Figure 1. A typical example of His bundle electrogram (A) and atrial monophasic action potential (B) recordings. S = stimulus; A = atrium; H = His bundle; V = ventricle; S-A stimulus-to-atrium intervals; A-H = atrium-to-His bundle interval; MAPD⁹⁰and MAPD⁵⁰= monophasic action potential duration at 90% and 50%, respectively; BCT = basic conduction time.