Most Common arrhythmias in smalls Flashcards
Ventricular Extrasystoles (VPC)
- HR: normal, low or high i.e irregular!
- Rhythm: irregular due to the premature beat
- P-waves: not associated with P waves (except fusion beat). The normal sinus P-waves may distort the ST segment or T-wave of extrasystole!
- QRS: WIDER AND LARGER
- ST-segment: abnormal
- T waves: abnormal, OPPOSITE POLARITY TO THE QRS
- Pause: fully compensated, no resting
VPC left ventricular origin
**look at direction of QRS complexes
Large (-) deflection
Large (+) P waves
VPC right ventricular origin
Producing (+) waves that are wider and larger than simus waves
Ventricular tachycardia (many extrasystoles)
Sustained vs non-sustained
Uniform vs multiform
Accelerated idioventricular rhythm
Torsade de pointes
Flutter, fibrillation
What 2 features are ALWAYS seen with ventric tachycard?
- A captured sinus beat- when you see the sinus firing at the correct moment
- Fusion beat- combo of sinus and the ventric originating ectopic beat. The depol is coming from 2 direstions
May have to wait some time before you eill see the 2- but you will always see the 2
Accelerated idioventricular ryhthm
Most commonly the HR<160bpm with this
Therefore often known as slow ventric tachycard
The slow HR is convenient as it allows us to see the sinus beats and fusion beats
Torsade de pointes
Means “changing of the points”
from (+) to (-)
Multiform, v. fast ventric tachycard
Emergency situation
Ventricular flutter, fibrillation
Flutter= reentry
Fibrillation=disorganised beats
Causes of ventric arr
Cardiac
Extracardiac
Drugs/toxins
Cardiac causes of ventric arr
Myocardial injury
Myocarditis
Cardiomyopathy
Pericarditis/ haemocarditis
Endocardosis/itis
Congenital HD
Base and myocardial tumours
Amyloidosis
Extracardiac causes of ventric arr
Same as for causes of arr in general discussed prev
Drugs/toxins causing ventric arr
DADADDEC
Digitalis
Anaesth
Doxorubicin
Atropine
Dobutamine
Dopamine
Epi
Chocolate…
Extra steps to be included in the new arr protocol if it suspected of being ventric
BP- however hyperT usually does not cause!
Inflamm markers: c- Tr-1: IC in myocytes, is heart specific and could indicate myocarditis!
CRP and SAA
Congenital Ventric arr
ARVC in BOXERS, bulldogs and cats
DCM: in dobermans and great danes
Ventric tachycard: german shepherds
ARVC in boxers
Autosomal dominant
All with the mutation are sick, but with different phenotypes because varying penetration
Signs when older than 6 although after no clinical signs (rxcept PCV)
Maye see extrasystoles in eCG
Syncope during stress/exercise
Maybe sudden death
Fibrous/fatty degen of the RV
ARVC in boxers- waht you must treat
The syncope- only if fainting due to the disease and not acc to another systemic illness eg insulinoma or SAS
Bradyarrhythmias=vasovagal syncope
the ventric tachycard: on an ECG can see up to 1000 VPC’s per day! pairs, triplets, tachycard, R on the T wave.
For this give Mexiletin or Sotalol (PO) or Atenolol
Diagnosis of ARVC in boxers *
Holter: Bradyarr and syncope!!
Bradyarr: after the syncope there are only a few VPCs because there is a compensatory incr in vagal activity after a symp surge! e.g when the dog is stressed/happy
This leads to vasoD… decr BP… dog faints
Try to avoid triggers and can tell the owner to elevate the HL’s when there is a fainting episode!
*eCG readings: the QRS complex is positive because the VPC is originating from the R ventricle
DCM in Dobermans
Holter for screening and treatment.
Should do US and eCG also
Often sudden death
Treatment of DCM in Dobermans
- HF and sinus ryhthm/ atrial fibrillation: diuretics and pimobendan. Beta blockers when no congestion and low dose digoxin
- HF and ventric arr: Mexiletine and Sotalol
- Syncope without HF: must screen with Holter to exclude bradyarr! beta blockers (sotalol) and Na channel blockers
- No clinical signs but VPCs on Holter: sotalol and pimobendan if the heart is enlarged
Supraventricular Extrasystoles
Causes:
- HD- atrial stretch and hypoxia
- Extracardiac
- Sometimes in healthy animals witha. high vagal tone
Checkand treat underlying cause ONLY!!
If symptoms: Digoxin, beta blockers, Ca channel blockers and Amiodarone
Supraventricular Extrasystoles appearance on eCG
Supraventric premature beats but usually cannot see origin
No preceeding P-wave
Junctional
Narrow QRS complex tachycradia
Narrow QRS always indicates SUPRAVENTRIC!! dogs<70ms cats<60ms
*wide QRS indiactes VENTRIC (sometimes supraventric)
Sinus tachycard
Supraventric tachycard:
- FAT: focal atrial tachycard
- Junctional tachycard
- OAVRT= bypass tachycard
- Atrial flutter
Atrial fibrillation
Sinus Tachycardia
- HR: fast but usually not above 200 bpm
- Rhythm:P–P distances and R—R distances only vary slightly (<10%)but have paroxysmal form i.e gradual acceleration and deceleration
- P waves: positive II or avF, there is a P for every QRS complex but it may be lost in prev ST segment or T wave. Could be higher in tachycard
- PQ distances: normal but could shorten when HR incr
- QRS complex: regular or abnormal if intraventricular conduction disorder
Causes of sinus tachycard
Mainly extracardiac e.g pain, fever, gastric dilation
Atrial fibrillation
Disorganised atrial activity
- HR>180-200 bpm but this may be normal in giant breeds e.g in the case of lone fibrillation
- Rhythm: is irregular thereofore it is an absolute arr
- P-waves: missing or f-waves
- QRS complex: usually normal (maybe abnormal)
Atrial fibrillation- appearance on eCGs
chaotic electric depol waves
Unudlations of membranes
Flatlines btw QRS complexes
Lone atrial fibrillation
physio in large breed dogs
HR is normal
Treatment of atrial fibrillation
- treat the HD: treat the HF and if the ventric rate still high, slow with digoxin, diltiazem or beta blockers e.g amiodarone
- If caused by extracardiac then find and treat! e.g if high symp or comp parasym tone. Or post anaesth/induction of high vagal tone– wait and see, maybe give lidocaine IV
- Lone fibrillation- try and find the casye e.g hypothryroidism? do US and look for DCM
Overall- danger of thrombosis is low because of contraction of the atria therefore no need for anticoag therapy
**atrial fibrillation in cats- suspect enlarged atrium- then prescribe antithrombitic medication
Junctional tachycard
P waves move in and out of QRS complexes
OAVRT
(-) P waves
Depol begins at the AV and then moves up to the atria!
Treatment of Supraventric arr
Dont treat: nonfrequent atrial or junctional extrasytoles or lone fibrillation
Goal 1: restore sinus rhythm!! the phys methods! however only chest thump when you have excluded VT from SVT with wide QRS
Give Diltiazem or Esmolol IV- these drugs impact the AV node- will delay the conduction so the flutter slows down but doesn’t stop
What is bradycardia?
Dogs: >60-70 bpm
Cats: <140 bpm
Caused by SA dysfunction or conduction disorders
Sinus bradycardia
Usually occurs in a relaxed animal
Incr intracranial/IOP
HyperT
Hperkalaemia
Hypothyreoisis
Hyptglucaemia
Hypothermia
SSS
Check and treat the possible causes
Conduct atropine reaction test- could diagnose high vagal tone bradycard and (SSS)
Canine Sinus Node dysfunction (SND) and SSS
Sinus bradycard
Sinus arrest— AV block (therefore it is often accompanied by AV blocks or BBBs)
Tachycard- bradycard syndrome
Escape rhythms
Female>make
Mini schnauzer, westie, springers, cockers, labs, pugs, daschunds
SND +/- signs but SSS always signs
Many of the dogs reaxt to atropine which is misleading- should be used to diagnose parasymp diseases but this is a nodal problem
Treatment of SND and SSS
If reacted to atropine then likely to react to theophylline, terbutaline and propantheline bromide
Sympto- pacemaker
Often diagnosed during anaesth
Atrial standstill/ silent atrium
Hyperkalaemia induced bradyarr!!!
NO atrial conduction!! therefore sinoventricular conduction must take place through internodal tracts
Slow escape rhythm– this is what is keeping the animal alive!!!!
Causes of atrial standstill/ silent atrium
Renal failure
Urinary tract obstruction
Leakage
Addisons
Reperfusion syndrome
AV blocks
1st-3rd degree
Can be functional or physio
Causes:
- Drugs/toxins
- High vagal tone therefore reacts to atropine
- Hyperkalaemia
- Hypothyreoisis (1st)
- Inflamm, neoplasia, amyloidossi and fibrosis– autoimmune e.g Lyme!
Different degrees of AV blocks appearance on eCG
1st: prolonged PQ interval
2nd: Mobitz-1-Wenkebach phenomenon due to high vagal activity therefore responds to atropine
3rd: many non-conductive PQ therefore requires pacemaker
Bradyarrhythmias
- Sinus bradycardia
- sinus arrest
- SA/AV block
- if sinus nodal origin then give terbualine or theophylline ]Atropine test
- Check electrolytes- maybe hyperkalameia?
- bloods: kindey function (e.g lower excretion of K)
- Biomarkers e.g cTR-1 for myocarditis
- Immune/autoimmune-Lyme, AHA- gove doxycycline or preds
- Echo
Treatment of bradyarr
Stops Drug treatment- eliminate toxins!!!
All antiarr and digoxin are contra!!!
Pacemaker: for high degree AV block or SSS
