EKG Junctional Rhythms


Terms in this set (...)

Junctional Rhythms

What are the normal rates for Junctional?

40-60 bpm
Any rhythm originating in
-The AV node
-The bundle of his

*the arrhythmias include:
-Junctional Bradycardia
-Accelerated Junctional
-Junctional Tachycardia
-Premature junctional contractions (PJC)
-Junctional escape complexes and rhythm
Junctional rhythms cont.
Usually result as an "escape" rhythm during periods of significant Sinus Bradycardia or Sinus Arrest.

-"We usually see these post cardiac arrest. The heart isn't fully functioning yet so we will see these junctional things start popping up there."

*The AV Junction has an intrinsic rate of automaticity = 40 - 60 bpm

*If SA Node automaticity is below 40 bpm (significant Bradycardia), stops completely (Sinus Arrest), or the SA Nodal impulses fail to reach the ventricles (complete heart block)...
"When there is a complete heart block, the ventricles should take over so there is some sort of response. In the blocks the SA is firing so there will be P-waves and just no response. Every once in a while at the rate of around 40ish the junction will fire off. It's a thin QRS but it's not related to the atria firing.

*The AV Junction takes over as the heart's "pacemaker"
-Serves as a "safety feature" to ensure continued pacing of the heart

"At a rate of 40-60 wont keep you conscious."
Example of Junctional Escape Rhythms
*Examples of Junctional ESCAPE Rhythms include:

-Junctional Bradycardia = < 40 bpm
-Junctional normal is 40-60 so below 40 is bradycardic for the junctional.

-Idio - Junctional = 40 - 59 bpm
-"All idio means is working on its own- by itself. The junctional is firing and it's firing at its own normal rate. It's by itself in control of the heart.. Hence: Idio-junctional. The only difference is the speed."

Accelerated Junctional** = 60 - 100 bpm
-"The junction has taken over the pacemaker of the heart and it is maintaining a normal HR for the person. It's accelerated for the person. Just like the sinus, it can go above its normal rate."

*Junctional Tachycardia is >100.
-"if it goes over a 100 bpm it's junctional tachycardia. Rarely seen because the junction does not have enough 'umph' to get that high."

**Accelerated Junctional can result from decreased SA Nodal automaticity OR increased AV Nodal automaticity
When depolarization of the myocardium begins in the AV Junction the following will occur:
"If the AV junction is the pacemaker, the impulse will travel retrograde to the atrium. Remember that electricity goes every direction at once, so it's going to shoot down the bundle of his into the ventricles but it's also going to shoot to the atrium to depolarize them. If the P-wave is visible, it is ALWAY inverted in lead 2. Remember that the normal sinus rhythm the atria fired, QRS fired, then we a T-wave and it would go on from there. But now that it is going backwards, the P-wave will be upside down and everything else will stay normal. The PR interval will get shorter because there is no longer the nice long delay of the AV node because the delay is getting eaten up by the electricity going in other directions. Remember electricity is normally going towards the positive electrode in lead 2 so it will normally show a positive P-wave. So, when it is going backwards it makes sense why it's inverted.
The thing here is there is a lot of cells and the bundle too, so you tend to only see the inverted P-wave if it's one of the cells close to the Atria that takes over the pacemaker. This gives the Atria time to repolarize because most of the delay is still there. If it's one of the cells further down, the inverted P will still be there but it will more than likely be buried in the QRS. This is why we don't usually see a P-wave. "

*Conduction through the ventricles is normal because the right and left bundle branches are acting as normal. The problems with the heart are much higher up so the junction is taking control."

-When the AV junction takes over pacemaking responsibility, the atria and the ventricles will be depolarized at nearly the same time because the impulses spreads in two directions at one time.
The 3 rules to ventricular rhythms

1. When the impulse (P Wave) is initiated above the A/V* septum
-This is when we see our upside down P-wave.
-If it's upside down you know it's junctional. There is no way that the SA node can fire off and produce an inverted P-wave.
-An inverted P-wave does not mean ischemia.. It means retrograde of electricity which means it has to be from the junction.

2. When the impulse (P Wave) is initiated within the A/V septum
-The P-wave is there you just can't see it.
-"Timing is everything to the heart... If there is no P-wave, Is there Atrial kick? No, because without the PR interval to allow all the blood in the atria to be forced into the ventricles, they don't get overfilled so we lose starlings law.. This means we lose that 20-30% atrial kick. They are still going off, but they are going off at the same time as the ventricles. So the ventricles pressure is so much higher and they will fire but they're technically not able to move any blood. This will be hard on them and the valves will be working a little bit of overtime which is bad."

3. When the impulse (P Wave) is initiated below the A/V septum
-If it's initiated below the AV septum, you could have P-wave follow the QRS.
-"At this point it is happening so far down in the junction that it shoots straight to the ventricles and fires them off. The PRI is reversed and it is slowed down so by the time the ventricles have fired off it's ready to fire off a P-wave. So the atria fire backwards."
Junctional Bradycardia
*Junctional Bradycardia (escape rhythm)
-It's an escape rhythm- the heart has stopped and the junction is trying to escape death.

-Rate of < 40 bpm
"Any rate under 40 will have no P-wave or an inverted P-wave. It will be regular. "

-SA Node automaticity is lost; AV Junction automaticity is slowed.
^"The SA node has quit for whatever reason.. It may have just been killed off."
^"The AV node is sick too. If the heart is sick enough that the SA node was killed, would the AV node not be damaged? Of course it would. They share the same blood supply (In most people)."

Causes: MI, hypoxia, increased parasympathetic tone, toxicity (cardiac drugs)

-To fix this, we will pace them. Once their BP is up we can give them the versed.

-"If after the QRS to the T wave never goes to flat line, it more than likely is the P-wave."
Junctional Bradycardia Interpretation
*Junctional Bradycardia Interpretation:

*Rough Rate = Very Slow (Long R-R)

-Rhythm (R to R) = Regular
-"Whenever part of the junction has taken over the pacemaker of the heart it will be a regular rhythm. Which ever part of the junction decides to take over will and start firing off at it intricate rate."

Rate (Use Triplicate) = < 40 bpm
-Because it's a rate under 150.

P Waves = Inverted or Absent; may appear before or after QRS

PRI = < .12 - IF the P Wave precedes the QRS
-"If there is a P-wave to count the PRI, it will always be less than 0.12. It cannot be normal because no matter where in the AV junction it starts, some of the delay is removed because it goes in both directions instead of having to travel the entire way through. It's like starting in the middle of the road, both are going to be quicker because they don't have to walk to the full distance."

QRS = .08 - .12; Consistent Morphology
-"The QRS will be consistent and normal. By the time the ventricles fire, they fire through their normal mechanisms through the bundle branches and the purkinje fibers. This does not effect the ventricles at all. All the ventricle power is reserved minus the atrial kick."
^"This is even if the P-wave is before the QRS. The atria fired back but it wasn't pushing blood into the ventricles so much as it was slowing blood return down to the ventricles, so we reduced cardiac output by removing ventricular stroke volume AND we have a low HR. You will not find these people hypertensive. You have two decreases in cardiac output."
Idio-Junctional (Escape rhythm)

(Within normal range for whatever the pacemaker is Idio)

Normal range for Junctional (AV) is 40-60 bpm
*Idio-Junctional (escape rhythm)

-Rate = 40 - 59 bpm (triplicate method)
-Rough rate= slow
-Rhythm= regular

-The rate of SA Node automaticity is below the intrinsic rate of AV Junction automaticity OR the SA Node fails to fire completely
>The SA node has been killed off.

-The AV Junction serves as a "safety feature" to ensure continued pacing of the heart

-Causes: SA Node disease, MI, hypoxia, increased parasympathetic tone, toxicity (cardiac drugs)

-Increased parasympathetic tone: We are looking at some sort of vagal tone stimuli. We could fix this by knocking out the vagal tone.
-If you are suctioning and they start to vagal out, you stop suctioning. If you tubbed them and they start a quick fix would be Atropine. It will knock out the vagas nerve and the HR will come back up.

*P Waves = Inverted or Absent; may appear before or after QRS

*PRI = < .12 - IF the P Wave precedes the QRS

*QRS = .08 - .12; Consistent Morphology
Accelerated Junctional (Escape Rhythm)

Faster than the normal but not tachycardia
*Accelerated Junctional (escape rhythm)

-Rate = 60 - 100 bpm (use triplicate)
-Rough rate= Normal to fast rhythm.
-inverted or absent P-waves; b4 or after QRS

-"The junctional is actually giving us a decent HR. We still lost the Atrial kick but the HR is still capable of keeping us stable. Do you want to walk this type of patient to the stretcher? NO, because the second they stand up they wont have any sort of compensatory mechanism kick in to adjust for all the blood rushing to their feet and they're going to go unconscious. These are the patients we want to keep flat and pick them up ourselves and move them to the stretcher (still flat). "

-The rate of SA Node automaticity is below the rate of AV Junction automaticity

-SA Node is firing too slowly or AV Junction is firing too fast

-An accelerated junctional rhythm results from increased automaticity in the AV junction, causing the AV junction to discharge faster than its intrinsic rate.

-Causes: SA Node disease, MI, hypoxia, increased parasympathetic tone, toxicity (cardiac drugs)
Junctional Tachycardia
*Junctional Tachycardia- irritable rhythm

-Rate > 100 bpm (Triplicate or 6 sec)
-Fast to very fast

-Can be Paroxysmal Junctional Tachycardia (PJT)
^"They can come and go on their on especially if they are caused by meds."

-Paroxysmal = sudden onset and abrupt stop

-"Over 150 will be Atrial- Tachycardia. Under 150, sinus tach and junctional tach wont look alike anymore. You will notice the absent P-wave."

*Significantly increased automaticity of the AV Junction overrides the firing of the SA node
-"In this case the SA node doesn't have to quit. The AV junction has gone insane and starts pacing faster the SA node which causes the SA node to drop out. It will just start following along."

-Causes: Ischemic heart disease, stimulant usage (cocaine, heroin), anxiety
PJC- Premature Junctional Contraction
*Premature Junctional Contraction (PJC) or Junctional Escape Beat

-A single electrical impulse, originating in the AV Junction, that occurs during a Sinus Rhythm

-PJC - an impulse that results in premature depolarization of the heart before the next expected sinus beat

-Junctional Escape Beat - an impulse that results in depolarization of the heart after the next expected sinus beat.

-Why should you be more concerned with an Escaped beat?
-Because it means that the node failed. The premature beat is somewhat concerning because it means wherever the origin of the Premature complex is irritated for some reason. It could be medication, hypoxia, drug ingestion, etc. Something is irritating the heart.
The normal pacemaker of the heart failing entirely and needing another pacemaker to kick it back on is really scary! All we need for a full cardiac arrest is for the junction to not fire the escape beat."
-"Knowing which type it is, is important. A premature may only need oxygen and could be knocked out right out. An escape beat you want a 12-lead, a large bore IV, and 2 liters of O2 to knock it out. It's a huge warning sign that something else is going on. "
A PJC can result in either a compensatory pause or noncompensatory pause, depending on whether the SA node is depolarized.
*Noncompensatory: occurs if the premature beat depolarizes the SA node and interrupts the heart's normal cadence.

*Compensatory: occurs only if the SA node discharges before the premature impulse reaches it.
Junctional Escape Complexes and Rhythms
A junctional escape beat, or junctional escape rhythm, is an arrhythmia that results when the rate of the primary pacemaker, usually the SA node, is slower than that of the AV node.
Retrograde conduction
*When the atria are depolarized in a "backward" fashion, it's called retrograde conduction because the electrical impulse travels in the opposite direction it usually takes.

-The mechanism that enables the AV junction to depolarize the atria with a backward flow of electricity is called retrograde conduction.

-When retrograde conduction occurs in AV junctional rhythms, the electrical impulse that depolarizes the atria is traveling toward the negative electrode.

-In AV junctional arrhythmias, the atria are depolarized via retrograde conduction at approx. the same time as the ventricles are depolarized normally.
Where did the arrhythmia originate...
*Inverted P-wave following QRS complex= The rhythm originated in the AV junction

^But if the inverted P-wave precedes the QRS complex, you need to determine whether it originated in the AV junction or in the atria.

^The important clue will come from the PRI.
-If it was in the atria, PRI will be normal length (0.12-0.20)
-If it was in the AV junction, it would take less time to get to the ventricles so the PRI would be less than 0.12 (normal is 0.12-0.20).

*So if the rhythm has an inverted P-wave and a normal PRI, it originated in the atria.

*And if the rhythm has an inverted P-wave and a PRI less than 0.12, it originated in the AV junction.