Anti-Arrhythmic Flashcards
4 ways of decreasing spontaneous activity
Decrease phase 4 slope
Increase threshold
Increased maximum diastolic potential (hyperpolarize)
Increase APD
2 ways of increasing refractoriness
Na channel blockers - shift voltage dependence of recovery - delay Na recovery
AP prolonging drug - extend ERP w/out interacting w/Na channels
State dependent blockade
block fast inward Na channels when in open/inactivated but not resting
MOA Class I agents
Block fast inward Na channels to varying degrees in conductive tissue Decrease Vmax Reduce automaticity delay conduction prolong ERP
Class 1a Na targets
open > inactive
dissociation in seconds
MOA Quinidine
moderate binding to Na = decrease Vmax
block K = increase APD
block alpha adrenergic = decrease BP
block M2 = increase HR
TX Quinidine
Mainly used in refractory pts to:
convert AF/AFl
prevent recurrence of AF
Treat life-threatening ventricular arrhythmias
Also atrial/ventricular arrhythmias (re-entrant SVT, VT)
AE Quinidine
N/V/D - most common
cinchonism
hypotension (adrenergic)
proarrhythmic - TdP (QT)
1a agents
Quinidine
Procainamide
Disopyramide
MOA Procainamide
block Na = slow conduction, automaticity, excitability of A/V/Purk
block K = prolong APD and refraactoriness
Quinidine vs Procainamide
Procainamide has little vagolytic activity and does not prolong QT as much
TX Procainamide
Life-threatening ventricular arrhythmias**
Ventricular arrhythmias immediately post MI
convert VT
Acute supraventricular:
Re-entrant SVT
A fib
A flutter w/WPW
Requires adequate time - not emergency
AE Procainamide
Arrhythmia aggravation TdP - contraindicated in long QT, HX of TdP, hypo-K heat block/sinus node dysfunction SLE like syndrome GI N/V - common Decrease kidney fx
1b Na channel
inactive»_space;» open
dissociate in under 1s
1b agents
Lidocaine
Mexiletine
MOA Lidocaine
block inactivated»_space; open Na = reduced Vmax
shorten AP
more effective in ischemic tissue
lower slop of phase 4 = lower threshold for excitability
slows ventricular rate
potentiates infranodal block
TX Lidocaine
Used to be first-line for ventricular arrhythmias (post MI)
Now - second choice for immediate life-threatening or symptomatic arrhythmias
Ineffective:
prophylaxis after MI
Atrial tissue
PKX Lidocaine
Extensive first pass - IV use
Multiple loading doses and maintenance infusion
AE Lidocaine
Rapid bolus: tinnitus, seizure
High dose: drowsy, confused, hallucination
CV decreased
1c agents
Propafenone
Flecainide
1c Na channels
Strongest binding to Na channels
O state
slow dissociation = strong effects on p0 depol
MOA Propafenone
strong inhibitor of Na channel
can inhibit B-adrenergic
structurally similar to propranolol
TX Propafenone
Ventricular arrhythmias in pts w/ no HD and preserved ventricular fx atrial arrhythmias (Afib, PSVT)
MOA Flecainide
potent Na channel blockade = prolonged p0 + wide QRS
markedly slows intraventricular conduction**