## **Core Concept**
Wide-complex tachycardia can be caused by either ventricular tachycardia (VT) or supraventricular tachycardia (SVT) with aberrant conduction. The differentiation between these two is crucial for management and prognosis. ECG criteria help in distinguishing VT from SVT.

## **Why the Correct Answer is Right**
The correct answer, , indicates that AV dissociation is actually a feature that supports the diagnosis of ventricular tachycardia. AV dissociation, where there is no association between atrial and ventricular contractions, is a hallmark of VT. This occurs because the ventricular rhythm originates from a focus within the ventricles, independent of the atrial rhythm.

## **Why Each Wrong Option is Incorrect**
- **Option A:** is a feature of VT. In VT, the QRS complexes are typically wide (>120 ms) because the electrical impulse originates from a ventricular focus and travels through the ventricles in an abnormal manner, leading to a wider QRS complex.
- **Option B:** is also a feature of VT. The presence of fusion beats, which are complexes that represent a fusion of the ventricular tachycardia beat and a normally conducted supraventricular beat, is diagnostic of VT.
- **Option D:** can be seen in VT. Although not specific, a left axis deviation or right axis deviation can be seen in VT, depending on the origin of the tachycardia within the ventricles.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that in VT, the ECG often shows AV dissociation, where P waves are seen at a different rate than the QRS complexes, and there may be fusion beats. The presence of these features strongly supports VT over SVT with aberrancy.

## **Correct Answer: .**