Antiarrhythmic Drugs Flashcards
What are the phases of cardiac cycle (0,2,3,4)
Phase 0 - depolarization. Na+ entering the cell
Phase 2 - More potassium leaving the cell than Calcium coming in, leading to plateau
Phase 3 - Much more potassium leaving, repolarization
Phase 4 - Ready for depolarization in non-pacemaker cells, pacemaker cells depolarizing
How do you treat bradyarrthymias?
Atropine + Beta agonist
What are afterdepolarizations? What can they cause?
These occur when abnormal calcium influx into cardiac cells during or immediately after Phase 3 of ventricular action potential. May lead to extra systoles and tachycardia.
What is the mechanism of the Class IA antiarrhythmics?
Sodium channel blockers, these decrease automaticity and prolong refractory period
Name the 3 Class IA drugs?
Procainamide, Disopyramide, Quinidine
What is a negative side effect of Procainamide?
Causes Lupus erthyremotosis, reversible
What is a side effect of quinidine?
cinchonism - tinnitus
What is the most powerful Class I A drug?
Disopyramide, decreases contractility the most so most likely to cause HF.
What are the side effects of the Class I A drugs?
Ventricular tachycardia, syncope, AV block, decreased contractility leading to HF, Decreased blood pressure due to vasodilation of vascular smooth muscle (lack of sodium)
What is the mechanism of the Class IB antiarrythmics?
These shorten the duration of the action potential, shortening the refractory period. Still sodium channel blockers.
Name the Class IB drugs?
Lidocaine, Tocainide, Mexiletine, Phenytoin
What is significant about Lidocaine?
number 1 drug used to treat arrthymias. Acts as a local anesthetic. Effects takes about one hour.
What are the longer acting Class IB drugs?
Tocainide and Mexiletine (also used to treat pain from diabetic neuropathy). These last about half a day.
What is Phenytoin used to treat?
Digitalis-induced arrthymias, anticonvulsant
What are side effects of Class I B?
Tremors, convulsions, slowed AV nodal conduction velocity which can cause heart block
What are the Class 1C Antiarrhythmics?
These are sodium channel blockers with no effect on action potential.
Name the Class IC drugs?
Flecainide, Propafenone. Side effects: proarrhthmogenic, hyperkalemia increases cardiotoxicity.
What is the mechanism of the Class II antiarrhythmics?
These are Beta Blockers, Slow Phase 4 depolarization. High doses block sodium channels.
Name the 4 Class II drugs used?
Propranolol, Acebutolol, Esmolol, Sotalol
What is the most important effect of Class II Antiarrythmics?
Only class of drugs used to reduce/prevent sudden death from myocardial infarction.
What are Class II antiarryhthmics used for?
Sympathetic-induced tachycardia, paroxysmal supraventricular tachycardia, a-flutter and a-fib, prophylaxis post-MI to prevent sudden death
What are the B1 selective Class II antiarrhythmics?
Esmolol and Acebutolol. Esmolol used in OR for anesthesia induced arrhythmias.
What is Sotalol?
Class II Beta Blocker. Racemic mixture, L-isomer is Beta Blocker and D-isomer is Potassium Channel Blocker.
What are the side effects of Class II drugs?
Decreased HR and conduction, sedation, asthma for non-selective, HF, sexual dysfunction, and decrease in CO.
What are the Class III antiarrhythmics?
Potassium channel blockers, block exit of potassium from the cell. Prolong action potential, effective refractory period and repolarization. Slows cells down.
When do you use the Class IIIs
When ventricular arrhythmias refractory to other types of therapy
What is Amiodarone?
Class III, K+ channel blocker, but also blocks sodium and calcium channels. Can cause thyroid dysfunction and deposit metabolites in lens/cornea.
What is a major (problematic) side effect of Class III antiarythmics?
can produce torsades de pont
What are the 4 class III drugs?
Amiodarone, d-Sotalol, Ibultilide, Dofetilide
What is important to remember about Dofetilide?
requires certification for doctor and hospital because of high toxicity
What is ibutilide used to treat?
Convert A flutter and A fib to normal, sinus rhythm. Highly arrtyhmogenic. single injection.
What are class IV antiarryhthmics?
Calcium channel blockers (L-type). Reduce calcium entry during action potential and during Phase 4. Conduction velocity slows, refractory period prolongs.
Which calcium channel Blockers ARE NOT USED for arrthymias?
Dihydropyridine calcium channel blockers
Which Class IV drugs are used in arrythmias?
Verapamil, Diltiazem, Bepridil
What is a serious side effect of Verapamil?
can increase serum digoxin concentrations
Which drugs causes constipation in the Class IVs?
Verapamil
What condition do you avoid Class IVs?
Wolff-Parkinson White syndrome.
When is adenosine used?
during life threatening ventricular arrhythmias and paroxysmal supraventricular tachyarrythmias including Wolff-parkinson white. Stops the heart for 5-10 seconds.
When do you give magnesium?
torsades de pointes, MI, cardiac arrest with suspected hypomagnesia.
What are the effects of hypokalemia and hyperkalemia on arrhytmias?
Hypokalemia increases risk, which hyperkalemia decreases conduction and causes re-entry type arrthymias.
What is the only antiarrtymic that doesn’t become arrhtyhmogenic at higher doses?
amiodarone
How do you treat atrial flutter?
Beta blocker, Calcium channel blocker, Digoxin
How do you treat A fib?
Beta blocker, Potassium channel blocker (amiodoraone - also blocks Ca2+ and Na+)
How do you treat AV Nodal re-entry
beta blocker, calcium channel blocker, digoxin
How do you treat acute SVT
adenosine
How do you treat acute VT
Lidocaine, amiodorone
How you treat Vfib?
Amiodorone, epi
