Figure 32.6

Averaged surface maps relating to atrial activation and recovery in a normal subject, at the instants or time indicated by the vertical line crossing the ECG at top of each figure. The time interval between the (a) and (d) is 88 ms. The zero equipotential line is dashed. The plus and minus signs indicate the value of the positive and negative peaks in microvolts; + P and − P indicate the step (in microvolts) between adjacent positive and negative equipotential lines.