The effectiveness of magnesium chloride in the treatment of ventricular tachyarrhythmias due to digitalis intoxication

Abstract

Efficacy of magnesium chloride in treatment and prevention of digitalis toxicity was studied in 39 dogs. A persistent ventricular tachycardia, lasting more than five minutes was induced in 29 dogs by deslanoside, 0.18 mg. per kilogram intravenously. In 19 animals, administration of magnesium chloride (5 to 10 ml. of a 20 per cent solution) administered intravenously converted the ventricular tachycardia into a sinus rhythm. The cardiac output was found to be increased following this treatment (P < 0.01). The serum electrolytes and digoxin levels remained unchanged. With larger doses of magnesium chloride, significant bradycardia occurred in two instances following abolition of ventricular tachycardia. When pretreatment with magnesium chloride (10 ml. intravenously and 20 ml. intramuscularly of a 20 per cent solution) was employed in a group of five dogs prior to administration of deslanoside, ventricular tachycardia from the usual or greater doses of the glycoside was invariably prevented. Deslanoside dosage larger by 83.3 per cent was then required to produce cardiotoxicity; however, VT appeared in only one out of five dogs, whereas serious A-V conduction impairment was seen in other dogs. None of the magnesium-pretreated animals developed ventricular fibrillation in spite of marked bradycardia. In 10 dogs used as control animals, the ventricular tachycardia either persisted or deteriorated into ventricular fibrillation. In conclusion, the experimental data demonstrate that magnesium chloride is effective in treatment of digitalis-induced ventricular arrhythmias.