Catheter ablation of subepicardial ventricular tachycardia using electroanatomic mapping

In patients with left ventricular tachycardia (VT) and failed endocardial ablation, a subepicardial substrate may be considered.

Seven patients with drug-refractory VT of right bundle branch block morphology were investigated to identify the arrhythmogenic substrate using three-dimensional (3-D) electroanatomic endocardial and epicardial mapping.

In three patients with repetitive monomorphic VT, endocardial and epicardial mapping during tachycardia showed a focal pattern with an earliest activation preceding the onset of the QRS complex by 20 and 28 ms in the lateral aspect of the epicardial outflow tract in two patients and by 24 ms near the posterolateral mitral annulus in one patient; in two patients with sustained VT, endocardial mapping during tachycardia displayed a focal pattern with a wide breakthrough, and epicardial mapping showed a macroreentrant VT with an isthmus located in the left anterior wall in one patient and in the left inferolateral wall in the other. In the remaining two patients, endocardial and epicardial mapping were performed during sinus rhythm. An area with fragmented and late potentials as well as low amplitude was only identified in the epicardial left inferolateral wall. During tachycardia, a diastolic potential was only recorded on the epicardium and coincided with the late potential during sinus rhythm in the same area. A focal or linear epicardial irrigated lesion terminated the VT and resulted in noninducibility in all seven patients. During a median follow-up of 16 months, VT recurred in two patients without antiarrhythmic drugs. The recurrent VT was successfully reablated in one patient and treated with oral amiodarone in the other.

Subepicardial left focal and macroreentrant VT may present as focal origin on endocardial mapping and can only be abolished by radiofrequency (RF) applications in the epicardial space.