Case: 8: A 79 year old woman presents with substernal chest pain. History of hyperlipidemia. She had a narrow QRS on an ECG in 1986.
Vent. rate 116 bpm
PR interval 178 ms
QRS duration 152 ms
QT/QTc 410/466 ms
P-R-T axes 83 -10 71
The QRS is wide. Does this represent a bundle branch block?
Can you diagnose ischemia or infarction from this ECG?
The answer to first question is yes, its Complete left bundle branch block. And secondly we can diagnose ischemia or infarctionn on that ECG, It shows acute anterolateral (subepicardial) injury (acute MI).
We have said that when there is ST-elevation in LBBB and the elevation is in the opposite direction as the main QRS deflection that it is likely to be secondary to the LBBB. There has been some work to determine the magnitude of ST-elevation beyond which, superimposed (primary) injury should be suspected. That is, how much is too much to ascribe to merely the LBBB. Studies have indicated that when there was >5 -7mm of discordant ST-elevation (that is, in the direction opposite the QRS deflection), that injury should be interpreted to be present. Look at the ST-elevation from V3 in the current ECG.
This patient was treated with thrombolytic agents at an outside hospital and ruled in for an acute MI by enzymes. Future LBBB cases will highlight when one can suspect an old MI in the face of LBBB.
Happy Learning !!!
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