Comprehensive Guide to AV Blocks and Bundle Branch Blocks Explained

[Music] [Music] hello friends myself dr durga i am from

chattanooga hospital and research institute in this lecture

today we are going to discuss about the av blocks that is the atroventricular block which is also known as heart

blocks and bundle branch block in the next two slides i am going to discuss about the conduction system and the

normal ecg just to revise past c this is the assay node from the s node there is initiation of

the electrical impulses which leads to start the contraction now these electrical impulses

from the bundle of thoral backman and venky back why atrial myocardium goes to the av

node in the what is the unique property of this av node the av node has a

decremental response or a delays what is important of this delay actually this protects the ventricle from the fast

atrial arrhythmias after this av node it is the bundle office by the bundle office it goes to the left and right

bundle branch and in the left bundle branch it goes the left anterior division and left posterior division

both these bundle branch ultimately divides into a network of conducting

system which is known as purkinje fibers so this is how there is the activation which starts from the atria and comes to

the ventricle okay here we are going to discuss about the blocks which occurs in the av node and the bundle branch

see this electrical impulse generation of these electrical impulses and traversing through the atrial ventricle

mechanic produces a changes in the action potential which can be seen in the ecg so through the different

waves we all know that we see the three four waves that p q r s t okay so this p wave actually represents the atrial

depolarization qrs complex represent the ventricular depolarization this pr segment represents the

av nodal that is atromantic nodal conduction time and then t wave represents the ventricular

repolarization so these are the features of the normal ecg the rate is usually between 100 to 60 bits per minute with

regular rhythm p wave is usually applied in lead 1 and 2 and negative in avr each qrs complex

is preceded by a p wave and these qrs complex is usually less than 100 millisecond white

vr interval remains constant pr interval remains constant okay so these are the features of the normality

here you can see this is the p wave this is pr segment then this is qrs and then this is t wave this is how the normal

complex looks like okay now we will go to the our topic that is the

atrioventricular nodal blocks or heart block so what is this atomic blocks or heart blocks

whenever there is a disturbance in conduction of the impulses through the av node

there it leads to av blocks okay whenever there is a disturbance of conduction through the heart which is

particularly occurring at the av node it can be because of any disease or damage of the av node either there is a

delay or there is a total block of impulses to get pass through the av node these conduction defects can be detected

from the ecg see this av nodal conduction time as i told you is represented in the ecg by a pr segment

but usually we not measure pr segment we measure pr interval so what is the difference between this pr segment and

pr interval look at this ecg pr segment is starts from the end of p wave to the start of r wave but the p r

interval is from start of p wave to the start of rv okay this is what is the difference between

the pr segment and pr interval visually we do not measure pr segment we measure pr interval

so when so this hard blocks can be divided into three types that is the first degree heart block second degree

heart block and third degree heart block this third degree hard block is also known as complete heart block

and then again the second degree hard block is divided into other three subtype that is the mobitz type one

mobitz type two and advanced second degree hard block in this advanced second degree hardware we will be just

looking at the two is to one block okay so first is the first degree hard block actually to call it as a block is a

misnomer there is no block there is a delay in the conduction through the av node

there is a delay in the conduction so actually the av node conducts more slowly than

the normal so there is occurrence of the prolonged pr interval pr interval is prolonged but it is usually constant

pr interval is greater than 0.2 seconds or more than 5 small squares but it is constant so p

wave will become pv will be normal qrs will be normal there will be only prolongation of the pr interval more

than 5 small boxes so you can see in this the rhythm given below

just see if you count the pr interval this is 1 2 3 4 5 6 here one two three four five six one two

three four five six so it is prolonged more than five boxes but it is constant in each of the

in all the rhythms okay so so what are the points you should

remember about the first degree heart block there is a prolonged av conduction which

leads to prolongation of the pr interval uh usually the qrs complex is narrow and if qrs complex is narrow it suggests

that the block is in the av node the site of environment can be atria can be a b node can be hisper knz usually we

find out by the qrs so the qrs is usually if it is narrow then it says the origin is in the av node

clinically the patient does not have any symptoms the prognosis is good and no treatment is required

then comes the second degree heart block this second degree av block is diagnosed when one or the more impulses of the

atria is not transmitted to the ventricles when some of the atrial impulses are not transmitted to the

ventricles then it is known as second degree heart block as i told you the second degree heart block is of three

types type mobitz type one that is venky back mobitz type two and advanced second degree

heart block so first is mobitz type one so what occurs in mobitz type one is

there is progressive increase in the pr interval or

progressively delay in the conduction of impulses which leads to increase in the pr interval until one of the atrial beat

or p wave is not transmitted to the ventricle until one of the

atrial impulse is not transmitted to the ventricle see in the rhythm below sorry

so this is pr interval if you see this pr interval is progressively increased this says that the conduction to the eb

node is progressively increasing and then this is the p wave which is not getting transmitted this is what is drop

beat this is what is drop beat okay progressive increase in the conduction

time followed by one of the entire impulse will not be transmitted so what you have to remember about the

mobitz type one is the pr interval is not constant and it is increasing progressively till one of the bit is

not transmitted that is drop beat the pr interval is longest just before the drop beat and shortest just after

the drop beat if you look at the difference between the longest and the

shortest pr interval the it is more than 100 milliseconds

the ratio of p is to qrs is usually 3 is 2 2 but it can be 4 is 2 3 or 5 is to 4 commonly being is 3 is to 2. so

what are the symptoms which you get usually lethargy fatigue or lightheadedness and sometimes confusion

this rhythm is usually benign does not produce any hemodynamic changes if at all the patient is symptomatic you can

just give atropine are needed you can go with the pacemaking this can be transmitted to third degree heart block

but the risk of transmitters hot block is low so here i'm giving you one scenario look a 70 year old female comes

with a history of hypertension and diabetes and dyslipidemia present to the casualty with a history of

intermittent palpitations and breathlessness she also stated that she has a

disney on exertion on inquiring she does not give any history of chest pain or syncope or near cinco coffe or any other

complaints and while looking at the monitor we get the following rhythm in the ecg let's see

here just look at the pr interval take the last radamstream look at the pr interval see this pr interval is

progressively increasing till one of the p wave is not transmitted so this is drop beat okay

the pr interval just before the drop beat is longest and the pr interval just after

the drop beat is shortest if you take the difference of the shortest and the longest pr interval is definitely more

than 100 milliseconds you can count these small boxes and subtract and you will get the difference is more than 100

milliseconds so with this criteria we can say in this ecg the patient is having a

block mobitz type one block okay and this phenomena is known as this

progress increase is known as pinky back phenomena next come is the mobitz type 2 block

so what happens some but not all the sinus p waves

is transmitted to the ventricle so there is a there is a drop beats but this

conduction failure this conduction failures occur suddenly see in the last what we said that there

will be progressive increase in the pr interval and then one of the ah p wave will be dropped here what

happens is suddenly one or two p waves will not be transmitted to the ventricle so there is a sudden failure of

conduction of some but not all sinus p waves to ventricular that is drop bits but the pr interval is constant look at

this rhythm strip this p wave is not transmitted here this p wave is normally transmitted here it

also here also but suddenly again this p wave is not transmitted okay so there is a certain figure without any preceding

increase in the pr interval and if you see the pr interval it is 1 2 3

here also it is one two three in this beat also it is one two three so the pr interval is constant so constant pr

interval with sudden failure of conduction of the atrial impulse to the ventricle

that gives to mobitz type 2 block so what are things we should remember in the mobitz type 2 block is conduction

fails suddenly and unexpectedly without any preceding change in the pr interval and usually the qrs complex is wide

the pr interval is constant both before and after the occurrence of a drop beats mostly the problem is in the infra nodal

conduction system so there is one important clue the important clue is when you want to

differentiate between the mobitz type one block and type two block so in the mobitz type one block what happens there

is progressive increase in the pr interval then a drop beat here the pr interval will be constant and then

subtle appearance of a drop beats this is how you differentiate between the moments type one and type two block okay

here also the symptoms is maybe fatigue or dizziness or spiritual cope and syncope there is high chances that it

may land up in third degree heart block so permanent pacemaking is the treatment of

choice so here i'm giving you one more scenario the 70 year old female known case of

diabetes and hypertension presented with lightheadedness dizziness and pre-syncope since last two days no

history of nhs been on examination you found that the patient is having regularly irregular pulse

the bp is 90 50 and the heart rate is round about 47 and when you look at the

ecg monitor you got the fall algorithms so look at the rhythm this is qrs which is

white and this is p wave which is not transmitted again this is a p wave which

is transmitted with a wide qra this p wave is transferred to the void qrs again these are the two previous which

are not being transmitted okay so there is a sudden appearance of a sudden failure of the impulses to get

transmitted to the ventricles and then these are all drop beats okay if you look at the this is drop bit if you look

at the pr interval the pr interval will be constant even before and after there is no change in the pr interval

so with these features you can say that the patient is having a mobitz type 2 block okay

now comes the advanced second degree block when we are not able to categorize

these blocks into mobitz type 1 and type 2 then we classified it as a advanced second degree heart block

in this we will just see our two is to one block for every two p waves there will be one qrs see in this rhythm below

this p wave is not transmitted this p wave along with a qrs so one two p waves for two pvf there is one qrs again one

and two p waves for one p waves for two pvf there is one qrs okay so what are things occurring here there

is every alternating p waves are not conducted or blocked it is difficult to diagnose the level of

lesion in this case narrow qrs complex may be no longer in front order but white qrs is almost always in front

order this can also progress to third degree heart block usually symptoms are uncommon but the same symptoms some

light headedness dizziness lethargy can be there see if the lesion is at the

level of av node and the patient is asymptomatic then usually the prognosis is good you don't have to treat the

patient but if the patient is symptomatic then

irrespective of the node or av or infra nodal you have to treat the patient with the permanent facing okay this is

what is advanced heart block now i will move on to the so here one ecg

here also you can see in the last rhythm strip one

p wave is not transmitted another is so all the alternating p waves is not being transmitted okay

this p wave not transmitted this is with qrs this again is not transmitted so every alternating p wave is not

transmitting if the patient is having the fixed ratio two is to one block okay now this is the third degree heart block

which is also known as complete heart block so there is a complete absence of atrial ventricular conduction none of

the impulse from the atria is transmitted to the ventricles there is a complete heavy dissociation with the

atria and ventricles is having their independent rates no relation between the p and qrs and usually the patient is

having a severe bradycardia there is an escape pacemaker this escape pacemaker can be in the av node or it can be infra

nodal in the his bundle bundle branches or distal to it even the myocardium itself which has a

automaticity of 10 to 15 bits per minute okay usually the patient is symptomatic busy

spell uh there can be pre-syncopes in co francs in cope even sudden cardiac arrest can also occur

now this the level of block can be at the level of a b node or at the level of hisper knz system when it is at the

level of av node it shows a junctional rhythm with narrow qrs when it is level of per key it shows ventricular escape

rhythm with white qrs so what are the points we should remember for saying the patient is

having a complete heart block p wave rate is normal complete dissociation between the

p waves and qrs complexes p can fall on st t segment and usually the atrial rate will be faster than the ventricular rate

you can just see this is the p wave it shows the atrial rate here the p wave is here then here here

here here so p is going on its own there is no connection between the p and the qrs

this qrs is going on its own if you see the rate difference between the rr and ppc the adrenal rate is higher

than the ventricular rate okay so these are the features of a complete heart block there is a b

dissociation and then p wave rate is faster than the ventricular rate so ah you are getting uh uh an old lady

female bring what are the casualty you observe her skin is cyano take it blue she's sweaty

she's having gcs of only 8 bar 15 she's only responding to painful stimuli and then the paramedic says that her bp is

only 44 systolic with a heart rate of around about 34 beats per minute and in the ecg the following rhythm is c

and look at the monitor this is the rhythm so here with this you can say this is p

wave so somewhere here this is p wave this is p wave this is p wave this is pv so p

wave is going on its own and qrs is going on its own so there is a av

dissociation you can see the atrial rate is more than the ventricular rate here in this issue it

is also visible the patient is having an st elevation okay so patient is having an acute mi

so acute mi is also one of the cause for the complete heart block so in with these findings in this ecg we can say

patient is having a acute mi with a complete heart block now we will move on to the

bundle branch block so first is the right bundle branch block

there are three criterias to say the patient is having a right bundle branch block first is the qrs duration will be

greater than equal to 120 milliseconds the qrs duration should be greater than equal to 120

milliseconds there is r s r dash pattern or notched r waving even c r s r dash small

r s and then dash okay bigger so r s r dash pattern in lead v1 along with it terminal s

wave in lead 1 avl and v6 if you look at the lead 1 avl and v6 there will be

white terminal s wave these are three criterias by which you can say the patient is having a right bundle branch

block now the the there are two types like complete and incomplete there is not much difference

between complete and incomplete we want to say the patient is having an incomplete right bundle branch block

this is only the qrs duration differs the qrs duration in those patients is in between

110 to 120 millisecond it will be more than 100 but less than 120 milliseconds to say the

rbb of incomplete type but you remember these three criteria to say if the patient is having

right bundle branch block or not okay so these are some of the causes and then if we say about the clinical

significance rpp is commonly seen and including in adults and usually benign but when this right bundle branch block

occurs in setting of mi acute my garden function then the patient is usually

have some poor prognosis and it indicates that the patient is having a proximal led

occlusion then comes the left bundle branch blocks so these are the five criterias for a

left bundle branch block if you want to see the patient is having a left bundle branch block that is lbpb qrs duration

should be greater than equal to 120 milliseconds there should be a broad r wave with the initial swearing you can

see there is a broad r way with initial slurring in lead 1 avl v5 and v6

broad rv with slurry in lead 1 avl v5 and v6 see there will be prominent q s or small

r and s pattern in lead v1 prominent qs or rs pattern in lead v1 then there is absence of

absence of small q wave in lead v6 normally there is a small q wave present in the lead six

which will be absent if the patient is having a lbpp

and then the prolonged r wave peak time is greater than 60 milliseconds in lead v5 and v6

this is r wave peak time is greater than 60 ml usually normally it is less than 35 seconds but in lbbb it becomes more

than 60 seconds in lead v5 and v6 so you have to take the pointed this is our wave and this is

from here to here you you have to see this difference this difference is

more or this duration is more than 60 milliseconds to say our way peak time is prolonged so these criteria says that

the patient is having a left bundle branch block first is qrs duration more than 120 milliseconds then there is a

slurring of the r wave in the elite 1 avl

v5 and v6 so there is a broad r wave in v1 ava in lead 1 avl v5 and v6 there is a qs or rs pattern in lead v1 there is a

qs or rs pattern in lead v1 then there is an absence of small q wave in lead v6 and the

r wave peak time is more than 60 milliseconds okay

these are the few causes of the left bundle branch block then comes the clinical signal it is

this lbbb is almost always pathological and generally a marker of the underlying

left ventricular heart disease new answer to lppbbb says the patient might have an

underlying ischemia and infection and needs a thrombolytic therapy then lbb in the setting of

mi acute mi deteriorates the prognosis also if we want to uh and

say about the left ventricular hypertrophy if the lbbb is present then the normal lvh criteria is not

applicable and the presence of this lpbp says there is a ventricular dissynchrony in presence of heart failure so the

identical both the right and left ventricle should contract in a synchronized way the patient is having

lbb in presence of heart failure then it says the patient is having a dissynchrony ventricular discinchron

so this is about lbbb then a small few things about the halter monitoring alternative small variable divide that

keeps track of heart rhythm a halter monitor uses electrodes and recording device to track the hearth rhythm for 24

to 48 hours it is also known as ambulatory electrocardiography

here we can record the ecg or get the ecgs or rhythms for a extended period of time

so how it works this there is a small monitor just size of the playing card and there are several leads and wires

which are attached to these monitor there are three surface electrodes and these surface electrodes are connected

on the chest wall with the help of a gel to this the metal electrodes are connected and this conducts the hearts

elect electrical activity through the wire to the halter monitor where it is recorded

so when you should go for a halter monitoring when you want to diagnose and assess the cardiac

arrhythmia and conduction abnormality whether the patient is symptomatic or asymptomatic you can use this if the

patient is having a recurrence in cope near syncope or episodic dizziness or if the patient is having a

uh recurrent palpitations unexplained then you can

go with the harder monitorings so how it helps the advantages is it gives you uh 24 to 48 hours of full disclosure

is available in that and that you get the heart rate graphs and atrial fibrillation burden grafts

all those things disadvantages is 24 to 48 hours is a short duration and

sometimes the patient may not have the symptoms at that specified period of time then it is difficult to diagnose if

the symptoms are very much intermittent then the yield of the test is low but

say if you get these type of differences in halter monitoring it is alarming

if you get a second mobitz type 2 or third degree av block that is alarming sinus process if it is more than three

milliseconds three seconds then it is alarming marked bradycardia during waking hours or techy arrhythmias

all these things if present this is the patient is having an alarming arrhythmias okay

with this i am finishing my topic

thank you so much