Disopyramide

Propafenone and disopyramide enhance post-ischemic contractile and metabolic recovery of perfused hearts

The effects of sodium channel blockers, propafenone and disopyramide, on post-ischemic contractile dysfunction of perfused rat hearts were examined. Isolated hearts were subjected to 35 min ischemia, followed by 60 min reperfusion with and without administration of either drug during 3 min of pre-ischemia. Ischemia/reperfusion induced complete cardiac dysfunction, rise in left ventricular end-diastolic pressure, increase in perfusion pressure, accumulation of Na+ and Ca2+ and loss of K+ and Mg2+, and release of creatine kinase and purine nucleosides and bases from the heart. These observations suggest that ischemia/reperfusion in the current study induces cardiac cell necrosis or an increase in cell membrane permeability to ions, substrates and macromolecules. Treatment of perfused hearts with either propafenone at concentrations ranging from 5 to 70 microM, or disopyramide at concentrations of 100 microM or higher resulted in a pronounced contractile recovery of the heart, associated with suppression of reperfusion-induced tissue ion alteration and inhibition of reperfusion-induced release of creatine kinase and purine nucleosides and bases. Ischemic insult itself caused tissue Na+ accumulation and K+ loss without any change in tissue Ca2+ and Mg2+. The alterations in the electrolytes were attenuated by treatment with either agent. The results suggest that prevention of ischemia- and reperfusion-induced ionic disturbance of cardiac cells by propafenone and disopyramide plays a role in the improvement of post-ischemic contractile dysfunction.

QT-interval prolonging drugs: mechanisms and clinical relevance of their arrhythmogenic hazards

The antiarrhythmic principle of drug-induced QT-interval prolongation is well known. However, with the widespread use of the presently known and new Class III antiarrhythmic agents under investigation, and the growing number of agents not primarily designed as antiarrhythmic drugs that potentially cause QT prolongation, we have also become aware of the proarrhythmic hazards associated with many of these agents. The proarrhythmic risk differs markedly from one agent to another and interferes with many individual clinical variables (e.g., hypokalemia, sinus bradycardia). This paper summarizes the present data on the proarrhythmic risk of drug-induced QT prolongation, including the value and problems of the rate-corrected QT interval, the mechanisms involved in the genesis of proarrhythmia, and the clinical cofactors that facilitate the occurrence of proarrhythmic events. In addition, an extensive database provides information on the known proarrhythmic risk of all currently used QT-prolonging agents.