This ECG was taken from a 78-year-old man who was experiencing chest pressure in the morning, after having left shoulder pain since the night before. He has a history of hypertension and hypercholesterolemia, and has an implanted pacemaker.
Right bundle branch block
Today’s ECG is from a 74-year-old man for whom we have no clinical information. It shows a “classic” right bundle branch block. It also shows an example of the ECG machine getting some of the interpretation wrong. An early mistake in the interpretative algorithm caused a cascade of inaccuracies.
REVIEW of RIGHT BUNDLE BRANCH BLOCK ECG CRITERIA
* Supraventricular rhythm
Question: What is the cause of an apparent right bundle branch block pattern in a paced rhythm?
Answer: Is There a Pacemaker Wire Problem… or Not?
During one of my orientations as a young internal medicine house officer, the cardiologist lectured to us on the essentials of how to check pacemakers. Since none of us had any ECG interpretation background our comprehension was less than sterling. But I remember him stressing the point that a properly paced pacemaker lead would result in a left bundle branch block pattern on the ECG. A right bundle branch block pattern in V1, on the other hand, meant that the pacemaker wire had inadvertently wandered into the left ventricle – a highly undesirable situation.
“Not to worry,” he said. “Such things rarely happen and you will probably retire before seeing such a thing!” That evening I saw my first pacemaker 12-lead ECG with a right bundle branch block pattern in V1. Fate wasted no time with me.
I ordered a 3-view chest x-ray and as far as I could see, the wire looked like it was in the right ventricle where it was supposed to be. I called the cardiologist on-call who happened to be in the hospital at the time and he dropped by the ward. Back then, we didn’t have ultrasound or echo available. But he, too, was convinced the pacemaker wire was in the right ventricle. It really was and so I still hadn’t seen a RBBB pattern due to a pacer wire in the left ventricle. I still haven’t, but I have seen a number of pacemaker ECGs with a RBBB pattern in V1.
How do we know if such a finding represents a real left ventricular pacer wire or a pseudo-malplacement?
First, just be aware that a wire that really IS in the left ventricle is going to present with a RBBB pattern in V1. It will NOT ever present with a LBBB pattern. However, a wire that has been correctly placed in the RIGHT ventricle can – from time to time – present with a RBBB pattern in V1. In my years as an attending in the emergency department, I saw this seven or eight times.
Second, the axis of the pseudo-malplacement tends to demonstrate a significant left axis deviation, between -30 ° and -90 °. Since the right ventricle is activated first, the vector finishes by pointing up and to the left. If the wire were actually located in the left ventricle, the mean frontal axis would be to the right of +90 °
Third, when we look in the precordial leads, we know that Leads V1 and V2 overlie the right ventricle and leads V5 and V6 overlie the left ventricle. Leads V3 and V4 are in between. If the pacemaker wire is in the right ventricle, whatever is causing it to have an RBBB pattern in V1 will disappear before V3. A pacemaker wire in the right ventricle will show a LBBB pattern (QS) by Lead V3. If the wire is truly in the left ventricle, the RBBB pattern will extend to V3 and usually beyond. So a quick check is this: if you see a RBBB pattern in V1 in a pacemaker patient, look at V3. If the RBBB pattern is in V3 also, the wire is truly in the left ventricle. If V3 has a predominately negative QRS (QS), the wire is safely in the right ventricle where it is supposed to be.
A fourth check is to look for an S wave in Lead I. Remember: one of the most characteristic features of RBBB is that slurred S wave in Lead I (as well as the other left-sided leads). If the ECG shows an RBBB pattern in V1 and an S wave is present in Lead I, then that is most likely a real RBBB pattern and the wire has somehow made its way into the left ventricle.
This ECG is taken from an 82-year-old man who called 911 because of chest pain. He has an unspecified “cardiac” history, but we do not know the specifics.
This ECG is a good example of sinus rhythm with aberrantly-conducted PACs. The tracing was donated to the ECG Guru several years ago by Dr. Ahmed from Sanjiban Hospital in India. We have no patient data for this tracing.
This ECG is from a 59-year-old man who was a patient in the Emergency Department with mild chest pain. He had a history of coronary artery disease. We have no other information about his medical history, medications, or outcome.
This interesting ECG is a great one for your more advanced students who are ready to discuss the anatomical and physiological differences between the AV blocks, as opposed to just measuring PR intervals.
This is an example of right bundle branch block - with a couple of twists. It has the usual ECG characteristics of right bundle branch block: widened QRS (154 ms), supraventricular rhythm (sinus bradycardia), and an rSR' pattern in V1. In addition, wide little S waves are clearly seen in Leads I and V6. This secures the diagnosis of right bundle branch block (RBBB). Each QRS complex in every lead starts off with a very normal appearance, or morphology. Then, as the right ventricle is depolarized late, an additional wave is "added on".
This ECG depicts an extensive and ultimately, fatal, injury. There is marked ST segment elevation in Leads V2 through V6 (anterior wall). There is also ST elevation in Leads I and aVL (high lateral wall). The ST elevation in aVR is indicative of a very proximal lesion in the left coronary artery, which supplies the anterior wall, including the anterior portion of the septum, the high lateral wall, and, in this case, the low lateral wall. The inferior leads, II, III, and aVF, show reciprocal ST depression.
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