1. The ventricular rate depends on how healthy the AV node is.
2. The sinus node is reset by retrograde P waves. These retrograde P waves can be found within the QRS. The next sinus beat is determined by adding the usual P-P interval to the time at which the R wave occurred.
e.g. R wave at 3:05:09pm. P-P interval 1 second in a patient with a heart rate of 60bpm. Therefore expect to see the next P wave at 3:05:10pm.
3. Usually in CHB you will see P's at twice the speed as the R's, i.e. 2P for every R. If there is almost 1:1 then this is called "CHB with isorhythmic dissociation".
Saturday, October 3, 2009
What recommendations stem from a Holter
PAUSES:
To get a pacemaker you need to have:
- 5 second asymptomatic pause if have AF
- symptomatic pause of 3 seconds
AF CONTROL:
You say that someone has good AF control if they have:
Average heart rate 60-80bpm (50-70 if have LV dysfunction)
To get a pacemaker you need to have:
- 5 second asymptomatic pause if have AF
- symptomatic pause of 3 seconds
AF CONTROL:
You say that someone has good AF control if they have:
Average heart rate 60-80bpm (50-70 if have LV dysfunction)
How to report a Holter Monitor
A model conclusion:
"24 hour Holter monitor, good quality recording to assess patient report of x. Average heart rate xbpm with x% of the recording in sinus bradycardia and x% in sinus tachycardia. Maximum heart rate xbpm at 17:56 was a sinus tachycardia and minimum heart rate xbpm at 04:32 was a sinus bradycardia. Longest R-R interval of x seconds at 04:31 during sinus bradycardia. Rare isolated SVE. Frequent isolated ventricular ectopy, rare couplets and triplets. Patient symptom report of x correlated with isolated ventricular ectopy".
Useful phrases:
When you have a fast rhythm that looks like sinus but it is an old person:
"Likely appropriate sinus tachycardia. No patient events recorded at this time".
When you have a slow night-time sinus heart rate:
" Appropriate nocturnal sinus bradycardia with appropriate junctional/ectopic atrial escape as a result of vagal tone"
ttk: because vagal tone preferentially affects the SA node
When you have an ectopic without a P wave:
"Junctional beat with retrograde concealed penetration of the AV node, leading to the next sinus beat having the usual P wave morphology but a longer PR interval".
When you have an SVT where you see the P wave walk in and walk out of the T wave:
"Accelerated junctional rhythm for x beats with failure of the SA node to capture the ventricle"
OR
"Competing junctional and sinus pacemakers for x beats"
When you have long pauses at night in a patient with AF:
"Longest nocturnal pause in AF was x seconds".
When you have a seemingly long QT:
" A 12 lead ECG is recommended to assess the QT interval." (and add if patient on anti-arrhythmics)
When you have a broad complex relatively slow tachycardia without P waves visible:
" Period of tachycardia without discernable P wave. Cannot exclude slow VT in this patient on/not on anti-arrhythmics. Possible accelerate junctional rhythm with aberrancy. Unlikely to be AF as there is not enough difference in the R-R intervals".
OR
"Period of tachycardia without discernable P wave. Differential diagnosis includes accelerated junctional tachycardia with abberancy & slow VT. Unlikely to be AF as there is not enough difference in the R-R intervals".
When you are describing an SVT:
There are two types - "sustained" and "non-sustained".
You must describe three things:
a. Onset. The usual phrease will be "onset following PVC".
b. Duration in beats.
c. Speed.
It will be hard to describe the type, but the options are SIX:
- AT, AFL, AF, AJT, AVNRT, AVRT, .
"24 hour Holter monitor, good quality recording to assess patient report of x. Average heart rate xbpm with x% of the recording in sinus bradycardia and x% in sinus tachycardia. Maximum heart rate xbpm at 17:56 was a sinus tachycardia and minimum heart rate xbpm at 04:32 was a sinus bradycardia. Longest R-R interval of x seconds at 04:31 during sinus bradycardia. Rare isolated SVE. Frequent isolated ventricular ectopy, rare couplets and triplets. Patient symptom report of x correlated with isolated ventricular ectopy".
Useful phrases:
When you have a fast rhythm that looks like sinus but it is an old person:
"Likely appropriate sinus tachycardia. No patient events recorded at this time".
When you have a slow night-time sinus heart rate:
" Appropriate nocturnal sinus bradycardia with appropriate junctional/ectopic atrial escape as a result of vagal tone"
ttk: because vagal tone preferentially affects the SA node
When you have an ectopic without a P wave:
"Junctional beat with retrograde concealed penetration of the AV node, leading to the next sinus beat having the usual P wave morphology but a longer PR interval".
When you have an SVT where you see the P wave walk in and walk out of the T wave:
"Accelerated junctional rhythm for x beats with failure of the SA node to capture the ventricle"
OR
"Competing junctional and sinus pacemakers for x beats"
When you have long pauses at night in a patient with AF:
"Longest nocturnal pause in AF was x seconds".
When you have a seemingly long QT:
" A 12 lead ECG is recommended to assess the QT interval." (and add if patient on anti-arrhythmics)
When you have a broad complex relatively slow tachycardia without P waves visible:
" Period of tachycardia without discernable P wave. Cannot exclude slow VT in this patient on/not on anti-arrhythmics. Possible accelerate junctional rhythm with aberrancy. Unlikely to be AF as there is not enough difference in the R-R intervals".
OR
"Period of tachycardia without discernable P wave. Differential diagnosis includes accelerated junctional tachycardia with abberancy & slow VT. Unlikely to be AF as there is not enough difference in the R-R intervals".
When you are describing an SVT:
There are two types - "sustained" and "non-sustained".
You must describe three things:
a. Onset. The usual phrease will be "onset following PVC".
b. Duration in beats.
c. Speed.
It will be hard to describe the type, but the options are SIX:
- AT, AFL, AF, AJT, AVNRT, AVRT, .
Terminology and handy hints on reporting holter monitors
Things to know:
1. Orthodromic means you can't see the P wave, but it implies that there is an AVRT.
2. The compensatory pause that you see after a ventricular ectopic is due to retrograde P waves.
3. When you are seeing night-time bradycardias down to 30bpm, you're expecting to see a few junctional escape beats.
4. A common cause of SVT is AJT (accelerated junctional tachycardia) - the junction entrains the AV node here.
5. In whom will you be expecting to see atrial tachycardia? It doesn't occur in stretched atria, rather in emphsematous atria or those that have had surgery because the scar creates reentrance.
6. When a patient with AF is exercising you will sometimes see a few P waves amongst the AF - this is because the patient's sinus node is competing with the AF chaos when the patient is exercising (because autonomic tone increases the sinus node output).
7. Commonest reason for AF is a sick sinus syndrome, whether it be caused by a scarred sinus, a stretched sinus or a degenerated sinus. What happens is that there is sinus node failure and so the AF is an escape rhythm.
8. Is it AF or an SVT? AF will regularize at heart rates >160bpm. Until then there will be a significant difference in the R-R intervals, so you can deduce that there is no AF if the R-R intervals are relatively close together and there is a relatively slow tachycardia.
9. The only time to really worry about the QT interval is when you look at the slow heart rates and note what it is, and then look at the fast heart rates and note that it is longer...because the QT interval is meant to SHORTEN with tachycardia...and it's when it doesn't that you get VF, because you set up an R on T phenomenon.
10. How do you decipher the cause of a pause?
Well, it's pretty easy because there's 3 steps:
1. Is there a PAC? Yes= blocked PAC. ...or a PVC? Yes= concealed retrograde conduction that has reset the AV node.
2. Is there at least a P? Yes= AV block
3. If there's no P, then the possibilities are a vagus sinus (sinus arrhythmia) or a sick sinus. If you think that it's a sick sinus, then you have to decide which disease it has?
The diseases that sinuses get are:
1. Sinus arrest...diagnosed because it ends in a junctional escape beat AND the length of the pause will NOT be a multiple of the R-R* interval of previous beats
2. Sinoatrial exit block, which can be Type I or Type II...diagnosed because it ends in a sinus beat AND Type II differentiated by the length of the pause being a multiple of the R-R interval of previous beats (because the sinus node discharge was BLOCKED but NOT interrupted)**.
*because the R-R interval is the same as the P-P interval.
** in Type I 2nd degree SAEB, the P-P interval progressively shortens.
SO...if you get down to the third step of there being no P and you don't think it's vagus, all you have to do is MEASURE THE R-R INTERVAL and MEASURE THE PAUSE (WHICH WILL ALSO BE AN R-R INTERVAL). If they don't match as multiples then you have either SA or SAEB1.
How to tell the difference between SA and SAEB1?
3 steps:
1. If the R-R pause is GREATER than the preceding 2 preceding R-R intervals added together, then it is SA because SAEB1 will always be LESS. Done!
2. If it's less, then you need to look at the 3 preceding R-R intervals, not just the 2 preceding ones. IS the first longer then the second and the second longer than the third? YES= SAEB1.
OR you could use the 2 you already measured and measure the first R-R after the pause. Same rule applies - that R-R after the pause will be longer than the one before the pause.
1. Look at the previous 3 P-P intervals. If they get shorter
1. Orthodromic means you can't see the P wave, but it implies that there is an AVRT.
2. The compensatory pause that you see after a ventricular ectopic is due to retrograde P waves.
3. When you are seeing night-time bradycardias down to 30bpm, you're expecting to see a few junctional escape beats.
4. A common cause of SVT is AJT (accelerated junctional tachycardia) - the junction entrains the AV node here.
5. In whom will you be expecting to see atrial tachycardia? It doesn't occur in stretched atria, rather in emphsematous atria or those that have had surgery because the scar creates reentrance.
6. When a patient with AF is exercising you will sometimes see a few P waves amongst the AF - this is because the patient's sinus node is competing with the AF chaos when the patient is exercising (because autonomic tone increases the sinus node output).
7. Commonest reason for AF is a sick sinus syndrome, whether it be caused by a scarred sinus, a stretched sinus or a degenerated sinus. What happens is that there is sinus node failure and so the AF is an escape rhythm.
8. Is it AF or an SVT? AF will regularize at heart rates >160bpm. Until then there will be a significant difference in the R-R intervals, so you can deduce that there is no AF if the R-R intervals are relatively close together and there is a relatively slow tachycardia.
9. The only time to really worry about the QT interval is when you look at the slow heart rates and note what it is, and then look at the fast heart rates and note that it is longer...because the QT interval is meant to SHORTEN with tachycardia...and it's when it doesn't that you get VF, because you set up an R on T phenomenon.
10. How do you decipher the cause of a pause?
Well, it's pretty easy because there's 3 steps:
1. Is there a PAC? Yes= blocked PAC. ...or a PVC? Yes= concealed retrograde conduction that has reset the AV node.
2. Is there at least a P? Yes= AV block
3. If there's no P, then the possibilities are a vagus sinus (sinus arrhythmia) or a sick sinus. If you think that it's a sick sinus, then you have to decide which disease it has?
The diseases that sinuses get are:
1. Sinus arrest...diagnosed because it ends in a junctional escape beat AND the length of the pause will NOT be a multiple of the R-R* interval of previous beats
2. Sinoatrial exit block, which can be Type I or Type II...diagnosed because it ends in a sinus beat AND Type II differentiated by the length of the pause being a multiple of the R-R interval of previous beats (because the sinus node discharge was BLOCKED but NOT interrupted)**.
*because the R-R interval is the same as the P-P interval.
** in Type I 2nd degree SAEB, the P-P interval progressively shortens.
SO...if you get down to the third step of there being no P and you don't think it's vagus, all you have to do is MEASURE THE R-R INTERVAL and MEASURE THE PAUSE (WHICH WILL ALSO BE AN R-R INTERVAL). If they don't match as multiples then you have either SA or SAEB1.
How to tell the difference between SA and SAEB1?
3 steps:
1. If the R-R pause is GREATER than the preceding 2 preceding R-R intervals added together, then it is SA because SAEB1 will always be LESS. Done!
2. If it's less, then you need to look at the 3 preceding R-R intervals, not just the 2 preceding ones. IS the first longer then the second and the second longer than the third? YES= SAEB1.
OR you could use the 2 you already measured and measure the first R-R after the pause. Same rule applies - that R-R after the pause will be longer than the one before the pause.
1. Look at the previous 3 P-P intervals. If they get shorter
SICK SINUS SYNDROME
I've never really understood this, but now I do. It's all about escape rhythms.
So, because the sinus node is malfunctioning, the atrium takes over and you get tachycardia - either flutter, AF or EAT.
Then, when the tachycardia finally tires and stops, there's nothing to take over. So, there's standstill ("sinus pause")...till a ventricular or a junctional escape rhythm takes over.
Other things you see are sinus bradycardia, 'cos when the sinus node does work, it doesn't work well, sinoatrial exit block 'cos when the sinus node does work, it doesn't work well, AV block and BBB because the whole conduction system tends to be shot in these patients.
A pearl for diagnosing SSS from a tachycardia is that you will not see a very fast ventricular response because of the AV node conduction disease.
So, because the sinus node is malfunctioning, the atrium takes over and you get tachycardia - either flutter, AF or EAT.
Then, when the tachycardia finally tires and stops, there's nothing to take over. So, there's standstill ("sinus pause")...till a ventricular or a junctional escape rhythm takes over.
Other things you see are sinus bradycardia, 'cos when the sinus node does work, it doesn't work well, sinoatrial exit block 'cos when the sinus node does work, it doesn't work well, AV block and BBB because the whole conduction system tends to be shot in these patients.
A pearl for diagnosing SSS from a tachycardia is that you will not see a very fast ventricular response because of the AV node conduction disease.
Multifocal atrial tachycardia
This occurs because several foci become automatic - so have multifocal automatic atrial tachycardia (MAAT). It is usually seen in people with exacerbated airways disease.
Sunday, September 27, 2009
Determining what the fast rhythm is
Most atrial tachycardias are due to reentry. Only some are due to delayed afterdepolarizations, which is a triggered activity that occurs when the heart is racing.
So, the thing to look for is to see if there is a P wave before the QRS.
There are two types of paroxysmal lone AF. There is the vagal type that occurs in men at night or after a meal. And there is the catecholamine type that occurs in young women under stress or after coffee.
So, it's all down to the P wave for SVT.
If before QRS then this is atrial tachycardia (which can be automatic or reentrant) or atrial flutter - differentiate by looking to see if the QRS is distorted.
If just after QRS, then this is AVNRT..or...AUTOMATIC JUNCTIONAL TACHYCARDIA
If a little after QRS but still before the T wave then this is AVRT or AJT. The P wave will be inverted.
If a lot after the QRS, such that it's almost at the next QRS, then it's atypical (fast-slow)AVNRT with retrograde conduction up the slow pathway
So, once again:
P wave in QRS= AVNRT or AJT
P wave in ST or ascending limb of T wave= AVRT or AJT
P wave after T= "AT" or "flutter" or "atypical AVNRT" or "AVRT with retrograde conduction via a slow bypass tract"...how to tell the difference? The pearls are:
- distorted baseline means flutter
- large P waves means AVRT or atypical AVNRT ("size does matter")
However, often you don't see any P waves, so then have to rely upon the initiating beat:
- if the initiating beat or terminating beat is VPB, then it's AVRT.
- if the initiating beat is a PAC and the PR interval is long, then it's an AVNRT because you've just seen the dual AV node pathway!
The other trick is to see if there develops a rate-related bundle. If it does AND the ventricular rate slows, then this is an AVRT.
Differentiating between AVNRT and AJT:
AVNRT doesn't go slower than 150 and both appears and disappears suddenly , AJT doesn't go faster than 130 and can be seen to speed up and down.
So, the thing to look for is to see if there is a P wave before the QRS.
There are two types of paroxysmal lone AF. There is the vagal type that occurs in men at night or after a meal. And there is the catecholamine type that occurs in young women under stress or after coffee.
So, it's all down to the P wave for SVT.
If before QRS then this is atrial tachycardia (which can be automatic or reentrant) or atrial flutter - differentiate by looking to see if the QRS is distorted.
If just after QRS, then this is AVNRT..or...AUTOMATIC JUNCTIONAL TACHYCARDIA
If a little after QRS but still before the T wave then this is AVRT or AJT. The P wave will be inverted.
If a lot after the QRS, such that it's almost at the next QRS, then it's atypical (fast-slow)AVNRT with retrograde conduction up the slow pathway
So, once again:
P wave in QRS= AVNRT or AJT
P wave in ST or ascending limb of T wave= AVRT or AJT
P wave after T= "AT" or "flutter" or "atypical AVNRT" or "AVRT with retrograde conduction via a slow bypass tract"...how to tell the difference? The pearls are:
- distorted baseline means flutter
- large P waves means AVRT or atypical AVNRT ("size does matter")
However, often you don't see any P waves, so then have to rely upon the initiating beat:
- if the initiating beat or terminating beat is VPB, then it's AVRT.
- if the initiating beat is a PAC and the PR interval is long, then it's an AVNRT because you've just seen the dual AV node pathway!
The other trick is to see if there develops a rate-related bundle. If it does AND the ventricular rate slows, then this is an AVRT.
Differentiating between AVNRT and AJT:
AVNRT doesn't go slower than 150 and both appears and disappears suddenly , AJT doesn't go faster than 130 and can be seen to speed up and down.
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