Concealed conduction

No clinical hx. Why is there sudden prolongation in PRI of QRS#6 and non-conducted P wave after QRS#7?

Image 1 - Image Case

The strip shows sinus rhythm (~50 bpm) with pri of 160 ms but the PRI in QRS #6 is prolonged at 280 ms (7 small squares) and the P wave after QRS # 7  is not conducted.

Something is happening in the AV node not seen on surface ecg or something is concealed. 

Image 2 - Ladder Diagram

The PVC's (QRS #5 and 7) were retrogradely conducted reaching the AV node. The P wave before QRS # 6 arrived at the AV node while it is still in relative refractory period prolonging the conduction (prolonging the PRI) and the P wave after QRS 7 was not conducted because the AV node is in the absolute refractory period.

Interpretation: sinus rhythm with concealed conduction (prolonging a PRI and causing non-conducted P).

A Simple Arrhythmia Complicated by a Common Phenomenon

What is your interpretation?

Image 1 - ECG case

Image 2 - Ladder diagram

A rhythm like this is better deciphered using a ladder diagram. A ladder diagram traces an impulse from the A (atria) tier, AV (junction) tier to the V (ventricle) tier. Marking the P waves in the A tier and the R wave in the V tier are the easy part. The challenging part is connecting the A to the V tier because the AV tier is an electrically silent suface ECG phenomenon. This means that it does not create a positive deflection on the surface ECG.

Cherchez le P

Image 3 - The P wave in A tier

Cherchez le P means search for the P in French. Electrocardioraphers would like to use this term because it sounds sexy in French. Looking for P is the first thing we look for. In image 2, P waves are numbered in red. 

The P waves looked regular with a rate that starts at about 60 bpm and increased to about 68 bpm. P4 and P7 appeared early and the morphology is different from the rest of the P waves. So, P4 and P7 are premature atrial complexes (PAC). We put the dot lower (A tier) in the ladder diagram and the rest in the upper part of the A tier.

Image 4 - The QRS in the V tier

Marking the the V tier is straightforward. Just trace the R waves and make a vertical line in the V tier

Image 5 - Connecting the AV junction

There are 2 QRS morphologies (shapes) in lead II. Most have a Rsr moprhology except R3 and R5 which is predominantly R (red arrows). The RR interval in R2R3 and R4R5 is about 1700 ms or a rate of about 30 bpm. We can conclude that from this R3 and R5 are non-sinus beats but are junctional beats. So, we put the dots in the AV junction. It is also possible that this junctional impulse will conduct retrograde. This will make the junction refractory to an incoming supraventricular impulse. Thus, P4, P5 and P8 are not conducted.  

P7 (PAC) is blocked because the AV node is still refractory from P6 capture. 

The Controversial R5

There is a P (P8) wave near R5. We can measure the PRI at about 0.20 seconds. However, sometimes surface ECG will give you a clue as to the origin or source of the impulse. In the case of R5, it has the same morphology (shape)with R3. Thus, R5 is a junctional beat.

So, what we have here is sinus rhythm with AV Wenckebach interrupted by non-conducted PACs with junctional escape with concealed retrograde conduction.

Take Home Message

1. For complex rhythm, use the ladder diagram.

2. Cherchez le P (Search for the P).

3. Examine the shape of P and QRS morphologies.

4. Examine RR intervals.

5. Some ECG's do not read books.

* I would like to thank Dr. K Wang for checking the ladder diagram and agreeing with it.

# 658

Concealed Transeptal Conduction

Image 1

To the left is a left bundle branch block (LBBB) morphology at cycle length ~ 800 ms with a PRI ~ 160 ms. Same thing is to the right with normal QRS duration.

It can be said that the LBBB in this case is not a fixed phenomenon. There is normalization after a PVC (coming from the LV - RBBB morphology). 

Persistence of BBB at lower cycle length and termination by a PVC

The persistence of BBB at lower cycle length (here ~ 800 ms) can be due concealed transseptal conduction. Concealed simply means you cannot see it in surface ECG but can be recognized from its effect on the subsequent impulse. The LBB here is not fixed so something is making the LBBB. 

In this tracing we may not know the initiating event of the LBBB but it continued. Its perpetuation may be due to impulse coming from the right bundle that penetrated (transeptal-retrograde) and collided with the incoming (antegrade) impulse of the left bundle.

The abrupt recovery was due to the PVC that excited the left bundle early and allowed more time for it to recover ("peel back refractoriness"). 

Image 2

Ref: 

Fisch C., Zipes DP and McHenry PL. 1973. Rate Deependent Aberancy. Circ 48:714-724 (http://circ.ahajournals.org/content/48/4/714.ful l.pdf+html)

Fisch C and Knoebel SB. 2000. Electrocardiography of Clinical Arrhythmia. New York. Futura Publishing Co.

Neiger JS and Trohman RG. Differential Diagnosis of Tachycardia with a Typical LBBB Morphology. WJC 3(5):127-134

http://www.wjgnet.com/1949-8462/full/v3/i5/127.htm

Prolonged PR Interval due to Concealed Ventriculoatrial (VA) Conduction

An adult with h/o of HTN came in due to mechanical fall. 

 

Figure 1 - Lead II

Why is the PR interval longer on the left than on the right?

  

Complex-looking arrhythmias are better interpreted when viewed in full disclosure and numbered.

 

Figure 2 - Full disclosure

There are bigeminal premature ventricular complexes (PVC) . QRS complexes 1,3,5,7,9,11 are conducted with prolonged PRI's (~280 ms or 0.28 sec). The PRI's of complexes 13 and 14 are shorter (~160 ms or 0.16 sec). The P wave after QRS complex # 12 is not conducted.

The possible explanation as shown in the ladder diagram is PVC with concealed retrograde conduction. 

Figure 3 - Ladder diagram

Prolonged PRI

The sinus P wave following the interpolated PVC reaches the AV node during it relative refractory period (induced by concealed retrograde conduction of the PVC) and is conducted with prolonged PRI.

Blocked P  wave

The P wave (after complex # 12) reached the AV node during its absolute refractory period (induced by concealed retrograde conduction of the PVC) and failed to conduct.

Reference: Fisch C and Knoebel, 2000, Electrocardiography of Clinical Arrhythmias, Futura Publishing Company Inc, NY

#438

Sudden PR interval prolongation due to concealed conduction

 

Figure 1 - ECG case

 

An adult patient admitted for altered mental state.
What is the probable reason of the prolongation of the PRI (red

arrow)?

 

Answer: Concealed retrograde conduction of a premature junctional beat delaying AV conduction (prolonging a PR interval)

 

 

Figure 2 - ladder diagram

#321

Concealed retrograde conduction

Sinus bradycardia with blocked/non-conducted sinus beats due to concealed retrograde conduction of PVC's (multifocal)

#624

Sudden prolonged PRI due to concealed conduction by Dr. Tính Nguyễn Chí

Image 1 : The ECG of the middle-age man who was diagnosed as myocarditis.

Image 2 - ladder diagram

As we can see, beats # 1, 2 are normally conducted complexes. Beat #3 is an interpolated PVC. Beat # 4 is sinus rhythm but with the prolonged PRI and beat 5 is also a PVC with retrograde atrial capture and then the cycle repeats. Notice that beats # 3,8,13 are interpolated PVCs and beats # 4,9,14 have the prolonged PRI. The possible interpretation for the prolonged PRI of beat 4,9,14 is the  concealed retrograde conduction of the premature ventricular complex. The sinus P waves after the interpolated PVCs reach the AV node during its relative refractory period ( caused by the concealed retrograde conduction of the interpolated PVCs), so they take much more time  to penetrate the AV node. That phenomenon created the long PRI (beats #4, 9 and 14).

Concealed conduction affecting the AV conduction

An adult with h/o of HTN came in due to mechanical fall. What is your interpretation? 

Image 1

As you can see, there are bigeminal PVC's. QRS complexes 1,3,5,7,9,11 are conducted with prolonged PRI's (0.28 sec). The PRI's of complexes 13 and 14 are shorter (0.16 sec). The P wave after QRS complex # 12 is not conducted.

Image 2

The possible explanation as shown in the ladder diagram is PVC with concealed retrograde conduction. 

Prolonged PRI

The sinus P wave following the interpolated PVC reaches the AV node during it relative refractory period (induced by concealed retrograde conduction of the PVC) and is conducted with prolonged PRI.

Blocked P  wave

The P wave (after complex # 12) reached the AV node during its absolute refractory period (induced by concealed retrograde conduction of the PVC) and failed to conduct.

Interpretation: Sinus rhythm, prolonged PRI and non-conducted P wave due to concealed retrograde conduction of PVC's .

* You can read (samples) compiled ECG's in the "ECG Rhythms Flashcards" in the link. If you have time please leave a comment. Thank you.

Reference:

Fisch C and Knoebel, 2000, Electrocardiography of Clinical Arrhythmias, Futura Publishing Company Inc, NY

#498