Characteristics of local electrograms with diastolic potentials: Identification of different components of return pathways in ventricular tachycardia

Background: Diastolic potentials are often sought as a possible site for ca theter ablation in post-infarct ventricular tachycardia. However, delivery of energy at such sites is often unsuccessful. The purpose of this study wa s to determine the characteristics of local electrograms with diastolic pot entials and to identify activation pattern which might indicate the critica l portion of the return path of the ventricular tachycardia. reentry circui t. Methods: In 17 patients with post-myocardial infarction ventricular tachyca rdia, 30 ventricular tachycardias were mapped with an 112 bipolar endocardi al baboon at the time of surgery. Diastolic mapping of the return tract in ventricular tachycardia was performed. Four activation patterns were observ ed (15 figure 8 patterns, 2 circular patterns, 2 biregional patterns and 11 monoregional patterns). Of 3,360 local electrograms, 207 (6.2%) demonstrat ed a, diastolic potential in ventricular tachycardia They were classified i nto following four categories, based on the appearance and timing of the sy stolic component. Type A-1 electrogram: systolic activation was of low ampl itude (<2 mV) and was prolonged (greater than or equal to 100 msec), but pr eceded the onset of the surface QRS in ventricular tachycardia. Type A-2 el ectrogram: systolic activation was of low amplitude, was prolonged, but fol lowed the onset of the surface QRS. Type B electrogram: systolic electrogra m was fractionated, but relatively normal amplitude (2.0-3.6 mV). Type C el ectrogram: systolic electrogram was almost normal. Results: Of all electrograms with diastolic potentials, three type A-1 elec trograms (1.4%) were located at the exit of the return pathway II type A-1 electrograms (5.3%) were located at the pre-exit site. No type A-1 was foun d at an entrance/bystander area 21 type A-2 electrograms (10.1%) were at th e pre-exit and 83 type A2 electrograms (40.2%) were located at the entrance /bystander area, but such electrograms were never found at the exit site. 7 1 type B electrograms (34.3%) and 18 type C electrograms (8.7%) were locate d at the entrance/bystander area. To distinguish the type A-2 electrograms at the pre-exit site hom those at the entrance/bystander area, the diastoli c potential to QRS interval was measured. This interval at the pre-exit was significantly shorter than that at the entrance/bystander area (-47.2 +/- 10.7 vs -96.3 +/- 31.3 msec, p = 0.0001). Conclusion: Type A-1 electrograms indicated the exit or pre-exit site of re turn pathway. Type A-2 electrograms with diastolic potential to QRS interva l <-50 msec indicated the pre-exit site. However, the other types of local electrograms with diastolic potential did not indicate the critical portion of the ventricular tachycardia circuit. These observations may be helpful during catheter mapping and ablation of patients with post-infarct ventricu lar tachycardia. Condensed Abstract. Diastolic potentials are often sought to direct cathete r ablation in post-infarct ventricular tachycardia. We investigated the cha racteristics of local electrograms showing diastolic activity in an attempt to determine whether critical portions of the ventricular tachycardia circ uit could be identified by a typical "signature." In 17 patients with a rem ote myocardial infarction, 30 ventricular tachycardias were mapped with 112 bipolar endocardial baboon at the time of surgery. Diastolic potentials in association with low amplitude (<2 mV) and prolonged (greater than or equa l to 100 msec) systolic electrograms preceding the onset of QRS were found at the exit Bite and pre-exit site of return pathway A similar systolic ele ctrogram occurring after QRS onset with a diastolic potential to QRS interv al of <-50 msec was found at the pre-exit site. However, other local electr ograms with diastolic activity were at sites remote from the exit or pre-ex it of the return pathway. These observations may be helpful during catheter mapping and ablation in patients with ventricular tachycardia.