Demonstration of the Reentrant Circuit of Verapamil‐Sensitive Idiopathic Left Ventricular Tachycardia: Direct Evidence for Macroreentry as the Underlying Mechanism

Abstract

The exact reentrant circuit of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) remains unclear. This case report demonstrates the reentrant circuit of ILVT. A 20-pole electrode catheter was placed along the left posterior fascicle during electrophysiologic study. ILVT was reproducibly induced by programmed ventricular stimulation. During the tachycardia, sequential diastolic potentials bridging the entire diastolic period were observed in the recordings from the electrodes positioned from left ventricular mid-septum to inferoapical septum. The slow conduction zone appeared to be composed of a false tendon in this patient. Entrainment of the ILVT from the right ventricular outflow tract at a different pacing cycle length revealed that a dominant conduction delay occurred at the proximal site of the slow conduction zone. Entrainment studies from several sites on the left ventricular septum confirmed that these sites where sequential electrical activity was recorded were included within the reentrant circuit. However, the left posterior fascicle itself seemed to be a bystander. This report provides the direct evidence of macroreentry as the underlying mechanism of this ILVT, adjacent to the left posterior fascicle.

Ventricular Tachycardia Originating From the Posterior Papillary Muscle in the Left Ventricle

“…7 In this arrhythmia, discrete fascicular potentials can be recorded over a significant portion of the interventricular septum at the site of successful ablation. [7][8][9] In addition, this arrhythmia demonstrates the classic criteria for transient entrainment with rapid ventricular pacing and has been conclusively demonstrated to be due to a macro-reentrant circuit. 9,14 Interfascicular reentry and automatic fascicular VTs usually occur in patients with dilated cardiomyopathy, although they may also occur in structurally normal hearts.…”

“…1,2 Fascicular VTs usually involve the posterior fascicle of the left bundle branch but may also involve the anterior fascicle or the upper septum of the LV 7 ; these forms of VT are often based on a reentrant mechanism and may be sensitive to verapamil. [7][8][9] We describe a distinct clinical syndrome of VT that is exercise induced and arises from the base of the posterior papillary muscle (PPM) in the LV.…”

Isolated Conduction Within the Left His-Purkenje System During Sinus Rhythm and Idiopathic Left Ventricle Tachycardia

“…[4][5][6] The connection strand serves as the antegrade limb, the fascicles serves as the retrograde limb, and the earliest retrograde PP is usually recorded at the beginning of retrograde limb. 6 Partially conforming to those findings, the current study found that the earliest retrograde PP was recorded along the predefined LPF and averaged 15 mm away from its distal end. All VTs could be successfully abolished by ablation at the earliest retrograde PP.…”

“…[2][3][4] Reentry involving the left His-Purkenje system (HPS) was thought to be the underlying mechanism. 5,6 Ablation directed at the earliest retrograde presystolic potential (PP) or diastolic potential (DP) was proved feasible and effective. 4,7 Functionally, the main branch of left HPS is insulated from the adjacent myocardium and exhibits isolated conduction during sinus rhythm (SR), but in vivo study in human beings is very limited.…”

Fascicular Ventricular Tachycardia Originating From Papillary Muscles

“…[18][19][20] A fibromuscular false tendon is a fine muscular strand which carries Purkinje fibers and may traverse the LV cavity between the PMs and the intraventricular septum. It is possible that in some cases of PM-FVT, there is an anatomical and electrical connection between the APM and PPM, which may explain the changes in QRS morphology from superior to inferior axis deviation during ablation.…”