By Ken Grauer, MD

Professor Emeritus in Family Medicine, College of Medicine, University of Florida

Dr. Grauer reports no financial relationships relevant to this field of study.

A 47-year-old man presented with a history of intermittent dizziness over the previous two days. He was hemodynamically stable at the time the ECG in the figure below was obtained. How would you interpret the rhythm? Is there any clue to a possible etiology for this patient’s arrhythmia?

The underlying rhythm is sinus, as determined by the presence of upright P waves with a fixed and normal PR interval before beats 1 and 6 in lead II. Two consecutive sinus beats occur at the beginning of lead V1, which tells us that the underlying sinus rate is ~70/minute. Sinus beats are interrupted on three occasions by runs of a wide tachycardia. These runs are regular for the most part, although some irregularity can be seen in lead V1. Do these runs of wide beats constitute aberrant conduction of a supraventricular rhythm or ventricular tachycardia (VT)?

Although VT usually is a fairly regular rhythm, this is not always the case. The slight irregularity for the run of wide beats in lead V1 is not inconsistent with VT. QRS morphology of the wide beats in leads I, V1, and V6 resembles a pattern consistent with right bundle branch block aberration. That said, QRS morphology of the wide beats in each of the inferior leads reveals an all-negative complex. This constitutes extreme axis deviation, and is highly suggestive of VT. This is because there is almost always at least some positive deflection in the inferior leads when the rhythm is supraventricular.

An additional finding in support of VT: The etiology of the runs of wide beats is inherent in assessment of the sinus-conducted beats. Thus, beats 1 and 6 in the inferior leads show Q waves, ST segment coving with some ST elevation, and T wave inversion. In the chest leads, sinus-conducted beats 1 and 2 show ST segment coving with fairly deep, symmetric T wave inversion in leads V3-V6. These ECG findings strongly suggest acute or recent infarction with ischemia, which is a common precipitating substrate for runs of non-sustained VT.

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