LBBB and Cardiac Memory

Report:

Sinus rhythm 77/min

SVEBs

First degree AV block

PR interval 0.26”

Aberrant conduction, LBBB type

Anteroseptal T wave inversion V1-V3

Prolonged QTc 0.49”

Comment:

Sustained LBBB or RV electronic pacing may induce T wave inversion not unlike the one seen here when the conduction normalises. This phenomenon has been known for some time39, but in a surprising number of cases this transient T inversion becomes subject of “further investigation”. Below (Fig 69a) is the “causal” LBBB tachycardia 120/min occurring earlier that day. She also had other, faster SVTs, some with normal ventricular conduction. And also slower sinus rhythm with LBBB conduction (Fig 69b).

Another source of T wave inversion is preceding paroxysmal tachycardia regardless of the QRS morphology: the “post-tachycardia syndrome”. It can be thrown in the same basket as post-LBBB changes; the molecular basis for both is gradually being elucidated40.

The LBBB-aberrant SVEBs here are, obviously, a clue as to the cause of T inversion. It is remarkable that the “memory” of their occurrence exists in the subsequent beat, with incomplete LBBB morphology. This is opposite of what happens in Case 43, with gradual completion of the LBBB there.

Fig 69a. SVT with LBBB aberrancy.

Fig 69b. Sinus rhythm with LBBB and 1o AVB conduction.

Fig 70. 76 year old lady with asthma and chest infection.