That is: i ) Usually the ST segment in lead V1 with RBBB is depressed - and not at the baseline, as it is in Figure-3.

While not definitive - I thought the appearance of ST-T waves in several of the chest leads leads in which this supraventricular RBBB conduction morphology appears was potentially suspicious for a recent ( or acute ) cardiac event.

Beats #4,5,6 manifest RBBB conduction.

As a result - I did not think much could be said about the possibility of recent infarction from assessment of ST-T wave appearance of beats #1,2,3 in Figure-3 - because these first 3 beats in the rhythm presumably arise from a ventricular escape focus.

Assessment of ST-T wave changes during a ventricular rhythm is usually difficult ( and often not possible).

They explain why despite RBBB conduction - the QRS complex does not look overly wide for beats #4,5,6 in the long lead II rhythm strip (ie, the initial part of the QRS in lead II lies isoelectric with the baseline).

These lines begin just before the onset of the QRS complex. Finally - I dropped verticle BLUE lines passing through simultaneously-recorded leads for beats #1, 4 and 6.I thought this finding made it much more likely that beats #1,2,3 represent a ventricular escape focus ( possibly arising from the right bundle branch ).The finding of similar ( if not identical) QRS morphology for conducted beat #4 - and non-conducted 'escape' beats #5,6 - essentially localizes the site of this 'escape' focus to the AV Node.The fact that these 2 R-R intervals are different - suggests there are 2 different 'escape' rhythm sites. I found it interesting that caliper measurement reveals an equal R-R interval between beats #1-2 and beats #2-3 ( = 1480 msec.) - and - that this R-R interval is different than the R-R interval between beats #4-5 and beats #5-6 ( = 1530 msec.).Presumably - the first 3 beats in this tracing, that manifest AV dissociation with more pronounced QRS widening (ie, beats #1,2,3) - are arising from an 'escape' site below the AV Node (ie, either from the right bundle branch or from ventricular myocardium ).The wide terminal S wave in simultaneously-recorded lateral leads V5 and V6 for beat #6 - is consistent with RBBB conduction. Because QRS morphology of 'escape' beats #5 and 6 in the long lead II rhythm strip is similar to QRS morphology of conducted beat #4 - this suggests that the site of these escape beats is from the AV Node.The 1 beat in Figure-2 that is conducted ( = beat #4) - is conducted with an underlying RBBB ( based on the typical rSR' morphology of this beat in lead V1 - as was highlighted in Pearl #2 above ).But because at least 1 QRS complex is conducted (ie, beat #4) - the degree of AV block can not be complete! High- grade2nd-degree AV Block is present in the long lead II rhythm strip in Figure-2 - because there are many P waves that clearly have more than adequate opportunity to conduct, yet fail to do so.This suggests that beats #5 and 6 must be ' escape' beats that manifest ( at least in lead II) a similar QRS morphology as conducted beat #4. We know this because: i ) None of the P waves associated with these last 2 QRS complexes occur at a point in the cardiac cycle when they would be expected to conduct and, ii )The R-R intervals between beats #4-5 and beats #5-6 are equal to each other - and - these R-R intervals are significantly longer than the R-R interval preceding beat #4 that we know is conducting. Part-3: The remaining 2 beats in Figure-2 ( = beats #5 and 6) are not conducted.Part-2: As we have already deduced (ie, in Pearls #1 and #2 above) - the degree of AV block for the rhythm in Figure-2 can not be 'complete' - because beat #4 is conducted! We know this - because beat #4 occurs earlier-than-expected - beat #4 is preceded by a normal PR interval - and QRS morphology of this beat #4 changes from the LBBB-like appearance of the first 3 beats in Figure-2 - to a QRS morphology consistent with RBBB conduction.This suggests that at the least - there is high-grade 2nd-degree AV Block. The 1st, 3rd and 5th P waves in the long lead II rhythm strip ( = the first 3 RED arrows) have clearly had more than adequate opportunity to conduct - yet failed to do so. The 6 P waves associated with these first 3 beats appear completely unrelated to the QRS (ie, with a constantly changing PR interval).The QRS complex for these first 3 beats is wide - with a morphology potentially consistent with LBBB ( Left Bundle Branch Block). Part-1: Look at the first 3 beats in Figure-2.

Ivcd ecg images