Arrhythmia Flashcards
What do class 1 drugs do?
- block Na channels
- as a result upward curve of AP is shifted to right
- slow conduction within cardiac tissue (phase 0)
What is the effect of class 2 drugs?
- beta blockers
- affects calcium inflow to heart
- slightly increases AP duration
- diminishes phase 4 depolarisation and automaticity
What is the effect of class 3 drugs?
- blocks K channels
- phase 3 and 4 occur later
- refractory period is extended
- so QT interval is extended
- increases action potential duration
- potential of causing pro-arrhythmia
What is the effect of class 4 drugs?
- calcium blockers
- decreases phase 4 spontaneous depolarization
- affects plateau phase of AP
- slows cardiac action potential
- changes slope of phase 0
- increases refractory period
- slows conduction
What drugs affect automaticity (ability of heart cells to spontaneously depolarize and generate AP)?
- B agonist
- muscarinic agonists
- adenosine
Procainamide
- rarely used
- decreased conduction (phase 0 decreased)
- increases refractory period (increases action potential duration)
- decreases automaticity (decreases slope of phase 4)
- increases threshold
- uses: acute IV treatment of supraventricular and ventricular arrhythmia
- lupus-like syndrome and other 1A side effects
Quinidine
- oral or IV
- same effects as procainamide
- has anticholinergic action to speed AV conduction used with digitalis, B blocker or Ca channel blocker
- effects on ECG: increased QRS and QT
- uses: maintain sinus rhythm in AF and atrial flutter and to prevent recurrence, Brugada syndrome
What are the side effects of class 1A drugs?
- rarely used
- hypotension, reduced CO
- proarrhythmia (ex. Torsades de Points)
- dizziness, confusion, insomnia, seizure (high dose)
- GI effects (common)
Lidocaine
- iv only
- affects phase 0 and conduction in fast beating or ischaemic tissue
- fast binding offset kinetics
- no change in phase 0 in normal tissue
- ADP slightly decreased in normal tissue
- increases threshold (Na)
Mexiletine
- given orally
- fast binding offset kinetics
- no changes in phase 0 in normal tissue
- decreases phase 0 conduction in fast beating or ischaemic tissue
- increases threshold (Na+)
- ADP slightly decreased in normal tissue
What are the uses,side effects, and effects on ECG of class 1B drugs?
- uses: acute ventricular tachycardia (esp. during ischaemia)
- not used in atrial arrhythmias or AV junction along arrhythmias
- side effects: less proarrhthymic than class 1A (less QT effect), CNS effects (dizziness, drowsiness), abd upset
- ECG effects: none in normal, in fast beating or ischaemic
- increases QRS width
Flecainide and propafenone (class 1C)
- oral or IV
- very slow binding offset kinetics
- substantially decrease phase 0 in normal tissue
- decreases in automaticity
- increase in APD and refractory period
Effects on ECG
-increase PR, QRS, QT
Uses
- wide spectrum
- used for atrial fibrillation and flutter
- premature ventricular contraction
- WPW
Side effects
- proarrhythmias and sudden death especially with chronic use and in structural heart disease
- increased ventricular response to atrial flutter
- CNS and GI effects like other local anesthetics
Propranolol
- oral or iv
- long-acting
- class 2
Bisoprolol
- class 2
- oral only
Metoprolol
- class 2
- 5mg IV or oral
- shorter acting
Esmolol
- class 2
- IV only
- very short acting
What are the cardiac effects, effects on ECG, uses and side effects of class 2 agents (propranolol, bisoprolol, metoprolol, and esmolol)
- increases APD and refractory period in AV node to slow AV conduction
- decreases phase 4 depolarisation
Effects on ECG
-increase PR and decreases HR
Uses
- treating sinus and catecholamine dependant tachycardia
- converting re-entrant arrhythmias at AV node
- protecting the ventricles from high atrial rates (slow AV conduction) in atrial flutter or atrial fibrillation
Side effects
- bronchospasm
- hypotension
- don’t use in partial AV block or acute heart failure
Amiodarone
- class 3
- oral or IV (central line because thrombophlebotic)
- half life is 3 months
Cardiac effects
- increases refractory period and APD
- decreases phase 0 and conduction
- increases threshold
- decreases phase 4 (B and Ca block)
- decreases speed of AV conduction
Effects on ECG
- increases PR, QRS and QT
- decreases HR
Uses
-very wide spectrum: effective for most arrhythmias especially ventricular tachycardia
Side effects
- very serious that increase with time
- pulmonary fibrosis
- hepatic injury
- increase LDL cholesterol
- thyroid disease
- photosensitivity
- optic neuritis (transient blindness)
- must look at benefit-to-risk ration
Sotalol
- class 3
- oral
Cardiac effects
- increased APD and refractory period in atrial and ventricular tissue
- slow phase 4 (B blocker)
- slow AV conduction
ECG effects
-increases QT and decreases HR
Uses
-wide spectrum: supraventricular and ventricular tachycardia
Side effects
-proarrhythmia, fatigue, insomnia
Describe class 4 agents (Verapamil and diltiazem)
- verapamil: oral or iv
- diltiazem: oral
Cardiac effects
- slow conduction through AV (Ca)
- increases refractory period in AV node
- increases slope of phase 4 in SA to slow HR
Effects on ECG
- increases PR
- increase or decrease HR depending on BP response and baroreflex
Uses
- control ventricles during supraventricular tachycardia
- converts supraventricular tachycardia (re-entry around AV)
Side effects
- caution when partial AV block is present, can get asystole from B blocker
- caution when hypotension, decreased CO or sick sinus
- some GI problems (constipation)
Adenosine
- rapid iv bolus, very short half-life
- natural nucleoside that binds A1 receptors and activates K+ currents in AV node and SA node
- decreases APD
- hyperpolarization causes decrease in HR
- decreased Ca currents and increased refractory period in AV node
- slows AV conduction
Uses
- converts re-entrant supraventricular arrhythmia s
- diagnosis of coronary artery disease (scans)
Vernakalant
- iv bolus over 10 min
- blocks atrial specific K+ channels (outward channel class 3)
- slows atrial conduction
- increases potency with higher heart rates
- used for termination of new onset AF
Side effects
- hypotension, AV block
- sneezing and taste disturbances
Uses
-convert recent onset AF to normal sinus rhythm
Ivabradine
- orally in 2.5mg bd dosing up to 10mg bd
- blocks If ion current highly expressed in sinus node
- slows the sinus node but doesn’t affect BP
Side effects
- flashing lights
- teratogenicity not known (avoid in pregnancy)
Uses
- reduce inappropriate sinus tachycardia
- reduce HR in heart failure and angina (avoid BP drops)
Digoxin (cardiac glycoside)
- enhances parasympathetic activity
- last resort drug
- slows AV conduction and slow HR
Uses
-treatment to reduce ventricular rates in AF and flutter
Atropine
- selective muscarinic antagonist
- block parasympathetic activity to speed AV conduction and increase HR
- treat parasympathetic bradycardia
- give pacemaker for a more long-term plan
Which drugs are used in AF?
- rate control (slow conduction through AV node to reduce heart back to normal levels): bisoprolol, verapamil, diltiazem, maybe digoxin
- rhythm control: sotalol, flecainide with bisoprolol, amiodarone
Which IV drug for VT?
- depends on what drugs already prescribed: metoprolol/bisoprolol, lidocaine/mexiletine, amiodarone
- IV metoprolol/lidocaine or amiodarone
Should flecainide be used alone in atrial flutter?
- no
- give AV nodal blocking drugs to reduce ventricular rates in atrial flutter
Best drug for treatment WPW?
- flecainide
- amiodarone
List drugs that could be used in re-entrant NCT?
- acutely IV: adenosine, verapamil, flecainide
- chronic (repeated episodes, orally): bisoprolol, verapamil, sotalol, flecainide, procainamide, amiodarone
Which drugs for ectopic beats?
- bisoprolol first line
- flecainide, sotalol or amiodarone
Which drugs to treat sinus tachycardia?
- ivabradine (no drop in BP)
- bisoprolol, verapamil
