Case report: alternating exit sites in reentry circuit of ventricular tachycardia with nonischemic cardiomyopathy - relationship between ablation site and inner loop

An intriguing case of regular RR and QRS alternans during idiopathic left posterior fascicle ventricular tachycardia

This study represents a case of idiopathic left posterior fascicle ventricular tachycardia (LPF-VT), which is intriguing due to regular alternation of short-long RR intervals and QRS morphology. Transthoracic echocardiogram analysis did not detect any structural heart disease. A baseline electrophysiological study was performed. Intracardiac recording during tachycardia showed V-A dissociation, confirming the final diagnosis of idiopathic LPF-VT. No regularity in the monomorphic VT was recorded. Previous relevant studies suggested that a single focus with two exits in distal branches of the left posterior fascicle or two different foci localized in the Purkinje-myocardial network of the left posterior fascicle can clarify the mechanisms. Our team proposed an additional explanation that combines the physiological refractory period with the Ashman phenomenon in individual reentrant LPF-VT circuit.

Insight Into the Mechanism of Macroreentrant Atrial Tachycardia With Cycle Length Alternans Using Ultrahigh Density Mapping System

Background:

Atrial tachycardia (AT) with cycle length (CL) alternans is a rare phenomenon. We aimed to identify the characteristics and precise mechanism of this special category of ATs by using an ultrahigh density mapping system.

Methods:

We identified 7 ATs with alternating CL in a total of 478 ATs from 2 institutions mapped with an ultrahigh density mapping system. Activation maps were performed for long CL (289±35 ms; mapping points, 21 520±11 103) and short CL (251±18 ms; mapping points,17 594±8059) separately.

Results:

We classified ATs with CL alternans into 2 types. Type 1: There existed 2 potential loops with different routes. CL alternans resulted from an intermittently 2:1 conducting block within the channel of the smaller loop. Type 2: CL alternans resulted from different conduction velocity through 2 closely spaced gaps within preexisting linear lesions. Catheter ablation successfully terminated all the 7 ATs.

Conclusions:

Ultrahigh density mapping provides an opportunity to delineate the precise mechanism of AT with CL alternans. Intermittent conduction block or slowing of a channel was essential for the maintenance of AT.

Ablation of left atrial tachycardia with cycle length alternans after atrial fibrillation ablation: significance of fractionated electrogram mapping

INTRODUCTION

Atrial tachycardia (AT) with cycle length alternans occurring after atrial fibrillation ablation has not been previously described.

METHODS

Among 66 patients with left AT, stable AT with 2 alternating cycles was registered in 5 cases. Activation mapping of both alternating cycles was performed in all 5 patients. Entrainment and fractionated electrogram mappings were also carried out.

RESULTS

Among 10 AT cycles, activation maps suggested underlying mechanism of 5 cycles (50%) in 3 patients. Entrainment pacing was helpful in 2 patients (confirmed mechanism of 2 AT cycles). Catheter ablation successfully terminated AT in all 5 patients: ablation of sites with fractionated potentials in 4 patients and mitral isthmus ablation in 1 patient.

CONCLUSION

Consecutive activation mapping of both AT cycles is feasible for mechanism determination in some patients. The results of our small study suggest that fractionated electrogram-guided ablation might be a reasonable approach for termination of this type of AT.

Two ventricular tachycardias with cycle length and QRS alternans: insights into the mechanism from mapping and ablation of the tachycardias

This case describes a patient with two separate foci of idiopathic ventricular tachycardia in the right ventricle. Both of the tachycardias manifested cycle length and QRS alternans. Both were successfully ablated and information from the electrophysiologic study and ablation procedure indicated that both tachycardias were focal, secondary to triggered activity, and that the best model to explain the cycle length and QRS alternans during tachycardia was that of "self-entraining modulated parasystole."