Macroreentrant Loop in Ventricular Tachycardia From the Left Posterior Fascicle

Abstract

Background— The underlying mechanisms of reentry during left posterior fascicular ventricular tachycardia (LPF-VT) remain unclear. The purpose of this study is to describe the components of LPF-VT reentry circuit and their electrophysiological properties. Methods and Results— Fourteen consecutive patients with LPF-VT underwent electrophysiology study and radiofrequency ablation. Via a multipolar electrode catheter placed from a retrograde aortic approach, a sharp inflection, high-frequency potential (P1) was detected in 9 patients (64%). The ranges of length and velocity of recorded P1 were 9 to 30 mm and 0.5 to 1.2 mm/ms, respectively. Macroreentry involving the ventricular myocardium was confirmed to be the mechanism in all patients by premature ventricular stimuli delivery or entrainment of LPF-VT with progressive fusion, or both. During LPF-VT, the earliest left posterior fascicle (LPF, P2) was considered to be the site of connection between P1 and P2, and the site of the earliest P2 along the left posterior ventricular septum correlated well with the His-ventricular interval during tachycardia. Radiofrequency ablation focused on the P1 potentials (9 patients with a recorded P1) or earliest P2 (5 patients without a recorded P1) was successful in all 14 patients. After 4.5±3.0 months of follow-up, no patients had recurrence of LPF-VT. Conclusions— The LPF-VT macroreentrant loop involves the ventricular myocardium, a part of the LPF, a slow conduction zone, and in certain cases, a specially conducting P1 fiber. The His-ventricular interval during LPF-VT correlates with multiple electrophysiological measures and is a useful marker for identification of the optimal ablation site.

Catheter ablation for verapamil-sensitive fascicular ventricular tachycardia guided by precise mapping using a multi-spline duodecapolar catheter with small electrodes and close spacings

“…Recently, there have been a number of reports on so-called “Purkinje-related arrhythmias,” including F-VT 1, 3. Although P1 is the common target of catheter ablation for F-VT, P1 cannot be recorded in up to one third of cases using linear catheters 4 . There may be some anatomical limitations in such cases: P1 fiber may not be long or parallel to the long axis of the LV, which makes it difficult to record P1 with linear catheters.…”

Idiopathic Left Ventricular Tachycardia Originating in the Left Posterior Fascicle

“…found that the sharp retrograde Purkinje potential (PP) following the local ventricular ECG could be recorded at the left posterior fascicular region during normal sinus rhythm in patients with LPF-ILVT. [ 25 ] They also demonstrated that the retrograde PP during normal sinus rhythm correlated with the diastolic PP during tachycardia. Ablation at the retrograde PP sites rendered tachycardia non-inducible ( Figure 7 ).…”

“…Ouyang et al speculated that the reentrant circuit of LPF-ILVT may consist of antegrade and retrograde Purkinje potentials, bridged by ventricular myocardium. [ 24 ] Recently, further investigation of the mechanism of LPF-ILVT was reported by Liu et al[ 25 ] In that study, multipolar electrode catheters were used to continuously record the P1 and P2 potentials. Both the P1 and P2 potentials could be recorded in 64% of patients, which is consistent with the findings of Nogami’s study.…”

What is the mechanism of wide QRS tachycardia?

“…First, the timing of the earliest ventricular activation at the anteroseptum in parallel with the onset of QRS does not support a diagnosis of ILVT or the participation of the NF fiber with a breakthrough remote from the basal ventricle as the antegrade conductive pathway during the pre‐excited tachycardia. Furthermore, this does not exclude the participation of the NV fiber (Figure ) …”