By Ken Grauer, MD
Professor Emeritus in Family Medicine, College of Medicine, University of Florida
The ECG in the figure below is a post-exercise tracing. There are four wider and slightly early occurring beats in the long lead rhythm strips. Are these beats premature ventricular contractions (PVCs) or premature atrial contractions (PACs) conducted with aberration?
It is common to see PVCs during exercise, especially if the degree of exercise is challenging for the patient. Although the much wider and different-looking appearance of the four early beats in the figure suggests these are PVCs, that is not the case.
The underlying rhythm in this tracing is sinus at a rate of ~100 beats/minute. Two QRS morphologies are seen for the four wide beats. This is perhaps best appreciated in the long lead V5 rhythm strip, which shows a notched-R morphology for premature beats 2, 10, and 14 (that is different than the all-positive R wave morphology for premature beat 6).
Looking vertically upward from premature beat 10 in the long V5 rhythm strip, we see a predominantly negative QRS complex for beat 10 in simultaneously obtained leads V1, V2, and V3. This QRS morphology is perfectly consistent with left bundle branch block (LBBB) conduction. The fact that premature beat 14 in simultaneously obtained lead V6 manifests an all-positive widened QRS complex confirms a QRS morphology consistent with LBBB conduction for at least beats 2, 10, and 14 in the long lead V5 rhythm strip.
Confirmation that each slightly early, wide complex beat in the long lead rhythm strips are PACs is forthcoming from the presence of a premature P wave in front of beats 2, 6, 10, and 14 in at least several of the 12 leads. This premature P wave is subtle, and perhaps best seen in the long lead II. Note the small, negative notch that immediately precedes each wide beat, but which is not present after the T wave of all the normally conducted beats (i.e., there is no negative notch after the T wave of beats 3, 4, 7, 8, 11, 12, and 15).
The rhythm in the figure is atrial quadrigeminy (i.e., every fourth beat is a PAC) in which there is LBBB aberration for at least three of the four early beats, with some other form of aberration for beat 6.
For more information about and further discussion on this case, please click here.
The ECG in the figure is a post-exercise tracing. There are four wider and slightly early occurring beats in the long lead rhythm strips. Are these beats premature ventricular contractions or premature atrial contractions conducted with aberration?
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