Arrhythmics Flashcards
Pathway of a heartbeat
- SA node
- R/L atria - atria contract
- AV node
- Bundle of His > ventricles
- right bundle branch
- left bundle branch
purkinje fibers
Arrthymia is caused
by a disruption somewhere in the conduction system:
-SA node can be firing at an abnormal rate or rhythm
-Scar tissue from a prior MI
another part of the heart may be acting like a pacemaker
Phase 0
rapid ventricular depolarization
-influx of Na = ventricular contraction (represented by the QRS)
Phase 1
early rapid repolarization
-Na channels close
Phase 2
influx of Ca and efflux of K
Phase 3
rapid ventricular repolarization
efflux of K = ventricular relaxation (T wave)
Phase 4
resting membrane potential is established
atrial depolarization occurs (represented by P wave)
QT prolonging drugs: antiarrhythmics
class Ia, Ic, III
QT prolonging drugs: anti-infectives
antimalarials, azole antifungals (all except Cresemba), macrolides, quinolones, lefamulin
QT prolonging drugs: antidepressants
SSRIs (escitalopram and citalopram), TCAs, mirtazapine, trazodone, venlafaxine
QT prolonging drugs: antimetics
5-HT3 receptor antagonists, droperidol, metoclopramide, promethazine
QT prolonging drugs: antipsychotics
1st gen (haldol, chlorpromazine, thioridazine)
second gen (ziprasidone)
QT prolonging drugs: oncology medications
ADT (leuprolide)
TKI (nilotinib)
Oxaliplatin
QT prolonging drugs: other
cilostazol, donepezil, fingolimod, hydroxyzine, loperamide, methadone, ranolazine, solifenacin, tacrolimus
Class I
Disopyramide, Quinidine, Procainamide
-pro-arrhythmic
Class Ib
Lidocaine, Mexiletine
-pro-arrhythmic
Class Ic
flecainide, propafenone
-pro-arrhythmic
Class II
BB
-slow ventricular rate in AF
Class III
dronedarone, dofetilide, sotalol, ibutilide, amiodarone
Class IV
Verapamil, diltiazem
Way to remember classes of antiarrthymics
Double Quarter Pounder
Lettuce Mayo
Fries Please!
Because
Dieting During Stress is always
Very Difficult
Class I: Na channel blockers
proarrhythmic
Class II: BB
slow ventricular rate in AF
Class III: K channel blockers
-amiodarone and dronedarone block K channels, Ca channels, Na channels, and alpha- and beta-adrenergic receptors
-amiodarone and dofetilide are used for AF in patients with HF
Class IV: Ca-channel blockers, non-DHP
slow ventricular rate - DO NOT USE IN PATIENTS WITH HFREF
Digoxin
Na-K-ATPase blocjer
-decrease HR by enhancing vagal tone and positive iontropy
Adenosine
activates adenosine receptors to decrease AV node conduction
-used for paroxysmal SVT
Valvular AF
AF with moderate to severe mitral stenosis or with mechanical heart valve; long-term anticoagulation with warfarin is indicated
Non-valvular
AF without moderate to severe mitral stenosis or mechanical heart valve `
Goal resting HR in those with symptomatic AF
<80 BPM
Goal for resting HR for those with asymptomatic AF
< 110 BPM
Rate control
BB or Non-DHP CCBs (sometimes digoxin in patients with refractory or those who cannot tolerate first line agents)
Rhythm control
-restore and maintaine NSR
-Class Ia, Ic, or III drug or cardioconversion (must be anti-coagulated before cardioconversion)
-if AF is permanent, avoid rhythm-control strategy
Stroke ppx
-NOACs are preferred over warfarin for stroke prevention in non-valvular AF
-warfarin is indicated for stroke prevention in patients with AF and a mechanical heart valve
Amiodarone safety
-pulmonary toxicity
-hepatotoxicity
-iodine hypersensitivity
-Hyper/hypo thyroidism
-optic neuropathy
-photosensitivity (slate blue skin discoloration)
-peripheral neuropathy
Amiodarone induced thyroid disorder
inhibits peripheral conversion of T4 to T3
Amiodarone infusion
infusions > 2 hours require a non-PVC container (polyolefin or glass); PVC tubing is okay
-use 0.22 micron filter, central line preferable
-incompatible with heparin (flush line with saline); many Y-site additive incompatibilities
Amiodarone and digoxin
decrease digoxin dose by 50%
Amiodarone and Warfarin
decrease dose by 30-50%
Amiodarone and simvastatin and lovastatin
20 mg TDD of simvastatin and 40 mg TDD of lovastatin
amiodarone and sofosbuvir
increases the bradycardiac effect of amiodarone - do not use together
Digoxin range for AF
0.8-2 ng/mL
when to draw digoxin levels
12-24 hrs after dose
digoxin antidote
Digifab
What disorders increase the risk of digoxin toxicity
Hypokalemia, hypomagnesemia, and hypercalcemia
disopyramide
anticholinergic (myasthenia gravis)
Quinidine
take with food or milk
-hemolysis (G6PD deficiency)
-DILE
-Cinchonism - tinnitus, hearing loss, blurred vision, headache, delirium
Procainamide
-injection
-active metabolite NAPA and is renally cleared
-therapeutic level: 4-10 mcg/mL
-boxed warning: agranulocytosis, antinuclear antibody (ANA) that leads to DILE
-acetylation leading to drug accumulation and toxicity
Lidocaine
-injection
-refractory VT/cardiac arrest
Flecainide
do not use in HF or MI
Propafenone
do not use in HF or MI
-metallic taste
Dronedarone (Multaq)
-increased risk of death, stroke and HF in patients with decompensated HF or permanent AF
-Do not use strong CYP3A4 inhibitors and QT prolonging drugs
-hepatic failure, pulmonary disease,
-does not contain iodine and has little effect on thyroid
Sotalol (Betapace AF, Betapace, Sotylize Sorine)
-CrCl < 60 mL change the frequency and adjust dosing to CrCl
