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Flashcards in Arrhythmias Deck (41):
1

Sinus arrhythmia

  • P for every QRS but R-R varies
    • All PQRS complexes look the same--rate is just what is varying
  • SA node rate varies w/ respiration
    • HR increases w/ inspiration, decreases w/ exhalation
  • Vagal tone--fit, brachycephalic, chronic bronchitis
  • Eye/abdominal surgery
    • Atropine
  • No treatment required
  • Not normal in cats--only dogs

2

Wandering atrial pacemaker

  • P waves from outside SA node
  • Variable morphology/amplitude of P wave
    • Usually goes in nice wave pattern (+, -, +, etc.)
  • Variable P-R interval
  • Increased vagal tone usually
  • No hemodynamic consequences--no treatment

3

Sinus bradycardia

  • Rate
  • Outside the heart--drugs, lytes, thyroid, vagal tone--eye/gut, respiratory, lesions, idiopathic (atropine test)
    • Atropine test: kills vagal tone--> HR goes up
    • Drugs: digoxin (causes any arrhythmia), xylazine, beta blockers, lidocaine
  • Inside the heart--fibrosis, infect, trauma, neoplasia, idio 
    • Signs if > 6-8 s
  • Exercise animal to make sure HR goes up (could just have a normally slow HR)

4

Treatment for sinus bradycardia?

  • Remove the cause
    • Correct the drug dose/use
    • Lower the K
    • Treat the hypothyroid
  • Atropine or glycopyrrolate test
    • + = look for vagal problems 
      • Terbutaline/isoproterenol/isopropamide/ probanthine
      • Need to counteract PNS--can't block it so increase SNS instead
    • - = pacemaker if clinical

5

Pacemaker

  • Pulse generator
  • Pacing leads endo/epicardial
    • Transvenous (through jugular vein--> bottom of right heart)
    • Epicardial 
    • Transdiaphragmatic
  • Demand; exercise
  • Infection; scarring; twitching; arrhythmias; effusion
  • Cannot re-use human pacemakers

6

Sinus arrest

  • Failure of SA node--1/more beats
  • Drugs/lytes/vagal tone, etc. as before
  • > 6 s = signs
  • Atropine test, check lytes; treat as you would for sinus arrhythmia

7

Junctional (nodal)/ventricular escape beats

  • Keeps circulation going to brain (keeping animal alive) when the sinus beat fails to materialize
  • Normal QRS but no P wave = junctional
  • Abnormal QRS + no P wave = ventricular
  • Junctional escape will occur first, then ventricular (often if junctional doesn't work)

8

Which monitor can be used to record junctional/ventricular escape beats?

  • Holter/cardiac event monitor--continuous recording, only remembers last 30-60 sec; hit button to record last minute to permanent memory

9

What is the treatment of junctional/ventricular escape beats?

Positive chronotropes/pacemaker

10

Hyperkalemia

  • Renal failure; ATE; hyperadrenocorticism; crush
  • Raises resting membrane potential--> heart fibrillates
  • Bradycardia
    • T waves tall
    • P waves disappear
    • Prolonged QRS
    • Sinusoidal shape
  • Bicarb/glucose, Ca glutonate for treatment
    • Give fluids that don't contain K
    • Boluses of glu better than insulin--glu raises insulin levels 
    • Bicarb works if underlying cause is acidemia
    • Ca effusion to lower resting membrane potential 

11

AV block

  • Delay or failure of transmission at the AV node
  • Outside heart--drugs, lytes, thyroid, vagus
  • Inside--ischemia, -itis, neo, trauma, genes, idio

12

1st degree AV block

  • PR > 0.13s/0.09s
    • Usually drugs or vagal tone
  • No treatment--monitor

13

2nd degree AV block--Mobitz type I

  • Intermittent failure of conduction
  • Mobitz type I
    • PR interval increases until QRS dropped--Wenkebach
    • Vagal tone/drugs
  • P wave consistent = sinus perfectly fine
    • QRS not responding consistently = intermittent AV block
  • Can hear clinically--watch chest to differentiate from sinus arrhythmia 

14

2nd degree AV block--Mobitz type II

  • No PR changes before dropped QRS
  • Node disease
  • Ratio-- P : QRS

15

2nd degree AV block--high grade node disease

  • Can't tell if it's Mobitz type I or II
  • Only 1 normal beat before dropped beat 
  • High grades more likely to develop into type III down the road (= BAD) --> poor prognosis

16

3rd degree AV block

  • No AV conduction
  • P waves and escape beats
    • AV/junctional (40-60 bpm)
    • Ventricular < 40 -- bizarre-looking
    • Completely independent of each other
  • Give atropine test, check lytes
    • Usually ends up being disease of AV node
    • Damaged--> replaced by fibrous tissue

17

What is the treatment for AV block?

  • Treat the cause--stop dig, treat itis
  • If symptomatic try drugs if responsive to atropine test
  • Emergency isoproterenol/dopamine IV (if responsive to atropine)
  • If not atropine responsive:
    • Pacemaker--inc. survival over 6 months
      • Need for grade III
  • Won't always show clinical signs (ex: old dogs who don't exercise)
    • Pay attention to dogs with low heart rates during physical exams--normally nervous/excited

18

Sick sinus syndrome

  • Abnormal sinus node and AV system
    • Sinus bradycardia
    • Intermittent sinus arrest/AV block
    • Paroxysms of tachycardia
  • Intermittent weakness/syncope
    • Send home w/ monitor
  • Drugs??--ventricular demand pacemaker
    • Can't use drugs to treat both--one will make the other worse
  • Pacemaker to treat sinus arrest, then drugs to control tachycardia

19

Sinus tachycardia

  • Increased HR-- > 160-180bpm/240bpm
  • Normal P QRST
    • ​No arrhythmia, HR just too fast
  • Physiological--fear, pain
  • Pathological--fever, anemia, thyroid
    • Anemia--heart beat is stronger--heart must pump fewer # of RBCs harder/faster to effectively reach tissues; "waterhandle" pulses
    • Common in cats with hyperthyroidism

20

SPD's and sinus tachycardia

  • Premature
    • Part of the atrium depolarizes spontaneously--> can become pacemaker--> premature depolarization
  • Variable P
  • May be buried in T wave
  • Normal QRS
  • Lab/boxer--8y--66% heart disease
    • Cardiomyopathy
    • Neoplasia
    • Re-entry 

21

Diagnosis?

Supraventricular premature depolarization

22

What are the signs/treatment of sinus tachycardia?

  • Signs occur if CO falls
    •  Weakness, syncope
  • Treat the underlying cause
  • Slow the heart
    • Emergency--esmolol/diltiazam (slow; BP)
      • Thump on chest, vagal maneuvers, cardioversions
    • Maintenance--sotalol (oral, BID)/diltiazem
    • Pathway ablation

23

Ventricular premature depolarizations (contractions)

  • Ectopic focus--ventricle
  • Hypertrophy, inflammation, trauma, hypoxia, drugs, systemic conditions, anesth., etc.
  • QRS--premature + no P wave
    • Wide and bizarre
  • Junctional escape beats--premature = occurs after very short beat

24

Triplets and fusion beats--what do they look like?

  • Mix of P wave and ectopic focus
  • Might look like multiple lesions-->look for P wave to ensure fusion beat

25

What is this an example of?

Bigeminy

26

What is this?

Doublets

27

What are the VPD signs?

  • Dropped heart sounds
  • Irregular pulse
  • Dropped pulses
  • Rarely--weakness/syncope
  • Commoner--sudden death
    • Not no's
    • Runs R-on-T

28

VPD treatment?

  • Underlying disorders
  • Specific therapy
    • If symptomatic**
    • If heart disease
      • Boxer cardiomyopathy
      • Doberman w/ DCM
      • Aortic stenosis
      • Hypertrophic cardiomyopathy
        • High rate, R-on-T, too many

29

Drugs for VPD?

  • In emergencies--parenteral
    • Lidocaine
      • Boluses--CRI--K and Mg?
      • Procainamide--IV, IM, SC
      • Esmolol IV then sotalol/propranolol
      • Magnesium
      • Amiadarone?
  • Non-emergency/when stable
    • Sotalol--contractility? (Boxers w/ ARVC)
    • Mexiletine (+ beta blocker) (Dobies w/ DCM)
    • Sotalol and mexiletine, beta blocker--contractility? SAS Procainamide

30

What is the treatment for VPD in cats?

  • Correct underlying causes
  • Initial control--propranolol/atenolol
  • 2nd = lidocaine--low dose boluses--CRI
  • Procainamide/quinidine
  • Sotalol? Amiodarone?
  • Maintenance
    • Oral propranolol/atenolol
    • Procainamide, quinidine
    • Mexiletine 

31

Ventricular tachycardia

  • Serious--maybe pre-fibrillatory--same causes as VPD
  • Runs at > 3VPDs at > 160-180 bpm
  • Sustained > 30s
  • Non-sustained--dec. ectopic focus firing/capture beats
  • Signs: 300 bpm for > 6-8s (heart fx)

32

Treatment for VT?

  • Treatment as for VPDs
  • Won't stop all VPDs or all deaths

33

Accelerated idioventricular rhythm/idioventricular tachycardia

  • Spontaneous ventricular depolarizations at 60-180bpm
  • Capture and fusion beats
  • Asymptomatic mostly

34

Treatment for accelerated idioventricular rhythm/tachycardia?

  • Correct underlying electrolyte/acid base imbalances or systemic conditions
  • Monitor--VT may be coming

35

Ventricular fibrillation

  • Usually terminal
  • Irregular and disorganized ventricular activity
  • No CO/coronary flow
  • Coarse or fine
  • Arises from ectopic foci/reentry/'R on T'

36

Treatment for ventricular fibrillation?

  • Electrical cardioversion--int/ext
  • Epinephrine
  • CPR

37

Atrial fibrillation

  • Common--DCM + lone AF
  • Chaotic activity
    • Multiple ectopic foci
  • No P waves
  • Normal QRS
  • R-R random
  • No "atrial push"
  • Tachycardia--Inc. myocardial O2 demand but dec. CO and dec. cardiac perfusion (coronary flow down 60%)

38

Atrial fibrillation--physical exam findings?

  • Chaotic heart sounds
  • Variable and dropped pulses
  • (Sinal tachycardia--animal would be extremely afraid, in shock, pain, heart failure, etc.)

39

Treatment for atrial fibrillation?

  • If heart function and rate normal
    • No treatment/cardioversion
    • Monitor with echo/Holter
  • If heart function normal but rate up (> 150bpm)
    • Slow ventricular response rate
      • Can't get rid of atrial fib at this stage
      • Diltiazam (Ca channel blocker)
      • Beta blocker--stops SNS from affecting heart--+ ionotropic effect (caution--can push into failure)
      • Cardioversion
  • If heart function decreased and rate up
    • Slow ventricular response rate
      • Digoxin and diltiazem/beta blocker until < 150bpm
      • Amiodarone/cardioversion (?)

40

Atrial fibrillation--cats?

  • Usually with hypertrophic cardiomyopathy
    • Treat HCM w/ beta blocker and will treat atrial fib as well
  1. Propranolol
  2. Diltiazem
  3. Digoxin contraindicated

41

Differential diagnoses for atrial fibrillation?

  • 60 Hz interference
  • Atrial flutter