Electrical heterogeneity and conduction block in reoxygenated guinea pig papillary muscles.

To investigate the changes in electrical activity after reoxygenation, guinea pig papillary muscles were reoxygenated with 5 mM glucose solution after various durations (30-120 min) of substrate-free hypoxia. Action potential duration recovered to the control level on reoxygenation following 30-120 min hypoxia. The recovery of developed tension or resting tension was incomplete after reoxygenation following longer periods of hypoxia. There was a high incidence of arrhythmias on reoxygenation after 60 min hypoxia, which have been shown to be triggered activities due to delayed afterdepolarizations. In some muscles reoxygenated after prolonged hypoxia (90-120 min), there was electrical heterogeneity which was shown by variable action potential durations and configurations. There was also conduction block around the microelectrode site in muscle. It was suggested that the electrical heterogeneity and conduction block could predispose to reentry, and that triggered activities and reentry could be involved in the genesis of arrhythmias on reperfusion.