Isorhythmic AV dissociation: SR + VT

A 70 yo patient admitted for shortness of breath. 

Is this ventricular tachycardia (VT) or aberrancy?

Image 1 - ECG case

Image 2 - Ladder diagram

The rhythm is sinus at a rate of about 100 bpm with a PRI of about 0.28 sec (first degree AV block). It is interrupted with episodes of wide QRS beats at a rate of about 94-107 bpm with predominant R wave in V1 with variable PRI. This would indicate that there is AV dissociation. If the sinus rate and the ventricular rate is almost the same then it is called isorhythmic AV dissociation. The presence of AV dissociation and the predominant R wave in V1 favors ventricular tachcycardia.Thus, this SR with first degree AVB with episodes of VT creating isorhythmic AV dissociation.

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