[Current status of pharmacologic treatment of arrhythmia]

Arrhythmias result from alterations in the electrophysiological properties of the heart: excitability, automatism, conduction, refractory period, and repolarization. These properties depend on the cellular membrane voltage. This voltage is a consequence of macromolecular tunnels permitting the flow of electrical charged particles and the action of the electrogenic pumps against electrochemical gradients. The voltage alterations in the membrane give rise to arrhythmogenic mechanisms resulting of automatism alterations or disorders in conduction, producing re-entry or circus movement. The medical treatment must be based on a correct integral diagnosis, knowledge of the trigger and maintenance mechanisms of the arrhythmia as well as on the pharmacology of the drug. The antiarrhythmic drug classifications are useful for didactic purposes but may be of little use in medical practice. In supraventricular arrhythmias, the mechanisms are known and can be identified; the re-entry pathways are also known and the electrophysiological mechanisms are normal, therefore the response to the drugs is predictable. In contrast, in ventricular arrhythmias, the mechanisms are variable, the circuits are very difficult to identify and involve healthy and sick tissues. The therapeutic indication is very difficult and incorrect in many occasions. It is possible that, in the future, the study of hereditary arrhythmias could be the basis for a better understanding of these problems.