Answer to ECG Quiz no. 13

Systematic analysis of the ECG reveals QRS width: The widest QRS needs to be measured.Normal width is up to 100ms or 2.5 little blocks.The fi rst QRS complex in both V5 and V6 is easiest to measure: just over 2.5 blocks, around 110ms: so not exactly narrow but not defi nitely wide either (>120ms).This patient has an underlying cardiomyopathy which may account for some slowing of normal conduction and widening of QRSs.It is also likely that if he had VT, the QRS would be defi nitely wide and not borderline.Are there any other clues for VT vs. more normal conduction?QRS morphology: In the chest leads there is obvious poor R wave progression.In V1 to V3 there are in fact no R waves and QS waves are noted.This would be quite compatible with an anterior myocardial infarction pattern, but we have been told that this man does not have ischemic heart disease.Such patterns can occur in dilated cardiomyopathy.A closer look at the QS waves is useful because one can observe that the initial component is very rapid: from onset of the QRS to the nadir of the QS wave is 50ms or just over 1 little block.If one had any concern that this ECG could be a narrowish VT rather than a conducted rhythm, this fi nding of this rapid conduction <70ms dispels that.But, clearly, these conducted QRS complexes are most abnormal.There is intraventricular conduction delay with double components in the limb leads.So is this Left Bundle Branch Block (LBBB)?