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We report a case of coronary sinus catheter entrapment in a Chiari network during catheter ablation for atrial tachycardia. Intracardiac echocardiography clarified the mechanism of entrapment and guided a bailout strategy using an OCTARAY mapping catheter introduced via the internal jugular vein. Bidirectional traction safely released the catheter without evidence of right atrial injury, suggesting a feasible alternative to conventional femoral snare-based approaches. Chiari network (CN) is a fenestrated remnant of the embryonic right valve of the sinus venosus and is observed as a reticular structure in approximately 2% of adults [1]. It has been reported to cause entrapment of electrode catheters [2] and pacemaker leads during invasive cardiac procedures [3]. We encountered a case in which a coronary sinus diagnostic catheter introduced from the inferior vena cava (IVC) became entrapped in a CN, making withdrawal difficult. The entrapment was successfully resolved using an OCTARAY multielectrode mapping catheter (Biosense Webster, Irvine, CA) introduced from the internal jugular vein as a bailout maneuver. The patient was a 50-year-old man who underwent catheter ablation for atrial fibrillation. A diagnostic duodecapolar catheter for coronary sinus mapping (Japan Lifeline, Tokyo, Japan) was advanced from the right femoral vein into the right atrium. The catheter was then deflected within the atrium to create a loop and rotated clockwise in an attempt to advance it into the coronary sinus. During this maneuver, the distal (poles 3–4) and proximal (SVC pole) electrode pairs of the looped catheter became fixed by a cord-like structure at the IVC–right atrial junction, suggesting entrapment. Gentle push–pull manipulation and counterclockwise rotation failed to release the catheter (Figure 1A). Intracardiac echocardiography (ICE) demonstrated that both the ascending (SVC pole) and descending (poles 3–4) parts of the catheter loop were firmly tethered by a filamentous structure at the IVC–right atrial junction (Figure 1B,C). Based on these findings, we inferred that the catheter had initially passed through the Chiari network when entering the right atrium from the IVC and then passed through it a second time when the loop was formed by flipping the catheter. Subsequent rotation likely caused the catheter to entangle the CN, resulting in the catheter becoming immobilized. Because release of the loop was considered essential for safe extraction, we elected to approach from the cranial side. An 8-Fr sheath was introduced via the right internal jugular vein, and an OCTARAY mapping catheter—originally planned for use in the ablation procedure—was advanced into the right atrium. The OCTARAY catheter was maneuvered to hook the looped duodecapolar catheter. By applying coordinated traction from both directions (caudally on the coronary sinus catheter and cranially on the OCTARAY catheter), we were able to disengage the loop and subsequently remove the coronary sinus catheter without resistance (Figure 2). In this case, ICE visualization of the fixed catheter segments was crucial for diagnosing entrapment within a Chiari network and for planning a safe bailout strategy. Because the catheter appeared to traverse the network twice and was additionally twisted, we judged that traction from the caudal side alone might increase the risk of right atrial injury and therefore selected a bidirectional traction approach from the cranial side. Previous reports have described bailout techniques using a large-bore sheath (approximately 20 Fr) introduced from the femoral vein, whereby a snare is used to grasp the catheter and withdraw it together with the Chiari network [4]. However, such an approach may carry a risk of right atrial damage due to traction on the network itself, puncture-site complications associated with a large-caliber sheath, and venous injury when retracting a looped catheter into the sheath. In our case, no tissue suggestive of Chiari network was attached to the retrieved catheter, and neither the ICE findings nor the subsequent clinical course indicated cardiac injury, suggesting that the bailout was achieved safely. Given the wide anatomical variability of the Chiari network, this type of complication cannot be completely prevented even with meticulous catheter manipulation. Nevertheless, when catheter entrapment is suspected, operators should avoid unnecessary additional rotation and consider cranial traction via an internal jugular approach as a viable and potentially safer bailout option. We thank the excellent Clinical Engineers and Clinical Laboratory Technologists at Sendai Open Hospital. The authors have no financial support for the present study. The authors have nothing to report. This research was conducted according to the principles of the Declaration of Helsinki. The patient provided written informed consent for publication of the details of this case. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.