Author + information
- Pablo Ávila, MD and
- Ángel Arenal, MD, PhD∗ ()
- ↵∗Electrophysiology Unit, Cardiology Department, Hospital General Universitario Gregorio Marañón, 46 Doctor Esquerdo Street, 28007 Madrid, Spain
We read with great interest the report by Mountantonakis et al. (1). In this study, the authors reported that ventricular tachycardia (VT) isthmus sites were contained within channels in only 37% of voltage channels, and raised concerns about the suitability of using such channels as a target for ablation of unmappable VT. The authors came to this conclusion after analyzing a subgroup of 24 patients from a group of 140 patients who underwent VT ablation. These findings differ from previous data in which the majority of channels were related with clinical or inducible VTs (2,3).
Could evidence derived from 17% of patients with monomorphic VT be applied to the great majority of VT patients? In our opinion, great care should be exercised in extrapolating these results to the full spectrum of VT because of these points:
1. Complete activation mapping during VT was not obtained, and the circuit exit sites were not identified. Therefore, a connection between the isthmus site and a close channel cannot be completely excluded.
2. VT isthmuses not related to conduction channels are shown in maps in which the lower voltage limit is set at 0.5 mV. Could it be that isthmus sites were in incomplete channels connected to the main channel, as it seems to occur in Figure 5A? In previous studies, VT-related channels were always located within dense scar defined by a voltage <0.5 mV (2).
3. Voltage channels were identified during sinus rhythm and VT isthmus sites during VT. How these sites were later incorporated into voltage maps is very relevant, taking into account that ventricular volume and spatial position of the left ventricle may change during VT.
4. The average cycle length of channel-related VT was significantly shorter than that of VT not related to channels (377 ± 67 ms vs. 440 ± 40 ms, p = 0.01), but similar to the VT cycle length (374 ± 59 ms) reported in the previous study in which the majority of VT isthmuses were in channels (2). Could it be that fast VT isthmuses are commonly located in voltage channels? Slow VT may have a more complex substrate in which differentiation of central isthmuses from the surrounding scar could be more challenging. If slow mappable VTs have a different substrate, studies based on entrainment mapping could introduce bias when studying the relationship of VT isthmuses and voltage channels.
- American College of Cardiology Foundation
- Mountantonakis S.E.,
- Park R.E.,
- Frankel D.S.,
- et al.
- Arenal A.,
- del Castillo S.,
- Gonzalez-Torrecilla E.,
- et al.