Exploring Postinfarction Reentrant Ventricular Tachycardia With Entrainment Mapping

Abstract

Ventricular tachycardia late after myocardial infarction is usually due to reentry in the infarct region. These reentry circuits can be large, complex and difficult to define, impeding study in the electrophysiology laboratory and making catheter ablation difficult. Pacing through the electrodes of the mapping catheter provides a new approach to mapping. When pacing stimuli capture the effects on the tachycardia depend on the location of the pacing site relative to the reentry circuit. The effects observed allow identification of various portions of the reentry circuit, without the need for locating the entire circuit. Isthmuses where relatively small lesions produced by radiofrequency catheter ablation can interrupt reentry can often be identified. A classification that divides reentry circuits into one or more functional components helps to conceptualize the reentry circuit and predicts the likelihood that heating with radiofrequency current will terminate tachycardia. These methods are helping to define human reentry circuits.

Saline-Cooled Versus Standard Radiofrequency Catheter Ablation for Infarct-Related Ventricular Tachycardias

“…Patients had to meet the following criteria: (1) sustained, monomorphic VT was present or inducible in the electrophysiology laboratory, and (2) pacing for entrainment was performed at a mapping site followed immediately by application of RF current for ablation, allowing assessment of whether VT terminated during the RF application. 3,4 Patient characteristics are shown in Table 1.…”

“…The mapping and ablation approach has been previously described. 3,4 Access to the left ventricle was achieved with a retrograde aortic or trans-septal approach. Systemic anticoagulation was maintained with the intravenous administration of heparin.…”

“…The reentry circuits can be large, and portions of the reentry path can be located deep to the endocardium. [1][2][3] Multiple radiofrequency (RF) lesions are often required, and inadequate lesion size likely contributes to failures. For any given electrode size and tissue contact area, RF lesion size is a function of RF power and duration of application.…”

“…3,4 We hypothesized that if salineirrigated ablation produced larger lesions in vivo in human infarct regions, it would be more effective in interrupting VT compared with standard RF ablation. Therefore, the effect of cooled RF ablation and standard RF ablation on induced, sustained VT was compared in patients undergoing VT ablation after infarction.…”

Unusual response to entrainment of ventricular tachycardia: In or out?

“…1 The presence of these responses is highly predictive of termination with ablation. 2,3 In this case, overdrive pacing of the slow VT (680 ms) is performed at 620 ms (10 mA @ 2 ms). Two distinct diastolic potentials are seen during VT, and it is important to distinguish the near-field EGM captured from far-field components in order to accurately measure the postpacing interval.…”