Figure 6. Extrasystoles originating from either Epi or Endo of the RVOT can trigger VF in the presence of terfenadine (8 µM). Origin of the extrasystole can be judged on the basis of the polarity of the R wave recorded from the pseudo-ECG. The stimulation electrode was located on the smooth surface of the Endo RVOT. The two traces were recorded from the same preparation.