Arrhythmias Flashcards
What are 3 causes of a disruption in conduction system leading to arrhythmia?
- SA node can be firing at an abnormal rate or rhythm
- Scar tissue from a prior heart attack can block and divert signal transmission (most common cause of arrhythmias)
- Another part of the heart may be acting as the pacemaker
What is the order of the conduction pathway?
- SA node
- Impulse travels from SA node to R and L atria, which causes atria to contract
- AV node
- Bundle of His
- Bundle of His divides into the right bundle branch for the right ventricle and the left bundle branch for the left ventifcle
- Signal spreads through ventricles via the Purkinje fibers, which causes ventricles to contract
What are the phases (0-4) of the cardiac action potential?
Phase 0: Influx of sodium, causing heartbeat to be initiated when rapid ventricular depolarization occurs. This causes ventricular contraction (QRS of ECG)
Phase 1: sodium channels close, leading to early rapid repolarization
Phase 2: influx of calcium and efflux of potassium, causing a plateau
Phase 3: Efflux of potassium, leading to rapid ventricular repolarization. This causes ventricular relaxation (T wave on ECG)
Phase 4: resting membrane potential is established, so atrial depolarization occurs (P wave on ECG)
What classes of antiarrhythmics can prolong QT interval?
Class Ia, Ic, and III
What classes of anti-infectives can prolong QT interval? (5)
antimalarials (ex. hydroxychloroquine)
azoles (all except isavuconazonium)
macrolides
quinolones
lefamulin
What classes/drugs of antidepressants can prolong QT interval? (5)
SSRIs (especially citalopram and escitalopram)
tricyclic antidepressants
mirtazapine
trazodone
venlafaxine
(sertraline is preferred)
What classes/drugs of antiemetics can prolong QT interval? (4)
5-HT3 receptor antagonists (ex. ondansetron)
droperidol
metoclopramide
promethazine
What classes of antipsychotics can prolong QT interval?
1st gen (haloperidol, chlorpromazine, thioridazine)
2nd gen (highest risk with ziprasidone)
What classes/drugs of oncology meds can prolong QT interval? (3)
androgen deprivation therapy (ex. leuprolide)
tyrosine kinase inhibitors (ex. nilotinib)
arsenic trioxide
What are 8 other medications that can prolong QT interval? (CDFHLMRS)
cilostazol
donepezil
fingolimod
hydroxyzine
loperamide
methadone
ranolazine
solifenacin
What drugs are Class I antiarrhythmics? (sodium channel blockers)
Ia (3) Double Quarter Pounder
Ib (2) Lettuce Mayo
Ic (2) Fries Please
1a:
- disopyramide
- quinidine
- procainamide
1b:
- lidocaine
- mexiletine
1c:
- flecanide
- propafenone
What drug class are Class II antiarrhythmics? (1)
beta-blockers
What drugs are Class III antiarrhythmics? (potassium channel blockers, 5)
Dieting
During
Stress
Is
Always
dronedarone
dofetilide
sotalol
ibutilide
amiodarone
What drugs are Class IV antiarrhythmics? (non-dihydropyridine CCBs, 2)
Very
Difficult
verapamil
diltiazem
Amiodarone - MOA, half life, boxed warnings (3), contraindications, other warnings (4), side effects (3), monitoring, IV notes (4)
MOA - class III antiarrhythmic, so K channel blocker. Also Na and Ca channel blocker. Also alpha and beta adrenergic receptor blocker.
Half life - 40-60 days
Boxed warnings
- pulmonary toxicity
- hepatotoxicity
- proarrhythmic
Contraindications - iodine hypersensitivity
Warnings
- hyper and hypothyroidism (usually hypo)
- visual impairment (optic neuropathy, corneal microdeposits)
- photosensitivity
- neurotoxicity (neuropathy)
Side effects
- hypotension
- bradycardia (may require decreased infusion rate)
- photosensitivity
Monitoring
- ECG, BP, HR, electrolytes
- LFTs every 6 months, thyroid function every 6 months, CXR every 3-6 months, regular eye exams
IV Notes
- Requires non-PVC container
- There are premixed IV bags, like Nexterone, that comes in a non-PVC, non-DEHP container
- Use 0.22 micron filter, central line preferable
- Incompatible with heparin
amiodarone is the drug of choice in heart failure
What adjustments need to be made when starting amiodarone if the patient is already on digoxin, warfarin, or simvastatin/lovastatin?
What drug can enhance the bradycardic effect of amiodarone so they should NOT be used together?
amiodarone has many drug interactions (weak inhibitor of CYP2C9/2D6/3A4, and pgp
Digoxin: decrease by 50%
Warfarin: decrease by 30-50%
Simvastatin: do not exceed 20mg/day
Lovastatin: do not exceed 40mg/day
DO NOT USE SOFOSBUVIR WITH AMIODARONE DUE TO BRADYCARDIA
What is the main side effect of disopyramide (class Ia)?
anticholinergic effects
What is an administration counseling point for quinidine (class Ia)? What are the warnings and side effects of quinidine?
Administration: take with food
Warnings
- hemolysis risk (avoid in G6Pd deficiency)
- can cause positive Coombs test
Side effects
- drug-induced lupus erythematosus
- diarrhea
- stomach cramping
- cinchonism (tinnitus, hearing loss, blurred vision, headache, delirium)
What is the formulation of procainamide (class Ia)? What is important about its metabolism? What is the goal therapeutic level? What are the boxed warnings (2) and notes (1)?
Metabolism
- has active metabolite (N-acetyl procainamide, NAPA)
- renally cleared (so consider dose reduction if necessary)
TDM: goal 4-10mcg/mL
Boxed warnings
- agranulocytosis
- long term use can lead to antinuclear antibody (ANA) -> can result in DILE (drug induced lupus erythematosis)
Notes
- metabolism to NAPA occurs by acetylation, so slow acetylators are at risk of drug accumulation and toxicity
What arrhythmias are class 1b drugs useful for?
only useful in ventricular arrhythmias (no efficacy in AF)
(lidocaine, mexiletine)
What are the boxed warnings (1) and contraindications (2) for flecainide (class Ic)?
Boxed warnings
- proarrhythmic effects, especially in AF (don’t use in chronic AF)
Contraindications
- Heart failure
- Myocardial infarction
What are the contraindications (2) and unique side effect (1) of propafenone (class Ic)?
Contraindications
- heart failure
- myocardial infarction
Side effect
- taste disturbances (metallic)
What are the boxed warnings (2), contraindications (1), warnings (2), and notes (2) for dronedarone (class III)
Boxed warnings
- contraindicated in decompensated HF due to increased risk of death, stroke, and HF
- contraindicated in permanent AF due to increased risk of death, stroke, and HF
Contraindications
- concurrent use of CYP3A4 inhibitors and QT prolonging drugs
Warnings
- hepatic failure
- pulmonary toxicity
Notes
- does not contain iodine, so has little effect on thyroid
- Avoid with strong inhibitors/inducers of CYP3A4 and drugs that prolong QT interval (adjust dose of digoxin, statins, and warfarin)
What are the boxed warnings (1) and note (1) for dofetilide (class III)
Boxed warnings
- Must be initiated in a setting with continuous ECG monitoring, experienced staff, and ability to assess CrCl for a minimum of 3 days due to QT prolongation
Notes
- One of the preferred antiarrhythmics in heart failure
