What is the mechanism of action of antiarrhythmic drugs?
Antiarrhythmic agents act by blocking the membrane sodium, potassium, and calcium channels, but no agent has exclusive action on a given type of channel. Arrhythmias resulting from reentry form the largest group of clinically significant arrhythmias.
What is the basic mechanism involved in arrhythmia?
The 3 main mechanisms responsible for cardiac arrhythmias are automaticity, triggered activity, and reentry.
What is the mechanism of action for medications prescribed to treat a rapid arrhythmia?
These drugs depress calcium-dependent action potentials in slow-channel tissues and thus decrease the rate of automaticity, slow conduction velocity, and prolong refractoriness. Heart rate is slowed, the PR interval is lengthened, and the AV node transmits rapid atrial depolarizations at a lower frequency.
What is the primary mechanism of action of Class 4 antiarrhythmic drugs?
Class IV agents are slow non-dihydropyridine calcium channel blockers. They decrease conduction through the AV node, and shorten phase two (the plateau) of the cardiac action potential. They thus reduce the contractility of the heart, so may be inappropriate in heart failure.
How does IB antiarrhythmics work?
Class IB antiarrhythmics suppress automaticity of conduction tissue by increasing the electrical stimulation threshold of the ventricle and His-Purkinje system and inhibiting spontaneous depolarization of the ventricles during diastole through a direct action on the tissues.
What are the different classes of antiarrhythmic drugs?
Overview
| Classes of antiarrhythmic drugs | ||
|---|---|---|
| Class | Examples | |
| Class I antiarrhythmics | Class IB antiarrhythmics | Lidocaine Mexiletine Phenytoin |
| Class IC antiarrhythmics | Flecainide Propafenone | |
| Class II antiarrhythmic drugs | Metoprolol Esmolol (short acting) Propranolol Atenolol Timolol Carvedilol Sotalol |
What are the mechanisms involved in the beating of the heart?
The impulse starts in a small bundle of specialized cells located in the right atrium, called the SA node. The electrical activity spreads through the walls of the atria and causes them to contract. This forces blood into the ventricles. The SA node sets the rate and rhythm of your heartbeat.
What are two mechanisms that give rise to tachycardia?
The three mechanisms responsible for tachycardia are 1) reentry, 2) enhanced automaticity, and 3) triggered activity. Electrocardiographic presentations of tachycardia are mechanism specific including its initiation, termination, and response to pacing maneuvers.
What are Class 3 antiarrhythmic drugs?
Class 3 antiarrhythmics are drugs that block cardiac tissue K channels. The medications in this class include amiodarone, dronedarone, sotalol, ibutilide, dofetilide, and bretylium. The main mechanism of action includes blocking the cardiac K channels to prolong repolarization.
What is the best treatment for irregular heartbeat?
Therapies to treat heart arrhythmias include vagal maneuvers and cardioversion to stop the irregular heartbeat.
- Vagal maneuvers. If you have a very fast heartbeat due to supraventricular tachycardia, your doctor may recommend this therapy.
- Cardioversion.
What is the main difference between Class 1A and Class 1C antiarrhythmic drugs?
Vaughan–Williams classification 1A: prolong the action potential. 1B: shorten the action potential. 1C: minimal effect on action potential duration.
What is the mechanism of action of amiodarone?
Amiodarone is a class III antiarrhythmic that blocks potassium channels. In acute therapy, most of its effects are due to its action as a sodium channel blocker, thereby reducing automaticity and conduction velocity in the ventricles.
What is reentry in cardiac arrhythmias?
Reentry occurs when a propagating impulse fails to die out after normal activation of the heart and persists to re-excite the heart after expiration of the refractory period. Evidence implicating reentry as a mechanism of cardiac arrhythmias stems back to the turn of the century.
What is the mechanism of action of antiarrhythmic agents?
Antiarrhythmic agents act by blocking the membrane sodium, potassium, and calcium channels, but no agent has exclusive action on a given type of channel. Arrhythmias resulting from reentry form the largest group of clinically significant arrhythmias.
What are the mechanisms of cardiac arrhythmias?
The mechanisms responsible for cardiac arrhythmias are generally divided into 2 major categories: (1) enhanced or abnormal impulse formation (ie, focal activity) and (2) conduction disturbances (ie, reentry) ( Fig. 1 ).
What determines whether reentrant arrhythmogenesis occurs?
Thus, both the conduction velocity (CV) and the refractory period determine whether reentrant arrhythmogenesis occurs. It is useful to describe this excitation as a propagating wave, with a wave front that represents action potential depolarization, and a tail that represents repolarization [40].