Antiarrhythmics Flashcards
Name the 4 Classes of Antiarrhythmic drugs.
Sodium Channel Blockers, BBs, Potassium Channel Blockers, CCBs (Specifically Verapamil and Diltiazem).
Key to understanding Antiarrhythmic agents is what?
Depolarization and Repolarization of the myocyte.
Class I Antiarrhythmics are which drugs and block which channels?
Voltage gated fast sodium channels responsible for upstroke in Phase 0. This decreases the slope and velocity of Phase 0. You cannot forget that they also block Potassium channels that mediate Repolarization at phase 3.
Sodium channels fluctuate between which 3 states? Class IA bind the channel during which state?
Resting, Open, then Closed. Quinidine, Procainamide, and Disopyramide bind channels in the Open state.
Class IB Antiarrhythics bind sodium channels during which states?
Both Open and Closed states.
Class IC Antiarrhythmics are potent blockers of which state?
Open state, and take the longest to dissociate.
Class IA Sodium channel blockers are especially helpful for which cardiac condition?
SVT or Vtach
ADRs of Class IA Antiarrhythmics are very High Yield. What are Tinnitus, HA, and visual problems, possible hearing loss part of?
Cinchonism.
Describe Cinchonism and DIL. Which drugs in Class IA can have these adverse effects on the pt?
Cinchonism is HA, tinnitus, hearing, loss, visual changes. DIL has fever, arthralgias, myalgias, rash.
What can Disopyramide cause as an adverse effect? And what can all 3 of Class IA cause?
Disopyramide can result in Heart Failure. All three can cause the fatal Torsades de Pointes due to the QT prolongation that occurs by blocking the repolarization of the Potassium channels at Phase 3.
All 3 can also cause Thrombocytopenia, tho mechanism is not well understood.
Which drugs fall under Class IB Sodium Channel Blockers and what is their mechanism?
Lidocaine and Mexiletine. (Technically also Phenytoin but it is more of an antiseizure drug). These drugs shorten the action potential.
When do we clinically prefer to use Class IB antiarrhythmics?
Especially post-MI and Digitoxin induced arrhythmias. Also used in Acute Vtach.
1B is Best Post-MI is to remind you of what?
That Lidocaine and Mexilitine are the DOC for post-MI or ischemic pts.
What is a serious potential adverse effect of Class IB drugs?
Anytime there is too much sodium, there is a risk of Cardiovascular depression. Both are also very lipophilic and can stimulate or depress the CNS as well.
Which of the Class IB Antiarrhythmics is classically known for triggering seizures?
Lidocaine think Seizures.
Flecainide and Propefenone are rarely used clinically due to dangerous side effects. Which class of drugs is this?
Class IC. NEVER GIVE POST-MI. Can cause serious arrhythmias.
Post MI you want to decrease the ARP by using what class of drugs?
A class IA drug will prolong the ARP because it increases the action potential (AP) duration. A class IB drug will decrease the AP and therefore decrease the ARP. A class IC drug will not change the ARP. Regardless of ARP action, all class I drugs decrease the slope of phase 0.
Describe the G protein pathway of Beta blocking in the heart.
β-Receptor antagonists work by inhibiting β-receptors, hindering the G-protein/cAMP mechanism. By reducing the amount of cAMP and protein kinase A (PKA) produced, β-receptor antagonists decrease the Ca2+ currents within the AV node. (Decreased production of cAMP and PKA reduces the Na+ current via phosphorylation-mediated downregulation of expression and other mechanisms)
