There are P waves (+) with regular PP intervals and a rate of 85 beats/min. The P waves have a normal morphology; they are positive in leads I, II, aVF, and V4-V6. This is a stable normal sinus ...

The tracing in Figure 2 shows a regular rhythm at a rate of 140 beats/min. One long RR interval is seen (↔). Although no obvious P waves are visible, a P wave is seen after the long RR interval ...