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 cardiac electrophysiological actions at their peril. In emergencies, action often needs to be taken by the most junior doctor in the team, and some rote recommendations are then necessary. The diagnosis and elective treatment of chronic, or episodic arrhythmias require greater skill to ensure that the correct balance between risk and benefit is achieved. As will become clear, antiarrhythmic drugs have a hard time proving superior safety or efficacy over other therapeutic (non-drug) options.
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