Right bundle branch block - Part I

How do you identify RBBB on the 12 lead ECG?

Forget about turn signals and bunny ears! They do more harm than good.

All you need for the ECG diagnosis of RBBB are the following:

• A supraventricular rhythm
• QRS duration equal or greater than 120 ms (0.12 s)
• Terminal R wave in lead V1
• S wave in lead I

It's that easy!

Let's look at an example.


What's the rhythm?

Borderline sinus bradycardia with 1°AVB and occasional PACs.

Is that a supraventricular rhythm? Yes!

Let's move on.

Is the QRS duration equal to or greater than 120 ms (o.12 s)?

In other words, are the QRS complexes "wide"?

Be careful! It's easy to fixate on the tight R wave and discount the S wave with RBBB. If this was a tachycardia at a rate of 150, it might appear to be a narrow complex tachycardia, when in fact, it would be a wide complex tachycardia!

The QRS duration is > 120 ms. Just barely, but it's like being pregnant. It either is or it isn't!

So we have a supraventricular rhythm with wide QRS complexes. This process is important because one of the most important and basic rules of electrocardiography is:

Wide complex rhythms are ventricular until proven otherwise!

Once you have determined that a supraventricular rhythm is wide, you can examine QRS moprhology to figure out what kind of intraventricular conduction delay is present.

Let's look at the 12 lead ECG.


Is there a terminal R wave in lead V1?

Yes!

What do we mean by "terminal R wave"?


The last wave of a QRS complex is the terminal wave, or terminal deflection. If a QRS complex ends in an R wave, then it has a terminal R wave. It can also be said that the terminal deflection is positive.

I would call the QRS complex in this 12 lead ECG an rsR' complex. Compare it to the rsR' complex in this PowerPoint slide.

It's important to think in terms of the terminal deflection (or terminal R wave) in lead V1 with RBBB because the QRS morphology can be quite variable!

Consider these examples.


All of these QRS complexes are different. Most are positively deflected but some are negatively deflected. Most start with an R wave, but a few start with a Q wave. However, they all share one important feature.

They all have a terminal R wave!

Why?

Ask yourself a question. If the right bundle branch is blocked, which ventricle depolarizes first?

The left ventricle!

So which ventricle depolarizes last?

The right ventricle!

What is the only precordial lead on the right side of the chest?

Lead V1!

A terminal R wave in lead V1 represents late right ventricular depolarization.

The terminal S wave in lead I represents the same thing, because the positive electrode for lead I is on the left shoulder. So, late left-to-right ventricular depolarization moves away from the positive electrode for lead I and toward the positive electrode for lead V1.

Remember when I said that the first step was to establish that you were dealing with a supraventricular rhythm?

The QRS complex in the top row, far right, was cropped from a run of VT (lead MCL-1 which is a surrogate for lead V1). The QRS complex in the bottom row, far right, was also taken from a run of VT.

So, you have a supraventricular rhythm, with wide QRS complexes, and a terminal R wave in lead V1. You're 99% of the way toward calling this a RBBB.

All we have to do now is search lead I for a terminal S wave.

Does lead I show a terminal S wave?

Yes!

ECG diagnosis: Borderline sinus bradycardia with 1°AVB and RBBB, occasional PACs.

See also:

Right bundle branch block - Part II

Right bundle branch block - Part III

Incredible video of soccer player saved by ICD

In this amazing video, 20 year old Belgian soccer player Anthony Van Loo is saved by his implantable cardioverter-defibrillator (ICD).



Are these cool times we live in, or what?

h/t Dr. Wes.

ST segment morphology

In a previous post, we discussed the problem of ST segment elevation.

Because acute myocardial infarction (STEMI) is not the most common cause of ST segment elevation in chest pain patients, we need to consider other factors like reciprocal changes to shore up the diagnosis.

It's also a good idea to be well versed in the typical appearance of the STE-mimics (paced rhythms, left ventricular hypertrophy, benign early depolarization, pericarditis, left ventricular hypertrophy, hyperkalemia, and so on).

Another factor that can assist you is an analysis of the morphology of the ST segment.

The normal ST segment should not be flat. It should have an upward concavity sometimes referred to as a "take-off".

When an ST segment loses its concavity and becomes straight or upwardly convex, it can indicate acute myocardial infarction.

Consider this image from WJ Brady, SA Syverud, C Beagle et al. Electrocardiographic ST-segment Elevation: The Diagnosis of Acute Myocardial Infarction by Morphologic Analysis of the ST Segment Acad Emerg Med 2001; 8(10):961-967


You can draw an imaginary line between the J point and the apex of the T wave. If the ST segment is below that line, then it's upwardly concave. If it's even with or above that line, then it's "non-concave" (straight or upwardly convex) which is suspicious for acute myocardial infarction.

If it helps you to remember, an upwardly concave ST segment makes a "smiley face" (good) and an upwardly convex ST segment makes a "frowny face" (bad).


Does that mean that acute myocardial infarction always presents with non-concave ST segments when ST segment elevation is present?

Not at all! This finding is not particularly sensitive. It is, however, fairly specific. When non-concave ST segments are present, it's another piece of the puzzle.

The STE-mimics almost always present with upwardly concave ST segments and an absence of reciprocal changes.

You might have noticed that I used the phrase "upwardly concave" as opposed to simply "concave".

That's because "concave" is "convex" depending on your perspective. That's why I always mention the direction of the concavity or convexity.

Sometimes this can get confusing! Consider this image from the AHA's new STEMI book.


The caption says "concave down" even though it's referring to an ST segment that is upwardly concave. This may have been a typo, but I think it's always helpful to use standardized definitions/language when it comes to medicine (or incident command)!

Regardless, if you look at this image from the STEMI book, the second window shows ST segments with a loss of upward concavity (ST segment straightening) and hyperacute T waves.

After PCI, you can see the development of Q waves and terminal T wave inversion (which usually indicates a STEMI that's been around for a while).

It's tough when a chest pain patient presents with an ECG with ST segments like we see in the third window. It's often difficult to determine the age of an ECG abnormality like that.

See also:

ECG mimics of acute STEMI

STEMI Activism and STEMI Etiquette

"Since I am an Emergency Department Physician, it is important to stress that these regional networks focused on improving the STEMI process outside the Cath Lab, not the STEMI procedure inside the Cath Lab.

The key is combining pre-hospital ECGs and STEMI networks, as pre-hospital ECGs without the network are about as useful as a cellphone without a wireless subscription. Receiving hospitals need to act on the information prior to patient arrival (even with short transport times), especially in the current era of ED and hospital over-crowding.

Moving forward, we need to continue to encourage regular healthcare providers to become STEMI Activists who promote evidence-based "change you can believe in" in their community. A local STEMI activist works to connect ALL the regional stakeholders so that STEMI-care becomes seamless and truly integrated. Anyone can be a STEMI Activist in their region, including Cath Lab staff, ER staff, EMS personnel, QI staff, or administrators. Helpful resources include the ACC D2B Alliance, the AHA Mission: Lifeline, and the ACTION-GWTG Registry...

[T]he best part of all these efforts is the multi-disciplinary camaraderie that leads to tremendous synergy and improves STEMI care for our patients. Some patients are treated so fast, that there STEMI is essentially "time-terminated" and they walk out the hospital a few days later with preserved LV function and a minimal bump in their cardiac markers.

Finally, we need to remember that we are treating real patients in these fast systems, not just making widgets. Hence, I suggest that all the diverse healthcare providers (EMS, ED, Cath Lab) tell their STEMI patients to "think positive," even as the team rushes to open up their blocked artery. I call this STEMI Etiquette."

- Ivan Rokos, MD[1]

Are you a STEMI activist? How is your STEMI etiquette?

Data quality, lead placement, your patient's dignity, and undressing female patients

I thought long and hard about allowing anonymous comments on the PH12ECG blog.

In my experience, anonymous posters don't exercise the same level of responsibility as posters who use their real names or blogger identities.

Anonymous posters are often bomb throwers. Or, they engage in proselytizing, propagandizing, sensationalizing, or advertising.

For them, there are no consequences. That's why it's almost always a mistake to get into a discussion with an anonymous poster.

On the other hand, some anonymous posters might have something of value to add. Perhaps they simply have not bothered to register with a blogger account. Or, maybe they have their own reasons for posting anonymously, but they are intelligent, responsible people who want to express their opinions.

I received a comment from an anonymous poster yesterday who was replying to Muscle Tremors, Your Patient's Dignity, and Staying Organized.

Anonymous wrote:

If you remove the bra of a female patient and you do not have her written consent be prepared for a law suit in most states. There is absolutely nothing to be gained in terms of quality unless you are a novice in removing the bra in doing an ekg. Remember this is not a decision that you make. The patients body belongs to the patient. NOT TO YOU.

Because this was in reference to a non-recent post, the comment ended up in my mailbox awaiting moderation.

This didn't sound like a random comment left by one of my usual readers.

Here's what I found under Recent Keyword Activity.


Whoever anonymous is, s/he typed the words "paramedics right to undress female patients" into Google and that's apparently how s/he found my blog.

Let's take this one step at a time.

If you remove the bra of a female patient and you do not have her written consent be prepared for a law suit in most states.

In the words of Daniel Patrick Moynihan, you are entitled to your opinion. You are not, however, entitled to your own facts.

Patients who possess the present mental capacity to understand their situation are presumed to have the ability to consent to medical procedures, and that consent need not be in writing.

Performing a 12 lead ECG is no different from placing a patient on oxygen, backboarding a patient, starting an IV, or taking a patient's blood pressure. Paramedics aren't required to obtain written consent for those procedures, and we aren't required to obtain written consent to remove a patient's clothes either.

If I explain to a patient that I need to perform a 12 lead ECG, and that I would prefer the patient be undressed from the waist up, and the patient says, "Do whatever you need to do." and then leans forward so that I can unfasten her bra (or I hold up a sheet while she unfastens her bra) then the patient has legally consented to the procedure.

There is absolutely nothing to be gained in terms of quality unless you are a novice in removing the bra in doing an ekg.

I do not consider myself a novice when it comes to capturing and interpreting 12 lead ECGs, and I have found it to be beneficial to remove a female's bra for several reasons, not the least of which is to help identify the correct landmarks for the placement of the V1 and V2 electrodes (which are frequently misplaced).

I have also found that attempting to place electrodes under clothing (including the bra) often leads to poor data quality.

As a practical matter, if the patient's arms are through the bra, and you start an IV (as you should for any patient complaining of chest pain, shortness of breath, syncope, etc.) then you will eventually have to pass the IV bag through the shirt and bra if the patient is not undressed at the beginning of the patient encounter.

What would be the point of all that?

The patient will end up undressed and gowned at the hospital anyway.

For a female patient who is particularly modest or uncomfortable being undressed from the waist up in the back of an ambulance, I can see unfastening the bra and having the patient remove her arms, but keeping the cups of the bra over the breasts, if that would somehow help the patient psychologically.

Having said that, you would still need to lift the bra up to correctly place the V1 and V2 electrodes.

So what's the difference between a bra and a sheet (or gown)?

In any case, you should only uncover the patient's breasts as long as necessary to complete the procedure, and you should make every effort to protect the patient's dignity.

I thought I had made that clear.

Remember this is not a decision that you make. The patients body belongs to the patient. NOT TO YOU.

I have no quarrel with the idea that the patient's body belongs to the patient.

However, there is a third possibility you are overlooking.

Maybe it's a decision you make with the patient's consent.

The patient or the patient's family, I presume, contacted 9-1-1 because some type of situation evolved beyond their span of control. Patients trust that paramedics will do what is in their best interest, with a high degree of expertise and professionalism.

In the 14 years I've been a paramedic, I have never had a female patient refuse to remove her bra for a 12 lead ECG once I explained the procedure, why it was indicated, and assured the patient that everything possible would be done to protect her dignity.

If, for whatever reason, my next female chest pain patient says, "I'd rather not take my bra off" then I'll explain that the lead placement will have to be modified slightly to accommodate the request, but I will respect the patient's right to refuse.

If I didn't explicitly say that in my previous post, it's because my readership consists mainly of medical professionals who already understand that.

Obtaining consent for procedures is part of every medical professional's basic education.

If you had a bad experience with a particular paramedic or EMS system, I would suggest contacting the director of that system and filing a written complaint.