The ECG demonstrates a sinus mechanism with a
complete RBBB pattern (QRS duration of >=120 ms, wide S waves
in Lead 1, aVL and V6 together with a predominant wide R wave
in V1 This may present as a monophasic R wave or as an rSR' (r
wave followed by an S wave and a second R wave)
- Q waves in the inferior leads point to a prior inferior wall
MI and the presence of ST segment elevation suggests that this
infarction is acute or recent. The history of chest pain and a
recent normal ECG reinforce this.
- An associated decrease in R wave voltage suggests that there
is loss of lateral forces as a result of an associated lateral
A complete LBBB pattern would have created a monophasic
R wave in lead 1, avL and the lateral leads with a small r and
deep-wide S waves in V1.
It is true that an S1-Q3 pattern may occur in patients with acute
pulmonary embolism. However, they usually do not have associated characteristics
of the inferior wall MI and complete RBBB pattern, as seen in this case.
Patients with an inferior wall MI and associated posterior wall MI
have prominent R waves in V1. However, in this case, the R wave in V1
is due to the complete RBBB with a QRS duration that exceeds 120 ms.
All the other options listed in
the question are true.
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