Inferolateral Infarction & LBBB

Report:

Sinus rhythm 88/min

Left bundle branch block

Acute inferolateral infarction

Comment:

Unlike the previous case’s IVCD, this one shows typical LBBB, with sharp S descent and slower ascent in V1. Despite this, there is a concordant ST segment elevation in the lead 2 (and some in V6) – a specific, however insensitive marker of infarction in the presence of LBBB62. In leads 3 and aVF, the elevation is more impressive, but directed opposite the terminal QRS, which requires, in some systems, more than 5 mm elevation. Given the small overall QRS size in those leads, one can reasonably argue the elevation of 4 mm (in 3) should suffice.

The next day (Fig 87a) the pattern is that of LBBB with secondary ST/T changes, except for V5, where the T wave is inverted concordantly with the S wave. This is abnormal, but hardly diagnostic of infarction. S wave in V6 may be63.

Infarcts with new LBBB (or RBBB) have worse outcome than those without conduction defects. This may not be the case for those with pre-existing LBBB, perhaps due to ischæmic preconditioning. In general, much of the prognosis in patients with LBBB is determined by age and co-morbidities57.

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