Resetting of ventricular tachycardia: Implications for localizing the area of slow conduction

Abstract

Analysis of local endocardial electrograms recorded during reentrant ventricular tachycardia does not provide direct information as to the participation of the recording site in the tachycardia circuit. To determine if programmed electrical stimulation at the recording site can assist in localizing areas of slow conduction that are participating in the tachycardia circuit, seven patients with sustained monomorphic ventricular tachycardia were studied. The cardiac cycle was scanned with single stimuli delivered during ventricular tachycardia at multiple endocardial sites. In four patients, an endocardial site was identified at which stimuli advanced the tachycardia with marked conduction delay and without alteration of the ventricular activation sequence, as indicated by a lack of change in the configuration of the QRS complex and endocardial electrograms distant from the stimulation site. This finding was seen only during stimulation at sites displaying abnormal electrograms and is consistent with premature depolarization of an area of slow conduction within the tachycardia focus by stimuli delivered at or near that area. Attempted endocardial catheter ablation at or adjacent to these sites in three patients was followed by persistent noninducibility of ventricular tachycardia in one patient, marked modification of the configuration and cycle length of inducible tachycardia in one patient and transient noninducibility of tachycardia in one patient. Programmed electrical stimulation during ventricular tachycardia at sites with abnormal electrograms may provide information about the proximity of the stimulation site to the tachycardia circuit.

ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death

“…Given the inhomogeneous scarring present in ischemic VT, mapping techniques have evolved that take into account the complex nature of the circuits, including bystander regions of abnormal conduction. The newer 3-dimensional mapping systems permit anatomical reconstructions and correlation of EP characteristics with anatomy (190,(305)(306)(307)(308). These systems have led to an approach whereby circuits can be mapped during sinus rhythm and can facilitate ablation in the ischemic patient who often does not tolerate VT well (303,309 -312).…”

Mapping of reset of anatomic and functional reentry in anisotropic rabbit ventricular myocardium.

“…Many studies have shown that the reentrant circuit after myocardial infarction comprises an area of slow conduction '5-20 and that such a segment of slow conduction influences the reset response. 21,22 ture stimulation during functional VT revealed a local excitable gap at the pacing site measuring 27% of the cycle length of VT. However, in only 3 of 8 hearts, premature stimuli could reset functional VT by 8%.…”

Differential Effects of a Segment of Slow Conduction on Reentrant Ventricular Tachycardia in the Rabbit Heart

“…A sloped reset curve is attributed to the presence of a partially excitable gap or conduction delay between the pacing site and the reentrant circuit. [32][33][34][35] In a study by Almendral et al 36 in 32 patients with chronic myocardial infarction, the 3 different reset patterns were approximately equally distributed. In another clinical study, Gottlieb et al 37 found that termination of VT by premature stimuli was more likely if the reentrant VT exhibited a sloped reset curve.…”