afib with paced beat
First Glance:
From across the room it looks like wide complex afib and one paced beat.
Discussion:
Afib? Probably. We have an irregularly irregular rhythm with a fibrillatory baseline.
The QRS complexes are borderline wide, or maybe just under 120ms in lead II. There is rsr’ morphology in II which is common in LBBB. Anecdotally, I see this LBBB-like morphology in II when there is a lateral LBBB as opposed to high-lateral LBBB (ie: left bundloid QRS in V5/6 but not I/AVL).
There is ST depression (appropriately discordant) and T wave inversion in II, but this does not suggest ischemia in the setting of LBBB. See Sgarbossa’s Criteria.
There is ST elevation in ‘V’ but again: appropriately discordant, and both of these leads are gained up significantly anyways.
There is a paced beat a little ways past the halfway point. You can clearly see the pacing spike, followed immediately by a bizarre complex. This is probably a pacer that has been sensing the ventricle, and is set to fire to maintain a heartrate of 60bpm (“demand pacing”, VVI mode). If you count boxes, the spike is exactly 1 second (ie: rate of 60 bpm) after the last QRS.
The paced QRS is predominantly negative in both leads. This makes sense, because pacer leads are generally screwed into the somewhere near the apex of the right ventricle. The depolarization wave would go from the apex to the base (ie: away from the positive electrode in II, therefore negative) and from anterior (where the RV sits) to posterior (away from the septal chest leads where this V lead is presumably positioned).
Final Impression?
Afib @ ~75 bpm suspicious for incomplete or complete LBBB, with one ventricularly paced beat.
Management implications:
Check old strips/12Ls to see if there is LBBB, and then if it is new. 12L to assess for more marked ST/T changes that would be suspicious for ischemia. The pacer appears to be working, assuming it is set to maintain a HR >60 (common setting).
The Take-home Point:
In the setting of LBBB, concordance is what is concerning for ischemia, not just ST segment deviation or T inversion.
Small ST elevations and depressions are both fairly uninteresting unless the ST deviation is concordant.
Examples of concordant findings:
- The QRS is upright and there is (upwards) ST elevation.
- The QRS is downwards and there is (downwards) ST depression.
- The QRS is downwards and there is (downwards) T inversion.
Two star strip. The meat and potatoes.