Complete atrioventricular conduction system pacing in dextrocardia-a case report.

Background: Conduction system pacing has been proven superior to conventional myocardial pacing in both atrial and ventricular conduction abnormalities. However, in dextrocardia, physiological pacing is difficult due to a lack of dedicated delivery tools. We present the case of a patient with dextrocardia and situs inversus, in whom both Bachmann bundle pacing and left bundle branch pacing were performed for advanced interatrial and atrioventricular block. Case summary: A 76-year-old patient with dextrocardia and complete situs inversus was admitted for recurrent syncope. The electrocardiogram showed advanced interatrial block and complete atrioventricular block. With no identifiable reversible factors for conduction abnormalities, we decided on complete atrioventricular physiological pacing. Using a modified 3D delivery catheter (inversion of the distal curve), we were able to reach both the interventricular and interatrial septum, where the leads were deployed. Conduction system potentials were recorded in the Bachmann and left bundle branch area, and conduction system capture was demonstrated using the current criteria. The pacing and sensing thresholds were optimal and stable at the 1-month follow-up. Discussion: Interatrial block and right appendage pacing are associated with a higher incidence of atrial fibrillation and adverse atrial remodelling, while long-term right ventricular pacing increases the risk for pacing-induced cardiomyopathy. By engaging the conduction system, physiological pacing leads to normal myocardial depolarization, thereby reducing the risk of the aforementioned adverse outcomes. Although atrial and ventricular conduction system pacing has been described in detail, this is the first case to illustrate these procedures in the setting of dextrocardia.