High-resolution 8-spline mapping and radiofrequency catheter ablation for middle cardiac vein diverticulum epicardial accessory pathways: Efficacy and safety.

UNLABELLED: Posteroseptal accessory pathways (APs) often involve epicardial connections, making radiofrequency catheter ablation (RFA) particularly challenging. We present the case of a 14-year-old boy in whom a heart murmur was detected after birth. Echocardiography revealed an isolated ductus arteriosus aneurysm with tricuspid regurgitation, while electrocardiogram (ECG) showed pre-excitation due to an AP. The aneurysm spontaneously closed during infancy. At age 13 years, the patient experienced brief monthly palpitations but did not seek medical treatment. By age 14 years, echocardiography showed reduced cardiac function, and a 12‑lead ECG revealed a posteroseptal AP. Contrast-enhanced computed tomography revealed a small middle cardiac vein (MCV) diverticulum located >5 mm from the right coronary artery. Electrophysiological study (EPS) and RFA were performed to improve cardiac function. Although EPS did not induce atrioventricular reciprocating tachycardia, intracardiac echocardiography and multipolar electrode mapping demonstrated continuous atrioventricular potentials with an AP potential at the MCV diverticulum neck. Low-power radiofrequency energy delivered with a QDOT MICRO™ catheter eliminated AP conduction within 2 s. Follow-up echocardiography confirmed resolution of left ventricular dyssynchrony and improved function. High-resolution electroanatomical mapping enabled precise localization of the AP, and low-power irrigation catheter use provided effective and safe ablation in pediatric posteroseptal AP.

LEARNING OBJECTIVE: The posteroseptal accessory pathway (AP) is a possible epicardial pathway often associated with anatomical abnormalities, such as the coronary sinus diverticula, and radiofrequency catheter ablation (RFA) is technically more challenging in such cases than in other APs. The combined use of a multispline high-resolution electroanatomical mapping catheter and a low-power irrigation catheter enables accurate and safe RFA, even in pediatric patients with an epicardial posteroseptal AP in the middle cardiac vein diverticulum.