Antiarrhythmics II Flashcards
what are the class III drugs
AiDS Amiodarone ibutilide Dofetilide Sotalol
mechanism of class III drugs
K channel blockers hence increase QT interval
special mechanisms of the class III drugs
- Amiodarone has class I (Na channel blocker), II (beta blocker), class III (K channel blocker), and class IV (calcium channel blocker) activity
- dofetilide has no extracardiac effects
- sotalol is a class III drug in addition to having weak beta blocking activity
clinical uses of class III drugs
- amiodarone - severe supraventricular and ventricular arrhythmias, acute VT refractory to cardioversion shock, maintain ventricular rate in a-fib pts
- dofetilide - maintenance of normal sinus rhythm, conversion of a-flutter or a-fib to normal sinus rhythm
- sotalol - life threatening ventricular arrhythmias, maintenance of sinus rhythm in pts with a-fib or a-flutter
adverse effects of class III drugs
- amiodarone: interstitial pulmonary fibrosis, hypo or hyper thyroidism, corneal deposits, blue grey skin discoloration, photosensitivity
- dofetilide: possible ventricular tachycardia, torsades de pointes
contraindication of class III drugs
- amiodarone can alter effects of digoxin, warfarin, theophylline, and quinidine (DWTQ - dancing with Tom Queen)
- bradycardia, hypotension, SA or AV block, severe respiratory failure
what are the class IV drugs
diltiazem and verapamil (antihydropyridines)
calcium channel blockers
mechanism of class IV drugs
calcium channel blockers and slows conduction in SA and AV nodes
major effect on cardiac and vascular smooth muscle
clinical uses of class IV drugs
- supraventricular tachycardia
- reduction of ventricular rate in a-fib and a-flutter
adverse effects of class IV drugs
excessive bradycardia, impaired cardiac conduction, depressed contractility
contraindications of class IV drugs
preexisting cardiac depressed function
verapamil increases the conc of simvastatin, lovastatin, digoxin, and dofetilide, (SLiDD)
what are the miscellaneous drugs used for antiarrhythmias
MAAD
magnesium, adenosine, atropine, digoxin
clinical use of digoxin
control of ventricular response rate in atrial fibrillation and flutter with impaired left ventricular function or heart failure
direct AV node blocking effects and activation of vagomimetic properties
adverse effects of digoxin
cardiac arrhythmias esp a-tach and AV block
toxic doses can lead to v-tach and v-fib
what is adenosine used for
abolishing acute supraventricular tachycardia
mechanism of action of adenosine
- enhances K conductance via G protein
- inhibits cAMP mediated ca2+
- hyperpolarization in AV node
adverse effects of adenosine
bronchoconstriction can occur in asthmatic patient for up to 30 mins
clinical use of magnesium
- torsades de pointes
- digitalis induced arrhythmia
- prophylaxis of arrhythmia in acute MI
mechanism of magnesium
functions as a calcium antagonist by preventing the influx of calcium into the cell
what is atropine used for
bradyarrhythmias
how is a-fib managed
- slow down ventricular rate
- prevent thromboembolism
- correction of rhythm disturbance
first line rate control options for a-fib
class II drugs - beta blockers (PEM - propanalol, esmolol, metapronol) class IV drugs - diltiazem and verapamil
when is amiodarone used in a-fib
- patients who are refractory
- or contraindications to beta blockers, calcium channel blockers, digoxin
patients with a-fib for longer than 48 hours or an unknown period should be given what and why
warfarin because a-fib can cause clots due to viscous blood (stasis) and can lead to stroke
how long is warfarin given to patient with a-fib
for three weeks prior to cardioversion and up to 4 weeks after effective cardioversion and return of normal sinus rhythm
what drug is given to patient with a-fib of less than 48 hours and before when?
heparin and prior to cardioversion (DCC - direct current cardioversion)
what are the recommended drugs for conversion of a-fib to normal sinus rhythm
F-PAD
flecainamide, propafenone, amiodarone, dofetilide
