Inability of helium to influence the occurrence of arrhythmias in cats, rats, and mice

In view of recent reports that breathing helium oxygen (He O₂) mixtures tends to inhibit the occurence of arrhythmias and ventricular fibrillation following left circumflex coronary artery occlusion in aensthetized dogs the effects of helium on the occurrence of arrhythmias induced pharmacologically were examined. The total intravenous dose of ouabain required to induce continuous arrhythmias in anesthetized rats, or to flatten the EKG in anesthetized mice, was identical in animals breathing He O₂ (80:20) and animals breathing air. Similarly, the presence of helium in the inspired gas did not alter either the intravenous dose of deslanoside required to induce continuous arrhythmias or the duration of arrhytrhmias induced by intravenous epinephrine in anesthetized cats. In light of these negative results, the authors examined finally whether respiring helium would affect the occurrence of arrythmias following occlusion of the left descending coronary artery in anesthetized cats: it was found that helium affected neither the frequency of arrhythmias nor the incidence of ventricular fibriallation. In conclusion, no evidence that helium possessed antiarrhythmic properties in the speciies studied.