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
What dose adjustment is there for sotalol (class III)? What are the boxed warnings (2), other warnings (1), side effects (1), and a note (1) for sotalol?
Dose adjustment: if CrCl < 60mL/min -> decrease frequency
Boxed warning
- Initiation in hospital due to risk of VT and QT prolongation
- Adjust dosing interval if CrCl is decreased due to risk of QT prolongation
Warnings
- bronchoconstriction
Side effects
- bradycardia
Notes
- sotalol is a non-selective beta-blocker
What is ibutilide (injection) indicated for?
Pharmacologic cardioversion
What are 2 notes about adenosine?
Notes
- half-life is < 10 seconds
- Used for supraventricular re-entrant tachycardias, aka PSVTs (not for ventricular tachycardia or converting AF)
What are the definitions of paroxysmal AF, persistent AF, and permanent AF?
Paroxysmal AF - Intermittent AF that terminates within 7 days of onset
Persistent AF - Continuous AF sustained for at least 7 days
Permanent AF - No further attempts at rhythm control
What are the HR goals for someone with symptomatic vs. asymptomatic AF? What drug classes are used in rate control?
Goal resting HR for symptomatic AF < 80 BPM
Asymptomatic and preserved LV function goal HR <110 BPM
Drugs:
- beta blockers
- non-DHP CCBs (not for HFrEF pts)
- digoxin can be added for refractory patients or if the pt cannot tolerate BP lowering of beta blockers/nonDHP CCBs
Digoxin - MOA, typical dose, when to adjust dose, therapeutic range for AF, what to monitor (3), toxicity symptoms (6), and what is the antidote?
MOA - Na-K-ATPase pump inhibitor, which causes a positive inotropic effect and enhances vagal tone to slow conduction through the AV node, resulting in a decreased HR.
Dose - 0.125-0.25mg PO daily
- decrease dose or frequency if CrCl < 60mL/min
- therapeutic range (AF): 0.8-2 ng/mL
Monitor: electrolytes, renal function, HR
Toxicity
- symptoms: N/V, loss of appetite, blurred/double vision, greenish-yellow halos, bradycardia, life-threatening arrhythmias
- increased risk of toxicity if hypokalemia, hypomagnesemia, or hypercalcemia
Antidote: DigiFab
What drug interactions do we need to worry about with digoxin?
Digoxin is a pgp substrate and minor CYP3A4 substrate
- so digoxin levels increase with pgp inhibitors (Ex. amiodarone, diltiazem, verapamil)
- decrease dose by 50% if given with concomitant amiodarone
When converting PO digoxin to IV digoxin, how much should you dose reduce?
The dose should be reduced 20-25% when converting digoxn from PO to IV
What are the options for rhythm control for A fib?
Cardioversion
Option 1. Electrical - shock, most effective
Option 2. Pharmacologic - amiodarone (PO or IV), dofetilide, flecainide, ibutilide, propafenone
**anticoagulation is usually required before and after successful cardioversion, regardless of CHADSVASc score.
- started 3 weeks prior to cardioversion
- continue for 4 weeks after cardioversion
