Anti-Arrhythmics Flashcards
Class 1B
VT
- lidocaine - POST MI
- mexiletine - LONG QT
UP K+ out = shorter AP duration
Class 1C
VT»>SVT
- Flecainide =
- IF NO HX OF ISCHEMIC DZ
- RHYTHM CONTROL
STRONG Phase 0 block
NO POST MI
ATAXIA S.E>.
Class 1A
VT»>SVT (RHYTHM CONTROL)
- Quinidine = SUPPRESS AFIB (W/ BB/CCB)
- Procainamide
- Disopyramide
DOWN K+ out = AP duration longer
S.E = anticholinergic (quinidine more), Torsades de Pointe (long QT), lupus-like syndr, IN HOSPITAL ONLY
Class 3
K+
VT + SVT
*amiodarone, dronedarone
*Sotalol, ibutalide
Class 4
Ca2+ block in AV node(L type) (rate control)
SVT
*verapamil
*Diltiazem
- slow pacemaker current
- slow conduction velocity
- longer ERP
Careful CHF = less cardio muscle contract
Class 2
Beta (rate control)
SVT
*metoprolol
- DOWN AV NODE conduction
- DOWN excitability (ectopic pace)
Post MI reduce mortality
Other
SVT
- digoxin
- adenosine
Interfere with Na+ channels
Rx
- lidocaine, Mexiletine
- flecainide
- quinidine, procainamide, disopyramide
Cause long QT
- quinidine, procainamide, disopyramide
* Amiodarone, dronedarone, sotalol, ibutalide
Rhythm control
- flecainide
- quinidine, procainamide, disopyramide
- amiodarone, dronedarone, sotalol, ibutalide
Rate control
- Verapamil, diltaziem
- Metoprolol
- digoxin, adenosine
General concepts
- antiarrythmics = possibly pro-arrythmic
- dirty rx (synergistic, too many S.E.)
- Tx of CHOICE = procedure (not Rx)
- Tx tachs that are SYMPTOMATIC
Action potential duration
Start of AP to end
Refractory period duration =
Action potential duration
Sodium channels work best + recover quicker at
Depolarized (-) state
Explain why RPD has no APs
Phase 0 Na+ voltage channels depolarizing
- Quick open/quick close
* Affect Velocity + ERP
Phase 2-3 Ca++ in channel depolarizing
- slow open/close
* affects AP duration
Just VT
Rx
Lidocaine, mexiletine
VT»>SVT
Rx
- Flecainide
- Quinidine
- Procainamide, disopyramide
VT + SVT
- Amiodarone, dronedarone
* Sotalol, Ibutalide
SVT
Rx
- Verapamil, Diltiazem
- metoprolol
- digoxin, adenosine
Phase 2-3 K+ (TEA) out channel repolarizing
- delayed rectifier
* affects AP duration
Phase 4 Na+ in channels depolarizing
- pacemaker
* affects heart rate (automaticity)
Phase 4 (3Na+ out/2K+ in) polarizing
- Defines RMP
* indirectly affects Ca++ out
Myocardium
What initatiates AP?
Na+ current starts AP
CCB doesnt’ affect
Pacemaker
What channel during AP?
Only Ca+ channel during AP
CCB affects nodes
QRS starts when
Depole ventricle starts (not purkinje)
PR interval from
Atrial depole to start of apex ventricle depole
Index of conduction velocity + AV node delay
QRS duration
- index of conduction velocity
* Duration of ventricular AP
Flutter
*organized tach (regular space b/w waves)
Fibrillation
Disorganized tach (uneven spacing)
CHD
What is
- regional hypoxia
* less depole = UP refractory period
Myocardium blood flow
Epi to endocardium
Endocardium MOST AT RISK for ischemia (ventricle, not for thin atria = less atrial reentry circuits)
Requirements for Reentry
- multiple conduction pathways
- refractory (late) tissue
- conduction time around circuit must be longer than late-refraction on late tissue
Ectopic pacemakers
- usually atrial
- faster than Sa node
- pulm vein
- fastest ectopic takes over rhythm
- AV node brakes signal (max 250bpm)
Rate control in Afib
- screw p wave = won’t be normal
- A-fib remains, a-fib conduction slowed
- metoprolol
- verapamil
- digoxin
Rhythm control in A-fib
Want normal P wave, abolish a-fib
*Rx/cardioversion
*amiodarone, flecainide
A-fib
Rate vs. Rhythm control
Either acceptable
A-fib
Anti-coag therapy
NOT ESSENTIAL IN EVERYONE
2+ CHA2DS2-VASc = high stroke risk, consider anti-coag
Goals of tachyarrythmia Rx therapy
- DOWN automaticity
- DOWN conduction velocity AV node (PR interval, QRS duration UP)
- UP AP duration (UP QT duration)
- interfere w/ Sympa regulation of HR at SA/AV nodes
Class 1 Na+ channel Rx
VT
*lidocaine, mexiletine
VT»>SVT
- Flecainide
- Quinidine, Procainamide, disopyramide
Class 1 Na+ channel drugs
Selectivity
- only block fraction of Na+ channels
- Channel must be open
- more selective for “diseased” tissue (unactivated state)
Class 1 Na+ channel Rx
Mech + ECG
- LESS activated channel
- LESS Na+ in
- LESS conduction velocity
- UP ERP (refractory period) = longer than AP, longer to reset
ECG: Longer PR + QRS
(Use to monitor efficacy/toxicity)
Class 1 Na channel Rx
Ectopic pacemakers
Make less excitable
Class 1 Na+ channel Rx
Reentry
Up ERP
- ERP now longer than conduction time around circuit = stops reentry
- reentries are predominantly ventricular
Class 1 Na+ effects
- block Open (activated) states
- UP ERP/recovery
- Ectopic pacemakers
- block reentry (UP erp)
Class 1 Na+ channel blocker
Prolongation of ERP comparison
1C > 1A > 1B
Inherited Long QT syndrome
Class 1A contraindicated
= Torsades de Pointes tach
Mutations:
- Rectifying K+ channel = tx metoprolol
- Na+ channel = mexiletine (1B)
WATCH giving RX with long qt side effect
Amiodarone
Class 3
*block K+ efflux (phase 3), LONG AP DURATION + REFRACTORY PERIOD
- Low dose = A-fib (rhythm control)
- High dose = VT (structurally abnormal hearts (post-MI))
Amiodarone
S.E.
Rhabdomyolysis, long qt, pulm fibrosis
BITCH
- B radycardia/Blue Man
- I nterstitial Lung Dz
- T hyroid (hyper/hypo)
- C orneal/Cutaneous (blue)
- H epatic/Hypotension (IV-solvents)
Sotalol
Class 3 = SVT + VT
- Block K+ Phase 3
- Longer AP Duration
Reduce repeated arrythmia (now amiodarone)
Ibutalide (semi-not important)
Class 3
Block K+ efflux, Long AP duration
ACUTE CARDIOVERSION SVT
Vtach after MI
Acute
Chronic
Acute = amiodarone, DC cardioversion
Chronic = ICD w/ or w/o amiodarone
Vfib
Acute crhonic
Acute= Defib
Chronic = ICD w/ or w/o amiodarone
Contraindicated in WPW
Rate control Rx. (Down AV conduction)
DIgoxin
Good choice w/ CHF
- Up vagal activity
- Long refractory period
- Down AV conduction
Adenosine
Down AV node conduction
IV
T1/2 = seconds
AV-node dependent narrow complex tach (TX + DX acute)
Afib / A tach
Acute
Chronic
CONTROL V RATE ACUTE/CHRONIC= *Verapamil/diltiazem *BBlocker *digoxin
RESTORE SINUS RHYTHM: ACUTE= *Defib *ibutilide CHRONIC= *Amiodarone
A flutter
Acute
Chronic
CONTROL V RATE ACUTE: *Verapamil/diltiazem *Beta-blocker *Digoxin CHRONIC: *ablation
RESTORE SINUS RHYTHM
*Defib/Ibutilide
