Sinus tachycardia is recognized on an ECG with a normal upright P wave in lead II preceding every QRS complex. This indicates that the pacemaker is coming from the sinus node and not elsewhere in ...

Bidirectional ventricular tachycardia is quite rare, but pathognomonic for digoxin toxicity. This ECG has ... the R' in lead V1 indicating a ventricular origin. Note the pause, one sinus beat ...