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Figure 6 Discordance With Heart Rate Acceleration
Discordant alternans initiated by heart rate acceleration in 1 patient. The top tracing shows surface electrocardiogram lead II at the commencement of atrial pacing at cycle length 500 ms. The bottom tracings show the beat-to-beat voltages (at identical time points in the JT interval) for epicardial electrodes (Epi) 1 to 16. This sequence begins with the last 2 sinus beats before pacing begins. The even and odd beats are indicated by an open circle and a filled circle, respectively. Discordant alternans between the apical (Epi 1 to 4) and basal electrodes (Epi 11 to 16) begins at the 10th beat and lasts for 24 beats. The intervening electrodes in the mid segment represent a node without alternans.
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