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. Author manuscript; available in PMC: 2016 Oct 1.
Published in final edited form as: Circ Arrhythm Electrophysiol. 2015 Jul 30;8(5):1255–1264. doi: 10.1161/CIRCEP.115.002720

Figure 4.

Figure 4

Advanced 3:1 AVB from Nkx2-5+/R52G mouse (7 months of age) detected shortly after anesthesia for EP study and HCN4-positive AV node vs. penetrating AV bundle. (A) Representative recording of surface and intracardiac recordings (RV or RA) demonstrating 3:1 AVB obtained from Nkx2-5+/R52G mice during EP analysis shortly after induction of isoflurane anesthesia with sinus cycle length of 135 ms. (B) Representative HCN4-stained normal heart tissues of Nkx2-5+/+ at 4 weeks of age including AV node and penetrating AV bundles traced by black dots. (C) Simplified illustration to define AV node vs. penetrating AV bundle with or without direct contact to atrial muscle. HCN, hyperpolarization activated cyclic nucleotide-gated potassium channel. A, right atrial electrogram; V, right ventricular electrogram.