Advanced Heart Block

Vignette: A 50 yo who is scheduled for surgery.

Figure 1 - Long lead V1,II and V5

This is:

a. Sinus rhythm with AV dissociation and junctional escape

b. Sinus rhythm with complete heart block

c. Ventriculophasic sinus arrhythmia, second degree advanced heart block

d. Sinus rhythm, second degree AV block type II (Mobitz II)

Inferior Wall ST Elevation Myocardial Infarction in a Patient with Pacemaker

Figure 1

Vignette: 75 yo with h/o HTN, hyperlidemia, AF, s/p PM

c/o nonpleueritic CP with no cough/fever

Figure 2

Non-paced beats (red boxes) are noted to have ST elevations in II, III and aVF with reciprocal changes in I and aVL. There are also ST depression and T wave inversion in V2 and STE V3 to V6.

Troponin ~5 and echo showed infero-posterior wall hypokinenia.

Cath showed lesion in the posterior descening artery.

Interpretation : Inferior Wall ST Elevation Myocardial Infarction (IWSTEMI) in a Patient with Pacemaker

Complete Heart Block (CHB) ? Think Again

No clinical hx. Is this complete heart block (CHB)?

Image 1

This is sinus rhythm (SR) at about 88 bpm, first degree AV block, second degree advanced heart block or high-degree AV block, right bundle branch block.

It is very tempting to call this CHB. However, the clue that a sinus P wave is conducted is the irregularity of RR interval. There is sudden shortening of the RR interval (R4R5) vs the rest of the RR interval. If this is CHB the RR interval would be the same in all because in CHB the ventricles will be under the control of an ectopic junctional or ventricular focus. So, it would beat like clockwork. If there was shortening or difference in the RR interval, this means that a sinus impulse was conducted.

A simple trick to differentiate CHB from advanced heart block is the regularity of the RR interval. 

Is this third degree AV block or NOT?

A pt c/o syncope. Complete heart block (CHB) or not?

Image 1

This is only a 10 sec strip of a very exciting rhythm. I intentionally printed this portion for the great visual display of the complexes. What the h@*#% is happening here?

In understanding these kinds of rhythms it is worthhile to watch this video blog of Dr. Ken G. - https://www.youtube.com/watch?v=WJWotBhmirM&feature=youtu.be. 

The question being asked is that is this CHB or not? If you watched the videp then it is very clear that this is not CHB because some of the sinus impulses were conducted to the ventricle.

The short answer for this strip is advance or high grade AV block. This patient eventually got a pacemaker.

What is happening here?

1. Look for the P

Image 2

Here a caliper is of utmost importance because you have to march it out. Start at the obvious P to P. Here you can use the P to P between QRS # 4 and 5 or 5 and 6. Whichever you like. Marked in red arrows are the obvious P's. The blue arrows are the P's hidden from view (buried in the QRS or distorting the T waves.) Thus, this is sinus rhythm (~ 94 bpm). 

2. Which one P waves were conducted?

Image 3

QRS #4,5 and 6 are likely captured beats. But there is more. The morphology of the QRS are different. QRs #4 is conducted with a right bundle branch block (RBBB) morphology (aberancy). QRS #5 is cconducted normally. QRS #6 looked like a morphology between the normal-looking QRS and the wide QRS. So, QRS #6 looked like a fusion beat (F).

During this event, there is a 2:1 conduction.

Measuring the R to R helps

Image 4

The wide QRS beats are obviously not captured beats considering the variable PR interval. Added to that is if you measure the R to R, it will help. R2R3, R7R8 are equal. As well as R6R7. Thus, going back, we are saying that R6 or QRS 6 is a fusion beat.So, R2,R3, R7 and R8 are venticular escape beats.

The mysterious R1

The RR interval of R1R2 is < than R2R3 (and the rest). If you also look closely at the morphology using lead II, R1 morhology is different from the rest of the wide QRs beats. we do not have enough information but we can probably assume that this could also be a captured beat (abberant is morphology).

So, we have here advance or high grade AV block. During capture it showed RBBB-aberrancy and fusion beats.

Image 5


*In the words of Dr. K Wang, in ECG interpretation there are alternative explanations.

Practicing Ladder Diagram

Is this complete heart block?

Image 1 -  ECG case

For seemingly complex rhythms, a ladder diagram is of value:

1. Look for P or "milk the P" (French - cherches le P)

The RED ARE OBVIOUS P'S AND THE GREEN ARE NOT SO OBVIOUS. Mark in the A tier (atrium)

Image 2 - P waves marked

2. Look for the QRS. Mark in the V tier (ventricle)

Image 3 (A and V tier)

This is easy since we just drop the line for sinus beats (A TIER) and QRS (V TIER)

3. Connect the AV tier

Image 4- (connecting the dots)

This is more interesting because we have to identify which impulse to connect. 

EXAMINE THE QRS MORPHOLOGY/SHAPE AND THE R TO R INTERVAL. 

If you do that it will be a bit easier.

QRS 1,2, 4 and 5 are wide.

QRS 3, 6 and 7 are narrow. 

HOWEVER, QRS #7 is DIFFERENT FROM QRS 3 AND 6.

The RR intervals of R1R2 AND R4R5 ARE THE SAME. Thus, we can say they must be from the same source. They are wide so they are ventricular in origin (asterisk at V tier).

QRS 3 and 6 looked narrow and the P is in the conductible distance. Second, there is shortening of the RR interval compared to the preceding RR interval (R1R2 and R4R5). 

"The way to recognize captured beats is not by finding an appropriate PR interval, but rather by detecting a shortening of the RR interval" - Dr. H Marriott.

So, R3 and R6 are captured beats (marked C).

QRS #7 looked different than R3 and R6. It looked narorw but the P seemed to be so close. So, this isfrom the junction.

Finally, we can say this is SR (~83 bpm) with long PRI, Second degree ADVANCE heart block (or high degree AV block). Complete heart block was rule-out because of the presence of captured beats.

#520

Is this Complete Heart Block?

Is this complete heart block?

Image 1 - ECG case

Complete Heart Block or Not?

Vignette:

A 70 yo patient with history of hypertension and hyperlipidemia is admitted due to dizziness. What is your interpretation of this ECG strip?

Image 1 - ECG case in full disclosure

Advanced AV block

An elderly c/o of dizziness. What is the rhythm?

Figure 1

Sinus rhythm, 2:1 AV block due to Mobitz II

This is a 70 yo pt who was admitted due to weakness. What is your interpretation?

Figure 1 - ECG case

Sinus rhythm, 2:1 AV block due to Mobitz II

Figure 2 - case marked

The sinus (atrial) rate is about 88 bpm and the ventricular rate is about  42 bpm. The QRS has right bundle branch block (RBBB) configuration. There are 2 P's for every 1 QRS. This is termed 2:1 AV block. A 2:1 AV block is a special form of second degree AV block. It can either be second degee type I (Mobitz I or Wenckebach) or second degree type II (Mobitz II). A longer strip is needed to elucidate the mechanism. In this case, this 10 second strip captured 3:2 AV conduction showing a dropped beat with no PR interval prolongation prior to the dropped beat. So, this is second degree AV block type II (Mobitz II) manifesting as 2:1 (predominantly) and 3:2 AV conduction.

Sinus rhythm, advanced heart block

Figure 3 - Advanced Heart Block

This 10 sec strips is minutres after the previous strip. QRS #2 is a conducted beat and after that there is AV dissociation due to accelerated idioventricular rhythm (AIVR). Obvious P waves are marked in read and hidden P waves are marked in green. When the AV conduction ratio s 3:1 or higher, the rhythm is called advanced AV block. This block occurs because of AV node or His-purkijne disease and not retrograde concealment in the AV node or His-Purkije system caused by junctional or ventricular escape complexes. A few minutes later, 2:1 AV blocked recurred (not shown). A permanent pacemaker was eventually placed.

Reference:

Surawicz B and Knilans TK. 2008. Chou’s Electrocardiography in Clinical Practice. 6th ed. PA. Saunders-Elseiver

Issa Z, Miller J and Zipes D. 2012. Clinical Arrhythmology and Electrophysiology A Companion to Braunwald’s Heart Disease 2nd Ed. PA Saunders

Das and Zipes. 2012. Electrocardiography of arrhythmias : a comprehensive review. Elsevier PA

#628

Complete Heart Block or Not?

No clinical history. What is the interpretation?

Image 1 - Long lead II

The rhythm is sinus at a  rate of about 68 bpm. Some of the P's are hidden from view or are merged with the QRS. The QRs interval is irregular. If you see an irregular RR interval then you should right away think that some of the sinus beats were conducted. Thus, this is not complete heart block (CHB).

In CHB, because the sinus beats cannot traverse the AV node then the ventricles are under the control of another pacemaker like the AV junction or the from the ventricles. These subsidiary or back-up pacemakers generate a regular pattern.

If you rely on lead II alone then a complex-looking arrhythmia becomes impossible to decipher. Then we need simultaneous leads in full disclosure view.

Image 2 - Full disclosure view with ladder diagram

What are clues of a captured QRS?

Sudden shortening of the RR interval would mean that the R with a shorter RR interval is conducted. In this strip, it is difficult to do that. Another clue is to use the morphology of the QRS. In using QRS morphology, you can use any lead where you can spot an obvious difference. In this case, we can use V1. 

R1, 4,5 and 7 shared the same QRS morphology and R2,3, 6 and 8 have the same morphology. 

Using deductive reasoning, R1 is near a P wave within a conductible distance and R2 is merging with the 3rd P wave. So, R1 is a captured beat and R2 is a junctional beat. If we follow the reasoning, then R1,4,5 and 7 are captured beats and R2,3,6 and 8 are junctional beats.

To make it easier to understand, a ladder diagram is constructed. By looking at the ladder diagram in R4 and R5 then there is some form of second degree AV block type I and an episode of advanced heart block considering (4 consecutive P waves are not conducted).

For this case, the 12L captured says SR, LAFB, first degree heart block. The initial  PRI I saw was ~ 300 ms. After years of watching strips, I know this P will drop and will manifest itself. Indeed it had several cycles of Wenckebach. The heart rate dropped some more and also captured this interesting portion. I know this 10 sec strip will stir imaginations and the challenge. 

#189

Is this complete heart block?

Deciphering an arrhythmia using ladder diagram and comparing QRS complexes

A common mistake is to call this pattern Mobitz II block

An elderly c/o of dizziness. What is the rhythm?

Image 1

As you can see, the P to P rate is about 100. Some of the P's are hiding in the T waves and distorting it. So this is 3:1 AV block. This is high-degree AV (or advanced) AV block.

According to Dr. Goldberger, a subset of second degree heart block occurs when there are multiple consecutive non-conducted P waves present (P-QRS ratios of 3:1 or 4:1). This is referred to as high-degree (or advanced) AV block. It can occur at any level of the conduction system.A common misnomer is to call this pattern Mobitz II block. 

This case went to complete heart block and a pacemaker was eventually inserted.

Reference: 

Goldberger A. 2013. Goldberger’s Clinical Electrocardiography : A Simplified Approach. 8Ed Ph Elsevier

#392