Anti-Arrhythmics Flashcards
what’s the goal of arrhythmia drugs?
reduce ectopic pacemaker activity
modify conduction or refractory to disable reentry
what do class I anti-arrhythmics do?
block Na+ channels
what do class IA anti-arrhythmics do?
blocks OPEN/ACTIVATED Na+ channels
what do class IB anti-arrhythmics do?
blocks INACTIVE Na+ channels
what do class IC anti-arrhythmics do?
blocks both open and closed Na+ channels
what do class II anti-arrhythmics do?
reduce adrenergic activity of heart
what do class III anti-arrhythmics do?
K+ channel block
what do class IV anti-arrhythmics do?
Ca2+ channel block
Quinidine is a class ___, ___ block
class IA
Na+ block
**also blocks M and alpha receptors
Quinidine indications
supraventricular and ventricular arrhythmias
Tx re-entrant arrhytmia (atrial fibrillation)
in dogs and horses
Quinidine binds to Na+ ___ channel to slow AP
active Na+ channels
what are the adverse effects of Quinidine based on each receptor it affects (alpha, M)?
alpha - hypotension, reflex tachy
M - increases HR, increase AV conduction
Quinidine adverse effects on dog vs horse
dogs - anorexia, V, negative inotropism
horse - colic, ataxia, nasal swell
Quinidine contraindications
myasthenia gravis
AV block
digitalis toxicity or on digotoxin
Procainamide is a class ___, ___ block
class IA
active Na+ block
Procainamide indications
ventricular arrhythmia
*NOT very effective in horse
Procainamide metabolite has class ___ activity before excretion
class III
which drug does more vagal (M and alpha) blocks, Procainamide or Quinidine?
QUINIDINE
Lidocaine is a class ___ , ____ block
class IB
INACTIVE Na+ block
Lidocaine indications
local anesthetic
Tx ventricular arrhythmia (NOT supra)
why does Lidocaine decrease AP duration and shorten ERP?
due to block of slow Na+ window currents
does Lidocaine decrease contractility?
NO
Lidocaine adverse effects
CNS signs in dogs - drowsy, muscle twitch, convulsions
hypotension
cardiac suppression and CNA excitation in cats
Propanolol is a class ___, ___ block
class II
Beta block
Propanolol indications
supraventricular tachycardia
atrial fibrillation
hypertension
ventricular tachy (horses, if not lidocaine)
Propanolol contraindication
concurrent RAO in horses
Atenolol is a class ___, ___ block
class II
Beta block
Atenolol indications
supraventricular tachyarrhythmias
hypertension
hypertrophic CM in ferrets
Atenolol is ___ acting than Propanolol
longer
Esmolol is a class ___, ___ block
class II
Beta block
Esmolol indications
ACUTE management of supraventricular tachy
decreases HR in dogs with ventricular tachy
**use this to test if long acting beta block would work better
Esmolol is ___ acting
VERY SHORT
Sotalol and Amiodarone are class ___, ___ blockers
class III
K+ block
Sotalol indication
arrhythmiogenic CM in boxers
Sotalol and Amiodarone effect on cardiac AP
prolongs AP and refractory period
decreased efficacy
Sotalol contraindication
asthma
since a beta block
Diltiazem is a class ___, ___ block
class IV
Ca2+ block aka CCB
Diltiazem indications
atrial fib
supraventricular tachy
hypertrophic CM
hypertension
Diltiazem blocks ___ channels
Ca2+ L type
Diltiazem effect on HR, AV conduction, periphery
decrease HR
decrease AV
dilate periphery
Diltiazem adverse effects
vasodilation, NO reflex tachycardia (since blocks AV)
bradycardia
GI/CNS issues
increase liver enzymes
negative inotropic effect
Diltiazem causes ___ bioavailability of Propanolol
increased
