Drugs Used in Cardiac Arrhythmias Flashcards
What cardiac structures are involved with the fast action potential?
1) Ventricular cardiomyocytes
2) Atrial cardiomyocytes
3) Purkinje fibers
What cardiac structures are involved with the slow (pacemaker) action potential?
1) SA node cells
2) AV node cells
What occurs during phase 0 of the fast action potential?
During phase 1?
Phase 2?
Phase 3?
Phase 4?
0) Na+ channels open due to depolarization and Na+ enters the cells
1) K+ exits cells
2) Plateau phase results from K+ exiting cells offset by and Ca2+ entering
3) Ca2+ channels close and K+ begins to exit more rapidly resulting in repolarization
4) Resting membrane potential is gradually restored by Na+/K+ ATPase and the Na+/Ca2+ exchanger
What occurs during phase 4 of the slow (pacemaker) action potential?
During phase 0?
Phase 3?
4) Slow spontaneous depolarization via T-type Ca2+ channels
0) Upstroke of Action Potential via L-type Ca2+ channels
3) Repolarization by inactivation of calcium channels with increased K+ efflux
What are the functions of the class 1A drugs?
1) Block sodium channels
2) Block potassium channels
What are the class 1A drugs?
1) Quinidine
2) Procainamide
3) Disopyramide
Procainamide has what effect on the SA and AV nodes?
What is its clinical use?
What adverse effect is noted with it?
1) Depresses their activity
2) Sustained ventricular tachycardias and arrhythmias associated with myocardial infarction
3) Lupus related side effects
Both Quinidine and disopyramide have what effect on the heart?
What is the clinical use of disopyramide?
1) Antimuscarinic effect
2) Recurrent ventricular arrhythmias
What adverse effect is seen with the class 1A drugs?
QT interval prolongation and induction of torsade de pointes arrhythmia and syncope
What is the functions of the class 1B drugs?
Block sodium channels
Why do class 1B drugs not prolong action potential or QT duration on ECG liek class 1B drugs do?
They do not block potassium channels
What are the class 1B drugs?
1) Lidocaine
2) Mexiletine
What is the clinical use of lidocaine?
What is the route of administration?
1) Stop ventricular tachycardia from acute MI
2) IV
What is the clinical use of Mexiletine?
What is the route of administration?
1) Ventricular arrhythmias
2) Oral
What are the functions of the class 1C drugs?
1) Block sodium channels
2) Block certain potassium channels
What are the class 1C drugs?
1) Flecainide
2) Propafenone
What are the clinical uses of flecainide?
1) In patients with normal hearts who have supraventricular arrhythmias
2) Refractory ventricular arrhythmias that are life threatening
What are the clinical uses of propafenone?
How is its effect on beta-blocking?
1) Supraventricular arrhythmias in patients without structural disease
2) Weak
What adverse effect is seen with the class 1C drugs?
Exacerbation of ventricular arrhythmias
Beta-Blockers (Class 2 drugs) have what effect on the pacemaker action potential?
1) Decreased slope due to effects on If (funny current) and T-type Ca channels
2) Increased threshold potential due to
effect on L-type Ca channels
Beta blockers have what effect on the SA node?
On the AV node?
1) Decrease HR and increase RR interval
2) Decrease AV conduction and increase PR interval