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The right ventricle has been the traditional site of transvenous pacing, but targeting the His bundle has emerged as potentially more physiologic, with reductions in pacemaker-mediated cardiomyopathy being suggested. Although the use of His bundle pacing (HBP) has increased dramatically since it was first clinically introduced in 2000,
Permanent conduction system pacing for congenitally corrected transposition of the great arteries: a Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study.
Improvements in procedural success and reductions in fluoroscopy times have been sought with the addition of 3-dimensional (3-D) electroanatomic mapping
Direct visualization of the His bundle pacing lead placement by 3-dimensional electroanatomic mapping: technique, anatomy, and practical considerations.
Transesophageal echocardiography (TEE) has been shown to successfully eliminate or significantly reduce fluoroscopy times in cardiac catheterization procedures,
Additionally, the acute assessment of atrioventricular valve–pacing lead interaction can potentially reduce the development of lead-related valvar regurgitation. The 3-D TEE provides advantages over 2-dimensional imaging for the evaluation of valve leaflets and can visualize the entire pacing lead course through several planes.
We report 2 pediatric patients in whom multiple imaging modalities (fluoroscopy, 3-D electroanatomic mapping, and 3-D TEE) were used to perform HBP.
Case report
Implantation technique
Three-dimensional mapping of the His bundle was performed using the EnSite Precision cardiac mapping system and WorkMate Claris electrophysiology system (Abbott Laboratories, Chicago, IL) for all patients. The 3-D TEE guidance used the Philips Epiq platform with X7-2t probe (Philips, Amsterdam, the Netherlands). Procedural time for HBP included venous access, 3-D mapping, and placement of the His bundle lead only.
Procedural methods were similar for all patients. Access to the left axillary vein was obtained and a 5F decapolar deflectable mapping catheter was advanced into the right atrium. The 3-D electroanatomic mapping was performed to obtain geometry of the right atrium and tricuspid valve annulus and tag the His cloud. The stimulus-QRS duration (ms) and His-QRS duration (ms) were recorded. The catheter location was tagged on the mapping system and marked on fluoroscopy and TEE, after which it was removed. A Medtronic SelectSite C304 deflectable sheath (Medtronic, Minneapolis, MN) was advanced via a 9F tearaway sheath, reaching the preidentified His location on fluoroscopy and TEE. A 3830 SelectSecure (Medtronic, Minneapolis, MN) pacing lead was connected to the electrophysiology system to obtain integrated bipolar sites, as has been previously described.
Direct visualization of the His bundle pacing lead placement by 3-dimensional electroanatomic mapping: technique, anatomy, and practical considerations.
In all patients, the pacing lead was placed initially into the right ventricle and pulled back toward the atrioventricular groove. If appropriate His electrograms, sensing parameters, and capture thresholds were obtained, the lead was fixed with 5–8 rotations of the lead body and the sheaths split/removed.
During the period 2019–2020, 3 patients were identified as having had HBP attempted or successfully performed. All patients had a dual-chamber pacing system implanted. Two patients had successful HBP during which 3-D TEE was used and are included in this description. The remaining patient did not use 3-D TEE and HBP was additionally not successful.
Patient 1
Patient 1 was a 14-year-old, 61.0 kg male patient with L-transposition of the great arteries (L-TGA) and late-onset development of complete heart block. A dual-chamber transvenous pacemaker was recommended. The 3-D electroanatomic mapping revealed a typical His bundle electrogram (balanced atrial and ventricular electrogram) in a more superior location as characteristic of patients with L-TGA. The anterior and posterior fascicular branches (deflection displaced to the ventricular electrogram) were identified and marked. The permanent pacing lead was advanced to the His bundle, targeting a more distal location, though prior to bifurcation of the fascicles tagged under 3-D TEE guidance, and integrated bipolar sites were recorded (Figure 1A and 1B ). Following lead fixation, capture with a stimulus-QRS of 2 ms and His-QRS of 34 ms was observed. Higher output pacing did not result in selective His bundle capture, although it did result in longer stimulus-QRS time with a narrower QRS, suggesting that a more proximal aspect of the conduction system was being activated. Overall capture thresholds were 0.5 V @ 1.0 ms with R waves of 9.8 mV. The 3-D TEE revealed only trivial mitral valve regurgitation despite an oblique lead course necessary for appropriate lead redundancy (Figure 1C). Procedural time for the HBP portion was 32 minutes; fluoroscopy time was 8 minutes. Total procedure time was 84 minutes and total fluoroscopy time was 10.1 minutes. After 24 months of follow-up, conduction system capture remains with a threshold of 0.75 V @ 0.4 ms (Figure 2).
Figure 1A: Three-dimensional (3-D) electroanatomic map demonstrating shadow of mapping catheter (green catheter), His ball (blue tagged location), and permanent pacing lead (gold catheter). Integrated bipolar signal from pacing lead reveals a small atrial electrogram (yellow arrow) with a His electrogram (red arrow), in a location consistent with the anterior fascicle of the left bundle branch. B: A 3-D transesophageal echocardiography (TEE) image demonstrating right atrium (RA), mitral valve (MV), left ventricle (LV), and right ventricle (RV), and pacemaker lead attaching to the basal septum. C: A 3-D TEE color Doppler demonstrating trivial mitral regurgitation (MR).
Figure 2A, B: Chest radiograph demonstrating His bundle pacing lead course (arrow) with redundancy to accommodate for subsequent patient growth. Lead testing was performed with various degrees of lead redundancy to ensure adequate sensing and pacing parameters with growth. C: Twelve-lead electrocardiogram demonstrating atrial and ventricular pacing with nonselective His bundle capture.
Patient 2 was a 16-year-old, 53.7 kg male patient with presumed congenital complete heart block and late diagnosis in adolescence. Progressive left ventricular dilation and exercise intolerance was noted, and a dual-chamber pacing system was recommended. Three-dimensional electroanatomic mapping was performed, and the permanent pacing lead was advanced to the previously tagged location under 3-D TEE guidance and integrated bipolar sites were recorded. Following lead fixation, selective His capture was noted with a threshold of 2.0 V @ 1.0 ms and nonselective capture with a stimulus-QRS of 8 ms and His-QRS of 49 ms was observed below this. R waves of 2.1 mV and a capture threshold of 0.75 V @ 1.0 ms were recorded. Procedural time for the HBP portion was 13 minutes; fluoroscopy time was 1.3 minutes. Total procedure time was 63 minutes and total fluoroscopy time was 2.3 minutes. After 22 months of follow-up, nonselective HBP capture remains with a threshold of 1.5 @ 0.8 ms. An increase in pacing threshold was noted at 6 weeks postimplant (1.2 @ 1.0 ms) and the pulse width was shortened with a concurrent increase in voltage, as this provided the longest estimate of battery life. There has been no change in pacing threshold over the remaining follow-up period.
Discussion
The use of HBP has increased dramatically since it was first clinically introduced in 2000, although reports in pediatric patients and those with congenital heart disease are limited. This report describes a multimodal approach to HBP in pediatric patients in which fluoroscopy, 3-D electroanatomic mapping (EAM), and 3-D TEE guidance were used for lead placement. In particular, 3-D TEE allowed for several adjunctive factors, including concurrent avoidance of tricuspid septal leaflet impingement, evaluation of atrioventricular valvar regurgitation, and the selection of differential pacing sites. No complications were observed with any patients.
Reports of HBP in pediatric and congenital heart disease patients
Permanent conduction system pacing for congenitally corrected transposition of the great arteries: a Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study.
first reported a pediatric patient with L-TGA undergoing HBP with a simultaneously placed permanent pacing lead into the subpulmonary, morphological left ventricle. Moore and colleagues,
Permanent conduction system pacing for congenitally corrected transposition of the great arteries: a Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study.
Direct visualization of the His bundle pacing lead placement by 3-dimensional electroanatomic mapping: technique, anatomy, and practical considerations.
and identified several factors that make 3-D TEE particularly useful in HBP. These include (1) the real-time assessment of atrioventricular valvar regurgitation, (2) the assessment for and prevention of impingement of the tricuspid valve septal leaflet, and (3) precise localization of both lead body and tip to allow for differential pacing site selection. While 3-D EAM and fluoroscopy can provide some of this information, neither modality can fully evaluate the underlying and changing hemodynamics.
Three-dimensional TEE guidance allows for the visualization of pertinent anatomical structures and can easily evaluate for the development of atrioventricular valvar regurgitation after lead placement (Figure 3). As opposed to 2-D imaging, 3-D TEE can more accurately evaluate the valvar anatomy and can also visualize the pacing lead course through multiple planes. Two-dimensional imaging struggles with leads coursing in an oblique plane and with tip localization. Pinning of the septal tricuspid valve leaflet is a known complication of HBP,
particularly when the delivery system is advanced from atrium to ventricle while searching for the His electrogram. Pediatric patients may have an additional risk of valvar regurgitation, as lead redundancy is required to accommodate for future growth. While 2-D TEE imaging could be helpful in making this assessment, fluoroscopy would require contrast injection and 3-D EAM is not helpful. Finally, 3-D TEE allows for acute assessment of ventricular function and the functional comparison of different pacing intervals. While this is not unique to 3-D imaging, it does provide a benefit over fluoroscopy and 3-D EAM.
Figure 3A: A 3-dimensional (3-D) transesophageal echocardiography (TEE) demonstrating moderate-to-severe tricuspid valve regurgitation with a right ventricle (RV) pacing lead (red arrow) seen coursing through the valve. B: A 3-D TEE looking from right atrium down to RV in systole with the pacing lead (red arrow) seen crossing the tricuspid valve and tethering the septal leaflet (yellow arrow). A broad zone of noncoaptation can be seen.
Patients with L-TGA may be the exception to this finding, as an elongated His bundle runs medially toward the upper septum to the site of the fibrous continuity between the right-sided mitral valve and pulmonary artery.
The His bundle may be more easily captured by a pacing lead than in structurally normal hearts with similar appearance to the type 1 (“standard”) or type 3 (“naked”) His bundle.
Targeted lead placement is of particular value when attempting to correct an underlying bundle branch block or in patients at risk for progressive distal conduction disease. Patients with L-TGA are prone to distal conduction loss as the anteriorly displaced atrioventricular node has an extended length of His bundle prior to its bifurcation.
By mapping the His bundle/bifurcation and using TEE during sheath manipulation, we were able to place the permanent pacing lead just proximal to the bifurcation and theoretically prevent subsequent conduction disturbances.
Previous institutional experience has suggested that 3-D TEE can result in reductions of procedure and fluoroscopy time for traditional pacing lead placement, although this current report demonstrates longer times likely secondary to the learning curve with HBP. There was a marked reduction in both parameters (including total time and the specific HBP portion) with consecutive patients. While a statistically significant reduction in these time markers is an appropriate endpoint for the evaluation of any adjunctive modality, the prevention of lead-related valvar interference and targeted lead placement are factors that may carry more overall significance but could not be fully evaluated in this limited cohort.
It is reasonable to consider that the aforementioned characteristics of 3-D TEE may be beneficial in left bundle branch pacing and other strategies of conduction system pacing. Echocardiographic confirmation of a septal lead location could also be advantageous for traditional midseptal pacing to avoid inadvertent lead placement on the anterior septum/right ventricular free wall, as this location may have a septal “appearance” in the left anterior oblique fluoroscopic view. The utility for left bundle branch lead placement or a comparison to traditional fluoroscopic views was not performed for the purposes of this report.
Key Teaching Points
•
Three-dimensional (3-D) transesophageal echocardiogram (TEE) during His bundle lead implant provides (1) the real-time assessment of atrioventricular valvar regurgitation, (2) the assessment for and prevention of impingement of the tricuspid valve septal leaflet, and (3) precise localization of both lead body and tip to allow for differential pacing site selection.
•
Patients with L-transposition of the great arteries have a conduction system that may be uniquely suited toward conduction system pacing.
•
The 3-D TEE can be used in conjunction with other modalities to enhance pacing lead implant.
References
Deshmukh P.
Casavant D.A.
Romanyshyn M.
Anderson K.
Permanent, direct His-bundle pacing: a novel approach to cardiac pacing in patients with normal His-Purkinje activation.
Permanent conduction system pacing for congenitally corrected transposition of the great arteries: a Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study.
Direct visualization of the His bundle pacing lead placement by 3-dimensional electroanatomic mapping: technique, anatomy, and practical considerations.
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