Antiarrhythmic agents: modulated receptor applications.

IT IS NOW well established that block of transmembrane ionic channels is frequently time and voltage dependent.' 2 Although the modulated receptor theory has been most extensively studied for sodium and calcium channels in cardiac tissue,3 it may apply to other membrane receptors as well. The present essay is limited to discussion of sodium-channel blockers and how their timeand voltage-dependent block can contribute to antiarrhythmic and arrhythmogenic actions. After a brief description of the modulated receptor theory and the definition of some commonly used but ill-defined terms, these principles will be applied to some clinical conditions. Although the general flavor of the present article should be palatable without studying previous reports describing the modulated receptor hypothesis, full appreciation of all the concepts may require some additional reading.2 4 It is my hope that these considerations will spark some tests in vivo of the modulated receptor concepts that will ultimately benefit the patient suffering from arrhythmias.