[Potassium channels and arrhythmia].
Cardiac repolarisation depends mainly on the cellular extrusion of positive electrical charge related to the potassium ion through different channels. There are many potassium channels which are responsible for repolarisation in different cardiac tissues. Prolongation or shortening of the repolarisation period may be both antiarrhythmic and proarrhythmic depending on the given experimental conditions. Different potassium channels may be opened or blocked by clinically prescribed drugs. Activators of the iK(ATP) channels may exert antiarrhythmic effects by inhibiting activity induced by prolonged repolarisation. Experimentally, they may exert a proarrhythmic effect by predisposing to arrhythmias during myocardial ischemia. However, these effects have not been clearly demonstrated clinically. Potassium channel blockers may have an antiarrhythmic effect by reducing the variability of repolarisation, by prolonging the atrial and ventricular refractory periods and by their antifibrillatory actions. Nevertheless, they may have proarrhythmic effects resulting in triggered activation under particular conditions of bradycardia and/or ischemia. Examples of these effects have been reported in man. The understanding of the relationship between potassium channels and arrhythmias is particularly complex because of the multiple factors regulating the duration of repolarisation and the effects of drugs on this duration. These factors include the activity of the autonomic nervous system, the heart rate, ischemia and acidosis and the differences in response to endocardial and epicardial tissues.
Funck-Brentano
C
C
Unité de pharmacologie clinique, hôpital Saint-Antoine, Paris.
D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000378:metabolism / Q000503:physiopathology*; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate; D006801:Humans; D015221:Potassium Channels / Q000187:drug effects
D000889:Anti-Arrhythmia Agents; D015221:Potassium Channels
Canaux potassiques et arythmies.