Northwest Axis of Ventricular Tachycardia

Report:

Ventricular tachycardia 167/min

Comment:

The diagnosis of VT rests on monophasic R wave in V1, rS in V6 and the bizarre, ‘Northwest’ axis in the limb leads. In V1 there is a soupçon of rabbit ears, with the left one taller than the right.

In the first half of the trace there is a subtle but definite T wave alternans, best seen in the inferior leads. Whether this is a true alternans or a superimposed alternating retrograde block (conduction) cannot be ascertained.

The patient had an electronic pacemaker, permanently set in the VVI mode and dissociated from the sinus rhythm (Fig 38a). This, too, makes the alternative diagnosis of tachycardia as aberrant most unlikely (but not impossible). Note that 3o AV block is by no means diagnosed by seeing non-conducted – dissociated – P waves below: they have no real opportunity to be conducted and maybe a slower pacing rate would show no AV block at all.

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