1. Normal sinus rhythm
2. Incomplete right bindle branch block
3. Non-sustained monomorphic ventricular tachycardia
This is a challenging ECG in regards to determining if the wide QRS complex rhythm is from ventricular tachycardia or "SVT with aberrancy" such as AV nodal reentry tachycardia causing a rate-dependent left bundle branch block. The Brugada criteria are used to distinguish these two entities. On this ECG, the, QRS complex has runs of wide-complexes in a left bundle branch pattern. The heart rate is quite fast (about 250 beats per minute).
If you look closely, there is "AV dissociation" that is best seen in lead II on the third run of ventricular tachycardia. March out the P waves and you will find them appearing in the negatively deflected part of the wide QRS complex here. If AV dissociation is present, then the rhythm is ventricular tachycardia. It also helps to know the clinical history of the patient. This ECG was from a patient with a non-ischemic cardiomyopathy and an ejection fraction of 25%, making ventricular tachycardia much more likely. Also, if there is ever a clinical doubt as to the rhythm diagnosis, treat it like ventricular tachycardia until proven otherwise. For a complete review of ventricular tachycardia click below. Also note that there may be "T wave alternans" in lead II which may signify an increased risk of ventricular arrhythmias and sudden cardiac death.