Ventricular tachycardia catheter ablation after repaired tetralogy of Fallot: how to overcome an electrical short circuit

A 30‐year‐old man with a history of surgical repair of tetralogy of Fallot and percutaneous pulmonary valve replacement (Melody, Medtronic, Minneapolis, MN, USA) was admitted for sustained ventricular tachycardia (VT) with a rate of 160 b.p.m., inferior axis and right bundle branch block morphology. The patient was scheduled for radiofrequency catheter ablation (RFCA) and pre-procedural multislice computed tomography was performed. At the electrophysiological study, an activation map during ongoing VT did show an “early-meets-late” pattern between the right ventricular outflow tract ant the tricuspid valve. No mid-diastolic potentials and only half of the VT cycle length were recorded, thus suggesting a focal mechanism and a line of block, due to a prior RFCA (Supplementary material online, Video). The site of origin (SOO) was localized at the septal aspect of the prosthetic pulmonary valve (local activation −17 ms to QRS begin, QS unipolar). Radiofrequency energy delivery at this site was not possible because of repetitive abrupt impedance drop due to intermittent contact with the valve struts (Panel A). Radiofrequency catheter ablation close underneath the SOO only resulted in temporary VT termination. Hence, the aortic root was mapped. A local presystolic signal (−18 ms to QRS begin, QS unipolar) could be recorded in the right coronary cusp (Panel B). Radiofrequency here promptly terminated VT and rendered the arrhythmia non-inducible. In our case, an intramural substrate was initially inaccessible because of an electrical short circuit with a prosthetic valve. Pre-procedural imaging and the use of a 3D-electroanatomical mapping system provided a good understanding of cardiac anatomy and allowed successful ablation from an alternative adjacent structure. The full-length version of this report can be viewed at: https://www.escardio.org/Education/E-Learning/Clinical-cases/Electrophysiology.