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. Author manuscript; available in PMC: 2014 Aug 1.
Published in final edited form as: Circ Arrhythm Electrophysiol. 2013 Jul 24;6(4):10.1161/CIRCEP.113.000114. doi: 10.1161/CIRCEP.113.000114

Figure 2.

Figure 2

Statistical coherence analysis of 4 pacing protocols (amplitude: ±1/±5 mA, pulse width: 30 ms, coupling: 10 ms) in the normal heart (n=9) for negative and positive alternans sequences. (A) Box-plot representation of the estimated coherence value at 0.5 cycle/beat for negative alternans (white boxes) and positive alternans (gray boxes) during baseline and following R-wave triggered pacing for body-surface and CS, LV and RV leads. For each set of body-surface leads and intracardiac leads, the median (horizontal solid line), 90-10% percentiles (box) and 95-5% percentiles (error bars) are shown. The dashed lines indicate the lead-dependent coherence threshold determined using the corresponding ROC curve. (n=36 for each of the body surface, CS, LV and RV leads; where n represents the overall sample size: 9 subjects for each of the ±1 mA and ±5 mA pacing interventions) (B) Sensitivity (Sn) and specificity (Sp) for body-surface and intracardiac leads as a function of their respected coherence threshold. (C) ROC curves for body-surface leads and intracardiac leads determined by changing the coherence threshold from 0 to 1 in steps of 0.001. For each lead, statistically significant comparisons (negative alternans vs. positive alternans) are marked by an asterisk.