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Silverstein & Hopper (+ West) > Chapter 47 - supraventricular tachyarrhythmias > Flashcards

Chapter 47 - supraventricular tachyarrhythmias Flashcards

1
Q

List 4 features that help differentiate between V tach and SVT w/ bundle branch block or antegrade conduction over an accessory pathway

A
  1. P waves w/ consistent relationship to QRS suggests SVT
  2. presence of QRS fusion complexes suggests V tach
  3. response to vagal manoeuvre suggests SVT
  4. response to lidocaine suggests V tach
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2
Q

which of the following are characteristic of atrial dependent SVT?

  1. continues despite AV block
  2. SVT terminated by VPCs
  3. SVT terminated by vagal maneuver
A

1.

Other 2 are characteristic of AV node dependent SVT

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3
Q

List 4 most common SVTs in small animals

A

atrial fibrillation
intraatrial reentrant tachycardia
orthodromic AV reciprocating tachycardia
automatic atrial tachycardia

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4
Q

Predisposing factors for SVT?

A

acid-base abnormalities
electrolyte disturbances
severe anemia
hypoxemia

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5
Q

describe the most effective vagal manoeuvre in small animals, effectiveness

A

sustained, gentle compression is applied for 5-10 seconds over the carotid sinus, immediately caudal to the dorsal aspect of the larynx. most often ineffective

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6
Q

initial drug of choice to terminate AV node SVT? MOA?

A

want negative dromotropy: in dogs diltiazem at 0.125-0.35mg/kg IV slowly over 2-3min, CRI at same dose/hr. calcium channel blocker (class IV)

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7
Q

what contraindication to use of B blockers (class II) such as esmolol may be present?

A

impaired ventricular systolic function

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8
Q

signs of calcium channel blocker toxicity?

A

hypotension
negative chronotropy (impaired SA node discharge)
negative dromotropy (impaired AV node conduction)
negative inotropy
impaired insulin release -> BG rises, intracellular Ca2+ drops

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9
Q

signs of B blocker toxicity?

A

severe bradyarrhythmias
impaired atrial & ventricular contractility
bronchospasm
decreased glycogenolysis, lipolysis, gluconeogenesis

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10
Q

4 effects of B1 stimulation

A

primarily heart & adipose tissue, coupling of B1 receptors with adenyl cyclase –> cAMP

  1. increased HR (stimulation of the funny current & L-type calcium current)
  2. increased myocardial contractility (L type Ca++ current influx stimulating increased sarcoplasmic reticular Ca++ release)
  3. improved myocardial relaxation (phosphorylation of phospholamban)
  4. enhanced automaticity of subsidiary pacemakers
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11
Q

list 4 antiarrhythmics effective for SVTs from the SA node, and 1 most common SVT

A 
Class II (B blockers), Class III, Class IV (Ca++ channel blockers), Digitalis
SA nodal reentry
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12
Q

list 3 antiarrhythmics effective for SVTs from the atrial myocardium, and 3 most common SVTs

A

Class IA, Class IC, Class III

a fib, atrial reentry, atrial automaticity

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13
Q

list 6 antiarrhythmics effective for SVTs from the AV node, and 2 most common SVTs

A

Class IC, Class II (B blockers), Class III, Class IV (calcium channel blockers), Digoxin, Adenosine
AV nodal reentry, junctional automaticity

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14
Q

list 3 antiarrhythmics effective for SVTs from the accessory pathway, and 1 most common SVT

A

Class IA, Class IC, Class III

AV reciprocating tachycardia

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15
Q

when/why procainamide?

A

class IA, prolongs effective refractory period, used for atrial and accessory pathway SVTs after another agent slows conduction (i.e. diltiazem)

dogs: 6-8mg/kg IV over 5-10min, 6-20mg/kg IM, CRI 20-40mcg/kg/min
cats: 1-2mg/kg slow IV, 3-8mg/kg IM, CRI 10-20mcg/kg/min

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16
Q

describe how you would perform a precordial thump, likelihood of success?

A

sharp concussive blow to left precordium w/ animal in R lat –> myocardial depolarisation, may disrupt reentrant tachycardia circuit. low success rate

17
Q

SVT can be broadly arranged into what two groups?

A

Atrial and AV node dependent tachyarrhythmias

18
Q

T/F: Tachycardiomyopathy can be partially or completely reversed.

A

True

19
Q

Why can SVTs cause sudden death?

A

Myocardial ischemia that gives rise to v-tach and v fib

20
Q

What are some signs that owners might notice with patients with SVT?

A

Exercise intolerance, weakness, signs of CHF, GI signs (v, inappetance), collapse, noticeable rapid HR, pulsing of the ears, bobbing of the head

21
Q

T/F PE findings of patients with supraventricular tachyarrhythmias can be normal.

A

True

22
Q

T/f: A narrow QRS complex tachyarrhythmia will almost always be an SVT.

A

True

23
Q

Up to what percent of wide complex tachyarrhythmias in humans are ventricular in origin?

A

80%

24
Q

What can you use to help you distinguish between SVT and v-tach? (4)

A

a. ID of P waves
b. QRS fusion complexes (v tach)
c. If tachycardia terminates in response to a vagal maneuver
d. If terminates with administration of IV lidocaine, likely v-tach

25
Q

If an SVT continues despite AV block, where is it’s origin?

A

Atrial

26
Q

If an SVT terminates because of a vagal maneuver, where is it’s origin?

A

AV node dependent

27
Q

What are the most commonly occurring SVTs in small animals?

A

A-fib, intra-atrial reentrant tachycardia, orthodromic AV reciprocating tachycardia, automatic atrial tachycardia

28
Q

What is the most effective vagal maneuver in small animals?

A

Carotid sinus massage

29
Q

What are some negative dromotropic classes of drugs that can be used to interrupt a tachyarrhythmic circuit?

A

B blockers, Ca channel blockers, adenosine

30
Q

In one study, what was superior in slowing AV nodal conduction while maintaining a favorable hemodynamic profile?

A

Diltiazem

31
Q

The effects of B1 receptor stimulation result in what? (4)

A
  1. Increased HR 2ndary to stimulation of the funny current and L-type calcium current
  2. Enhanced myocardial contractility through L-type calcium current influx stimulating increased sarcoplasmic reticular calcium release,
  3. Improves myocardial relaxation through phosphorylation of phasolamban
  4. Enhanced automaticity of subsidiary pacemakers
32
Q

Name three drug classes that slow AV nodal conduction.

A
  1. Digitalis glycosides
  2. Ca channel blockers
  3. B blockers
33
Q

This is a relatively B1 selective blocker that competitively inhibits the effects of catecholamines on cardiac B receptors.

A

Atenolol

34
Q

What do class I antiarrhythic drugs block?

A

Fast Na channels

35
Q

Name 2 Class III antiarrhythmic agents.

A

Sotalol and amiodarone

Silverstein & Hopper (+ West) (84 decks)

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