of 38 minutes (range: 19-62 minutes). 23 In the present study, the fluoroscopic time was 11.1 ± 3.5 minutes (range: 8-24 minutes) in comparison.
Although permanent His bundle pacing is ideal, this approach is limited in CHD patients because there is a lack of specific hardware for their altered anatomy. towing to the high pacing thresholds in His bundle pacing, there is also a necessity for early pulse generator replacement, even in patients with normal anatomy. 8,24 The other drawbacks of 3D-electroanatomical mapping-guided PPI include the high cost of the procedure, the requirement of 3D-mapping equipment, and personnel with expertise to perform both procedures. It may also be challenging to achieve long-term stability of physiological pacing because of the wide variations in the conduction system anatomy in CHD patients.
As noted in the present study, mid/high septal pacing did not cause systemic ventricular dysfunction, heart failure, or lead-related complications over medium-term follow-up. Considering the highly variable anatomical course of the AV node and His-Purkinje system, mid/high-septal pacing of the sub-pulmonic ventricle is likely to be a better option for CHD patients.

| LI M ITATI O N S
The present study is a single-center study involving a group of patients with CHD who underwent PPI. Further studies are needed in a larger number of patients to validate the results of the present study.
The current study results do not apply to those patients in whom the venous access is from the femoral, iliac, and hepatic veins. The procedure cannot be performed in patients with contraindications to angiography. The implanting physician should be familiar with the anatomy of CHD.

| CON CLUS IONS
Transvenous mid/high-septal pacing may be optimal for CHD patients requiring pacing therapy for bradyarrhythmia because of the lead stability, long-term performance, and patient outcomes associated with the procedure. Intraprocedural angiography is beneficial for such patients as it provides real-time cardiac and vascular anatomy data to guide mid/high-septal lead implantation. Angiography is a safe imaging modality for septal lead F I G U R E 5 Three-dimensional reconstruction of computed tomography and angiogram of the dual-chamber pacemaker in a patient with congenitally corrected transposition of the great arteries, inlet ventricular septal defect, and Eisenmenger syndrome.

ACK N OWLED G EM ENTS
The authors thank Editage for their assistance in editing and proofreading this manuscript.

CO N FLI C T O F I NTE R E S T
Authors declare no conflict of interests for this article.