Abstract 15951: Magnetocardiographic Analysis in Post-Infarct Patients with Ventricular Tachycardia: A Possible Mechanism Obscuring the Appearance of Late Potentials on SAECG
Backgroud: Late potentials(LP) are less commonly identified on signal-averaged ECG (SAECG) in patients after myocardial infarction (MI) with ventricular tachycardia (VT) than those with arrhythmogenic right ventricular cardiomyopathy (ARVC) with VT. Since depolarization generally lasts longer in the right (RV) than left ventricle (LV), local conduction delay in LV as arrhythmogenic substrates may be obscured by the concurrent physiological RV activation. To address this issue, we compared high resolution magnetocardiography (MCG) between post-MI and ARVC patients with a history of VT.
Methods: 64-channel MCGs (1kHz, Hitachi) and standard SAECG were analyzed in 17 post-MI patients (LVEF 35±14%) and 14 ARVC patients who experienced VT. 2-D QRS maps were used to determine LV conduction time (LVCT, an interval from QRS onset the instance when leftward LV currents disappear) and the latest ventricular activation site.
Results: LP was undetermined in 5 ARVC and in 5 MI patients due to CRBBB/IVCD on ECG (QRS≥110ms). LP was detectable in most (8/9, 89%) of ARVC patients, but in only 7 (53%) of 12 MI patients with QRS duration <110ms. Meanwhile, MCG detected abnormal conduction delay in RV area for all ARVC patients, and in LV area (compatible with infarct sites) for all MI patients, even presenting wide QRS. For MI patients with QRS<110ms, LVCT was similarly prolonged between patients with and without LP (84±9 vs 88±10ms, NS, 51+4ms measured in 25 healthy volunteers). Of note, the latest ventricular activation was recognized at the abnormally delayed activation site (infarct area) in all of 7 patients with LP, whereas significant RV activation was found during delayed LV activation in 4 of 5 patients without LP. (Figure).
Conclusions: MCG detected and localized marked conduction delay in the area corresponding to the infarct site in MI patients with VT. Physiological RV activation in the late QRS phase might obscure the appearance of late potentials originating from damaged LV.
- © 2012 by American Heart Association, Inc.