Introduction: Coronary artery (CA) injury is a rare complication following radiofrequency ablation (RFA) with the overall incidence of less than 0.1%. The risk of injury can be even higher (50%) if applying radiofrequency energy within 2mm of the CA. (1-3)

Case report: The patient, a 36-year-old Caucasian female was referred for an electrophysiology (EP) study (April 2022) after narrow complex tachycardia had been diagnosed in the Emergency Department. The patient is a healthy adult with highly symptomatic episodes of palpitations which occurred daily. The EP study was conducted, confirming the diagnosis of typical atrioventricular nodal re-entrant tachycardia (AVNRT). After the radiofrequency energy was applied on the slow pathway, solely the atypical AVNRT was re-induced. The site of the earliest activation was located on the posteroseptal part of the right atrium, next to the ostium of the coronary sinus (CS). An additional ablation was performed and the tachycardia was terminated. After the procedure, a single episode of ventricular fibrillation was observed, necessitating prompt defibrillation (Figure 1). Once the return of the spontaneous circulation has been re-established, electrocardiogram demonstrated changes indicative of an acute myocardial infarction of the posterior region (Figure 2). The next step involved an urgent invasive coronary angiography, which confirmed acute occlusion of the posterolateral (PL) branch situated next to the ostium of the CS (Figure 3). Percutaneous transluminal coronary angioplasty was performed and re-established the blood flow through the PL branch, but on the follow-up angiogram, a localised contrast extravasation was observed. After a prolonged balloon inflation, normal flow through the PL was restored. Over the course of the remaining hospitalization, the patient was hemodynamically stable, without residual chest pain and without segmental wall motion abnormalities or pericardial effusion on echocardiogram. New arrhythmias were not detected.

Conclusion: Even though the RFA is highly effective, caution is necessary when applying energy within the CS due to its close anatomical correlation with PL branch. Performing coronary angiography prior to the energy delivery may aid in the prevention of CA injury.