Rabbit Ears For and Against
Report:
Upper strip:
Sinus tachycardia 104/min
VEBs, late-diastolic (R-on-P âphenomenonâ)
Lower strip:
Sinus rhythm
SVEBs, probably of atrial origin
RBBB aberrancy
Couplet, second SVEB non-conducted
Comment:
Looking at the rabbit from behind, if the left rabbit ear is taller than the right the QRS in V1 is > 90% likely to be of ectopic ventricular origin. This classic criterion of Marriott's10 only applies to the left rabbit ear being taller. If the right ear is taller (as in most RBBB complexes) the probability is only 50% and is of the same value as tossing a coin.
The rabbit ears in the top strip are spurious in that the left ear is in fact a dissociated sinus P wave. The VEB is a monophasic R complex.
In the bottom strip, the qR complexes (with taller left ear) would "pass" for ectopic ventricular ones were it not for the preceding premature P' deflections, rendering all the other criteria of ectopy vs aberrancy irrelevant. If the patient had a run of SVT and previous ECGs were not available, those rabbit ears could cost him!
The question was designed as a trick question.
140. CCU monitor strips of a 59 year old man with unstable angina: two forms of trigeminy.
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