Ventricular Tachycardia or LBBB?

Report:

Ventricular tachycardia 166/min.

Fusion beats.

Comment:

The complexes could "pass" for LBBB aberrancy, except for QR morphology in lead 1 and the frontal plane axis of +85o. The occasional narrowing of the QRS is most likely result of ventricular fusion with a supraventricular, presumably sinus, impulse. Fusion in this setting is excellent evidence for the ventricular ectopic origin of the tachycardia.

The sinus rhythm ECG is shown below (Fig 196a).

196a. Normal baseline ECG. 197. 59 year old man with ectopic beats four days after an inferior infarction. He had a grand mal convulsion following a bolus and infusion of xylocaine, but the ectopics continued.

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