Antiarrhythmics Flashcards
FAST Cardiac AP
Cardiomyocyte (cardiac cells) action potential
FAST Cardiac AP
Phase 0
Rapid depolarization
Na+ channel opens → Na+ inward flow
FAST Cardiac AP
Phase 1
Begin repolarization
Na+ channel closes
FAST Cardiac AP
Phase 2
Plateau
Slow Ca2+ channels open → Ca2+ flows inward
Ø net ion movement
FAST Cardiac AP
Phase 3
Repolarization
Ca2+ channel close
K+ channel open → slow outward K+ efflux
FAST Cardiac AP
Phase 4
Pacemaker potential
Return to resting membrane potential
Diastole -90mV
SLOW Cardiac AP
Pacemaker action potential
SA/AV node
SLOW Cardiac AP
Phase 4
No resting membrane potential
Gradual depolarization
Slow inward Na+ & Ca2+ currents
Funny channels
SLOW Cardiac AP
Phase 0
Slower depolarization
Ca2+ mediated
Upstroke
Threshold -40mV
SLOW Cardiac AP
Phase 3
VGCa2+ channels close rapidly
↓Na+ permeability
↑K+ permeability → repolarization
Cardiac Pacemaker
SA node
NSR
Normal sinus rhythm
60-100bpm (70-80)
AV Node Conduction Rate
40-60bpm
Purkinje Fibers Intrinsic Rate
15-40bpm
Arrhythmia
Disturbance in the heart electrical activity
Atrial, junctional, or ventricular
When to intervene & treat arrhythmias?
Arrhythmias → cardiac dysfunction
↑demand ↓CO → hemodynamic compromise
Arrhythmia Types
Altered Automaticity
Latent pacemaker cells take over the SA node role → ectopic beats
Arrhythmia Types
Delayed After-Depolarization
Normal cardiac cell AP triggers abnormal depolarizations
Repetitive discharge or arrhythmias
Arrhythmia Types
Re-Entry
Refractory tissues reactivated repeatedly & rapidly d/t unidirectional block → causes abnormal continuous circuit
Arrhythmia Types
Conduction Block
Impulse fail to propagate in non-conducting tissues d/t ischemia, scarring, fibrosis (damaged tissue)
Non-Pharmacological Arrhythmia Treatments
Acute: - Vagal maneuvers - Cardioversion Prophylactic: - Radiofrequency catheter ablation - Implantable defibrillator Pacing - external, temporary, or permanent
Class I Antiarrhythmics
Phase 0 Na+ channel blockers → decreases AP propagation (depolarization rate) & slows conduction velocity
Sub-classes IA/B/C
Used to treat SVT, Afib, & Wolfe-Parkinson White
Class IA
Disopyramide (Norpace), Procainamide (ACLS), & Quinidine
Slow conduction velocity & pacemaker rate
Intermediate Na+ channel blocker (dissociation) ↓depolarization rate
Direct depressant effect on SA/AV node
↑AP duration
Used to treat atrial & ventricular arrhythmias
Class IA Prototype
Quinidine
No longer manufactured