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Electrogram Characteristics in Postinfarction Ventricular Tachycardia

Effect of Infarct Age

Frank Bogun, MD^_*,_*, Subramaniam Krishnan, MD, Mukarram Siddiqui, MD, Eric Good, DO^_*, Joseph E. Marine, MD, Claudio Schuger, MD, Hakan Oral, MD^_*, Aman Chugh, MD^_*, Frank Pelosi, MD^_* and Fred Morady, MD^_*

^_* University of Michigan Medical Center, Ann Arbor, Michigan
Henry Ford Hospital, Division of Cardiology, Detroit, Michigan

View larger version (12K): [in a new window]   Figure 1 (A) Shown are recordings from surface leads I, aVF, and V1, and intracardiac recordings from the mapping catheter electrogram (EGM) and the right ventricular apex (RVA). The local EGM that is recorded by the mapping catheter is normal. The amplitude is 7.8 mV, and the width is 65 ms. (B) The tracings are analogous to the tracings in panel A. The local EGM recorded by the mapping catheter displays an isolated potential (oblique arrow) that is separated from the ventricular EGM by an isoelectric line of 210 ms. The EGM amplitude is 0.12 mV, and the EGM width is 357 ms. (C) The tracings are again analogous to the tracings in panel A. The recorded EGM is fractionated; the amplitude is 0.37 mV, and the width is 192 ms. (D) The tracings are again analogous to the tracings in panel A. The local EGM is abnormal. The amplitude is 0.7 mV, and the width of the EGM is 112 ms.

View larger version (22K): [in a new window]   Figure 2 (A) This figure displays a user-defined map of a view of the septal aspect of the left ventricle (LV) and shows the LV outflow tract and part of the mitral valve annulus (MVA). The map is color-coded according to the measured electrogram (EGM) width. Three EGMs are displayed. Two of them have isolated potential (sites #1 and #3; isolated potentials are indicated by arrows) and represent the widest EGMs identified in this patient. Sites at which fragmented EGMs without isolated potentials are recorded separate them (site #2). The different EGM widths are indicated below the EGMs. Areas with isolated potentials are marked in blue, areas with fragmented electrograms are marked in white, and the area where the His was recorded is indicated as orange dots. The map was obtained in a patient who had an inferior wall myocardial infarction 30 years before the mapping study. (B) The scheme represents the same view as outlined in panel A. The cross-hatched area corresponds to areas with low-voltage EGMs and the black area represents the area where EGMs are broader than 200 ms. Areas in white correspond to sites with higher voltage EGMs (>1 mV). (C) This figure illustrates a voltage map of the same view shown in panels A and B. Low-voltage areas are differentiated from higher voltage areas.

View larger version (17K): [in a new window]   Figure 3 (A) This figure shows a user-defined map of the infero-posterior wall of the left ventricle (LV), including the LV apex and the mitral valve annulus (MVA). As in Figure 2A, the electrogram (EGM) width is color-coded. The patient had an inferior myocardial infarction one year before the mapping study. The EGM shown is the broadest endocardial EGM obtained in this patient and represents the site of effective ablation of the targeted ventricular tachycardia during sinus rhythm. The EGM width is 150 ms; an isoelectric segment of 26 ms separates the ventricular EGM from the isolated potential (arrow). (B) The scheme represents a view of the same area outlined in panel A. The striped area corresponds to areas with low-voltage EGMs, and the black area represents the contiguous area with an EGM width of >133 ms. The white area correspond to sites with higher voltage electrograms (>1 mV). Black area = EMG >133 ms; striped area = EGMs <1 mV; white area = EGMs >1 mV. (C) This figure illustrates the voltage map of the same view outlined in panels A and B in this patient, delineating the low-voltage areas from areas with higher voltage (>1 mV).

View larger version (31K): [in a new window]   Figure 4 This figure shows the distribution of electrogram (EGM) types into different electrogram width categories: 133, >133, >160, and >200 ms. The EGM types include normal electrograms (nl EGM), abnormal electrograms (abn EGM), fractionated electrograms (frag EGM), and EGMs with isolated potentials (IP).

View larger version (14K): [in a new window]   Figure 5 Shown is the maximal width of the local electrogram (EGM) obtained in each patient plotted against the infarct age. There is a significant association between infarct age and maximal EGM width (R = 0.84).