Antiarrythmics Flashcards
Quinidine
Class IA
used for atrial, junctional AND ventricular arrhythmias …blocks both Na+ (giving moderately ↑QRS) and K+ (giving ↑QT)…given IV only…can produce an atropine-like muscarinic blockade, resulting in ↑AV conduction and worsening of SVTs (so not indicated for all atrial arrhythmias)…side effects = hypotension, torsades, insomnia, seizure, GI …potential drug-drug interaction with digoxin (both ↓K+ so combined create an ↑risk for hypoK+ - use ther. drug monitoring -TDM
Procainamide
Class IA
used for atrial, junctional AND ventricular arrhythmias …blocks both Na+ (giving moderately ↑QRS) and K+ (giving ↑QT)… given IV only… side
effects = hypotension, torsades, insomnia, seizure, GI PLUS lupus-like syndrome…TDM levels routinely reported w/ NAPA metabolite (it’s also cardioactive)
Lidocaine
Class IB
used ONLY for ventricular arrhythmias (ischemias) with little effect on atrial cells…blocks Na+ current only (resulting in slightly ↑QRS)…binds only briefly, meaning significant effects are seen only on sodium channels in ischemic tissues with no effect (no ↑QRS) on phase 0 in normal resting heart (drug is gone by the time near beat comes along) – this is referred to as frequency-dependent blockade meaning the higher the HR, the better its efficacy…given IV only due to high first-pass effect…side effects = dizziness, blurred vision, confusion, torsades (long-term)
Flecainide/Propafenone
Class IC
WIDE-SPECTURM used for conversion/stabilization of Afib/Aflutter, AV reentry PVC, ventricular tachyarrythmias, WPW…blocks Na+ and
K+ currents both, giving ↑QRS along with ↑QT…very slow binding offset kinetics, meaning huge decrease in phase 0 slope due to massive Na+ blocking and largely
↑QRS – this is referred to as tonic blockade because it stays on receptor from beat to beat…side effects = CNS/GI/pro-arrhythmic side effects seen with all local anesthetics, pro-arrhythmic quality more pronounced compared to other anti-arrhythmics (CAST study), hence why they are more indicated for converting patients out of acute episode then you wean them off…can be given PO or IV
Propranolol
Beta Blocker-class II used for sinus and catecholamine-dependent tachycardias, considered “first line” drug for post-MI prevention of arrhythmias…AT LEVEL OF AV NODE: ↑APD and Refractory period (by blocking K+ repolarization), ↓Phase 0 slope (by blocking Ca+ influx), and ↓phase 4 slope (by blocking If (funny) Na+ current), all of which slows AV conduction (giving ↑PR interval…will also see ↓HR)…propranolol give PO while esmolol MUST be given IV (very short half-life and is used acutely)…side effects = bronchospasm, hypotension, elevated blood glucose, DO NOT GIVE WITH CCBS OR DIGITALIS due to increased risk of AV block
Esmolol
Beta blocker-class II given IV, short half life (9 min), slow AV conduction to ↑PR, AT LEVEL OF AV NODE: ↑APD and Refractory period (by blocking K+ repolarization), ↓Phase 0 slope (by blocking Ca+ influx), and ↓phase 4 slope (by blocking If (funny) Na+ current), all of which slows AV conduction (giving ↑PR interval…will also see ↓HR)
Amiodarone/Dronedarone
WIDE SPECTRUM (#1 ACLS DRUG) used for Vfib, VTach (drug of choice for these), atrial arrhythmia conversion to sinus…ONE OF THE VERY FEW ANTIARRYTHMICS THAT CAN BE USED IN HEART FAILURE PATIENTS…blocks Ca+ (giving ↓phase 4 SAP slope - ↓HR), Na+ (giving ↓Phase 0 FAP slope - ↑QRS), K+ (giving ↑ADP and refractory period - ↑QT), and Beta receptors (works as BB - ↓HR) - the only receptor it doesn’t work on is alpha receptors – put into Class III category but it actually blocks a lot of things…can be given PO, 3 month half-life…side effects = thyroid disease (structurally similar to iodine), pulmonary fibrosis, hepatic injury, blue skin, Dronederone can cause torsades
Ibutilide
used for conversion of AFib or AFlutter but generally not given once patient is stable/longterm (given as rapid IV infusion)…pure Ikr channel blocker which only exists in the heart – net result is ↑APD and ↑QT….once patient is converted, they are placed on dofetilide…side effects = torsades
Dofetilide
given oral (vs. IV-infusion of Ibutilide) but first 5 doses given in hospital …also works by purely blocking Ikr channel, leading to ↑APD and ↑QT…used for maintenance of sinus rhythm after Ibutilide stabilization…higher risk of torsades than ibutilide
Verapamil/Diltiazem
blocks Ca2+ L-type channels (decreased slope of phase 0 and slowing AV conduction – gives ↑PR interval), K+ current (giving ↑refractory period in AV node) and Ca2+ L-type channels to ↓phase 4 slope in SA node (gives ↓HR)…can technically be used interchangeably with Beta-blockers, used to control ventricles during atrial arrhythmias, convert supraventricular tachycardia (reentry AV node) and prevent recurrence (i.e. post MI)…verapramil can be given PO or IV while diltiazem given IV only…side effects = AV block when given on top of Beta-blocker or existing partial AV block, hypotension leading to reflex tachycardia, some GI problems
Adenosine
activates K+ currents in SA and AV node, leading to massive hyperpolarization and ↓HR (vagal stimulation/ACh has essentially the same
effect)…given via rapid IV infusion and has very short half-life (used only acutely in ER setting)…extremely effective in abolishing AV nodal arrhythmias (i.e. PSVTs) –
this is a conversion drug, essentially a chemical version of cardioversion…if the drug doesn’t work, then arrhythmia is ventricular in origin
Digioxin
cardiac glycoside (can also be used in heart failure)…enhances vagal activity leading to ↑K+ repolarization, ↓Ca2+ current, and ↑refractory period…similar to adenosine/Beta blockers/Ca2+ blockers, it slows AV conduction and slows HR…used to treat AFib and AFlutter
Atropine
selective muscarinic antagonist, blocking vagal activity to speed AV conduction and increase HR…used to treat vagal bradycardia (i.e. the more severe
AV blocks)
Magnesium
given IV in patients who have gone into Torsades before any other anti-arrhythmic is given (ACLS)
DC (Synchronized) Cardioversion
TREATMENT OF CHOICE for any patient who has UNSTABLE arrhythmias (VTach, VFib) – always done BEFORE any
pharmacotherapy is given
