Session S31.3

Spatial Characterization of Ischemia in 12-Lead ECG Recordings during PCI Using Both Depolarization and Repolarization Indices

D Romero*, E Pueyo, M Ringborn, P Laguna

Universidad de Zaragoza
Zaragoza, Spain

Spatial characterization of ischemia from the ECG is of great clinical interest in order to improve risk stratification by knowing the area and location of the ischemic myocardium. In this study, spatial characterization is addressed by evaluating different 12-lead ECG-derived indices during both depolarization and repolarization.
The ST level measured at J point plus 60 ms (STJ+60), high-frequency QRS components in the band 150-250 Hz (HF-QRS), the S wave amplitude (Sa) and the recently proposed upward and downward QRS slopes (IUS and IDS) were evaluated during prolonged elective PCI-induced transmural ischemia in a population of 83 patients (with a mean occlusion duration of 4 min and 26 s). The absolute change of each index I during coronary occlusion, ?I, was quantified, and the relative change, RI, was measured as the ratio between ?I and the standard deviation of I at a pre-PCI control recording. Spatial characterization of ischemia was assessed by computing lead distributions of relative ischemic changes for each of the analyzed indices (i.e. RI as a function of lead), separately in the three groups according to the occlusion site (LAD in 25 patients, LCX in 18, and RCA in 40).
The indices showing the most pronounced changes during the PCI were STJ+60, Sa, and IDS, with a mean absolute change during occlusion of 14.5, 15.2 and 6.2 times their normal variations in pre-PCI recordings, respectively. The other indices, HF-QRS and IUS, presented lower relative changes (mean RHF-QRS = 2.01 and mean RIUS = 5.39). Spatial lead distributions were very similar for the three most sensitive indices, with very distinctive lead-profiles depending on the occlusion site. In the LAD group, STJ+60, Sa, and IDS showed their highest changes in the precordial leads V2-V4 (with mean values across those leads being: RSTJ+60 = 29.8 ± 7.74, RSa = 39.2 ± 8.12, RIDS = 16.1 ± 3.25). In the LCX group, predominant changes were observed in V4-V6 (mean: RSTJ+60=10.7 ± 4.55, RSa=13.7 ± 4.05, RIDS= 5.08 ± 1.28). In the RCA group, ischemic changes were more predominant in leads II, aVF and III (mean; RSTJ+60 = 24.4 ± 5.49, RSa = 21.4 ± 5.01, RIDS = 6.13 ± 0.98).
In addition to conventional ST segment changes, ECG-derived indices from the final part of the QRS complex showed high sensitivity for detection of PCI-induced ischemia. Moreover, their spatial distribution showed the largest changes in leads closest to the region represented by the occluded artery. The analysis of depolarization changes presented in this study hence allows both temporal and spatial characterization of regional ischemia, where the marked and distinctive spatial profile could be considered for occlusion site identification.

(Abstract Control Number: 18)