Session S44.4

Ventricular Repolarization Dispersion during Ischemia Course Measured by Temporal and Spatial ECG Parameters

PD Arini, FH Baglivo, JP Martínez, P Laguna*

Instituto Argentino de Matemática
Buenos Aires, Argentina

This work studies the evolution of Ventricular Repolarization Dispersion (VRD), as measured on the ECG during the time course of induced ischemia by coronary angioplasty (PTCA). The study group consisted of 93 patients receiving PTCA at LAD (n=29), RCA (n=45) and LCX (n=19) arteries. 12-standard and XYZ orthogonal ECG leads were used. VRD was quantified with indexes of Temporal Duration of Repolarization (TDR): T-wave width (Tw) and T-wave peak to end (Tpe) interval and indexes of Spatial Complexity of Repolarization (SCR): the ratio of the 2nd to the 1st eigenvalues (SCR1) in the repolarization SVD, the ratio of the 2nd eigenvalue to the RMS of all 15th eigenvalues (SCR2), and the ratio of the non-dipolar components to the total energy (TWR). Previous to the computation of the VRD indexes, ECG delineation was performed on the 15 leads by a wavelet transform delineator. We used a multilead rule with outlier protection for selecting the global Ton as the earliest reliable T-onset at any lead, Ten as the latest reliable T-end, and as Tp the median value in the 15 leads. Tw, Tpe, SCR1, SCR2 and TWR temporal series were measured at different times during the procedure: just before the start of occlusion taken as control (C), start of occlusion (OS), one (O1), two (O2) and three (O3) minutes after the OS, respectively, and the occlusion end (OE). The indexes during PTCA showed significant differences with respect to C (*p<.05, **p<.01, +p<.005, ‡p<.001, §p<.0005, #p<.0001). For LAD occlusion, Tpe in (C) =80.1±3.1; OS=84.9±3.0*; O1=88.1±3.6*; O2=89.8±3.8*; O3=85.9±2.4*; OE=89.2±4.3* ms. For RCA occlusion, Tpe in (C)=80.4±1.6; OS=92.5±3.9‡; O1=88.2±3.4+; O2=85.7±2.4**; O3=89.6±3.5*; OE=88.1±3.2** ms. For LCX occlusion Tpe does not change significantly at any time instant. Tw does not change significantly for any artery or time instant. For LAD occlusion, SCR1 in (C) =6.8±0.9; OS=11.5±1.2*; O1=12.2±1.9**; O2=13.7±3.1*; O3=11.5±1.8*; OE=10.3±1.7(NS) % . For RCA occlusion, SCR1 in (C)=5.8±1.1; OS=9.6±1.9 (NS); O1=10.7±1.9+; O2=11.5±1.9§; O3=12.8±1.9§; OE=14.4±2.2# %. For LCX occlusion, SCR1 in (C)=8.5±2.9; OS=10.2±1.8*; O1=13.7±2.5**; O2=12.5±2.0*; O3=13.6±2.4**; OE=16.3±3.0** %. TWR does not change significantly for any lead occlusion and SCR2 change significantly at the same situations as SCR1 does.
Conclusions: PTCA resulted in an increase of the Tpe suggesting increased transmural dispersion at early ischemia stages (slight reduction or no change in the endocardial APD while the epicardial APD is reduced in a larger proportion). No significant differences were found for the Tw, possibly due to the difficulties of Ton delineation during ST elevation. Changes observed in the SCR indexes are concordant with a widening of the of the T-wave loop during ischemia. On the other hand, TWR does not significantly change suggesting that the increase of VRD during ischemia does not modify the validity of the dipolar assumption.

(Abstract Control Number: 1)