case_images: PMC11718398_01
case_images: Electrocardiogram at admission in the emergency room showing a regular wide QRS tachycardia (A); and after amiodarone administration showing ventricular pre-excitation with a morphology suggestive of a right posterior accessory pathway (B).
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case_images: He had previously been admitted to the ER for persistent, rapid palpitations and a haemodynamically tolerated regular tachycardia, with a cycle length of 377 ms, wide QRS complexes with a left bundle branch block pattern and superior axis (Figure 1A). The basal ECG in sinus rhythm showed ventricular pre-excitation with morphology suggestive of a right posterior AP (Figure 1B). Ventricular-atrial dissociation was documented during ventricular stimulation (see Supplementary material online, Figure  S1A) and atrial pacing resulted in a narrow QRS with absence of pre-excitation (see Supplementary material online, Figure  S1B).
case_images: Surface electrocardiogram at the beginning of the electrophysiology study showing anterograde ventricular activation with pre-excitation through a right lateral accessory pathway. A premature atrial contraction ( ) with conduction through a posteroseptal pathway can be suspected with a more negative deflection in aVF.
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case_images: Surface ECG at the beginning of the study showed anterograde activation with pre-excitation through a right lateral pathway, with a single premature atrial contraction compatible with conduction through a posteroseptal pathway (Figure 2).
case_images: EnSite Precision  3D images showing the local activation time of both the right (A) and left (B) accessory pathways. Radiofrequency ablation was performed in both locations (C).
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case_images: Abbott) and EnSite Precision  (Abbott) electroanatomic mapping system (Figure 3). A FlexAbility  (Abbott) irrigated ablation catheter was positioned at the tricuspid annulus, at the site where the shortest atrioventricular (AV) interval was observed. AP conduction within the first 5 s (Figure 3A). A transseptal puncture was then performed to access and map the left cardiac chambers. Radiofrequency was also applied at this site (40W, 15 mL irrigation, maximum temperature of 42 C), successfully eliminating conduction through this pathway (Figure 3B). Ablation of both the right lateral and left lateral pathways was considered successful (Figure 3C).
case_images: Surface electrocardiogram at the beginning of the second ablation procedure showing pre-excitation with delta wave with superior axis, negative in aVR and positive in aVL, isoelectric in V1 and positive in V2, suggestive of a posteroseptal accessory pathway.
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case_images: AP location (Figure 4). Apical right ventricular stimulation demonstrated decremental and concentric retrograde conduction, which was exclusively nodal.
case_images: 3D electroanatomic image (COLUMBUS , Microport) showing a continuous atrioventricular activity next to the ostium of the coronary sinus (A). Radiofrequency ablation eliminated the conduction through the accessory pathways (B). CS, coronary sinus; SVC, superior vena cava; IVC, inferior vena cava; TA, tricuspid annulus.
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case_images: COLUMBUS  system (Microport) (Figure 5A). Continuous AV activity was documented at the CS ostium, with a negative monopolar morphology. Radiofrequency was applied using an irrigated FireMagic  (Microport) catheter (40 W, 15 mL irrigation, maximum temperature of 40 C), eliminating conduction through the AP after four seconds (Figure 5B).