Antidysrhythmics Flashcards
Automaticity (vocab)
Heart’s ability to generate an electrical impulse.
Conductivity (vocab)
Ability of cardiac tissue to transmit electrical impulses.
Cardiac Action Potential (Patho)
Action potentials are generated by movement of ions into and out of the cell
Two types of action potentials in the heart:
Fast
Myocardium and His-Purkinje system
Conduct electricity quickly through the heart
Slow
SA and AV nodes
Differences in which ions impact each phase of the action potential
Formation of dysrhythmias (Patho)
Disturbances of automaticity
Cells other than the SA node depolarize and initiate an electrical impulse which causes a contraction
Can result in:
Tachydysrhythmias
Bradydysrhythmias
Area creating these impulses is called ectopic
Disturbances of conduction
Changes in electrical flow through the normal pathway in the heart
Can result in:
Atrioventricular block
Reentry pathways
Ectopic (vocab)
When the heart either skips a beat or adds an extra beat
Common dysrhythmias
Type of dysrhythmia divided based on location:
Supraventricular
Ventricular
Ventricular dysrhythmias more dangerous
Treatment includes 2 phases:
Termination of the dysrhythmia acutely
Long-term suppression of the dysrhythmia
Supraventricular dysrhythmias
Different types:
Supraventricular tachycardia
Atrial fibrillation
Atrial flutter
Less dangerous than ventricular dysrhythmias
No in cardiac output
Dangerous if:
Electrical impulses cross the AV node
↑ ventricular rate
GOAL:
Decrease impulse transmission through the AV node to decrease ventricular rate
Supraventricular tachycardia
Tachydysrhytmias
HR:>150 beats/min
Intervention:
Valsalva: forceful attempted exhalation against a closed airway, usually done by closing one’s mouth and pinching one’s nose shut while expelling air out as if blowing up a balloon.
Cardio version: shock/cpr
Atrial Fibrillation
Tachydysrhytmia
No coordinated atrial contraction
Stroke risk
Intervention:
Cardio version
Drug therapy:
Adenosine
Class II or IV
Atrial Flutter
Tachydysrhythmia
Coordinated atrial contraction
Stroke risk
Intervention:
Cardio version
Class II or IV drugs
Anticoagulation
Ventricular Dysrhythmias
Sustained ventricular tachycardia
Ventricular fibrillation
Torsades de pointes
Dangerous because these impact cardiac pumping and cardiac output
GOAL:
Abolish the dysrhythmia
First-line therapy typically cardioversion
Drugs are second-line
Classification of antidysrhythmic drugs
4 major classes
Class I: Sodium Channel Blockers
Class II: Beta-blockers
Class III: Potassium Channel Blockers
Class IV: Calcium Channel Blockers
Other: digoxin and adenosine
General Principles of Antidysrhythmic Agents
All antidysrhythmic drugs can also cause dysrhythmias
Balance risk and benefit
Only use when benefit outweighs risk
Type of dysrhythmia is the patient experiencing
Phases of treatment
Long term treatment: Drug selection and evaluation
Minimizing risks
Start with low doses
Monitor drug levels if indicated
Class I: Sodium Channel Blockers
Drugs:
Class IA
Disopyramide
Quinidine
Procainamide
Class IB
Lidocaine
Mexiletine
Class IC
Flecainide
Propafenone
Acronym
Double
Quarter
Pounder
Lettuce
Mayo
Fries
Please
Class I: Sodium Channel Blockers
Effects are secondary to sodium channel blockade
↓ conduction velocity in the atria, ventricles and His-Purkinje system
Divided into 3 subtypes
Similar in action and structure to local anesthetics
Disopyramide (Class IA)
Indication:
Ventricular dysrhythmias
Route:
Oral
IV
Adverse effects:
Anticholingeric properties
Negative inotrope
Other:
Limited clinical application
Monitor: ECG
Only given PO
Quinidine (Class IA)
Indication :
Ventricular
Supraventricular dysrhythmias
Route:
Oral IV
Adverse effects:
Diarrhea
Cinchonism
Other:
Monitor: ECG, signs and symptoms of stroke
Procainamide (Class IA)
Indication :
Ventricular
Supraventricular dysrhythmias
Route:
Oral
IV
Adverse effect:
Systemic Lupus Erythematosus
Blood dyscrasias
Arterial embolism
Other:
Start with IV then transition to oral therapy
Monitor: ECG, signs and symptoms of stroke
Lidocaine (Class IB)
Indication:
Ventricular dysrhythmias
Route:
IV
Adverse effects:
CNS effects
Toxic doses:
Seizure
Respiratory arrest
Monitor:
Narrow therapeutic index
Drug levels
No effect on the ECG
Make sure you’re using the correct product!
Mexiletine (Class IB)
Route:
PO
Adverse effects:
Nausea/vomiting
Constipation
Tremor/seizures
Monitoring:
No effect on ECG
Decrease dose in liver impairment or failure
Flecainide (Class IC)
Indication:
Supraventricular dysrhythmias
Route:
PO
Adverse effects:
Nausea/vomiting
Dizziness
Blurred vision
Monitor:
VERY pro-dysrhythmic
Close attention to ECG
Increase mortality in post-MI patients with asymptomatic Vtach
Propafenone (Class IC)
Indication:
Supraventricular dysrhythmias
Route:
PO
Adverse effects:
Nausea/vomiting
Dizziness
Blurred vision
Monitor:
Pro-dysrhythmic (not as much as Flecainide)
Close attention to ECG
Has some beta-blocking properties, use in caution in pts with AV block
Class II Beta Blockers
Drugs Examples:
Propranolol
Acebutolol
Esmolol
Sotalol
Metoprolol
Labetalol
Bisoprolol
Carvedilol
Class II Beta Blockers (continued)
Many different beta-blockers
Only 4 approved for treating dysrhythmias
Physiologic effects:
↓ automaticity in SA node
↓ conduction velocity through AV node
↓ myocardial contractility
Indications:
Sinus tachycardia
Atrial fibrillation/flutte
