ECG intermediate Flashcards
What is this rhythm?
Ventricular flutter
280bpm
What rhythm is this?
Flutter
Which leads can you see flutter waves? What are they?
II, III, aVF
Self-perpetuating loop (or circus movement) that whirls around atria -> contraction each time
Why do all flutter waves not get conducted?
Due to refractory period of AV node
What is this? Why does it look like this?
Paced rhytm - see pacing spikes
Electrode in Right heart -> ventricle are stimulated from R hear which means QRS morphology is similar to LBBB
what does this show
Atrial tachycardia with variable AV conduction
[Irregular QRS
p waves in green - can see some hidden as atrial activity is regular approx 170bpm]
What is the difference between ST and paroxysmal tachycardia?
Paroxysmal - comes on suddenly with sudden off
ST slowly increases and decreases
What are the two most common causes of broad complex rhythms?
BBB
Pacing
Broad tachycardias - What is supraventricular tachycardia with aberration?
How does this look different to VT?
Supraventricular tachycardia with aberration = Atrial tachycardia with bundle branch block
-> each QRS is preceded by p with a constant distance
VT - atria and ventricles beating independently -> no constant p waves
p waves
broad QRS LBBB
VT
not p waves hidden in complexes
Which leads are p waves most obvious in?
v1
Rapid broad complex tachy ~ 200
Probably atrial tachy with BBB (lead v1)
Rapid regular narrow complex tachy
Which leads should p waves always be positive in for ST ?
I, II - atrial vector points towards these leads
Differentiate sinus tachy and atrial tachy on symptoms
ST comes on slowly,
AT much more abrupt
Key features of an reentry tachy on ECG? what are the two main types and pathophysiology?
Atria depolarised retrogradely
-> negative p waves in II,III and aVF and positive in aVR
1) AV reentrant tachy (AVRT) in WPW
- Impulse travels through AV node and back to atria through bundle of kent
-> takes longer to reach atria
-> the retrograde (negative) p wave will be found some distance from QRS
2) AV nodal reentry tachy (AVNRT)
-Impulse travels down fast pathway -> returns via slow pathway (within AV node) immediately
-> retrograde p wave found within or immediately after QRS complex
How to spot retrograde p waves hidden in QRS in AVNRT?
Notch at end of QRS in v1 (pseudo r prime)
[p wave positive lead v1, but negative in I and II]
Sinus tachy, atrial tachy, AVRT and AVNRT
What direction of p waves in I and II?
Where are the p waves found?
Key differentiating factor between AVRT and AVNRT?
Flutter with 2:1 conduction
Flutter waves are always the most obvious II, III, aVF
What causes an atrial tachycardia
Ectopic area of atria takes over pacemaker function
p waves in I and II could be positive or negative
What causes the delta wave in WPW
Depolarisation coming through the bundle of kent
Why are the p waves following in leads I and II negative in AVRT (WPW)?
The direction of atrial depolarisation is from bottom to top via bundle of kent
AVNRT - what’s going on with the fast tract and slow tract?
Some people have 2 tracts (rather than 1) in the AV node
Usually, impulse travels from the atria to ventricles through the fast tract
In AVNRT if the fast tract is in a refractory period, the impulse can travel via the slow tract. When it reaches the bundle of his -> can now depolarise the fast tract from the bottom up creating a re entry circuit.
How do the p waves appear in AVNRT
p wave negative in I and II (retrograde) and comes immediately after QRS (or within)
Which re entry tract is longer AVRT or AVNRT? What does this mean?
AVRT longer - p waves further from QRS
Rhythm?
Broad complex tachy
Atrial tachycardia with RBBB - look at at aVF for p waves
Following vagal manoeuvres
Narrow complex tachy without obvious p waves
Look closer:
Note negative T waves in II and III, with positive in aVR -> could be negative p waves occurring some distance from QRS
-> AVRT (WPW)
AVNRT
~150bpm
No p waves preceding QRS
Negative p immediately after QRS seen clearly in aVF
Positive p (pseudo r waves) in v1
Broad complex tachy - RBBB
VT
Can see some p waves III - the double wave - probably going at 110bpm which is slower than the rate
Part rapid and irregular -> AF
Also wide complexes with beat-to-beat variation in size
= AF in WPW
[When they have AF there are 3 types of impulse:
1) most impulses through AV node producing narrow QRS complexes
2) When impulse through the bundle of kent -> wide complex
3) Occasionally impulse through the bundle of kent and partially depolarises at same time impulse through AV node -> QRS complexes which are a mixture of the 2]
Tachy 160
Flutter with 2:1
After adenosine
What’s going on with p waves here? what does that mean?
negative in II and III
Positive in aVR
= upper junctional rhythm
Pathophysiology of upper junctional rhythms
Depolarisation starts in upper part of AV node
-> travels up to aVR (positive p) and away from II and III (neg p)
-> travels to ventricles normally -> narrow QRS
p is still before QRS as closer to the start
What is this? Explain it
Regular QRS without p waves - mid junctional rhythm
Impulse from mid AV node
-> travels to atria and ventricles at same time
-> p waves lost in QRS complex
[AV nodal pacemaker fires at regular intervals -> regular rhythm]
What is this? explain it
Lower junctional rhythm -
Regular QRS with sharp negative deflections following QRS segment in II and III
Pacemaker in caudal (lower) part of AV
AV nodal conduction reaches ventricles fast
-> impulse gets to atria slower (retrograde)
Why is this AF and not flutter
morphology of p waves varies
distance between waves varies
distance between waves and qrs varies
What is actually going on in AF
Multiple reentrant loops which whirl around atria unpredictably (up to 800bpm)
[This can be way too fast and you just see a flat line on ECG]
Only some are conducted down AV -> irregular unpredictable pattern
What rhythm do these p waves correspond to? Which lead is it best to look for the hallmark features of each
A - sinus
-Positive p waves in I and II
B - Junctional
-Negative p waves is II and III
C - Flutter
- Sawtooth in II and III
D & E - AF
- Best in v1
[In E, the rate of fibrillation is so high that the isoelectric line remains flat]
If there is negative p waves in I and II what do you suspect? Differentiate the causes
Upper junctional rhythm - p before QRS
Lower junctional rhythm - p after QRS
How to differentiate mid-junctional rhythm and AF?
no p waves in either
mid junctional - QRS is regular
Why are p waves positive in I and II in sinus rhythm
Impulse travels towards them
Upper nodal (junctional) rhythm
negative p waves preceding QRS in II and III
LGL syndrome
Flutter
2:1
Lower junctional rhythm
Sinus brady with 1st degree AV block
Note QRS amplitudes are low with wide t and u waves
= hypothyroidism
usual cause of this?
Bradycardic AF
- Usually due to b blockers or digoxin
P waved triggered paced rythm
- Usually if you have a issue with bundle of his
-> p waves trigger pacemaker
-> good as follows rate that the SA node is trying to trigger
Roughly what is the bpm of SN, AV node and ventricular driven?
How do you find all the p waves on an ECG
p waves have a constant interval - ie the rate is regular
Therefore you just need to find 1 p wave and the p-p interval and you can work out where they all are
- Even if hidden in QRS complexes
How many p waves are here
8
Flutter with variable block
2:1 mostly with a single 1:1
How many p waves here? What is going on?
6 p
q waves in II and III -> subacute inferior infarction with 2:1 AV block
Mobitz type 1
not inferior q in II and III -> inferior infarction
What are the high degree AV blocks
Second degree AV block - Mobitz 1 (wenchebach)
Second degree AV block - Mobitz 2
3 rd degree
What is going on in 3rd degree block? What is the usual rhythm of the SN at this time?
Are the p waves regular or irregular?
Are the QRS complexes regular or irregular?
No conduction through AV node
Usually, atria are still in SR
-> p waves regular
[ but sometimes can be AF / flutter / junctional / atrial tachy]
Regular QRS - ventricular pacemaker fires at a regular rate
Here is an example of 3rd degree block.
What determines if the QRS complexes in complete heart block are narrow or wide?
The location of the ventricular pacemaker:
If close to bundle of his -> narrow (as use fast conduction system)
If far from bundle of his ->wide (as slow conduction pathways)
What goes on in Mobitz type 1 (Wenchebach)? Are the QRS regular or irregular?
Progressive lengthening PR -> dropped beat
Irregular QRS complexes
What is going on with mobitz type 2 block?
Constant PR intervals with dropped beats
Is a 2:1 second degree AV block mobitz 1 or 2?
You cant tell as there is only 1 PR interval in between each beat (ie no way of knowing if it is getting longer)
Which types of high degree AV block have variable PR intervals? How to differentiate these 2?
2nd degree type 1 (Wenchebach) - Irregular QRS
3rd degree - Regular QRS
There are more p waves than QRS complexes which means? Differentiate the types?
There is a high degree AV block
Spot 3 things
2:1 AV block
RBBB with LAD - bifasicular block
Spot 2 diagnoses
Mobitz type 1
LBBB
2 diagnoses here
AF
Note regular wide QRS complexes at rate of 37
-> AF + complete AV block
2 things
2:1 AV block
q waves II and III - inferior infarction
2 things
Inferior stemi
Complete heart block
2 things
Mobitz type 1
Inferior MI
Mid junctional rhythm
Note T-U waves - likely digoxin / hypokalaemia
what is the arrow pointing to
escape beat
- unexpected beat which terminates a pause
Intermittent WPW
Spot 3 things
Mobitz type 1
Escape beat
LBBB - M in lead I
Difference between an ectopic and an escape beat?
Ectopic - R-R interval preceding shorter
Escape - R-R interval preceeding longer
Sinus rhythm
with frequent ectopics and compensatory pauses
Sinus rhythm
Ectopic beat with compensatory pause
Sinus rhythm
Ectopic beat with compensatory pause
Sinus rhythm with an ectopic
Sinus?
2 other things
Sinus rhythm
Ectopics with compensatory pause
Unexplained pause
SR with intermittent LBBB
Why is this not flutter -> SR
- Leads I - III
The ‘flutter’ appearing waves are in lead I. You can usually only see them in II and III.
In III can see sinus rhythm
= Normal sinus; + right arm tremor eg parkinsons
How do you know something is a ventricular ectopic?
no p wave preceding
Wide QRS
Compensatory pause
[The sinus node continues to fire regularly
-impulse will reach ventricles that are still in the refractory phase so p will be lost in QRS
-> Compensatory pause]
What is an interpolated ventricular ectopic?
Differentiate from ventricular ectopic
The refractory period is already over when SN impulse reaches
-> no compensatory pause
What is a supraventricular premature beat?
Extra complex from an ectopic region in the atria
-> extra abnormal p wave with QRS
[looks different as impulse from different area]
This impulse resets SN (when it reaches it) -> get the next beat at the normal R-R interval following the reset SN
->meaning you get a small compensatory pause
What happens if you get an SVE when the AV node cant conduct yet
Either delayed AV conduction or blocked
[note the SVE p wave is abnormal looking, but will still reset the SN]
Describe the ectopics
Supraventricular (p waves and normal narrow QRS)
p waves are negative in II and III -> originate from the junctional area
Note the first SVE is a different shape and wider - indicates there is some ventricular conduction issues
= Junctional premature beats with aberrant conduction
Describe the ectopic
Ventricular ectopic with compensatory pause
[no p preceding - can see likely hidden p wave
-Also the distance between 2 normally conducted beats remains 2 R-R intervals]
Difference in R-R intervals in the sinus conducted beats in ventricular vs supraventricular ectopics
VE - the SA node keeps firing at usual rate so R-R stays the same though with 1 non conducted (bar interpolated VEs)
SVE - the SA node is refractory for a period as stimulated from the ectopic impulse
-> there is a gap slightly shorter than 2 R-R intervals between the 2 normally conducted beats
Bigemeny
Describe the ectopic. Anything else?
interpolated VE
[no interruption to usual sinus beats)
q wave II and III with QRS in v2
-> Likely inferior and anterior infarctions at points
What are the ectopics here
1) negative p followed by wide QRS
-> SVE with aberrant ventricular conduction
2) There is a p wave in the section which looks like a pause
->SVE with AV block
Rhythm? ectopics?
Upper junctional bradycardia rhythm
Interpolated VEs
[note goes into SR on last beat]
Ectopic here? Why is the PR interval slightly long following the ectopic?
interpolated VE
[no p wave preceding and no compensatory pause]
Some of the conduction pathway is still refractory so takes a little longer following the VE
Describe ectopic here
What else is there
VE
- There is p wave preceding, however the p is not premature. [remains rate of SN]
-The VE falls just after p wave rather than it being a SVE
LBBB with LAD
Whats seen here
Complexes 1, 3, 6 - Sinus
Note extra p waves - High degree 3:1 AV block
polymorphic VE couplet - during which the R wave lands on the T wave
= R on T
At end of tracing again there is R on T triggering polymorphic VT
What is this pause? Explain the causes
SA block
[when only one beat missed called ‘intermittent SA block’]
1) SA node generated impulse but not conducted to atrial myocardium
2) SA node did not fire - Sinus arrest
What is this pause
Compensatory pause following VE
What are the pauses in these 2?
Top - Mobitz type 2
Bottom - Mobitz type 1
What is sick sinus syndrome?
SA block + intermittent atrial tachycardias
Whats this pause ?
Preautomatic pause - Pause during rhythm switch
[here A flutter -> sinus]
Whats this pause?
Non conducted premature atrial beat
[p wave just at the end of the t wave]
Whats this pause
Non conducted premature atrial beat
What are the 3 types of SA block
Sinus arrest - SA node not working
Intermitted SA block - Only one beat omitted
Sick sinus syndrome - SA block + intermittent tachycardia
What is this
3rd degree AV block
What is this? why is it not complete heart block?
AV dissociation
there is the same number of P and QRS complexes but they are dissociated
There is both a sinus pacemaker and a junctional ventricular pacemaker
The junctional pacemaker is faster than the sinus node -> junctional depolarises ventricles and they are in refractory period when Sinus impulse reaches them
Patients are usually asymptomatic of this
Rate?what is it?
Approx 160
A flutter - the varition in amplitude is due to super imposed T waves onto the flutter waves
Is the first ectoptic supraventricular or ventricular?
Ventricular. The preceding p wave does not come early
What are the rhythms here? what type of pause is it?
Initially AF
Last 2 beats are sinus
Preautomatic pause - occurring when rhythm switches to normal
Is this sinus?
No - its AV dissociation.
Junctional rhythm approx 110. Note p waves becoming lost in QRS
Whats this?
AV dissociation
In this the junctional rhythm is causing some retrograde p wave depolarisation
What is the pause here?
SA block with junctional escape beat
No P wave when you would expect it
Note the negative p waves following the junctional exape beats beats
What do the 4 digits on pacemakers relate to?
1 - Where the pacing impulse is DELIVERED
A - atria, V - ventricle, D dual
2 - Where the impulses are RECORDED
A - atria, V - ventricle, D dual
3 - The consequence of the infor
T - Triggered impulse, I inhibited impulse, D -dual
4 - Rate responsiveness
What is a D D D pacemaker
Electrode in R Atria and ventricle
Senses both chambers
When a normal impuse is detected i can inhibit the next pacmaker impuse.
When there is no impuse it can trigger a new pacemaker impuse
What is a VDD pacemaker
1 electrode in ventricle that senses both the ventricle and atria
When a premature beat occurs it can inhiti the next impuse
When no beat occurs it can trigger an impuse
What type of pacemaker for people with sinus node dysfunction but normal AV function
AAI
1 electrode in RA where it senses and paces
If it senses a sinus beat it inhibits the next impuse
2 types of typical flutter. How to differentiate on ECG
Typucal Anticlockwise Reentry: Commonest form of atrial flutter (90% of cases). Retrograde atrial conduction produces:
Inverted flutter waves in leads II,III, aVF
Positive flutter waves in V1 — may resemble upright P waves
Clockwise Reentry: This uncommon variant produces the opposite pattern:
Positive flutter waves in leads II, III, aVF
Broad, inverted flutter waves in V1
What is atypical flutter? Issue?
Often associated with higher atrial rates and rhythm instability
Less amenable to treatment with ablation
anticlockwise flutter:
Inverted flutter waves in II, III + aVF at a rate of 300 bpm (one per big square)
Upright flutter waves in V1 simulating P waves
2:1 AV block resulting in a ventricular rate of 150 bpm
Note the occasional irregularity, with a 3:1 cycle seen in V1-3
Describe? When would you see this
Flutter with 4:1 block
There are upright flutter waves in V1-2 (= anticlockwise circuit)
There is 4:1 block, resulting in a ventricular rate of 65 bpm
The relatively slow ventricular response suggests treatment with an AV nodal blocking agent
Atrial Flutter with Variable Block
The block varies between 2:1 and 4:1
The presence of positive flutter waves in lead II suggests a clockwise re-entry circuit (= uncommon variant)
Which block? Why?
Typical ECG of LAFB, demonstrating:
rS complexesin leads II, III, aVF, with small R waves and deep S waves
qR complexesin leads I, aVL, with small Q waves and tall R waves
Left Axis Deviation(LAD): Leads II, III and aVF areNEGATIVE; Leads I and aVL arePOSITIVE
Associated featuresinclude:
QRS duration normal or slightly prolonged (80-110ms)
Increased QRS voltage in limb leads
