Fig. 3.

Examples of lead II ECG recordings of arrhythmic events in Scn5a+/ΔKPQ mice. A: bradycardic episodes occurring before and after a period of normal sinus rhythm. Insets show that the corresponding detailed ECG waveforms were normal. bpm, beats/min. B: sinus pause occurring after a sequence of seven normal P wave deflections. C: sinus arrest showing an episode in which P waves were absent. D: persistent second-degree 2:1 atrioventricular block in which QRS complexes failed to follow alternate P waves. E: episodes of third degree atrioventricular block showing dissociation between P wave and QRS deflections.