Comprehensive Guide to Sinus Rhythms and Junctional Arrhythmias

[Music] [Music] in this lecture video i am going to

discuss about sinus rhythms and braid arrhythmias i am going to discuss about sinus rhythm

sinus bradycardia sinus tachycardia and braid arrhythmias at the end of the lecture video you will

be able to identify sinus rhythms and how to differentiate sinus rhythm from junctional rhythms and how to identify

and differentiate between sinus pass sinus arrest and cyanoatrial exit block what is an arrhythmia an abnormality in

cardiac rhythm is called an arrhythmia sa node is the predominant pacemaker of the heart and it depolarizes

spontaneously it is a modified cardiac muscle situated at the superior part of lateral wall of

right atrium the fibers of a sa node are continuous with fibers of atrial muscle so once the

impulses are generated it spreads rapidly through the atrial muscle the rate of sinus node discharge is

controlled by autonomic nervous system there are conditions which lead to sinus node dysfunction such as fibrosis

degenerative condition or ischemia of the sinus node this leads to variety of arrhythmias

commonly found in elderly and they may be asymptomatic or present with symptoms such as dizziness palpitation or

syncopal attack management depends on the patient's symptoms and may be by drugs to improve

the heart rate or with permanent pacemakers the point i want to stress upon here is

it is vital to differentiate these rhythm abnormalities based on the ecg and to intervene early to prevent any

life threatening conditions next point i am going to discuss is what happens if the sa node is dysfunctional

or suppressed and what are subsidiary pacemakers and what is their role

if sa node is dysfunctional or suppressed in order to continue hot beating other subsidiary pacemakers in

the av node specialized conducting system and muscle may initiate electrical activation

but typically subsidiary pacemakers discharge at a slower rate these are the various pacemaker size and

rate of depolarization sa node depolarizes at a rate of 6200 beats per minute

av node depolarizes at a rate of 40 to 60 bits per minute and ventricles at a rate of 20 to 40 beats per minute

before discussing about sinus bradycardia and sinus tachycardia let me explain about sinus rhythm

what is sinus rhythm if the depolarization begins in the sa node of the heart it is said to be in sinus

rhythm in the ecg p wave characterized by positive p waves in lead 2 3 avf

negative p wave in avr and biphasic p wave in v1 next about bradycardia and how to

differentiate sinus bradycardia with junctional rhythms so bradycardia is defined as heart rate

less than 60 bits per minute in adults during faithful state bradycardia results from either failure

of impulse initiation or impulse conduction depressed automaticity leads to failure

of impulse initiation asymptomatic bradycardia can be seen in people with high vagal tone such as in athletes so

it is vital to differentiate bradycardia as whether physiological or pathological to intervene accordingly

so there are many causes for bradycardia there are some extrinsic causes and intrinsic causes extrinsic causes such

as hypothyroidism drugs etc and intrinsic causes are ischemia and information of the sinus node

fibrosis of the sinus node or six sinus syndrome bradycardia may be due to sinus

bradycardia junctional rhythms or atrioventricular blocks

now how to recognize sinus bradycardia and how to differentiate sinus bradycardia from junctional rhythm

so in this ecg let us first calculate the rate to do that first trace the

r waves so here is an r wave here is an r wave in between there are 1 2 3 4 5 6

6 big boxes so 300 divided by 6 is equal to 50 the rate here is less than 60 so it is bradycardia

now how to say sinus there is a p wave which precedes the qrs complex

and here is a p wave which precedes the qrs complex and there is a fixed pr

interval so to say sinus

there is an upright p wave present in the qrs complex and

followed by a p wave preceding a qrs complex so this is an

example of sinus bradycardia if there is no p wave present in the qrs complex then it is called junctional

rhythm now moving on to sinus tachycardia when the sinus rate is accelerated more

than 100 beats per minute then it is called sinus tachycardia sinus tachycardia may be due to intrinsic

sinus node abnormalities such as enhanced automaticity or due to abnormal autonomic regulation of the heart such

as enhanced sympathetic tone or depressed parasympathetic tone it is a secondary phenomenon and

underlying causes to be investigation there can be acute or chronic causes acute causes such as exercise pain

anxiety fever acute heart failure pulmonary embolism etc and chronic causes such as anemia

thyrotoxicosis catecholamine excess etc so in this ecg let us calculate the rate here so this

is an r wave this is an r wave in between there are one two three four five six seven eight nine

there are nine small boxes so let us take ten thousand five 1500 divided by 10 is equal to 150 the rate

here is more than 100 so it is called tachycardia now how to say sinus there is a p wave which precedes the qrs

complex followed by a t wave then a p wave which precedes the qrs complex followed by a t wave so this is an

example of sinus tachycardia then moving on to junctional rhythm junctional dysrhythmias originate in the

av junction there is area around av node and bundle of his junctional rhythm is identified based on

the rate which is usually less that is around 40 to 60 bits per minute as it originates from other than sinus node

based on the qrs width which is usually normal as it follows the usual conduction system and importantly based

on the morphology of p waves this point i want to stress upon again that sinus p waves in lead 2 is upright

or positive and junctional p waves may be inverted which comes before or after the qrs complex or it may be a hidden p

wave this picture explains about normal sinus conduction and about junctional

conduction so based on the sequence of depolarization there are several

possible outcomes so these are some of the complexes here in that we can see various p wave

morphologies so this is a p wave morphology which is negative which comes before the qrs

complex and there is shortened pr interval and here you cannot able to find a p

wave and it is a hidden p wave here and in this complex you can see a p wave which comes after the qrs complex

so this p wave which is negative and before the qrs complex indicates that atria is depolarized from bottom up

and the hidden p wave indicates that atria and ventricles are depolarized simultaneously

and p wave which comes after the qrs complex indicates that av node initiated depolarization

but ventricles depolarized just before the atria now i am going to discuss about

junctional rhythms such as junctional escape rhythm accelerated junctional rhythm as well as

junctional tachycardia junctional escape rhythm arises from av junction at a rate of 40 to 60 beats per minute

it is characterized by heart rate around 40 to 60 bits per minute rhythm which is regular and p

waves which are inverted may appear before during or after the qrs complex and qrs complexes are relatively narrow

as is it usually follows the usual conduction system if p wave is present pure intervals will

be shorter than normal let us take this example first let us calculate the rate here is an r wave

here is an orbit in between there are one two three four five there are five big boxes so 300 divided by phi is equal

to 60 the rate here is 60 and the rhythm is a regular rhythm and you cannot able to see a p wave here

so there is a hidden p wave in this ecg and the qrs is normal as it follows the

usual conduction system this is an example of junctional escape rhythm

next about accelerated junctional rhythm which arises from the av junction at a rate of 60 to 100 bits per minute

it is due to increased automaticity of the av node or decreased automaticity of the sa node which is characterized by

rate around 60 to 100 beats per minute a regular rhythm p waves

may be inverted appear before during or after the qrs complex qrs

complexes are relatively narrow and p waves if present and the pure interval will be shorter than normal

let us take this example this is an r wave over here this is an r wave over here there are one two three

big boxes so 300 divided by 3 is equal to 100 so the rate is 100 the rhythm is a regular rhythm

and p wave which comes before the qrs complex and it is inverted and there is a shorter pr

and the qrs complex is normal as it usually follows the normal conduction system this is an example of accelerated

junctional rhythm next about junctional tachycardia it is a fast ectopic rhythm

arises from bundle office at a rate more than 100 bits per minute it is characterized by rate more than 100 bits

per minute regular rhythm p waves are inverted may appear before during or after the qrs

complex and qrs complex is normal in this example you can see r wave here and an r wave here

and you can see one two two big boxes between two r waves so 300 divided by 2 is equal to 150 the rate is more than

100 and the rhythm is a regular rhythm and if you see the p wave it has come

after the cures complex and the cures complex is normal this is an example of junctional tachycardia

next i am going to discuss about sinus pass sinus arrest and how to differentiate

sinus pulse sinus arrest from sa exit block sinus node consists of p cells or

pacemaker cells which forms the impulses and t cells which transmit the impulses to the atrial

muscle sinus pass is the failure of atrial activation due to inability of sa node

to form impulses this resulted in pass without visible p waves

the differentiating point between sinus pass versus cynital exit block is that the

pass is not an exact multiple of preceding pp interval sinus pass is characterized by absence

of p waves for a duration of more than 1.5 seconds if the delay is more than 3 seconds then

it is called sinus arrest let us take this example

in this ecg there is a pass

and if you take this pp interval preceding pp intervals

the pass is not an exact multiple of preceding pp interval

so if we calculate the number of boxes between the r waves so 1

2 3 4 5 6 7 8 9 10 around 10 big boxes so 10 into 0.2 is equal to 2 seconds so the delay is

around 2 seconds so this is an example of sinus pass

seen in normal individuals with increased vegal tone hypersensitive corrected sinus drugs such as digitalis

and inferior wall myocardial infarction next about cyanoatrial exit block as the name indicates cynital exit block

is due to intermittent failure in conduction of sinus impulses into atria the differentiating point between

cyanoatrial exit block from sinus pass is that the pass here is an exact multiple of preceding pp interval

cyanital exit block is graded into three degrees first degree sa block second degree sa

block and third degree sa block first degree assay block in this time for propagation of sinus impulse into

atria is significantly prolonged this cannot be detected on a surface ecg let us take this example

top one is normal ecg and below is first degree sa block if you compare the arrow marks

of both ecgs instead of atrial depolarization over here it has been delayed

so there is a delay in atrial depolarization this is an example of first degree sa block

second degree xa block is further classified as mobitz type 1sa block and mobit's type 2 assay block

mobility's type 1 assay block is characterized by progressive prolongation of sa conduction with

intermittent failure of impulses to conduct to surrounding atrial tissue no p waves appear for one beat and the

sequence begins again there is a phenomenon called group beating that means grouping of pqrs

complex with progressively shortened pp interval followed by a pass

and the pass is less than twice the shortest cycle if we take this as an example

this is a pp interval and compared to this pp interval that is

around 23 small boxes next pp interval is around 21 small boxes and followed by a

pass and then the sequence begins again so this pass is less than twice the

shortest pp interval so this is an example of mobitz type 1 block

mobitz type 2 block is characterized by fixed pp interval there is no change in sa node conduction

before and after the pass the pass is multiple of

preceding pp interval let us take this example so

compared to this pp interval this pp interval is

equal followed by a pass over here and the pause is an exact multiple of

the preceding pp interval so this is an example of

mobitz type 2 essay block third degree or complete sa block which is manifest as no p waves with long

pauses leading to ectopic atrial or ventricular rhythms so if you see there is a p wave over

here and next p wave comes over here so there is a long pass over here this is an example of

third degree or complete essay block summary electrical activation of the heart normally originates in the sa node

if sa node is dysfunctional or suppressed other subsidiary pacemakers may initiate electrical activation

subsidiary pacemakers discharge at a slower rate if the depolarization begins in the sa

node of the heart it is said to begin sinus rhythm bradycard is defined as heart rate less

than 60 bits per minute and results from either failure of impulse initiation or impulse conduction

tachycardia occurs when the heart rate is more than 100 bits per minute junctional rhythm originates in the av

junction and it is identified based on the rate qrs width and morphology of p waves

junctional p waves can be inverted p wave and it comes before or after the qrs complex or it may be a hidden pva

sinus pause or arrest is the failure of say no to discharge sa exit block

is due to intermittent failure in conduction of sinus symptoms into atria sa block is graded into three degrees

first degree is a block second degree assay block which is further classified into type one mobitz block and type two

mobitz block and third degree is a block these are my references thank you