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Figure 2 Quantifying ECG CL for Focal AT (Right Atrial) and Macro–Re-Entrant AT (Lower Loop Re-Entry)
Panels show (A) focal AT and (B) macro–re-entrant AT. (I) For each tachycardia, leads X (V5), Y (aVF), and Z (V1). The selected template was cross-correlated successively to the ECG to yield a correlation time series for each axis as shown. (II) Autocorrelation, or correlation of the series to itself with successive time-shifts. The first peak of the autocorrelation function indicates the time-shift required to bring the signal "back into phase." It thus estimates the CL, which was 258 versus 262 ms measured for the focal AT in (A) and 236 versus 239 ms measured for macro–re-entry in (B). (III) Spectral CL estimates were accurate for focal AT in (A) 3.78 Hz (=265 ms), but not for (B) macro–re-entry, 5.49 Hz (=182 ms). Abbreviations as in Figure 1.
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