Junctional Tachycardia: True or False

Vignette: A 67 yo with history of Diabetes Mellitus, Coronary Artery Disease, S/P CABG, Heart Failure with reduced Ejection Fraction (HFrEF), peripheral artery disease, s/p stenting is admitted due to sepsis. In telemetry, the several premature ventricular complexes (PVC's), couplet and nonsustained ventricular tachycardia (VT's) were noted. Aside from that the ventricular rate would jump from 60's to 100's (Image 1).

Image 1 - Heart Rate Trend or Heart Rate Histogram

When the patient is in the 100's, the telemetry strip would look like this (Image 2):

Image 2 - ECG case

Q: This is junctional tachycardia (True or False)

Atrial Arrhythmia Triggering AVNRT

A 70 yo c/o of palpitations.

Image 1- ECG Case 

Image 2- ECG Case with P waves marked and ladder diagram

It initially starts as sinus rhythm with a PAC. Later, an atrial arrhythmia (likely atrial tachycardia) in noted (black arrows). PRI interval initially is slightly longer compared during sinus rhythm but on the 3rd beat, there is marked prolongation of the PRI. After that, inverted P waves in the precordial leads can be seen right after the QRS (red arrows). Thus, we see a supraventricular tachycardia that is called AV nodal reentry tachycardia (AVNRT).

In some individuals, there exist 2 AV nodal pathways. One conducts the impulse fast but recovers slow or has a long refractory period (fast pathway or FP) and the other conducts slow but recovers fast or has short refractory period (slow pathway or SP). During sinus rhythm, the impulse is conducted via the fast pathway (red line). 

Image 3 - Dual AV Node Physiology

ANVRT is almost always initiated by a premature atrial beat like a PAC. A PAC is blocked in the fast pathway (because the FP has not recovered from the previous sinus impulse) and it is conducted anterograde via the slow pathway (creating a long PRI in the surface ECG) and it is retrogradely conducted via the slow pathway (because the SP has already recovered). This completes the circuit and the AVNRT is initiated.

Image 4 - Initiation of AVNRT by a PAC

In our case, the first 2 AT beats are conducted with slightly longer PRI than during sinus rhythm. It traveled the SP but not only after the 3rd beat (markedly long PRI) that it was slow enough to allow reentry and initiated the AVNRT. This can probably be like initiation in the laboratory of an AVNRT by rapid atrial pacing.

Image 5 - 12L of the case during the tachyardia (AVNRT)

Reference:

Josephson, Mark E. 2008. Clinical Cardiac Electrophysiology: Techniques and Interpretations, 4th Edition. Lippincott Williams & Wilkins

#685

Which SVT? The need to capture the beginning of an SVT

An adult with complex medical hx.

Image 1 -  (tachycardia cropped)

Image 2 (beginning)

This is the initiation/beginning of the narrow complex tachycardia (NCT). 

The blue asterisk is most likely a PAC that travelled the slow pathway. It hard to measure the PRI in this limited strip. The red arrows are (inverted P waves). Here the impulse went up/back/reentered using the fast pathway. So, this is a short-RP narrow complex tachycardia.

For seasoned ecg lovers, all heard of dual AV node physiology. For beginners, this might be the first. It means in the AV node the supraventirular impulse has to 2 ways to reach the His-Purkinje. One pathway, the impulse travels fast (fast pathway or FP) and other the impulse travels slow (slow pathway or SP). The FP recovers slow and the SP recovers fast. 

Image 3 (PAC diagram)

When there is a PAC, the impulse will travel the SP (creating a long PRI) because the FP did not recover yet. As the impulse go down, the FP has recovered and the impulse go reenter/go up using the FP (creating a short RP). 

Image 4 (mid cycle)

This is middle of the tachycardia cycle. It is hard to see the inverted P' in this strip. If you only see this, it is hard to say w/c SVT is it (sinus tachycardia, atrial tachycardia. atrial flutter, AF, VNRT or AVRT).

Image 5 - Termination

This is the termination. The last few complexes had a longer R to R meaning it kind of slowed down before the spontaneous termination.Hard to say if this terminated in a P wave.

From its behavior, this is most likely typical (slow-fast) AV nodal reetry tachycardia (AVNRT) using slow AV nodal pathway for antegrade conduction and the fast pathway for retrograde conduction. Typical AVNRT are initiated by a PAC and rates vary from 118-264 (181 +/- 35).

Image 6 - Diagram

Ref:

Kumar UN et al. 2006. The 12L Electrocardiogram in Supraventricular Tachycardia. Cardiology Clinics ;24: 427-437

Bonnow et al. 2014. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 10Ed. PA Saunder

#506

A Narrow Complex Tachycardia

Vignette: 70 yo with history of HTN and COPD c/o SOB.

Image 1

Can you see the P?

The P wave or organized atrial activity is one of the keys to decipher the rhythm. If you have been watching these waves for so long then it becomes easy. When I say so long, it does not mean reading multiple 10 seconds strips but watching hours of continuous multiple lead ECG's. I do not know how to explain to you how to improve that skill but I can show some strips collected to search for those P waves. One tip I think that can verify whether those bumps are not artifacts is to check simultaneous leads. If they are consistent then those are real atrial activities.

In this exercise, I will show to you multiple leads and not only 2 leads. For people who are satisfied in interpreting rhythms using 2 leads then you are missing a lot of things.

Case # 1 - Can you see the P waves?

Figure # 1 -

A Supraventricular Tachycardia

 Vignette: A 50 yo with h/o of HTN and is a smoker came in due to shortness of breath and palpitations. Patient is awake with VS 160/90 RR 20 and 99% at 3LPM via NC. What is the rhythm?

Figure 1 - ECG case

SVT (probably AVNRT) with spontaneous normalization

Figure 1 - ECG case

No clinical history. 

Is this ventricular tachycardia (VT) that converted to supraventricular tachycardia (SVT)?

Long RP tachycardia

A 50 yr old pt with LLQ pain and found to have a renal stone. 

What are the probable rhythm diagnosis?

The probable ECG interpretations are:

• Atrial tachycardia

• Atypical AV nodal reentry tachycardia (AVNRT) - fast-slow or fast antegrade and slow retrograde pathway.

• Paroxysmal junctional reciprocating tachycardia - AV conduction over the AV node and the ventriculo-atrial conduction over a slowly conducting accessory pathway.

References:

Kistlet et al. 2006. P-wave Morhology in AT. JACC 48

http://content.onlinejacc.org/article.aspx?articleid=1137857

Kumar UN et al. 2006. The 12L Electrocardiogram in Supraventricular Tachycardia. Cardiology Clinics ;24: 427-437

Wellens HJ. 1996. The Value of the ECG in the Diagnosis of SVT. EHJ 17:10-20 http://eurheartj.oxfordjournals.org/content/17/suppl_C/10.full.pdf

#231

AV Nodal Reentry Tachycardia (AVNRT) for non-cardiologist

The effect of a spontaneous PVC in a supraventricular tachycardia: It's significance

Image 1

A 65yo pt c/o of shortness of breath.

As most will call it, this is a supraventricular tachycardia (SVT). A SVT is a narrow complex  (unless there is aberrant conduction) tachycardia that requires the atrial tissue or the atrioventricular (AV) node as an integral part of the arrhythmia.

SVT is classified as short RP' or long RP' tachycardia depending on the RP or PR interval. If the interval from the R wave to the next P wave exceeds the  interval from that same P wave to the next R wave, then the SVT is called long RP' tachycardia. If the interval form the R wave to next P wave is shorter than the interval from the same P wave to the next R wave, then the SVT is called short RP tachycardia.

Image 2 - Short RP' and long RP' tachycardia

Image 2A is a short RP' tachycardia and image 2B is a long RP tachycardia. 

These are the SVT's based on this classification

Image 3 - Short RP' and long RP' tachycardia

About 90% of AV nodal reentry tachycardia (AVNRT) and 87% of AV reentry tachycardia (AVRT) are short RP' tachycardia. Only 11% of atrial tachycardias (AT) are short RP' tachycardia. 

AVNRT is the the most common form of paroxysmal SVT.

Image 4  - ECG case highlighted

The ECG case  is a regular short RP narrow complex tachycardia (~190 bpm) . There is a pseudo-R' in V1 (red arrows) and pseudo-S in II, III and aVF (blue arrows).  There is lengthening of the RR interval before the termination of the tachycardia. The arrhythmia is terminated with a P wave (black arrow). A PVC can be seen that did not disturb the rate of the tachycardia. All this points to AVNRT.

The presence of a pseudo-S, a pseudo-R', or both is 90-100% specific for typical AVNRT and has an 81% positive predictive value for typical AVNRT. AVNRT terminates with a P wave. The change in the cycle length or the change in the RR interval prior to the termination is not diagnostic for AVNRT because it can also occur during AVRT.

The tachycardia RATE CANNOT BE USED TO DIFFERENTIATE BETWEEN SVT's. AVNRT can vary between 100-280 bpm (200-250). AVRT and AT can also have similar heart rates.

A short review on what creates the pseudo-S and pseudo-R and the concept of RP/PR classification

In some individuals, there are 2 atrionodal connections (dual AV node physiology). One connection (pathway) conducts fast but recovers slow (longer refractory period) and the other pathway has a slower conduction but recovers fast (shorter refractory period). 

Image 5 - Dual AV node physiology

In a short RP tachycardia, the retrograde conduction is via the FAST PATHWAY. This creates a short RP interval. The anterograde conduction is via the SLOW PATHWAY. This creates the long PR interval. The retrograde impulse also reaches the atria and creates an inverted P wave in II, III and aVF  (pseudo-S) and a small R wave in V1 (pseudo-R). 

In long RP tachycardia, retrograde conduction is via the SLOW PATHWAY and the antegrade conduction is via the FAST PATHWAY. Thus, on the surface ECG, there is a a long RP and shorter PR interval.

Effect of spontaneous PVC during a short RP tachycardia

Image 6 - PVC during AVNRT when HIS is refractory

During AVNRT, the retrograde conduction after a spontaneous PVC cannot reach the atrium because there is no alternated pathway. So, the AVNRT cycle is not changed and the PP interval is not change after the PVC. This means that the ventricles are not part of the circuit.

Image 7 - PVC during AVRT when HIS is refractory

During AVRT,retrograde conduction after a PVC cannot reach the atium (via the AV node) when the His bundle is refractory but can reach the atrium via the AP. So, the subsequent the atrial depolarization will occur earlier or the P wave on the surface ECG will occur earlier. This means the an AP is present. 

Image 8 - PP interval and the PVC

In this ECG case, the PP interval (red arrows) did not change as revealed in the simultaneous comparison of leads.

This termination of the tachycardia was due to adenosine.

Reference:

Bonnow et al. 2011. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th Edition. PA.Saunders 

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

Kumar UN et al. 2006. The 12L Electrocardiogram in Supraventricular Tachycardia. Cardiology Clinics ;24: 427-437

#618

A reentry phenomenon

Image 1

Came in due to CP. trop neg x3, pro-BNP-~ 10000, echo EF ~55, no WMA. Asymptomatic during at the time these ecg changes were noted. What do you think is happening here? 

Image 2 -ladder diagram

The tracing started as a sinus rhythm at about 70's bpm. After a PVC, retrograde P waves can be seen which can be seen distorting the ST segment. This created a short RP/long PR complex. The ladder diagram shown illustrates that as the impulse from the PVC was retrogradely conducted, it found the slow pathway in the AV node able to conduct (long PRI).  That same impulse later found the fast pathway able to conduct retrogradely. So, it created it the short RP. It then continued a few cycles. This arrhythmia was terminated by PVC's.

Image 3 - dual AV node physiology

This case illustrates dual AV node physiology (Image 3). In some persons, the AV node has 2 conducting pathways. One pathway is able to conduct fast and the other one is able to conduct slow. The fast pathway recovers slow (long refractory period) and the slow pathway recovers fast or short refractory period. These pathway can also conduct impulse retrogradely or in reverse direction. 

#176