Arrhythmias Flashcards Preview

• 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

• 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

• 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)

• 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

• 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

• 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

• 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)

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

Positive chronotropes/pacemaker

• 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 

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

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

• 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 

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

• 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

• 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

• 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