Epicardial and endocardial mapping of ventricular tachycardia in patients with myocardial infarction. Is the origin of the tachycardia always subendocardially localized?

Abstract

Background. Left ventricular endocardial reentry is the conventional concept underlying surgery for ventricular tachycardia (VT). We assessed the incidences of patterns showing complete reentry circuits at either the subendocardial or subepicardial level and of patterns in which left ventricular endocardial mapping could only in part account for a reentrant mechanism.Methods and Results. We retrospectively analyzed epicardial and left ventricular endocardial isochronal maps of 47 VTs induced in 28 patients with chronic myocardial infarction (inferior, 14 patients; anteroseptal, 14 patients). Electrograms were recorded intraoperatively from 128 sites with epicardial sock and transatrial left ventricular endocardial balloon electrode arrays. Given the methodology used in this study, the mapping characteristics of the tachycardias suggested five types of activation patterns: 1) complete (90% or more ofVT cycle length) subendocardial reentry circuits in seven VTs (15%) and seven patients (25%), 2) complete subepicardial reentry circuits in four VTs (9%o) and four patients (14%), 3) incompletely mapped circuits with a left ventricular endocardial breakthrough preceding the epicardial breakthrough in 25 VTs (53%) and 21 patients (75%), 4) incompletely mapped circuits with a left ventricular epicardial breakthrough preceding the endocardial breakthrough in three VTs (6%) and three patients (11%), and 5) a right ventricular epicardial breakthrough preceding the left ventricular endocardial breakthrough in eight VTs (17%) and seven patients (25%). After surgery, one type 3 VT and three type 5 VTs were reinducible. Thus, left ventricular endocardial reentry substrates (types 1 and 3) accounted for 68% of VTs, but substrates involving subepicardial (types 2 and 4) and deep septal layers (type 5) accounted for 32%

Electrocardiographic Recognition of the Epicardial Origin of Ventricular Tachycardias

“…One proposed explanation is that the reentry circuits may be located deep in the subendocardium or in the epicardium, making them inaccessible to current ablation techniques. 7,8 Epicardial mapping of arrhythmia foci or circuits has been attempted in open chest surgery 9,10 and with RF ablation catheters. 11,12 These studies suggest that the slow conduction zone may be located subepicardially in up to 33% of patients.…”

Relation Between Body Surface Mapping and Endocardial Spread of Ventricular Activation in Postinfarction Heart

“…27 We did not nd clear early endocardial activity within 10 msec of onset of the body surface QRS complex in 18% of VTs. In these cases, an earlier epicardial or intramural exit site was believed to be present, although this could not be con rmed due to lack of epicardial activation data.…”

Subxiphoid Surgical Approach for Epicardial Catheter-Based Mapping and Ablation in Patients With Prior Cardiac Surgery or Difficult Pericardial Access

“…A larger incision often is used for this purpose. 8,9 Our approach with limited exposure in the electrophysiology laboratory offers some advantages. Electroanatomic mapping systems, not generally available in the operating room, can be used to help define the abnormal regions and circuits.…”