Arrhythmogenic anatomical isthmuses identified by electroanatomical mapping are the substrate for ventricular tachycardia in repaired tetralogy of Fallot

Impact of surgery on presence and dimensions of anatomical isthmuses in tetralogy of Fallot

“…Of interest, isthmus 2, as compared with the other isthmuses, was relatively narrow and thin 12. Electroanatomical studies have shown that AIs with slow conduction were significantly narrower as compared with AIs with normal conduction 7. Narrow and thin isthmuses 1 and 2 may be more likely potentially arrhythmogenic.…”

“…Therefore, the smaller RVOT patches in specimens with a transatrial-transpulmonary correction <1 year might eventually result in a thicker and broader isthmus 1 when the heart is fully grown as compared with specimens with a transatrial-transpulmonary correction ≥1 year. Recent mapping data demonstrated that AIs with normal conduction were indeed broader and had more preserved voltages suggesting thicker myocardium, as compared with those with slow conduction 7. Therefore, in specimens with a transatrial-transpulmonary and with a correction <1 year, isthmus 1 may have less often the arrhythmogenic isthmus characteristics (narrow, thin) that are typical for VT-related isthmuses.…”

The year in cardiology 2016: arrhythmias and cardiac implantable electronic devices

“…Treatment with catheter ablation is difficult due to the complex anatomy after surgical repair. However, as recently shown detailed electroanatomical reconstruction and mapping of the conduction properties in the operated areas effectively identifies critical conduction isthmus that promotes VT. 33 In one of the largest patient series of Fallot patients with VT reported so far it could be shown that discrete ablation of the isthmus results in VT termination and rendered VT noninducible in the majority of patients. In patients with effective ablation VT recurrence was very low proving the benefits of this approach.…”

Improved understanding of ventricular tachycardia in patients with tetralogy of Fallot

“…Importantly, ablation was accomplished effectively even when formal propagation mapping was not possible owing to haemodynamic intolerance of VT. These observations not only refined the mechanistic understanding of VT reentrant pathways in TOF, but also provided a rationale for an empiric ablation lesion set based solely on substrate mapping that could be used in the operating room or electrophysiology laboratory for TOF patients with unstable VT.In the current issue of this journal, Kapel et al 7 provide an elegant follow-up to Zeppenfeld's 2007 report by examining the anatomy and electrophysiological properties of these anatomical isthmuses in more detail. The authors performed careful substrate analysis during electrophysiological testing in 74 TOF patients, including 13 subjects who had both clinical and inducible VT, another 15 who had inducible (but no clinical) VT, and 46 with neither clinical nor inducible VT.…”