Po-05-006 mechanisms underlying alternans and oscillation during sustain vt: insights from high density mapping of the isthmus

The mechanism of perturbations and spontaneous variations during monomorphic VT are unknown. We performed high density mapping of the isthmus during VT that exhibited alternans and spontaneous oscillation in morphology and rate to characterize the attributable components of reentrant circuit. The purpose of this study is to delineate patterns of activation change in human VT circuit that exhibit morphologic alternans and/or oscillations in tachycardia cycle length. We analyzed retrospectively 19 patients who underwent a high-density map during VT with QRS morphology change and TCL (tachycardia cycle length) oscillation. For each of the 19 VT episodes, activation maps were reconstructed with different QRS waveforms or different TCL with the same QRS. The distance between breakout sites and the difference in TCL, were measured and compared between the two groups: the QRS morphology change group and the TCL oscillation with same QRS group (Figure). Patients were 67±6.0 years old, male(78.9%), and had structural heart disease (NICM 52.6%, ICM 31.5%, and ARVC 15.8%). A total of 46 activation maps were evaluated for the 19 VTs episodes, with simultaneous endocardial and epicardial mapping performed on 4 of them. All 19 VTs shared part of the isthmus. Nine VTs in the QRS morphology change group showed a breakout shift in all 9 VTs, but no breakout shift was observed in the TCL oscillation with same QRS group (distance 16±4.8mm vs 0mm P<0.05). The TCL difference was significantly shorter in the QRS change group than in the TCL oscillation with same QRS group (22.3±33.7ms vs 61.0±33.8ms P<0.05). Shared isthmus and slight circuit alternans/oscillation were successfully visualized in both the QRS morphology change and the TCL oscillation with same QRS. Differences in activation patterns in the exit region contribute to QRS morphology changes and changes in TCL are attributable to intra-isthmus conduction characteristics.