University:
University of North Carolina at Chapel Hill
Course:
NURS 312 | Pharmacology
Academic year:

2020
Views:

441

Pages:

1
Author:

rehinhea0c

4.2 – “β Bras Brasss Quartet”: Class II Antiarrhythmics - β Physiology of SA SA/AV /AV node • SNS activation of β receptors increases cAMP activity, with multiple effects (Band camp poster) o ↑SA node automaticity by increasing pacemaker current causing ↑HR o increases conduction velocity though the AV node. • SA/AV nodal action potential o Funny current, dominated by Na+, is the pacemaker current (flat keys). o Phase 0: Upstroke. Ca dominated. o Phase 3: repolarization. K+ dominated. o Phase 4: depolarization. Ca-dominated. β blockers ((Beta Beta jazz clu club b with Louis Heartstrong & Beta Fitzger Fitzgerald; ald; muted bugle) • Include o A-BEAM cardioselective antagonists: Atenolol, betaxolol, Esmolol, Acebutolol, Metoprolol o nonselective propranolol & timolol o carvedilol & others that have partial α antagonist effects. • MOA: o prevent arrhythmia-promoting action of β action (rather than directly modifying ion channel function). Inactivation leads to closure of membrane Ca-channels (crushed ice-cream cartons). β blockers prolong depolarization in phase 4 (β is extending flat stretch of keys). o AV nodal conduction time & effective refractory period is especially prolonged by βblockers (disconnected heart light represents “disconnect” at AV node) • Indications: o Especially helpful in treating supraventricular arrhythmias (upper half of heart lit up) ▪ Include a-fib with RVR, a-fib, atrial flutter (TV screen) ▪ Particularly useful for controlling ventricular rate (metronome) ▪ note that the first goal of a-fib treatment is rate control, then rhythm, so as to prevent ventricular tachycardia o Can be given IV to treat intraoperative acute arrhythmias (Ivy) • Side effects/toxicity o Can potentially cause heart block d/t ↓AV conduction, and serious arrhythmias especially with other medications that affect AV conduction (hat shielding heart) o Heart block manifests as a prolonged PR interval on ECG (PR guy)