Age-related arrhythmogenic effects of oxidative stress in isolated rat hearts

The higher incidence and severity of malignant arrhythmias in the elderly is probably due to a direct effect of age on cardiac electrophysiology. Since, oxygen radical toxicity has been implicated in tissue aging, in the present study we tested the metabolic, electrical and mechanical response of hearts from 3-24 months old rats receiving 30 min. infusion of the oxidant hydrogen peroxide (H₂O₂, 60 μM), followed by a 15 min. wash-out. H₂O₂ infusion affected left ventricular end-diastolic pressure, induced an increase of ventricular arrhythmias (according to Lambeth Conventions) and determined an increase of cardiac release of oxidized glutathione (an index of the ability of the heart to inactivate peroxides) and of reduced glutathione (a marker of cell damage). These phenomena showed a significant age-related trend. Thus, the increase of arrhythmias in 24 months rat hearts is correlated to decreased metabolic and functional tolerance toward oxidative stress.