Intermittent QRS Widening Without Any History

===================================MY Comment by KEN GRAUER, MD (6/25/2020):===================================I ’ve labeled the ECG in Figure-1 as, “The initial ECG in this Case” — as I found this tracing fascinating. Imagine you knew nothing about this patient.HOW would you interpret this tracing?Is there bundle branch block?Are there acute changes?Figure-1: The initial ECG in this case (See text).First Impression: The 12-lead ECG and long lead II rhythm strip shown in Figure-1 is difficult to interpret for several reasons:There is much baseline artifact (especially for the first few beats in the tracing).Some beats are wide — and other beats are narrow.Despite marked variation in QRS morphology in several leads — there is only minimal change in QRS morphology in the long lead II rhythm strip.MY THOUGHTS on ECG #1: To facilitate discussion of the rhythm and 12-lead ECG in Figure-1 — I’ve labeled key findings (Figure-2):The underlying rhythm is sinus at ~85/minute. I believe the slight variation in P wave morphology in the long lead II is the result of artifact. The beauty of simultaneous leads — is that P waves marred by artifact in one lead, will often be clearly visible in other leads. Thus, despite not seeing any atrial activity in the long lead II rhythm strip before beats #1-through-5, and before beat #9 — clear...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs