Electroanatomical mapping-guided leadless pacemaker (MICRA-VR) implantation in the right atrium of a univentricular heart with Fontan circulation, an approach combining imaging and electrophysiology: insights from a case report.

Background: Patients with complex congenital heart disease, especially after Fontan repairs, face significant challenges in managing conduction disorders. This case illustrates the potential of leadless pacemaker technology, which is particularly relevant and promising in these patients, by combining an unusual implantation site with electroanatomical guidance. Case summary: This report describes a 41-year-old male with complex congenital heart disease, including tricuspid atresia repaired using a historical Fontan circulation (with the right atrial appendage connected to the pulmonary trunk). Severe right atrial dilation led to drug-refractory arrhythmias that necessitated several catheter-based ablation procedures. Additionally, the patient developed sinus node dysfunction and ultimately required pacemaker implantation. Due to anatomical challenges and extensive scarring in the right atrium, a leadless pacemaker (MICRA-VR) was implanted using both fluoroscopic and three-dimensional electroanatomical mapping techniques. At follow-up, the patient remained asymptomatic, with stable device positioning. Discussion: This off-label technique, which helps prevent device-related infections and venous system occlusion, should be considered a viable option in complex cases as leadless pacemaker technology continues to advance.