Does this single lead show a wide complex tachycardia?

A woman in her 50's had a v fib arrest and required defibrillation 10 times before resuscitation to an organized rhythm.

Here was the monitored rhythm:

ventricular tachycardia?

There are two clues that it is not:

1) The rhythm is irregularly irregular, which strongly suggests atrial fibrillation
2) There is a "shelf" on the upslope of the S-wave.  This suggests that it is ST segment, not part of the QRS.

Here is the 12-lead:

Here you can see in leads V4-V6 that the QRS is indeed narrow.  All of the apparent width is really ST segment depression, as well as ST elevation in aVR and V1.

Here I have placed lines to demonstrate the end of the QRS in all leads, using lead II across the bottom for orientation:

After resuscitation, her ECG normalized:

She was found to have an 80% LAD lesion, with open artery and good flow.  This was not definitely a culprit, and not definitely the etiology of arrest.

Lessons:

1. In the presence of ST deviation, the rhythm strip may deceive you into believing there is a wide complex.
2. ST depression is often seen immediately after resuscitation from cardiac arrest.  After a short period of stabilization, it will resolve if there is no underlying acute ischemia