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Figure 4 Typical tracings of intracardiac electrograms of three types of fast–slow AVNRT. In posterior type AVNRT, the CS3-4 (CS orifice) electrogram precedes the LSRA electrogram at the His bundle recording site by 20 ms. In the middle type, the LSRA electrogram precedes the CS3-4 electrogram by 5 ms (see the Definition of terms section). In the anterior type, the LSRA electrogram precedes the CS3-4 electrogram by 30 ms. Abbreviations as in Figure 2. Paper speed is 100 mm/s.