Click on image to view larger version.

Figure 3 Mean ERP after constant pacing (300, 400, 500, 600 and 700 ms) and after long–short (600 to 300 ms) and short–long (300 to 600 ms) sequences in patients pretreated with verapamil. Mean ERP during the long–short sequence is significantly shorter than ERP at 300 ms in these patients. However, the degree of this "overshoot" is smaller than that observed in patients in washout. The "overshoot" is not bidirectional, because no difference is present between ERP during the short–long sequence and ERP at 600 ms.