Test 1: lecture 8 arrhythmias Flashcards
antiarrhythmic drugs have no guarantee to —
prevent sudden death
can help decrease signs: syncope, weakness and CHF
3 major causes of arrhythmias
abnormal impulse generation
triggered activity
abnormal impulse conduction
altered automaticity of sinus node will cause
increased= too fast= sinus tach= increased sympathetic tone
decreased= too slow= sinus bradycardia = increased vagal tone
ventricular premature contractions
wierd and wide QRS
abnormal automaticity in myocardium leads to
ectopic beats
can be atrial or ventricular premature beats or tachycardia
caused by disease myocardium sending off signals when it should not
early afterdepolarization
EAD
arrhythmia caused by early impulse
is AP duration is prolonged
can be genetic defect in german sheperds
can be drug toxicity
leads to Vtach
goal is to shorten action potenial to skip these extra beats
delayed afterdepolarization
is calcium overload
can be from digoxin toxicity
leads to Vtach
if conduction velocity is too fast leads to
atrial or ventricular tachycardia
want to slow conduction to allow for normal HR
what can cause too low conduction velocity in the heart
AV block
leads to bradycardia
P waves do not lead to QRS, only ventricular contraction from escaped PVCs
need to fix through pacemaker
how does reentry cause arrhythmia
impulse hits obstacle
new impulse comes quickly and one lead unable to depolarize in time, allows impulse to loop around itself
Cardiac impulse is not completing the normal conduction pathway due to a block, but following an alternative circuit around the blocked area and looping back upon itself
what is needed for reentry to occur
premature beats
variable conduction velocity (block or damage that delays depolarization)
how to treat arrhythmias due to reentry
slow spontaneous depolarization
and conduction velocity
what are some common arrhythmias caused by reentry
Afib
AV reentry trachycardia
Vtach or Vfib
A fib
no P wave- wiggly baseline
R-R interval irregular
Vtach/ V fib
wierd and wide QRS
very fast
can’t see P waves
fast depolarization of Purkinje fibers, atrial / ventricular myocardial cells is by
sodium (Na) channels
repolarization of Purkinje fibers, atrial / ventricular myocardial cells is by
potassium (K)
leaving cell
slow depolarization of sinus node and AV cells is by
calcium
slow spontaneous depolarization of sinus node and AV cells is by
sodium (funny channels→slow leak)
calcium
class I antiarrhythmic
Na channel blockers
(prevents Na into cell, slows down depolarization of myocardial cells)
class II antiarrhythmic
beta-adrenergic blocker
class III antiarrhythmic
potassium channel blocker
prevents K from leaving cell, causes slower repolarization, leads to longer space between beats
class IV antiarrhythmic
calcium channel blockers
prevents depolarization of nodal cells
class I antiarrhythmic will work by — conduction velocity and suppress abnormal —
na channel blocker
slows conduction velocity of myocardial cells
→cause decrease in slope and disrupts reentry circuits
suppress abnormal automaticity in sick non-nodal tissues
→will slow down phase 4
→non-nodal tissues should not have automaticity (drug will stop them from beating on their own)
— is a class IB antiarrhythmic
lidocaine
ventricular arrhythmias can be treated with — antiarr
class I: Na channel blockers
ex: lidocaine (class 1B)
class III: K channel blockers
ex. sotalol
a little by class II Beta blockers (—olol), but they mostly decrease SYM to SA node cause decreased HR
why do class I anti-arrhy not cause bradycardia
effects the non-nodal tissues by blocking Na channels
does not cause change in nodal cells (sinus or AV node)
class I good for ventricular arrhythmias
what class of drug does this
class I- antiarrhythmic
Na channel blocker (lidocaine class Ib)
lidocaine is what class of drug and is used for
Class 1b antiarrhythmic
can only be given IV
used for Vtach
can cause depression, seizures (cats) vomiting
can cause transient hypotension under GA
side effects of lidocaine
Depression, seizures (cats are more sensitive), vomiting
transient hypotension noticed under GA
Class Ib anti-arrhythmic - Na channel blocker used for Vtach
what drug
lidocaine
treat Vtach
Class Ib anti-arrhythmic - Na channel blocker used for Vtach
how does class II anti-arrhythmic work
beta blocker
blocks sympathic tone to the heart
reduces HR by slowing sinus node
beta blockers are — drugs
class II antiarrhythmics
— is a 2nd gen class II antiarrhythmic
atenolol- selective for β1 receptors
beta blocker: slows down HR by slowing down impulse of sinus node
used for supraventricular arrhythmias: Afib, or tachycardia (feline hyperthyroidism)
what are some side effects of Class II anti-arrhythmics
beta blockers
negative inotrope: can cause reduced myocardial contractility and cardiac output
can worsen CHF and cause hypotension
atenolol is a 2nd gen class II AA
how to treat
atrial tachycardia
give beta blocker (IV esmolol)
will slow HR by slowing conduction through AV node → can cause AV block (P wave no QRS)
atenolol and esmolol (2nd gen class II beta blockers)
how does class III AA drug work
potassium channel blocker
prolongs repolarization: makes the AP all the same length (widens)
does not effect the conduction velocity
used for ventricular arrhythmias
L-sotalol: class III AA: K channel blocker causes widened AP (prolongs repolarization)
— is a class III AA
L-sotalol: class III AA: K channel blocker causes widened AP (prolongs repolarization)
used for ventricular arrhythmias
how does class III AA effect reentry
L-sotalol: class III AA: K channel blocker causes widened AP (prolongs repolarization): prevents ventricular arrhythmias
sotalol is —
L-sotalol: class III AA: K channel blocker causes widened AP (prolongs repolarization): prevents ventricular arrhythmias
what will sotalol do
L-sotalol: class III AA: K channel blocker causes widened AP (prolongs repolarization): prevents ventricular arrhythmias
before had sustained Vtach now has sinus rhythm with occasional VPCs
— class of AA will slow AV nodal conduction
IV
calcium channel blocker
— is a class IV AA
diltiazem
calcium channel blocker: will slow AV nodal conduction
will slow Afib, will stop supraventricular reentry arrhythmias in the AV node
diltiazem is used to slow conduction through —
AV node
class IV: calcium channel blocker
used to stop/slow supraventricular arrhythmias such as Afib
will also stop reentry through the AV node
will diltiazem effect Vtach?
no
class IV calcium channel blocker
will slow supraventricular arrhythmias such as Afib, by slowing conduction through the AV node
— is a calcium channel blocker used to relax vascular smooth muscle
will cause hypotension
amlodipine
calcium channel blocker= class IV AA
DOES NOT effect HR like other class IV AA diltiazem which slows conduction through AV node to stop AFib
digoxin is used for
slows ventricular response rate in Afib
will slow AV nodal conduction
parasympathomimetic effect
— are parasymptholytics that stop bradycardia
Atropine, Glycopyrrolate
rapid Afib should be teated with
digoxin: acts as parasympathomimetic, slows AV nodal conduction
diltiazem: class IV calcium channel blocker, will slow conduction through the AV node
how to treat Vtach
If VT rate is rapid over several seconds: can cause
weakness or collapse (poor cardiac output)
- If very rapid Þ If R on T phenomenon: VT can
degenerate into ventricular fibrillation (VF) Þ sudden
death! - Class I or class III antiarrhythmic drugs
class I: Na channel blocker: slowss conduction, suppresses abnormal automaticity from non-nodal tissue: lodocaine Ib
class III:K channel blocker: makes long repolarization: sotalol
V fib!
must shock back to rhythm
how to treat 3rd degree AV block
**no conduction through AV node
atria beating according to SA node
ventricles beating according to ventricle pacing/escape beat (very slow)
need to place pacemaker
how would you treat
pacemaker
sick sinus syndrome
bradycardia with long pause and escape beat
how to place pacemaker
through jugular vein
Lead tip is advanced in RV apex
Pacemaker generator in
subcutaneous pouch in neck
After 2 months the tip is fully scarred into the chamber wall
how to treat bradycardia
how to treat SVT other then Afib
how to treat AFib
how to treat Ventricular arrhythmias
graph
how to treat Vfib
graph
— class cause Reduce slope of phase 0 and peak of AP
class I
na channel blockers
lidocaine
— class will cause Small reduction in phase 0, shortens APD, decreases ERP, increases post-repolarization refractoriness
class I
na channel blocker
IB: lidocaine
— class of AA will Slows rate of spontaneous depolarization and conduction velocity in SA and AVN
type II beta blocker
atenolol, esmolol
— class of AA will cause Markedly prolongs repolarization (phase 3), lengthen ERP and APD
class III: K channel blockers
Amiodarone
Sotalol
— class of AA will cause Slows rate of spontaneous depolarization and conduction velocity in SA and AVN
class IV: Ca channel blockers
Diltiazem
Verapamil