Treatment of Cardiac Arrhythmias

An arrhythmia can be broadly defined as any significant deviation from normal cardiac rhythm.6 Various problems in the origination and conduction of electrical activity in the heart can lead to distinct types of arrhythmias. If untreated, disturbances in normal cardiac rhythm result in impaired cardiac pumping ability, and certain arrhythmias are associated with cerebrovascular accidents, cardiac failure, and other sequelae that can be fatal.1,2 16 Fortunately, a variety of drugs are available to help establish and maintain normal cardiac rhythm. 

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Hill. J.L. (1985) in Mechanism and Treatment of Cardiac Arrhythmias Relevance of Basic Studies to Clinical Management (Reiser, H.J. and Horowitz, L.N., eds.), pp. 173-182, Urban Schwarzenberg, Baltimore. 

Many local anesthetics have a selective depressant action on heart muscle when given systemically. This is useful in treatment of cardiac arrhythmias, and a lidocaine-like drug with this kind of action is tocainide (2). ... 

Phenytoin, introduced as an anticonvulsant drug in 1938, remains one of the drugs most frequently prescribed for convulsive disorders. The precise mode of action is unknown, but it appears to inhibit the accumulation of sodium in nerve cells, thus stabilizing hyperexcitable cell membranes (A13)—a property also utilized in the treatment of cardiac arrhythmias. 

VI.a.2.3. Quinine alkaloids. The quinine alkaloids include quinine and quinidine. Quinidine, the dextrorotatory diastereoisomer of quinine, is mainly used for the parenteral treatment of cardiac arrhythmias but it can be an alternative antimalarial in regions where Plasmodium falciparum is resistant to both chloroquine and antifolate-sulfonamide combinations. 

Cardiovascular and Renal Diseases D Pharnnacological Treatment of Cardiac Arrhythmias... 

Phenytoin (Dilantin) was originally introduced for the control of convulsive disorders (see Chapter 32) but has now also been shown to be effective in the treatment of cardiac arrhythmias. Phenytoin appears to be particularly effective in treating ventricular arrhythmias in children. 

Blockers competitively antagonize the responses to catecholamines that are mediated by (3-receptors (see Chapter 11).These drugs have a number of clinical uses, including treatment of cardiac arrhythmias (see Chapter 10) and angina pectoris (see Chapter 17), for... 

For systemic use in the treatment of cardiac arrhythmias (Details are given in chapter Antiarrhythmic agents ). 

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. 

The rauwolfia alkaloids are now hardly ever prescribed in the UK, either as antihypertensives or as tranquillizers. Over a period of a few years, they have been rapidly superseded by synthetic alternatives. Reserpine has also been suggested to play a role in the promotion of breast cancers. Both ajmalicine (= raubasine) (Figure 6.76) and ajmaline (Figure 6.82) are used clinically in Europe, though not in the UK. Ajmalicine is employed as an antihypertensive, whilst ajmaline is of value in the treatment of cardiac arrhythmias. Ajmalicine is also extracted commercially from Catharanthus roseus (see page 357). 

Propranolol is the [3-adrenergic antagonist most widely used in the treatment of cardiac arrhythmias. However, Pi-specific drugs, such as metoprolol (see p. 77) reduce the risk of bronchospasm, and drugs with partial agonist activity, such as pindolol (see p. 77), may decrease the frequency of cardiac failure. 

Priestley KA, Ladusans EJ, Rosenthal E, Holt DW, Tynan MJ, Jones OD, Curry PV. Experience with flecainide for the treatment of cardiac arrhythmias in children. Eur Heart J 1988 9(12) 1284-90. 

International Symposium, Pathophysiology and Drug Treatment of Cardiac Arrhythmias. Preliminary Experience with a New Antiarrhythmlc Drug (Aprindlne), Acta Cardiol., Suppl. 18, 1 (1974). 

Only a few new pharmacological effects have been indicated for the alkaloids of the ajmaline group. Most of diem concern symaline (17) itself, wdiich has been known since 1959 (207) and is used in the treatment of cardiac arrhythmia (20S, 209). 

The only calcium channel blocking drug to have been licensed for the treatment of cardiac arrhythmias is verapamil. Its main uses are in the treatment of supraventricular tachycardia (SVT) and paroxysmal SVT. Because verapamil lengthens the ERP and FRP of the AV node and prolongs AV nodal conduction time [16], it can be used to control the ventricular rate in atrial fibrillation or atrial flutter and it usually terminates re-entry arrhythmias involving the AV node [208, 209], However, intravenous verapamil should not be given to patients who have the Wolff-Parkinson-White syndrome and atrial... 

Here I will mention only one example. Disturbances of cardiac rhythm are an important medical problem. Quinidine, the d-isomer of quinine, is one of the most effective agents available for the treatment of cardiac arrhythmias. The discovery that quinine, and subsequently quinidine, could be used to treat certain arrhythmias must be attributed to luck. A patient of Wenckebach, a famous Viennese physician, noted in 1912 that when he took quinine for his malaria it also caused his rapid, irregular pulse to become slower and more regular. In 1918 Frey compared several cinchana alkaloids and found that quinidine was more effective in treating atrial fibrillation than quinine. Subsequently, quinidine was found to be effective against many other cardiac arrhythmias. 

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