47- yo male with a history of palpitations for last 27 years. Paroxysmal atrial fibrillation (AF) has been documented in the previous ECG. He was referred for pulmonary vein isolation (PVI). At resting ECG no signs of preexcitation were present. During EPS dual atrioventricular nodal physiology was excluded. Later during incremental ventricular pacing AF occured. PVI was performed and then antazoline (class IC) was administered and SR was restored. During catheters maneuvering SVT (CL 340ms) was induced (Fig 1.). Entrainment pacing (CL 320ms) from cavo-tricuspid isthmus (CTI) was performer (Fig 2.).
How would you proceed?
- CTI ablation
- Another pacing maneuvers are needed
- Electrical cardioversion and further assessment
- Another PVs isolation confirmation
Fig 1. Supraventricular tachycardia (CL 340ms)
Fig 2. Entrainment pacing (CL 320ms) from cavo-tricuspid isthmus (CTI)
Due to a strong suspicion of CTI depend arrhythmia (PPI – CL = 20ms) (Fig 2) CTI ablation was performed. Atypically long CL of arrhythmia (340ms) was presumably due to previous class IC drug administration. During CTI ablation arrhythmia termination was observed. Bidirectional CTI block was confirmed by pacing maneuvers. Atrial pacing induced arrhythmia with the same cycle length again. Ventricular overdrive pacing (CL 310ms) revealed the accessory pathway (AP) (atrial activation was advanced during the “transition zone” – the beginning of ventricular pacing – red square) (Fig 3). AP retrograde conduction was proved during the para-Hisian pacing – constant SA interval during His capture (narrow QRS – blue line) and RV capture (wide QRS – red line) (Fig 4a). The right atrium map was obtained with the use of the 3D electroanatomical system during RV pacing. In the area of the earliest atrial activation application was performed (5mm from registered His potentials) resulting in the termination of AP conduction. The absence of AP conduction was revealed in para-Hisian pacing following the ablation – shorter SA interval during His capture (narrow QRS – blue line) and longer during RV capture (wide QRS – red line) (Fig 4b). The relatively short PPI during the entrainment pacing seemed to be caused by the low distance between the pacing area (medial part of the CTI) and the location of AP.