Arrhythmias atrial, treatment

The cardiotonics are used to treat HF and atrial fibrillation. Atrial fibrillation is a cardiac arrhythmia characterized by rapid contractions of the atrial myocardium, resulting in an irregular and often rapid ventricular rate. See Chapter 40 for more information on various arrhythmias and treatment. 

QuinidJne. Quinidine, an alkaloid obtained from cinchona bark (Sinchona sp.), is the dextrorotatory stereoisomer of quinine [130-95-0] (see Alkaloids). The first use of quinidine for the treatment of atrial fibrillation was reported in 1918 (12). The sulfate, gluconate, and polygalacturonate salts are used in clinical practice. The dmg is given mainly by the oral (po) route, rarely by the intravenous (iv) route of adniinistration. It is the most frequentiy prescribed po antiarrhythmic agent in the United States. The clinical uses of quinidine include suppression of atrial and ventricular extrasystoles and serious ventricular arrhythmias (1 3). 

Newly developed class III drugs comprise dofetilide, a specific Ik, blocker, and ibutilide, which blocks IKl and activates the slow iNa- Both drugs lack hemodynamic side effects. These drugs are scheduled for the treatment of atrial fibrillation and atrial flutter. As with class HI drugs, they can induce torsade de pointes arrhythmia. 

Common supraventricular tachycardias requiring drug treatment are atrial fibrillation (AF) or atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and automatic atrial tachycardias. Other common supraventricular arrhythmias that usually do not require drug therapy are not discussed in this chapter (e.g., premature atrial complexes, wandering atrial pacemaker, sinus arrhythmia, sinus tachycardia). 

The desired outcome depends on the underlying arrhythmia. For example, the ultimate treatment goals of treating AF or atrial flutter are restoring sinus rhythm, preventing thromboembolic complications, and preventing further recurrences. 

Tachy-arrhythmias may be treated with a /3i-selective blocker. Sotalol may be used in the treatment of postoperative atrial fibrillation, which is observed frequently following cardiac surgery. 

Management of hypothyroidism consists of identifying the underlying cause and then providing thyroid hormone replacement to normalize thyroid sta-ms. The goal of treatment is to reduce semm TSH levels to normal, which for most assays is roughly between 0.5 and 3 mU/1. Oversuppression of TSH levels is probably not advisable, as overtreatment may predispose to cardiac arrhythmias (particularly atrial fibrillation), and may have subtle effects on bone mineral density. 

Dofetilide is approved for the treatment of atrial fibrillation and atrial flutter. Because of the lack of significant hemodynamic effects, dofetilide may be useful in patients with CHF who are in need of therapy for supraventricular tachyarrhythmias. Dofetilide is not indicated for use in the setting of ventricular arrhythmias. 

It is indicated in tachyarrhythmias associated with WPW syndrome, atrial flutter and fibrillation, paroxysmal tachyarrhythmias not responding to other agents. Ventricular tachycardia and ventricular arrhythmia refractory to other treatment. 

Paroxysmal supraventricular tachycardia, atrial fibrillation and flutter. Not of benefit in treatment of ventricular arrhythmias Miscellaneous... 

Class I drugs have a local anaesthetic-like action, blocking the inward current in sodium channels. This depresses the fast depolarisation (phase 0) which initiates each action potential (Figure 8.5). This membrane-stabilising effect makes them valuable for the treatment of ectopic and tachycardic arrhythmias, such as atrial and ventricular fibrillation, extrasystoles, supraventricular and ventricular tachycardia. Class I drugs also decrease contractility. A sub-classification is made according to the effects on... 

This drug is only approved for oral administration in some countries. It is effective for conversion of atrial flutter or fibrillation or ischaemia-induced ventricular arrhythmias. It has significant anticholinergic properties (10% of the potency of atropine) that can offset its direct depressant effects on sinus and AV nodes. It has a pronounced negative inotropic effect and should be administered with caution to patients with a history of congestive heart failure. For acute treatment of perioperative arrhythmias it is given intravenously 0.2 mg-kg-1 over 10-15 min, then 0.2 mg-kg-1 over the next 45 min and a maintenance infusion of 0.4 mg-kg-l-h-1. 

The major therapeutic uses of the cholinomimetics are for diseases of the eye (glaucoma, accommodative esotropia), the gastrointestinal and urinary tracts (postoperative atony, neurogenic bladder), the neuromuscular junction (myasthenia gravis, curare-induced neuromuscular paralysis), and very rarely, the heart (certain atrial arrhythmias). Cholinesterase inhibitors are occasionally used in the treatment of atropine overdosage. Several newer cholinesterase inhibitors are being used to treat patients with Alzheimer s disease. 

Procainamide is effective against most atrial and ventricular arrhythmias. However, many clinicians attempt to avoid long-term therapy because of the requirement for frequent dosing and the common occurrence of lupus-related effects. Procainamide is the drug of second or third choice (after lidocaine or amiodarone) in most coronary care units for the treatment of sustained ventricular arrhythmias associated with acute myocardial infarction. 

In the USA, amiodarone is approved for oral and intravenous use to treat serious ventricular arrhythmias. However, the drug is also highly effective for the treatment of supraventricular arrhythmias such as atrial fibrillation. As a result of its broad spectrum of antiarrhythmic action, it is very extensively used for a wide variety of arrhythmias. Amiodarone has unusual pharmacokinetics and important extracardiac adverse effects. Dronedarone, an analog that lacks iodine atoms, is under investigation. 

Sotalol is approved for the treatment of life-threatening ventricular arrhythmias and the maintenance of sinus rhythm in patients with atrial fibrillation. It is also approved for treatment of supraventricular and ventricular arrhythmias in the pediatric age group. Sotalol decreases the threshold for cardiac defibrillation. 

Supraventricular tachycardia is the major arrhythmia indication for verapamil. Adenosine or verapamil are preferred over older treatments (propranolol, digoxin, edrophonium, vasoconstrictor agents, and cardioversion) for termination. Verapamil can also reduce the ventricular rate in atrial fibrillation and flutter. It only rarely converts atrial flutter and fibrillation to sinus rhythm. Verapamil is occasionally useful in ventricular arrhythmias. However, intravenous verapamil in a patient with sustained ventricular tachycardia can cause hemodynamic collapse. 

Vomiting is common in patients with digitalis overdose. Hyperkalemia may be caused by acute digitalis overdose or severe poisoning, whereas hypokalemia may be present in patients as a result of long-term diuretic treatment. (Digitalis does not cause hypokalemia.) A variety of cardiac rhythm disturbances may occur, including sinus bradycardia, AV block, atrial tachycardia with block, accelerated junctional rhythm, premature ventricular beats, bidirectional ventricular tachycardia, and other ventricular arrhythmias. 

Drugs that block beta-1 receptors on the myocardium are one of the mainstays in arrhythmia treatment. Beta blockers are effective because they decrease the excitatory effects of the sympathetic nervous system and related catecholamines (norepinephrine and epinephrine) on the heart.5,28 This effect typically decreases cardiac automaticity and prolongs the effective refractory period, thus slowing heart rate.5 Beta blockers also slow down conduction through the myocardium, and are especially useful in controlling function of the atrioventricular node.21 Hence, these drugs are most effective in treating atrial tachycardias such as atrial fibrillation.23 Some ventricular arrhythmias may also respond to treatment with beta blockers. 

Purerfellner H. Recent developments in cardiovascular drug therapy treatment of atrial arrhythmias with new class III drags and beyond. Curr Med Chem Cardiovasc Hematol Agents. 2004 2 79-91. 

Glycosides of the gitoxigenin series are less active than the corresponding members of the digitoxigenin-derived series. Digitoxin is the only compound routinely used as a drug, and it is employed in congestive heart failure and treatment of cardiac arrhythmias, particularly atrial fibrillation. 

Endogenous norepinephrine stimulates cardiac beta receptors. Receptor-linked cAMP-dependent protein kinases phosphorylate calcium channels to increase intracellular calcium. Elevated intracellular calcium increases conduction velocity (phase 0) and decreases the threshold potential in normal SA and AV node cells (see Figure 12.13). Beta blockers slow spontaneous conduction velocity in the SA node by approximately 10-20 percent. In addition, beta blockers can slow conduction velocity while increasing the refractory period of the AV node. These effects control the ventricular rate in atrial fibrillation or flutter and terminate paroxysmal supraventricular tachycardias. They are also safer, although somewhat less effective, than other drugs for suppression of premature ventricular complexes (PVCs). Drugs in this class approved by the FDA for treatment of various arrhythmias include propranolol, acebutolol, and esmolol. Problems with the beta blockers include drowsiness, fatigue, impotence, and depressed ventricular performance. 

This review focuses on the recent discovery and development of chemical entities targeting the Kvl.5 potassium channel subunit for the treatment of atrial arrhythmias. This strategy is based on the expression of the ultrarapidly activating delayed rectifier potassium current, /Run in atria but not ventricles of humans, and on the molecular characterization of the Kvl.5 channel subunit as a structural correlate of JRur [1-6]. Although no perfectly selective Kvl.5... 

Therapeutic uses Quinidine is used in the treatment of a wide variety of arrhythmias, including atrial, AV junctional, and ventricular tachyarrhythmias. Quinidine is used to maintain sinus rhythm after direct current cardioversion of atrial flutter or fibrillation and to prevent frequent ventricular tachycardia. 

Aminocycloalkyl cinnamide derivatives, (III), prepared by Beatch (3) were effective in the treatment and termination of atrial fibrillation/flutter arrhythmia events. 

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