Pharmacology of Arrhythmias Flashcards
Vaughn Williams classification system is based on?
the channel that the drug blocks
Class Ia
- what effect?
- example drugs?
-Na channel blockers - dec conduction velocity and prolonging repolarization
- quinidine
- procainamide
- disopyramide
Class Ib
- what effect?
- example drugs?
-Na channel blocker - shortened repolarization, slight dec in conduction velocity
- Lidocaine
- mexiletine
Class Ic
- what effect?
- example drugs?
-Marked Na channel blocking - dec conduction velocity, no effect on repolarization
- Flecinide
- propafenone
Class II
- what effect?
- example drugs?
-Beta blockers - lowered sinus rate
- Metoprolol
- atenolol
Class III
- what effect?
- example drugs?
-marked potassium channel blocker - marked prolongation of refractory period
- sotolol
- amiodarone
- ibutilide
Class IV
- what effect?
- example drugs?
-calcium channel blocker - lowered sinus rate
- verapamil
- diltiazem
3 basic things that antiarrhythmics do to effect heart electrophysiology-wise:
1) prolong resting membrane potention
2) prolong refractory period
3) harder to reach action potential
Quinidine
- class?
- uses? How?
- use today?
- class 1a
- atrial fib must give digoxin first
- not used today- many side effects and causes heart failure
Quinidine use puts patient at risk for?
torsades - do an EKG to see how QRS loks
Quinidine - major adverse effect?
-GI upset
quinidine drug interactions:
- digoxin
- amiodarone
- cimetidine
- verapamil
- phenytoin
Procainamide
- class?
- effect?
- use today?
- class 1a
- prolongs refractory period (QT)
- little effect on AV nodal conduction
- second line in ACLS algorithm for VT/VF
- not used today because neg hear effects.
Potential for drug induced lupus with?
procainamide
Disopyramide
- class?
- effect?
- use today?
- class 1a
- prolongs the duration of the action potential
- anti-cholinergic effects balance out depression of AV node conduction
- not used much today
Disopyramide - side effects?
- dry everything
- sleepy
- urinary incont
**(so many anticholinergic effects)
Disopyramide- dosing consideration with patient with certain diseases?
-must reduce dose in people with kidney disease* (renal failure)
Lidocaine
- what class?
- effect?
- useful for?
- use today?
- class 1b
- minimal QT or QRS
- increased VT of VF threshold
- effective for re-entral rhythms
- used to be used in post MI patients for prophylaxis
- no longer first line
Lidocaine administration?
*only IV and in hospirtal
no oral
Lidocaine is what type of drug?
-useful for arrhythmias but it is a AMIDE TYPE LOCAL ANESTHETIC
only has effect on ventricles?
lidocaine - no use for anythnig atria
Lidocaine side effects to know about?
-MANY CNS effects- crossed BBB = dizzy, parasthesias, confusion, lethargy,…
checking blood levels for this drug is actually useful?
-lidocaine - if patient has CNS effects –> check levels to see if you should lay off the dosing
Flecainide
- class?
- effect?
- use today?
- class 1c
- increases QRS
- potentn Na channel blocker
- used today in patients with atrial arrhythmias w/out ischemic heart disease
- rarely used in ventricular arrhythmias
Reduce dose of these drugs in patients with renal failure
Disopyramide
flecainide
sotolol
dofetilide
benefit to Class 1c drugs/
-well-tolerated and without weird adverse effects
main use for flecainide?
-supra ventricular tachycardias (A FIB) with normal cardiac function
propafenone
- class?
- effects?
- used for?
- class 1c
- slows atrial and ventricular conduction wihtout prolonging repolarization
- non-selective beta block
- less pro-arrhyhtmic that other 1c agents
- used in patients without significant CHF (patients without structural heart disease) that have atrial arrhythmias or sustained VT/VF
primarily used for a fib in US?
propafenone
two drug interactions of propafenone?**
digoxin
warfarin
Class 1 drugs are not use with what patients?
NOT with patients that have structural heart problems - aka CHF
only class of drugs that reduces mortality in arrhyhtmia patients?
beta-blockers
sotolol
- class?
- effect?
- used for?
- class III (potassium channel) but beta blocking agent too
- minimal effect on PR intervals
- dose dependent inc in QT interval
- used for prevention of A fib and VT/VF
sotolol adverse?
-Huge cause of torsades!!
sotolol primary prevention in US?
-prevent recurrence of a fib
*Amiodarone
-class?
effect?
-used for?
- class 3 ( has effects in all 4 classes though)
- delayed repolarizing by proonged APD and ERP
- first line for ACLS VT/VF
Main problem with amiodarone?
-long list of adverse effects - it pretty much hits every organ system!
- *amiodarone adverse effects?
- worst effects?
HEART:-low risk of torsades
-IN GENERAL PRETTY SAFE FOR THE HEART…
LUNGS: worst= pulmonary fibrosis or delayed hypersensitivity pneumonitis –> 10% die from this
THYROID - much of drug contains Iodine = hypo hyper thyoridism (hypo more common)
EYES: everyone on this drug long term gets corneal deposits (no effect on vision); halos; photophobia
NEURO: tremor common with long term, periph neuropathy
SKIN: photosensitivity; blue green discoloration (smurf drug)
LIVER: -asymptmatic elevations in bilirubin & transaminases; rare hepatitis
GI: N & V very common
Amidarone drug interactions?
pretty much everything unless proven otherwise
Amiodarone indications:
-prevent SVT (especially a fib), VT, and VF
Dronaderone
- what class?
- interesting about drug?
- used for?
- side effects?
- class III
- basically amiodarone without the iodines (since iodine was causing so many of the side effects)
- good for a fib
-FEWER ADVERSE EFFECTS BUT LESS EFFECTIVE THAN AMIODARONE
Dofetilide
-used for?
a fib!
even good in patients with structural heart disease
dofetilide - big problem?
huge incidence of torsades - more than sotolol!!
-cleared mostly by kidneys = not good if kidneys are bad
patient gets frequent ventricular arrhythmias - give?
-implantable cardioverter defibrillator (ICD) - gives them a shock when its monitoring of the heart determines that something isnt right
A fib and no heart disease give?
- flecanide
- propafenone
A fib with CAD but no CHF give?
sotolol
A fib with CHF give?
amiodarone
dofetilide
