The pathophysiology of cardiac arrhythmias is complex and the actions of drugs that are useful in stopping or controlling them may seem equally so. Nevertheless many patients with arrhythmias respond well to therapy with drugs and a working knowledge of their effects and indications pays dividends, for irregularity of the heart-beat is at least inconvenient and at worst mechanisms by which the failing heart may be sustained are now better understood; carefully selected and monitored drugs can have a major impact on morbidity and mortality in this condition. Drugs for cardiac arrhythmias. Principal drugs by class •. | SECTION 5 Cardiac arrhythmia and cardiac failure SYNOPSIS The pathophysiology of cardiac arrhythmias is complex and the actions of drugs that are useful in stopping or controlling them may seem equally so. Nevertheless many patients with arrhythmias respond well to therapy with drugs and a working knowledge of their effects and indications pays dividends for irregularity of the heart-beat is at least inconvenient and at worst mechanisms by which the failing heart may be sustained are now better understood carefully selected and monitored drugs can have a major impact on morbidity and mortality in this condition. Drugs for cardiac arrhythmias Principal drugs by class Specific treatments including those for cardiac arrest Drugs for cardiac failure OBJECTIVES OF TREATMENT In almost no other condition is it as important to remember the dual objectives which are To reduce morbidity and To reduce mortality. Arrhythmias are frequently asymptomatic but may be fatal. Indeed an estimated 70 000 deaths per year are ascribed to ventricular arrhythmias in the United Kingdom. In addition all antiarrhythmics are also capable of generating arrhythmias and should be used only in the presence of clear indications. In addition antiarrhythmic agents are to a variable degree negatively inotropic except for digoxin and amiodarone . A second reason for a careful approach to antiarrhythmic treatment is the gulf between knowledge of their mechanism of action and their clinical uses. On the side of normal physiology we can see the spontaneous generation and propagation of the cardiac impulse requiring a combination of specialised conducting tissue and inter-myocyte conduction. The heart also has backstops in case of problems with the variety of pacemakers. By contrast the available drugs may be considered still to be at an early stage of evolution and useful antiarrhythmic actions such as that of adenosine continue to be discovered by chance. Doctors and drugs interfere with .
