Overview of Anti-Arrhythmic Drug Classes

Questions and Answers

What is the basic mechanism of the 4 classes of anti-arrhythmic drugs?

Class 1: Sodium Channel Blockers. Class 2: Beta Blockers. Class 3: Drugs that prolong cardiac action potential. Class 4: Calcium channel blockers.

Of the 4 classes of anti-arrhythmic drugs, which ones affect the electrical activity of the heart and which ones modify the myocardial response to electrical activity?

Class 2 & 4 (Beta Blockers & Calcium Blockers) modify electrical activity; Class 1 & 3 modify myocardial response.

Which classes of anti-arrhythmic drugs affect the nodes and which ones affect the myocardium?

Class 2 & 4 affect the nodes; Class 1 & 3 affect the myocardium.

What are the Class 1a drugs, what is their mechanism of action, and how do they influence the myocardial action potential?

Class 1a drugs are sodium channel blockers including Disopyramide, Quinidine, and Procainamide. They decrease the slope of phase 0 depolarization and increase action potential duration. Signup and view all the answers

With regards to myocardium, what subclass of Class 1 drugs results in a decreased phase 0 slope and can potentially increase action potential duration?

Class 1a drugs decrease the upslope of Phase 0 and may or may not increase action potential duration. Signup and view all the answers

Given the effects of Class 1a anti-arrhythmic drugs on myocardial action potentials, how do you expect them to alter the EKG?

Class 1a drugs prolong phase 0 depolarization, reflected as widening of the QRS complex and lengthening of the QT interval. Signup and view all the answers

What are the Class 1b drugs, what is their mechanism of action, and how do they influence the myocardial action potential?

Class 1b drugs are sodium channel blockers including Lidocaine, Mexiletine, Tocanide, and Phenytoin. They decrease the slope of phase 0 and shorten the action potential duration. Signup and view all the answers

With regards to the myocardium, which subclass of Class 1 drugs results in a shortening of the action potential duration?

Class 1b drugs shorten the myocardial action potential and decrease the slope of phase 0 depolarization. Signup and view all the answers

Given the effects of Class 1b anti-arrhythmic drugs on myocardial action potentials, how do you expect them to alter the EKG?

Class 1b drugs slow phase 0 depolarization and shorten the myocardial action potential duration, leading to a normal QRS complex duration and a decrease in the QT interval. Signup and view all the answers

What are the Class 1c drugs, what is their mechanism of action, and how do they influence the myocardial action potential?

Class 1c drugs are sodium channel blockers including Flecainide, Propafenone, and Moricizine. They decrease the slope of phase 0 depolarization and do not increase the action potential duration. Signup and view all the answers

With regards to the myocardium, what subclass of Class 1 drugs will result in a slower myocardial depolarization, but not affect the action potential duration?

Class 1c drugs will slow down phase 0 depolarization but will have no effect on action potential duration. Signup and view all the answers

Given the effects of Class 1c anti-arrhythmic drugs on myocardial action potentials, how do you expect them to alter the EKG?

Class 1c drugs will slow down phase 0 depolarization, causing the QRS complex to widen while QT interval remains unchanged or only slightly changed. Signup and view all the answers

Given that Class 1 anti-arrhythmic drugs are sodium channel blockers, what conformational state do these drugs bind most strongly to the sodium channel?

Class 1 anti-arrhythmic drugs bind sodium channels strongest when they are activated or in their refractory periods. Signup and view all the answers

Explain why Procainamide increases repolarization time (increased action potential duration) if this drug is a sodium channel blocker associated with depolarization?

Procainamide has secondary blockade effects on potassium efflux channels, resulting in prolongation of phases 2 and 3 of myocardium and phase 3 of the nodes. Signup and view all the answers

Study Notes