Arrythymias Flashcards
What is a normal rythym (NSR) on an ECG
normal sinus rhythym: signal starts at SA node and follows regular route
there’s a P followed by a QRS followed by a T in a regular metronomic rhythm!
What is an arrythymia on ECG?
any change to rate, regularity or origin of electrical impulses!
What is sinus arrhythmia (NSA)?
There is a P for every QRS but the R-R interval (rate) varies!
It is a result of the SA node rate varying with respiration (incr. vagal tone)
usually considered normal!
What are the 2 types of arrythmias?
Bradyarrhythmias
Tachyarrhythmias
What is a wandering atrial pacemaker?
what does it result in?
Is it a problem?
What else can be noted?
when the P wave originates outside the SA node
it results in a P wave that varies in size and shape; the PR interval is varied also
No hemodynamic consequences so no Tx!
There can also be incr. vagal tone also.
What is sinus bradycardia?
When will you see CS
when there is a regular rhythym under 60-70 bpm for dogs, 100 bpm for cats
if there is >6-8 seconds between beats!
In which animals might you expect to see sinus arrhythmias
Fit dogs
Brachycephalic breeds
dogs with chronic bronchitis
during eye or abominal sx
What is pictured here?
How did it occur?
Causes?
When will you see signs?
Sinus Arrest!
Failure of the SA node to fire for 1 or more beats
Can be same as for Sinus bradycardia
If no beats for >6 seconds!
What sp is sinus arrhythmias considered normal, in what sp not?
Tx required?
Normal in dogs
ABNORMAL in CATS!
No
How do you Tx sinus bradycardia?
Remove the cause:
Correct the drug dose/use
Lower the potassium
Treat hypothyroid
Atropine/glycopyrrolate test:
if +ve (response seen when atro given) → look for vagal problems, if needed drug Tx: PREFFERED→terbutaline (ßagonist- mainly ß2, used as bronchodilator in lungs but will have some effect on ß2 on heart to increase rate)
isoproterenol(ß1 &2 agonist, will cause vasodilation & BP problems)
isopropamide/probanthine- not so much used anymore
if -ve → pacemaker is indicated if clinical!
What bradyrrythmia is pictured here?
When does it occur?
What is the rate in a cat?
Junctional (nodal)/ventricular escape beat
It is heart’s Plan B & C respectively for regulating rate, if the SA node does not generate an signal then the junctional nodes first try to generate a signal and if that doesn’t work the ventricles generate their own signal.
A junctional (nodal) escape beat QRS will have more of a normal morphology but no P wave. (since it is using the Bundle of His for conduction) & 40-60 bpm
A ventricular escape beat QRS will have a wide/bizzare morphology & 20-40 bpm
80-100 bpm
What diagnostic test may be needed to dx escape beats?
Tx?
A Holter/cardiac event monitor
positive chronotropes or pacemaker
What electrolyte can cause a bradyrrhythmia?
What can cause ______?
Potassium
Hyperkalemia can be caused by renal failure, ATE (aortic thromboembolism- HCM in cats), hypoadrenocorticism, crush injury (due to sudden release of K from damaged cells)
What is the progression of ECG signs in hyperkalemia?
What is the ultimate result of hyperkalemia on heart?
Bradycardia with increase in size of T wave (should only be 1/4 of R for dogs, 1/3 for cats) and spike instead of mound, then P waves disappear, then QRS becomes strange & bizzare & sinusoidal in shape.
Fibrillation ⇒ DEATH!
Tx for hyperkalemia
fluids, furosemide, insulin (glucose better!), bicarb if acidosis present, Ca gluconate (cardioprotective)
What is AV block
a delay or failure of transmission at the AV node
There are multiple levels of AV block!
What is this arrythmia pictured here?
Tx?
1° AV block
the signal coming from SA node to AV node is delayed but still gets there
PR interval >0.13 sec
norm = 6.5 boxes
What is this arrythmia pictured here?
Causes?
2° AV block - intermittent failure conduction of the SA signal to the AV node
2 subtypes Mobitz type I & Mobitz type II
This is Mobitz type I: the PR interval gets longer until the QRS gets dropped
Caused by incr. vagal tone or drugs (digoxin)
What is this arrythmia pictured here?
Cause?
2° AV block Mobitz type II: no PR changes before dropped QRS
this is usually due to node dz not incr vagal tone so chances of incr serverity of dz high.
What is this special AV block arrythmia pictured here?
Cause?
This is a High Grade AV block. In reality since the block happens every other beat you cant tell if is a Mobitz Type I or II but it is more serious than regular Type II!
Nodal dz
What is the ratio designation seen on 2° AV blocks Mobitz Type II such as:
6: 4
2: 1
3: 1
the designation represents the number of P waves to QRS complexes seen, since the 2° AV blocks tend to occur cyclically!
6: 4 means for every 6 P waves there are 4 QRS complexes in the cycle
2: 1 means for every 2 P waves there is 1 QRS complex.
What is this arrythmia pictured here?
3° AV block - no AV conduction at all!
there are P waves and escape beats only!
the escape beats can be either junctional or ventricular
The P waves are regular at the norm rate (80 or so) and the junctional or ventricular beats are regular at their norm rate (40-60, 20-40 respectively)
Tx for 3° AV block?
treat the cause:
Stop digoxin, treat -itis
If symptomatic & positive response to atropine test can try terbutaline or another + chronotrope
if Emerg. then: isoproterenol/dopamine IV
may need pacemaker (will do better for 6mos than w/o)
What does this holter recording show?
Tx?
Sick sinus syndrome: Abnormal sinus node & AV system leading to: severe sinus bradycardia, intermittent sinus arrest/AV block, paroxysms tachycardia.
A pacemaker to tx bradycardia & drugs to tx tachycardia
What type of arrythmia is shown here?
caused by?
Sinus tachycardia
incr rate: >160-180 in dogs, 240 in cats
- P QRST will be normal*
physiological: fear, pain
pathological: fever, anemia, thyroid
These are examples of?
Superventricular Premature Depolarizations (SPDs)
Premature QRS complex, varied P’ wave (or absent). The signal originates somewhere in atria other than the SA node but uses normal route so QRS looks normal.
What is seen in this ECG strip?
1 SVPD
it looks like normal QRS the only thing wrong is timing of it (hint: find the rhythym/count the regular beats to determine where the SPD hits vs where it should be!)
This image shows 2 different ECG strips, the one on left represents? the one on right represents?
Are they related?
The left is a single SVPD. The right is SV tachycardia.
Yes if there are > 3 SVPDs in a row it is considered superventricular tachycardia!
Try to find the P on T which can be seen when the ventricles start depolarizing while repolarization is still happening!
When do CS occur? What are CS?
How is supraventricular tachycardia tx?
When the CO falls, weakness/syncope
Treat underlying cause if not too many SVTs. If emergency:
tx IV meds: esmolol (ß-blocker) or diltiazem (Ca channel blocker) to slow conduction from SA node down!
Be careful since HR can decr & BP can drop, must monitor!
For maintenance: oral meds, sotolol ((ß-blocker) or diltiazem (Ca channel blocker)
If SVPDs are supraventricular depolarizations what are VPDs?
Where does is the focus that creates the VPD come from?
Which are you more likely to see in practice?
Can you tell on ECG whether the ectopic focus is in L ventricle or R?
What morphology will the QRS have?
Ventricular premature depolarizations! (of course!!)
The ventricle itself
VPDs!
Yes, if the focus is in LV the deflection will mainly be (-), if focus in RV the deflection will mainly be (-) on ECG.
Wide, bizarre (as usual)
Can you tell which ventricle the VPD shown here started in?
Yes! the deflection is mainly negative (starts out -) so this would be a VPD with a LV ectopic focus
Can you tell which ventricle the VPD shown here started in?
Yes the deflection is mainly positive so the ectopic focus must be RV
What things can trigger VPDs (since they are more commonly seen)?
Xanthine derivatives (caffeine, theophylline)
GDV (gastric-dilation-volvulus), lots of systemic conditions (sepsis etc), anesthesia, splenic HSA
Remember no P wave & wide bizarre QRS since focus is coming from ventricles!
How would you differentiate between an escape beat and a VPD?
To be an escape beat there must be a long pause before! The VPD is a premature beat but there are beats before & after!!
When every other beat is a VPD what is that called?
Bigeminy
Can VPDs have more than one focal area (bad spots)?
Are multiple foci worse than a single foci?
What will you see if there are multi focal bad spots generating VPDs
What happens if a P wave is completed at the same time a VPD starts
Yes.
Yes because that means more than 1 spot in heart is bad.
Different morphology in the different VPD depending on foci of origination
You’ll get a fusion beat (looks like a P wave before a wide bizzare QRS but not as big as others seen on strip)
What is the arrow pointing at?
what would the series of VPDs be called? (Just think logically!)
A fusion beat!
Triplets!
What are CS of VPDs?
Dropped heart sounds, irregular pulse, dropped pulse
rarely: weakness/syncope
much more common: SUDDEN DEATH due to R-on- T (the heart goes into ventricular fib and dies)
Danger Will Robinson!!! Danger!!
Why?
This ECG shows how close the VPDs are coming behind the T. This situation could easily lead to R-on-T and DEATH.
Need to tx right away!
How are VPDs tx?
Is tx guarunteed?
Tx underlying causes
Specific therapy: if symptomatic or animal has heart dz known to be associated with sudden death!
e.g. Boxer cardiomyopathy
Doberman w/ DCM
Aortic stenosis
Hypertrophic cardiomyopathy (cats)
Tx is no guaruntee of no risk but if decr. VPDs may decr. chance of sudden death!
Tx for VPDs in dogs?
(guess why only dogs? - ‘cause cats are special!)
1 Lidocaine slow IV (or CRI)
In emerg- parental
-ck K & Mg level if response isn’t as expected
procainamide IV, IM/SC
esmolol IV → sotalol/propranolol PO
amiadarone (Class III antiarrhythmics) as last resort!
Non emerg
Sotalol (-) inotrope)
Mexiletine (+ ß-blocker (atenelol))
Sotalol & mexiletine
Procainamide
Quinidine
VPD tx in cats?
HCM causes VPDs in cats so…
correct underlying cause
initial tx ⇒ propranolol/atenolol (ß blocker to relax heart to allow diastolic filling)
or lidocaine - low dose bolus d/t cats are more sensitive
maintenance tx⇒ oral propranolol/atenolol
procainamide, quinidine or mexiletine
What is this image of?
Ventricular tachycardia
SERIOUS problem
runs of > 3VPDs @ >160-180 bpm
if sustained >30s then CS
Tx for VT?
Same as for SVT!
If there are wide, bizzare ectopic beats at a rate of 20-40 bpm what are they?
Ventricular escape beats
what happens if you get a string of VPDs at 100bpm?
Accelerated idioventricular rhythm/idioventricular tachycardia (fast escape beats!)
What is the rate range for Accelerated idioventricular rhythm?
anywhere from 60-180 bpm
Is Accelerated idioventricular rhythm symptomatic?
Tx?
Would you watch for something?
Mostly asymptomatic
Correct underlying electrolyte/acid-base imbalance or systemic conditions? Can also see with traumatic myocarditis (next day post HBC)
Yes! need to monitor VT may be coming
What is seen here?
Tx?
VFib or ventricular fibrillation
Usually a terminal arrhythmia!
Tx: electrical cardioversion
epinephrine
CPR
What causes Atrial fibrillation?
What might ECG signs be?
Common with DCM (giant breeds)
*whereas Dobies w/DCM have tend to have VPDs
No P waves (dirty baseline)
Normal QRS
R-R random
What is this arrhythymia?
is it on both strips?
A fib
note dirty baseline
with no P wave
R-R random
irreg rate (similar to sinus arrhythmia but DOESN’T correlate to respiration)
NO! bottom one is 60Hz interference!!
What are the only things that make normal QRS go together?
Sinus tachycardia
SVT
A fib (pictured here)
How can you differentiate Vtach from Afib?
Watch strip, there will come a moment where you can see baseline has no P wave just a QRS!
What is significance of Afib?
How dx?
heart working much harder than should:
incr. myocardial O2 demand but decr CO & decr cardiac perfusion
PE: chaotic heart sounds (boot in dryer or toddler on drums!)
variable & dropped pulses
Afib Tx?
heart funct & rate norm:
none
monitor with echo/Holter
heart funct norm but incr rate (>150)
slow ventricular rate
diltiazem/ß-blocker
or cardioversion
heart funct decr & incr rate
slow ventricular rate
digoxin & diltiazem/ß-blocker until <150 bpm
amiodarone, maybe cardioversion
Tx for cats with Afib?
Cats usually have HCM so…
- propranolol
- ditiazem
digoxin contraindicated!
What is image?
saw tooth baseline must be…
Atrial Flutter!!
The precursor to Atrial Fib!!
