Substrate mapping for unstable ventricular tachycardia

Abstract

The primary goal of catheter ablation of scar-related ventricular tachycardia (VT) is the interruption of critical areas of slow conduction responsible for the development and maintenance of the reentrant VT circuit. Most patients with scar-related VT present with unstable arrhythmias that are not amenable to interrogation from multiple sites to define the VT circuit based on the intracardiac activation sequence and the response to entrainment mapping. In order to effectively target unstable VTs, a number of ablation approaches have been described with the aim of targeting the abnormal substrate defined with mapping in sinus or paced rhythm. Some of these strategies (eg, late potential and local abnormal ventricular activity ablation or scar homogenization) target the entire abnormal substrate harboring abnormal electrograms, defined with a variety of different criteria. Scar dechanneling, linear ablation through sites matching VT with pacing, and the core isolation approach focus on more discrete regions within the abnormal substrate that have been proven relevant to the clinical and/or inducible arrhythmias by means of physiologic maneuvers, although this does not necessarily translate to fewer radiofrequency lesions to achieve the procedural end-point. Observational studies evaluating different substrate-based ablation techniques have reported fairly uniform arrhythmia-free survivals at short- and mid-term follow-up, although direct comparisons between different techniques are lacking. In this article, we summarize the different state-of-the-art substrate mapping and ablation approaches for targeting unstable VT, with a particular focus on the relative merits and limitations of the described techniques.

Three‐dimensional myocardial scar characterization from the endocardium: Usefulness of endocardial unipolar electroanatomic mapping

“…UNIP voltages are, therefore, influenced by the electrical activity occurring within a wide field of view and quite often distant electrical activity accounts for some component of the UNIP potential. 1,6 The exact "field of view" of UNIP and BP recordings is not completely predictable and depends on a number of variables including (1) the degree of contact of the electrode(s); (2) the electrode orientation with respect to the tissue; (3) the differences in proximal vs distal electrode sizes and the distance between them (BP recordings); (4) the activation vector of the ventricular depolarization; and (5) the presence of anisotropic conduction. During the acquisition process of the BP signal, the influence of remote electrical activity thus becomes reduced, the remote signals contributing to the BP EGM only by a product of third power of the distance, whereas such contribution to the UNIP EGM is a product of the square of the distance.…”

Extracorporeal Membrane Oxygenation for Hemodynamic Support of Ventricular Tachycardia Ablation

“…Furthermore, multiple comorbidities may increase the risk of acute hemodynamic decompensation and periprocedural multiorgan failure [2][3][4] and mortality triggered by myocardial stunning secondary to prolonged times under general anesthesia. Current mapping techniques allow the accurate identification of the arrhythmia substrate and subsequent effective modification during sinus rhythm (SR), 5,6 thus avoiding prolonged activation and entrainment mapping times during hypotensive VT. Substrate modification, however, may not be always effective. Reasons include an absence of defined SR targets, an absence of a well-defined scar as in the setting of idiopathic dilated cardiomyopathy, 7 and residual VTs that may be induced even after an otherwise successful substrate modification procedure.…”

Scar voltage threshold determination using ex vivo magnetic resonance imaging integration in a porcine infarct model: Influence of interelectrode distances and three-dimensional spatial effects of scar

“…Moreover, VT ablation is being performed in increasingly different cardiomyopathies with more complex substrates (patchy non-subendocardial scars), where it is essential to associate voltage mapping-ideally using patientspecific thresholds-with an accurate qualitative analysis of electrograms (ie, presence of split, late, and/or fragmented potentials). 5 These are also the substrates in which real-time image integration holds a promising future in the field of substrate-based VT ablation, 6 as once more shown here by the important insights gained with ex vivo MRI integration.…”