ECG bootcamp 6 & 7

Ventricular rhythm disorders originate from where?

"Infra-His" - come below the bundle of His

differential dx narrow complex tachycardia with retrograde P waves after QRS

"Orthodromic" AVRT and AVNRT both giving you narrow complex retrograde P wave. there is another rhythm that can do the same thing - there are rhythms that just have a focus that are beating fast automatically. what if you get an automatic ectopic tachycardia located in the junction? that will conduct down to the ventricle and will conduct retrograde up to atrium when you see narrow complex tachycardia with retrograde P waves after QRS you have a differential dx of 3 rhythms: AVNRT, AVRT, or junctional tachycardia. usually it's ANVRT is pretty common, AVRT (WPW) is rare, junctional tachycardia is very rare

Supraventricular Arrhythmias: Recap

-Normal sinus rhythm too fast = sinus tachycardia (>100) too slow = sinus bradycardia (<50) -Sinus arrhythmia -Ectopic atrial tachycardia (aka PAT) -Wandering atrial pacemaker -Multifocal atrial tachycardia (MAT) -Atrial flutter -Atrial fibrillation (AFIB)

2 basic mechanisms for arrhythmias:

1. *Automaticity*: Ectopic focus takes over --> one of the places in the widespread conducting tissue takes off and starts depolarization for no reason by itself. that is also called an automatic rhythm. an ectopic focus goes crazy, has come weird behavior of channels and starts depolarizing rapidly all by itself 2. more common mechanism of dysrhythmias: *Re-entry*: creates a "Circus rhythm".

AV Re-entrant Tachycardia (AVRT) - 2 types

1. Pre-excitation syndrome 2. Wolf-Parkinson-White Syndrome

Atrial flutter with 2:1 block ECG

1. complexes are very small - patient has low voltage 2. rhythm is very fast - 150 BPM 3. P waves are hard to see. is this sinus tachycardia at 150? whenever you see a tachycardia at exactly 150 BPM, think flutter with 2:1 block. 4. if you look at lead II you have a picket fence appearance to the complexes. the way to prove that this is flutter would be to try to transiently impose more AV block, decrease conduction through the AV node so you can actually see the flutter waves. you can do that with either a drug (beta blocker, adenosine for long term) but if you're in the ER and trying to get a quick answer you can count on the carotid reflex. if you rub on the carotid bulb, that will inc the delay through the AV node through reflex patterns and you may transiently get 2 or 3 complexes which are spaced out and will demonstrate the flutter pattern this patient had low voltage because she had a large pericardial effusion and the irritation of that induced atrial flutter

2 functional pathways of the AV node

AVNRT is a common rhythm, seen in young people, seems to be a congenital anomaly of the AV node. reflects the fact that are 2 functional pathways within the AV node: 1. alpha pathway - tends to conduct impulses slowly but recovers very quickly 2. beta pathways - has a much faster conduction time but takes longer to recover

Atrial flutter

Atrial flutter and Atrial fibrillation are 2 different rhythms but occur clinically in the same scenario. any condition in the heart in which the atria is stretched or under pressure is a predisposition to these 2 rhythms. atrial flutter is a circus rhythm in the atria so that an atrial impulse re-enters and keeps self-stimulating this circuit. every time it comes around, it travels through the rest of the atria and it stimulates atrial depolarization. atrial flutter classically occurs at exactly 300 impulses per min. the p waves are one big box apart. so classically, atrial flutter occurs at 300. under certain circumstances it might be slower at 280-260 the AV node can't conduct 300 impulses per min. if our ventricles were stimulated 300x per min, we would have a hard time filing and cardiac output would dive. that's one reason why we were built with this break in the AV node to prevent us from having exceedingly high ventricular rhythm. this break in the AV node saves us from excessive ventricular response to flutter and most people when they go into atrial flutter, they block every other beat. so the common heart rate is a patient with atrial flutter with 2 to 1 AV block is 150 BPM. the block may be higher than that - atrial flutter is not always a tachycardia. it entirely depends on the health of your AV node. with a depressed, elderly AV node and you go into flutter, HR may be 100 or 75 or some divisor of 300 BPM. the other thing that may give you a slower ventricular response to flutter is if you treat it with medication to further slow AV conduction. part of the tx of atrial flutter is to block AV conduction so that you only transmit a reasonable number of impulses. in this tracing we see flutter with 3:1 AV block, 2:1 AV block, 5:1 AV block --> variable AV block. atrial flutter is a circus rhythm, it gives you picket fence P waves at exactly 300 BPM

AV Re-entrant Tachycardia (AVRT) occurs in what patients?

Occurs in patients with a congenital fast conduction pathway ("accessory pathway" or "bypass tract") connecting the atria and ventricle accessory pathway = abnormal wad of tissue which conducts very fast which is usually somewhere connecting the atria and ventricle these accessory pathways make a super fast connection between the atria and the ventricle

ectopic atrial rhythm ECG

atrial depolarizing regularly, they all pretty much look the same. P waves are very close to the QRS complex (abnormal) are they normal or abnormal P waves - in lead 2 the P waves are upside down (abnormal P wave morphology). this is an ectopic atrial rhythm. it's not a tachycardia - it's less than 100 so it's just an ectopic atrial rhythm.

Genesis of AV Nodal re-entrant tachycardia

atrial premature beat = isolated, fast ectopic beat that's generated spontaneously within atrial tissue. all of us have occasional atrial premature beats, in and of itself it's not a pathologic occurrence if an atrial premature beat starts down the pathway, it can conduct quickly down the fast conducting pathway. remember that it's premature so it's hitting this fork in the road soon after a sinus beat. it's an early premature beat. it finds the fast conducting pathway able to conduct but the other side which has a longer recovery period is still refractory (not yet depolarizable). the impulse comes down this left leg and conducts down the normal pathway to the ventricle. by the time it gets to the fork, the right side finds that it can conduct

Multifocal atrial tachycardia ECG

concentrate on the rhythm strips** --> usually V1 and lead II because these leads are the ones where you can usually get the best looking P waves 1. first ask what is the atria doing --> be sure that every QRS has a T wave. there are prob some P waves hiding in some of the T waves. P waves look different, there is a P wave in front of most QRS. it's a fast rhythm so it's multifocal, it's atrial, and it's a tachycardia how to calculate the rate when there is not a fixed interval between each QRS complex, remember that on most ECGs it's hard to see but there are going to be 2 lines that represent 3 sec so you count up how many beats in 6 sec and multiply by 10

Re-entry arrhythmia mechanism

creates a "Circus rhythm" particularly in abnormal tissue (atria, ventricular, nodal - anywhere in conduction system). a piece or a branch of the interconnecting circuitous network of conduction fibers is partially blocked, conduction is slowed. when an impulse is traveling down the conduction tissue, it has normal conduction through one branch of this branching system but encounters slowed conduction in another branch. what happens is that impulses can go in either direction so the impulse conducts anterograde but when it gets down to the connecting point, it finds that it is able to conduct retrograde. so it conducts both anterograde and retrograde and it develops a circus rhythm concept of unidirectional block: conduction tissue is blocked in one direction but able to conduct in the other.

normal sinus rhythm

defined as a rhythm in which the P waves are occurring regularly, QRS complexes are occurring regularly, both at the same rate and there is a regular and physiologic relationship meaning there is a reasonable conducting interval. normal conducting interval between P wave and QRS is up to 200 ms or 1 big box

sinus tachycardia

defined as a rhythm of regular P waves, regular QRS, regular connection but fast the atrial rate is fast

antidromic WPW

ectopic early impulse finds the accessory pathway available and re-enters up the AV nodal pathway most important thing when confronting a wide complex tachycardia is to look at the patient - Vtac is not well tolerated. SVT unless it's incredibly fast is usually well tolerated if patient is failing, hypotensive, chest pain and you have overt signs of poor perfusion, you need to address this according to the ALS protocol delta wave = early ventricular activation, will also look like Vtac wide complex tachycardia has a wide dx. 1st thing to do - look at the patient because if the patient is hypotensive, having chest pain, or signs of poor perfusion you initiate protocol for wide complex tachycardia if the patient is stable or this is not a patient, you have to figure out if it is or not Vtac.

AVN Re-entrant Tachycardia: AVNRT - ECG

fast (faster than 100), narrow complex rhythm with an upside down or retrograde P wave which comes after the QRS complex if you look at the leads that show P waves the best, hanging on the end of each QRS is a small deflection that looks like an upside down P wave in rhythm strip II, there is an extra depolarization P wave hanging on the end of each QRS. this tells us that atrial activation is after ventricular activation speed is variable, can be modest (110) or very fast (200)

Atrial flutter with 4:1 block ECG

go to V1 or lead II and you will see a regular P waves. they are occurring exactly 1 big box apart. this is Atrial flutter with high degree block

narrow complex tachycardia with retrograde P waves after QRS - ECG

if it's a supra ventricular tachycardia, it's probably AVNRT

wandering atrial pacemaker

if there are at least 3 different P wave morphologies, that implies that the origin of the rhythm is coming from all different spots in the atrium there is a P wave for every QRS, but the P waves all look different from each other, PR interval varies this tells you that you have P waves coming from multiple different locations

irregularly irregular vs. regularly irregular

irregularly irregular = no pattern. ex: atrial fibrillation, MAT. can't define consistent P wave in the rhythm. regularly irregular = ex: wenckebach where you have conduction, conduction, drop. you will see regularly spaced QRS complexes and then a pause. there is a regular pattern.

Evaluating cardiac rhythm - 3 questions

is there an automatic focus or circus rhythm somewhere in the atria, node or ventricle 1. What is the atria doing? (are there P waves, what is their speed, do they look like normal P waves. normal P wave coming from the sinus node is traveling in an inferior and lateral direction so when you look at leads 2, 3, aVF, in which the examining lead is on the foot it detects current or impulse coming toward it so normal sinus P wave should be upright in leads 2, 3, aVF) 2. What are the ventricles doing? (QRS complexes - is ventricular complex narrow, wide, regular, or irregular) 3. Relationship between P and QRS? (Is there a P in front of every QRS? - most significantly - is the p wave conducting and leading to the QRS. is there a regular relationships between P wave and QRS and is that a normal PR interval, is it unusually long, etc))

AVN Re-entrant Tachycardia: AVNRT

it conducts down one leg, depolarizes the ventricle then re-enters the beta pathway which is now excitable and it sets up a circus rhythm but it also then depolarizes the atrium retrograde every time it conducts to the ventricle that is followed by retrograde atrial activation

Atrial fibrillation

may be the most common arrhythmia you will see, particularly in an elderly population it is a chaotic rhythm in the atria in which there are no discrete impulses controlling, it's just continuous chaotic depolarizations all over the atria. if you count up how many impulses are occurring, it's about 400 a min so clearly HR will depend on AV conduction Afib can be Afib with rapid ventricular responses (RVR) or ti can be Afib with slow ventricular response and present as a bradycardia or it can be Afib with physiologic ventricular response in Afib, you can see atrial activity but unlike flutter in which every single flutter wave looks like the previous flutter wave and you get a picket fence or saw tooth pattern, Afib gives you an undulating baseline where clearly there is something going on in the atria but it's not organized and it's chaotic.

sinus bradycardia

means that we still have the regular relationship but the P wave rate is slow (less than 50 or 60)

"Orthodromic" AVRT

narrow complex tachycardia can be very fast. when it re-enters by going down the normal conduction pathway and re-enters up the accessory pathway giving you a narrow complex tachycardia, that goes by the name "Orthodromic" AVRT. that will be in contrast to what happens when the circus rhythm is established but it goes in the other direction. when it goes in the other direction you have a tachycardia with a delta wave (you get fast ventricular activation and that gives you a wide complex tachycardia)

Are all wide complex tachycardias ventricular tachycardia?

no - there are a few situations in which a supraventricular rhythm can have aberrant ventricular conduction. or supra ventricular rhythm with a bundle branch block if you develop an otherwise benign supra ventricular tachycardia but you happen to have a bundle branch block, that is one way in which an SVT can actually have a wide complex WPW with a delta wave, if the circus rhythm of WPW is going down the accessory pathway and re-entering up the AV node, that is called an antidromic WPW and will look like a wide complex tachycardia Any supraventricular tachycardia (afib, aflutter, AVNRT, AVRT, etc etc etc) in a patient with a bundle branch block or other conduction abnormality that widens the QRS, can look like VT...

Atrial fibrillation with rapid ventricular response, and RBBB

no recurrent P waves here dx: it's irregularly irregular rhythm. can't be Vtac because it's irregularly irregular and Vtac is a circus rhythm. what rhythms are irregularly irregular? Afib, multi focal atrial tachycardia why is it wide complex? --> if confronted with a wide complex rhythm and it's not Vtac it must be a bundle branch block, look at lead V1 --> Right bundle branch block (Mary)

sinus arrhythmia

normal undulation of rate which usually undulates with the respiratory cycle rate speeds up slightly and then slows down slightly

why do patients with a ventricular tachycardia at 180 BPM collapse, get hypotensive and have no CO whereas with a supraventricular tachycardia at 180 BPM an otherwise healthy person might have palpitations but they don't collapse?

not the answer - the atria in most of the supraventricular rhythms either start with some type of ectopic atrial focus or it's a circus rhythm is indeed depolarizing because the atria is not coordinated with ventricular rhythm. if the ventricle contracts and then atria contracts right after it, it doesn't add to filling. in both cases, you lose coordinated atrial activity answer - it has to do with the symmetry and efficiency of cardiac contraction. the supraventricular rhythms which are narrow complex, ventricular activation is going around the usually pathways so impulse goes down to apex, apex contracts first and you get a progressive ringing motion which gives you effective SV. when you activate the ventricle from a random location (as in ventricular tachycardia), not only are you losing that coordinated apex to base contraction but the impulse is traveling around the ventricle very slowly so you get dyssynchronous ventricular activation what is the atria doing during Vtac? Vtac almost never conducts retrograde to the atrium, the impulses don't get there. one of the ways you dx Vtac is that you see regular P waves (evidence of atrial activity) but it's not connected with ventricular activity. if you see P waves, they are marching through the ventricular rhythm. it is the loss of coordinated contraction which follows the dyscoordinated depolarization of Vtac

Supraventricular rhythm disorders originate from where?

origin above the Bundle of His (SAN, atrial tissues, AVN).

Atrial fibrillation ECG

recognizable by the undulating activity might be tempted to say this is sinus rhythm because there is a P wave but there is another bump and if you look at longer intervals you see an unstable undulating baseline other thing that tells you this is prob atrial fibrillation is that if you put the calipers on the rhythm, you have longer and shorter intervals and it's irregularly irregular

ectopic atrial rhythm

regular relationship between P and QRS but in lead 2 the P wave vector is going in the opposite direction from normal if the P wave is upside down, it means it's going away from lead 2. that defines an ectopic atrial rhythm (also called nonsinus atrial rhythm - we know it's not coming from the sinus node but we would have to map it to find where its coming from)

Re-entrant supraventricular rhythms

supraventricular = rhythms generated above the bundle of His either within the atrium or within the junction which includes the AV node and the tissues around it but just above the interventricular septum above where the bundle of His is 1. AV nodal re-entrant tachycardia (AVNRT) - generated within the AV node 2. AV re-entrant tachycardia (AVRT) - involves the AV area but it's not generated within the AV node -"Pre-excitation syndrome", Wolf-Parkinson-White (WPW) Syndrome

AVRT: "circus rhythm"

the accessory pathway creates the substrate for a very fast circus rhythm if an atrial premature beat happens to conduct down the normal pathway and then reenter up the accessory pathway, you end up with a narrow QRS complex because it is conducting down the normal pathway but then you get retrograde activation of the atrium (upside down P wave) and you can set up a circus rhythm it can look exactly like AVNRT - how do you tell the difference? you have to look at previous ECGs on the patient and see that occasionally the surface ECG has classic delta waves

Pre-excitation: Wolf-Parkinson-White Syndrome - ECG appearance

the impulses coming from the sinus node can choose either to conduct down the normal conduction so the ECG will look perfectly normal or the impulses may randomly decide to be conducted down the accessory pathway you lose the interval b/t P wave and QRS. the ventricle starts depolarizing almost immediately after atrial conduction because the conduction is so fast. you see a *delta wave* - early ventricular activation (you lose the PR segments and you get early ventricular activation) it gives you an apparent wide QRS.

Ventricular rhythms (defintion + 4 types)

these are pretty bad - if you begin to mess up the pattern of conduction in the ventricle, you get disordered contraction pattern if all other pacemakers fail, the normal rate of depolarization of the tissues within the ventricle is very slow (about 20-30 BPM) and you will have a very abnormal wide depolarization pattern bc it takes a long time for impulses to spread through the His purkinje system in the ventricular muscle a bizarre wide complex rhythm at a very slow rate is a ventricular rhythm. that would be the escape rate if there were no other pacemakers available types: 1. idioventricular rhythm 2. accelerated idioventricular rhythm 3. ventricular tachycardia 4. ventricular fibrillation

how to tell that a rhythm is Supraventricular vs Ventricular on the ECG

think about what the ventricular depolarization would look like if the rhythm started with an impulse generated above the bundle of His as opposed to a rhythm that was generated within ventricular muscle --> a. supraventricular rhythms are usually narrow complex b. ventricular rhythms are usually wide complex *not always

AVN Re-entrant Tachycardia: AVNRT - ECG #2

this is very fast - about 210 you don't really see the inverted P waves because how do you know that's not an inverted T wave on the ECG, it's a narrow complex tachycardia. maybe because T waves are not really that pointy, there may be a P wave hitch hiking in the middle of the T wave

Paroxysmal atrial tachycardia (ectopic atrial tachycardia) ECG

this rhythm is really fast - it's actually faster than 150. ventricle is beating about 180, it's narrow complex, it's regular is there atrial activity? in the inferior leads, lead II there is an extra deflection that is likely the P wave. there is one in front of QRS complex could this be sinus tachycardia at 180 BPM? it could if this patient were at peak exercise but if this is a resting HR, adults do not get sinus tachycardia at 180. if this is an unmedicated, un-exercising patient, it's unlikely that it's sinus tachycardia this is paroxysmal atrial tachycardia - it's clearly atrial and a tachycardia. it's not sinus, the p waves are upright and it's coming somewhere in the atria prob not far from the sinus node could this be atrial flutter with 2:1 block with the extra flutter wave hiding somewhere in the previous T wave? this depends on arithmetic. when you have flutter with 2:1 block, almost by definition one of the flutter waves is going to be hiding in the QRS complex or in the T wave. there just isn't room to see the discrete flutter waves unless you have higher degrees of AV block

ventricular fibrillation

ultimate & fatal ventricular rhythm. ventricular tachycardia can deteriorate into this. this is sudden cardiac death ECG - low frequency, undulating, dyscoordinated ventricular activity

ventricular tachycardia

ventricular re-entrant rhythm. most often triggered by situations in which there is scarring within the ventricular myocardium so you have normal and scarred myocardium next to each other and that is the substrate to set up re-entrant rhythms which depend on variations in conduction speed b/t normal and abnormal tissue. so you have fast conducting next to slow conducting, you end up getting a block on one end that recovers and you end up setting up circus rhythms. you see ventricular tachycardia in ischemia, infarction, severe hypertrophy, hypoxia. it's an important sign of very serious disease

idioventricular rhythm

ventricular rhythm that is faster than normal but not excessively fast. between 40-120 BPM. accelerated ventricular focus, not seen very often. often seen in a situation in which a patient had a blocked artery and when we open up and reperfuse a blocked artery, an ischemic myocardium is recovering and sometimes you see accelerated idioventricular rhythms

review

wave forms that represent the progressive depolarization of the atria: the slow transmission of impulses through the AV node, bundle of His and then the activation of the depolarization of the ventricles followed by a period of repolarization - this is called the QRS complex but the individual components of the QRS complex are labeled only on the basis of the direction in which they go so any negatively directed complex is the Q wave, the first positively directed complex is the R wave, S wave etc

multifocal atrial tachycardia

when you see a variety of different P waves, a P wave for every QRS but it's very fast. classic multifocal atrial tachycardia - seen in very sick patients, correlates with hypoxia, it's an irritable rhythm of the atria

Atrial flutter with 2:1 AV block, LBBB

wide complex tachycardia at 150 BPM - ventricles atrial rhythm P waves? - rate of about 300 300:150 = 2:1