Interesting tracing from this 77-year old woman — who presented to the ED with an acute medical problem, but apparently no chest pain. I would add the following thoughts to the comment by Dawn.

As noted — there is a lot of baseline artifact on this tracing, and this complicates assessment. That said, I believe we DO still see sinus P waves — which begin in simultaneously-recorded leads I, II and III just after the vertical RED line that I drew in parallel to the heavy grid line (See attached Figure below). When it is difficult to see P waves — use of simultaneously-recorded leads may be invaluable for confirming that deflections suspected as atrial activity do in fact occur at the same instant in time in several leads. Thus, the rhythm is sinus tachycardia.

As per Dawn — there is RBBB (Right Bundle Branch Block). Although in theory, a triphasic (rSR’) pattern should be seen in lead V1 with RBBB — many factors (ie, infarction; scarring from cardiomyopathy; chamber enlargement) may contribute to altering the nature and sequence of depolarization forces with this conduction block. Normally, the QRS complex is predominantly negative in V1. If in association with a supraventricular rhythm — there is QRS widening with an upright complex in lead V1 in association with wide, terminal S waves in lateral leads I and V6 — then RBBB may be present despite the absence of a distinct triphasic pattern in V1. This is the case in the Figure.

The concept of “axis” in the setting of RBBB is problematic. Calculation of axis is based on the average direction of the heart’s electrical activity in the frontal plane. In the presence of RBBB — electrical activity first goes left-to-right (as the septum is depolarized) — then right-to-left (as the left ventricle is depolarized) — and then left-to-right again as the blocked right ventricle is finally activated via slow myocardial conduction through nonspecialized fibers. So, in the setting of RBBB — the “average direction” of the heart’s electrical activity does not reflect the actual zig-zag path of the depolarization impulse. BOTTOM LINE: Don’t worry about “axis” when there is RBBB. All we care about when there is RBBB is which of these 3 possible settings is operative: i) RBBB and nothing else; ii) RBBB plus LAHB (Left Anterior HemiBlock); or, iii) RBBB plus LPHB (Left Posterior HemiBlock). In this case — the predominantly negative QRS complex in the inferior leads tells us there is RBBB/LAHB (= bifascicular block).

In addition to RBBB — there are 2 Q waves that should be noted. The small-but-definitely-present Q wave in lead V2 (within the BLUE circle) should not normally be present when there is RBBB. This means that in addition to RBBB, it is possible there has been prior anterior infarction. Then, in lead aVL — the Q wave in this lead is a bit larger (and wider) than is usually expected. This could be reflective of prior lateral infarction, though I can’t rule out that this might also be a normal septal Q wave. That said, the ST-T wave depression in leads V1-thru-V4 is potentially consistent with RBBB. I see some nonspecific ST-T wave abnormalities— but these do not look to be acute. I suspect they will diminish once the patient’s underlying medical condition (and her resultant sinus tachycardia) are controlled.

Finally — there is much fragmentation of the QRS complex in this tracing. By this I mean the very prominent notching in leads V2, V3 and V4. Although a nonspecific sign — excessive fragmentation of the QRS complex often signals “scarring” that may reflect prior infarction and/or cardiomyopathy.

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NOTE: For more on Hemiblocks with RBBB — CLICK HERE (Begin with Section 07.17).

— For more on ECG Diagnosis of BBBs — CLICK HERE — and/or check out my 17-minute ECG VIDEO on the Basics of BBB —

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