title: Effect of magnesium sulfate on ventricular refractoriness and its efficacy for torsade de pointes.
abstract: The effect of magnesium sulfate on ventricular refractoriness and its efficacy for torsade de pointes (TdP) were studied in nineteen dogs. After the administration of quinidine sulfate (30 mg/kg), TdP was induced by ventricular pacing in ten of 19 dogs (52.6%), polymorphic ventricular tachycardia in seven (36.8%), ventricular fibrillation in two (10.5%). Quinidine sulfate caused significant increases in QTc interval, ventricular effective refractory period (ERP) and dispersion of ERP(dERP), and decrease in ERP/QT. Magnesium sulfate significantly increased ERP (p less than 0.01), but it did not change QT interval, resulting in significant increasing of ERP/QT (0.41 +/- 0.05 to 0.61 +/- 0.05, p less than 0.01). It decreased dERP but not significantly. Magnesium sulfate prevented the induction of TdP in eight of 10 dogs (80.0%) (30 mg/kg in four and 60 mg/kg in four). In conclusion, magnesium sulfate has value as first aid therapy for drug-induced TdP. If patients have ischemic heart disease or hypertension, we recommend infusion of magnesium for the initial therapy of TdP.
authors.affiliation: 2nd Department of Internal Medicine, School of Medicine, University of Tokushima, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Bando
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: A
authors.initials: A
authors.lastname: Nishikado
authors.forename: K
authors.initials: K
authors.lastname: Hamai
authors.forename: K
authors.initials: K
authors.lastname: Fujino
authors.forename: Y
authors.initials: Y
authors.lastname: Nakaya
authors.forename: A
authors.initials: A
authors.lastname: Shinohara
mesh_terms: D000818:Animals; D004285:Dogs; D004353:Drug Evaluation, Preclinical; D004558:Electric Stimulation; D006352:Heart Ventricles / Q000187:drug effects; D008278:Magnesium Sulfate / Q000494:pharmacology*; D011802:Quinidine / Q000008:administration & dosage; D016171:Torsades de Pointes / Q000188:drug therapy* / Q000517:prevention & control; D016277:Ventricular Function, Left / Q000187:drug effects*
chemical_list: D008278:Magnesium Sulfate; D011802:Quinidine