He presented to the hospital with a complaint of shortness of breath, and was determined to have an exacerbation of his COPD in the setting of a viral infection. He was treated with breathing treatments and steroids, and was discharged home in improved condition.
The ECG There is a sinus rhythm at 80 bpm. The QRS complex is wide at .18 seconds (180 ms). The PR interval is slightly prolonged at .24 seconds (240 ms), which is first-degree AV block. There is right bundle branch block (QR in V1 and rS in Leads I and V6 with a wide QRS). There is also a left posterior fascicular block (also called hemiblock), recognized by the right axis deviation (III is taller than aVF ). This is bi-fascicular block, which can be chronic or acute. There is very slight ST elevation with flattening in V1 and possibly V2. In RBBB, “normal” T waves are directed opposite the terminal wave of the QRS. V3 should, then, have inverted T waves. So, the upright T wave in this patient could be considered to be equivalent to an inversion in a normal ECG. V4 through V6 have biphasic T waves, which is not normal for RBBB. Because we do not have an old ECG, we don’t know which, if any, of these changes are chronic. With this patient’s past medical history, it is possible for any of them to be pre-existing.
I will admit that, when I first saw this ECG, the V1 rhythm strip at the bottom looked as though there were regular P waves at a rate of about 220-240, with one buried in each QRS and one in each T wave. In scrutinizing all the other leads, I cannot find evidence for an underlying atrial tachycardia or atrial flutter, so it is probably a coincidence that the P and T “march out” with the assumption of a hidden P wave in the QRS.
The Conduction Blocks AV conduction blocks (AVB) can occur in any part of the conduction system from the AV node through the fascicles of the bundle branches. The ECG can offer valuable insights into what type of block is present, and even the location of the block, but often an EP study is needed to actually pinpoint the conduction defect.
AV blocks can cause slowing or failure of conduction. They can be chronic, permanent, temporary, intermittent, or even rate-related. A block of one of the left fascicles is called a “hemiblock” or “fascicular block”. A “bifascicular block” is a block of two of the three fascicles. A left bundle branch block is a bifascicular block, because the left bundle has two main fascicles. A common bifascicular block is right BBB with left anterior hemiblock, because those two fascicles share a blood supply. There are
This patient has a more unusual bifascicular block: right bundle branch block and left posterior hemiblock. He also has first-degree AVB. It has become customary to call this combination “tri-fascicular block”, but this is a misnomer. One would have to assume that the first-degree block is in the anterior fascicle for this to be “tri-fascicular”. If the conduction delay is actually in the AV node, this is still have a bi-fascicular block. One example of true tri-fascicular block would be second-degree AVB, Type II, which is a bi-fascicular block with an intermittent block in the third fascicle (intermittent tri-fascicular block). Another example of tri-fascicular block is complete heart block (third-degree) as a result of blocks in all three fascicles. Third-degree AVB caused by fascicular blocks would result in a ventricular escape rhythm, as opposed to an AV node complete block, which might have a junctional escape rhythm. An EP study, with H-V intervals measured, would be necessary to be sure of the levels of the blocks. The important thing here is that this patient has very significant chronic illness, is elderly, and has demonstrated bi-fascicular and possibly tri-fascicular disease. His likelihood of progressing to complete heart block is significant. Should he develop a complete tri-fascicular block, he would require a pacemaker. Remember, atropine will not work on infra-Hisian blocks (fascicular blocks). Another important clinical pearl is that any fascicular block which develops during an acute M.I. is much more likely to progress.
Fortunately, this patient’s ECG remained stable, and his condition improved with treatment, and he was able to be discharged home.
We would like to thank Dr. Ahmad Nawid Latifi, MD for providing this ECG.