Reviewing yesterdays outpatient ECG tracings you find the following tracing:
25mm/s speed, 10mm/mV amplitude
First thing that comes to mind is ventricular tachycardia. Wide QRS complexes, fast heart rate, relatively regular, no clearly discernible P waves.
However, when taking a closer look you find that lead III actually shows normal sinus rhythm (small P waves in front of WRS, heart rate about 60 bpm, normal PR interval).
Every time you find one lead completely normal and not affected by any arrhythmia present in the other leads, this should make you suspicious of artifacts!
As in this case, the patients right arm was moving and thereby producing "right arm artifact".
There are several very good posts on ECG artifacts available. A nice demonstration of right arm artifact was postet by @Arron_Pearce_ on Twitter. Also enjoy watching The ECG Guy (https://www.youtube.com/watch?v=7rkskrVYZ0s) or Professor Johnson Francis (https://www.youtube.com/watch?v=sJwNLq0tzFQ) on YouTube.