Antiarrhythmic Agents (Chapter 45)

Flashcards covering mechanisms, classes, drug examples, uses, contraindications, adverse effects, and special notes from lecture notes.

What is the primary action of antiarrhythmic agents on cardiac cells?

They affect the action potential by altering automaticity, conductivity, or both, and can be proarrhythmic.

How are antiarrhythmics classified by mechanism in this course?

Class 0 (HCN blockers), Class I (sodium channel blockers), Class II (beta-adrenergic/ANS), Class III (potassium channel blockers), Class IV (calcium channel blockers).

Which drug class targets HCN channels and is mentioned as Class 0?

Ivabradine (Corlanor).

Name the four Class I subclasses and an example drug from each.

Ia: disopyramide, procainamide, quinidine; Ib: lidocaine, mexiletine; Ic: flecainide, propafenone; Id: ranolazine.

What is the primary electrophysiologic effect of Class Ia agents on the action potential?

Depress phase 0 and prolong duration.

What is the primary electrophysiologic effect of Class Ib agents on the action potential?

Depress phase 0 somewhat and shorten duration.

What is the primary electrophysiologic effect of Class Ic agents on the action potential?

Markedly depress phase 0 with little effect on duration.

What is the clinical use of Class I antiarrhythmics?

Used to treat potentially life-threatening ventricular arrhythmias.

List major contraindications for Class I antiarrhythmics.

Bradycardia, heart block (unless pacemaker), hypotension/shock, heart failure.

Name common CNS and GI adverse effects of Class I antiarrhythmics.

CNS: dizziness, fatigue, slurred speech; GI: N/V, changes in taste.

What is a key digoxin interaction with Class I agents?

Quinidine can increase digoxin toxicity; monitor closely when combined.

How can cimetidine affect Class I agents?

Class 1a serum levels may increase, raising toxicity risk.

Which interaction increases bleeding risk with Class I agents?

Increased risk of bleeding if combined with warfarin.

What dietary consideration is important with quinidine excretion?

Quinidine requires acidic urine; avoid urine-alkalinizing foods and grapefruit juice due to interactions.

Name the Class II antiarrhythmic drugs (beta-blockers) listed.

Acebutolol, Esmolol, Propranolol.

Besides beta-blockers, which other ANS drugs are discussed in Class II?

Digoxin (muscarinic receptor agonist), Atropine (muscarinic receptor antagonist), Adenosine (activates adenosine receptors).

What are the uses and actions of beta-blockers in arrhythmias?

Uses: rapid A-fib, A-flutter, PSVT, HTN, angina, PVC, VTach. Actions: decreased HR, decreased excitability, decreased CO, slowed AV nodal conduction, decreased renin.

How does digoxin affect atrial arrhythmias?

Increases force of contraction, increases CO and renal perfusion, slows HR, decreases AV nodal conduction.

What is the role of atropine in Class II discussions?

Muscarinic receptor inhibitor/anticholinergic; used for bradycardia and other AV conduction issues.

What is the mechanism and use of adenosine in arrhythmias?

Activates adenosine receptors in SA/AV nodes; used to convert SVT to SR when vagal maneuvers fail; rapid IV dosing and monitoring required.

What are Class III antiarrhythmics?

Potassium channel blockers: Amiodarone, Dofetilide, Dronedarone, Ibutilide, Sotalol.

What are the key uses and cautions for Class III agents?

Uses: life-threatening ventricular arrhythmias; ACLS use for amiodarone; maintenance of symptomatic A-fib/A-flutter. They are proarrhythmic and have significant drug interactions (e.g., with digoxin, quinidine; antihistamines can raise proarrhythmia risk). No contraindications in life-threatening VT when other options fail.

What is unique about amiodarone among Class III agents?

Amiodarone is also a non-selective adrenergic blocker; can cause hypotension and bradycardia.

Which drugs are included in Class III and commonly referenced for acute conversion?

Ibutilide and Sotalol (within Class III potassium channel blockers).

What are Class IV antiarrhythmics and which drugs are in this class?

Calcium channel blockers: Diltiazem and Verapamil.

What is the mechanism and effect of Class IV agents on the cardiac action potential?

Block calcium movement, depress generation, delay phase 1 and 2 of repolarization; slow automaticity and conduction.

What are the uses and adverse effects of Class IV agents?

Uses: A-fib, A-flutter, PSVT; also HTN and angina. Side effects: decreased BP, negative inotropy, dizziness, fatigue, depression, headache, GI effects.

What note is given about magnesium sulfate in relation to antiarrhythmics?

Magnesium sulfate is a calcium channel antagonist; used as treatment of torsades de pointes, not a Class IV antiarrhythmic.

What contrast is made between dihydropyridines and non-dihydropyridines in BP management vs arrhythmias?

Dihydropyridines are used for BP; non-dihydropyridines (e.g., diltiazem, verapamil) are used for arrhythmias.

What is ranolazine's classification and primary use?

Class Id agent; used for angina (not a typical antiarrhythmic; discussed in Chapter 46).