Left bundle branch area pacing in a patient with Ebstein’s anomaly from a functional right atrium using the sheath-in-sheath technique

Ebstein’s anomaly is a rare congenital cardiac malformation characterized by apical displacement of the septal and posterior tricuspid valve leaflets, resulting in right heart failure along with right atrial enlargement, known as atrialization of the right ventricle. Left bundle branch area pacing (LBBAP) is a pacing technique in which a pacing lead reaches the endocardium of the left ventricle by deep fixation through the right ventricular septum, enabling synchronized left ventricular pacing.^{,  ,  ,  ,}  Herein, we report a case of complete atrioventricular block (AVB) with Ebstein’s anomaly and successful LBBAP from the functional right atrium.

A 69-year-old male patient was referred to our hospital because of severe bradycardia and congestive heart failure. He was diagnosed with Ebstein’s anomaly and atrial septal defect (ASD) owing to a heart murmur when he was 15 years old, but he had no subjective symptoms and was not examined regularly. When he came to our hospital, he had complete AVB, and the chest radiograph showed an enlarged cardiothoracic ratio of 58% and bilateral pulmonary congestion. Echocardiography revealed a preserved ejection fraction of 56%, but apical displacement of the septal and posterior tricuspid valve leaflets and severe tricuspid regurgitation were noted (Figure 1A and 1B , and Figure 2A). Computed tomography scan showed no other obvious congenital malformations and no significant stenosis of the coronary arteries. In compliance with guideline-directed therapy, permanent pacemaker implantation was performed. A 7F peel-away sheath was inserted through the left subclavian vein, and right atrial angiography was performed using a pig-tail catheter (Figure 3A). A C315 His delivery sheath (Medtronic Inc, Minneapolis, MN) was then inserted through the 7F sheath, and the SelectSecure (model 3830; Medtronic Inc) pacing lead was delivered through the C315 His sheath. His bundle potential was recorded at the lead in a unipolar fashion, and on the ventricular side of the His bundle, the right ventricular potential was recorded even in a functional right atrium, above the tricuspid valve, and right ventricular septal pacing was performed there. Although deep lead fixation was attempted in the functional right atrial septum, the lead did not advance and QRS width shortening was not obtained. Thereafter, the 7F sheath was replaced with a 9F coronary sinus (CS) left ventricular (LV) lead delivery outer sheath (Medtronic Attain Command MB2; Medtronic Inc), and the C315 His sheath was advanced through the CS sheath. Deep lead fixation was attempted again in the functional right atrial septum and significant QRS width shortening was observed, resulting in successful LBBAP (Figure 3B and 3C). At implantation, R-wave amplitude was 7.5 mV; ventricular pacing threshold at 0.4 ms pulse duration was 0.5 V; pacing impedance was 627 Ω. Thereafter, an atrial lead (model 5076; Medtronic Inc) was implanted in the right atrial appendage, and the atrial and ventricular leads were connected to the pacemaker generator (Azure XT DR MRI; Medtronic Inc). Postoperative chest radiograph and electrocardiogram are shown in Figure 1C and 1D. Echocardiography showed that the ventricular lead was fixed from the atrial side of the septal tricuspid valve leaflet, and the lead tip reached deep into the left ventricular septum (Figure 2B), and there was no left ventricular dyssynchrony during ventricular pacing. Although the left-to-right side shunt owing to ASD remained after implantation, the Qp/Qs ratio using echocardiography was 1.2, which was not clinically significant, and no treatment was given for ASD. However, ASD closure should be considered after the pacing leads have stabilized to avoid the risk of future paradoxical embolism owing to residual ASD and endocardial leads. During the 1-month follow-up, the atrial and ventricular pacing thresholds were 0.5 V and 0.75 V at 0.4 ms, respectively, and the patient was doing well without subjective symptoms at an outpatient clinic.

According to previous reports, permanent His bundle pacing (HBP) for Ebstein’s anomaly is feasible and safe. However, in general, HBP has some challenging aspects, such as a low success rate and higher pacing thresholds than conventional right ventricular pacing, especially in cases of atrioventricular conduction disease.^{,  ,}  LBBAP has emerged as an alternative physiological pacing method to HBP and is capable of electrical synchronization of the left ventricle. Moreover, as reported in the literature, LBBAP has lower pacing thresholds and higher R-wave amplitudes than HBP. LBBAP is achieved by the deep lead fixation technique from the right ventricular septum using the SelectSecure pacing lead delivered through the C315 His delivery sheath, as previously described. Although the success rate of LBBAP is >90% in most sheath-delivered lead studies, in this case deep lead fixation was not possible initially. The C315 His sheath was advanced through the 9F CS LV lead delivery outer sheath, and we achieved successful LBBAP by this sheath-in-sheath technique. The method of performing HBP with the C315 His sheath through the CS sheath, reported by Vijayaraman and Ellenbogen, was effective in reaching the His bundle with the sheaths and the pacing lead in a patient with a significantly enlarged right atrium and/or right ventricle. In this case, the C315 His sheath and the lead reached the fixation site, but the sheath backup force was insufficient, which may have made deep lead fixation difficult. The use of the CS outer sheath provided sufficient backup force for the C315 His sheath and the lead to enable deep lead fixation from the functional right atrial septum and successful LBBAP. When using this technique, removing and pre-slitting the proximal portion of the CS sheath was necessary because the C315 His sheath and the CS sheath were almost similar in length, as previously described. In addition, since the hemostatic valve of the CS sheath was removed, the CS sheath was first slit and then the C315 His sheath was slit to avoid air embolism.

We experienced a case of complete AVB complicated by Ebstein’s anomaly, in which LBBAP was successfully performed by deep lead fixation from the functional right atrium using the sheath-in-sheath technique.