1. Irregular narrow complex tachycardia with no discernible P waves. Diagnosis is atrial fibrillation.
2. Regular narrow complex tachycardia with short RP intervals and variable relationship between P waves and QRS complexes. Diagnosis is AV nodal reentrant tachycardia (AVNRT).
3. Regular narrow complex tachycardia with sawtooth flutter waves and 2:1 conduction. Diagnosis is atrial flutter.