Anterior Infarction, LBBB & Its Escape Rhythm

Report:

Fig 89:

Sinus rhythm 76/min

Borderline LAA

LVH with ST/T changes

Anterior infarction ?age

Fig 89a (24 hours later):

Sinus rhythm 74/min

Alternating complete & incomplete left bundle branch block

Primary T wave changes

Fig 89b (an hour later):

Fascicular rhythm 76/min

1:1 retrograde conduction

RBBB/LAHB morphology

Anterior infarction ?age

Fig 89c (24 hours later):

Sinus rhythm 63/min

Left bundle branch block

Primary T wave changes

Comment:

The patient sustained a recent (about one week) infarction, but the Fig 89 ECG has little for or against chronicity. T waves may stay inverted forever and the slight anteroseptal ST elevation may reflect an aneurysm or a large akinetic area; the possibly reciprocal ST depression in 1 and aVL may also be due to LVH.

The next day’s ECG (Fig 89a) is more interesting. The narrow QRSs are a little wider than before and have lost their “septal” q waves in 1, V5 and V6, indicating incomplete LBBB. Alternate broad complexes are, of course, complete LBBB. The former have left axis, the latter normal axis with equal lack of conduction in the left anterior and the left posterior divisions of the left bundle branch. The anteroseptal infarctional Q waves have also disappeared.

However, an hour later, an accelerated rhythm escapes from the distal, unblocked part of the left bundle branch, now with more marked LAD and RBBB pattern (Fig 89b). The previously conducting left posterior division (with 2:1 block, causing alternating LBBB) now paces the heart and both the septal q in lead 1 and pathological Qs in the septal leads are back. This is a nice example how, in bundle branch blocks, distal foci will produce the picture of contralateral bundle branch block.

Finally, another day later, the left bundle stays completely blocked (Fig 89c); it remained so ever after. The only indication of a myocardial – as opposed to conduction system – disease is the unexpected, “primary” T wave pattern in several leads where the T wave is concordant with the terminal QRS.