First ECG: regular, sustained wide-complex tachycardia, approximately 190-210 bpm, with a uniform morphology. In this clinical setting it should be considered monomorphic ventricular tachycardia (VT) unless proved otherwise. The very broad QRS complexes and lack of clear preceding P waves support VT over SVT with aberrancy.

Second ECG, post-cardioversion: successful conversion to sinus rhythm, roughly 80-90 bpm, with narrow QRS complexes in the limb leads. There is striking abnormal/poor R-wave progression with predominantly negative anterior precordial complexes (V1-V5), which could reflect underlying structural or conduction abnormality, old anterior scar, or precordial lead-placement issue. Repeat correctly positioned precordial leads and compare with prior baseline ECGs.

So: sustained monomorphic VT successfully cardioverted to sinus rhythm.

A regular wide-complex tachycardia should generally be managed as VT until an alternative is firmly established, particularly when unstable. Tintinalli's Emergency Medicine: A Comprehensive Study, p. 156. The current AHA adult advanced life-support guidance similarly treats clinically significant wide-complex tachycardia as a high-risk rhythm.

Post-conversion workup should include electrolytes including K/Mg/Ca, troponin when appropriate, echocardiography, medication/toxin review, ischemia assessment as indicated, and cardiology/electrophysiology evaluation.

No. I agree it is not convincingly atrial fibrillation.

The post-cardioversion tracing has a fairly regular R-R interval on the long lead II rhythm strip, about 85-95 bpm, with small consistent atrial deflections before the QRS complexes. That favors sinus rhythm (possibly with atrial ectopy or artifact), not AF.

AF should have an irregularly irregular ventricular rhythm with no organized, reproducible P waves. Those features are not present here. The prominent broad negative complexes in V1-V5 are a separate morphology issue, and could be due to lead placement, ventricular activation/scar, or a conduction abnormality, but do not establish AF.

I would document it as: post-DCCV regular organized rhythm, likely sinus rhythm, not AF. A repeat 12-lead with verified precordial lead positions and a longer rhythm strip would settle any residual uncertainty.