AV Dissociation in VT

Report:

Sinus tachycardia 127/min

Left atrial abnormality (LAA)

First degree AV block (PR 0.22”)

Axis -100o (Northwest, no-man’s land, “nonsense” axis)

Probable left anterior hemiblock

Right bundle branch block

VEB, probably fusion beat (5th in V1)

Ventricular tachycardia 175/min (rhythm strip)

Fusion beat (first VT complex)

AV dissociation

Comment:

The P waves can be seen to march through the VT at the same rate as before the paroxysm. Of the 10 P waves involved, 7 can be clearly discerned as “bumps” occurring in the expected places. The remaining three are completely hidden by the broad R waves of the VT.

AV dissociation is, on statistical grounds, evidence for the ventricular (rather than aberrant supraventricular) origin of the broad complex tachycardia129. This evidence is not absolute: “You cannot tell a pacemaker by the company she does not keep!”4

Below (Fig 174a) is the 12-lead ECG obtained after the tachycardia. Its arm leads are reversed, perhaps due to the excitement generated by the occasion.